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‫فسلجة وتشريح‪ /‬الفصل الثاني عشر‬ ‫المرحلة الثانية‬ ‫مدرس المادة‪ :‬د‪.‬عباس فضال حمادي‬ ‫‪|Page1‬‬ 1-The respiratory system functions:-  1- Providing a large area for gas exchange between air and circulating blood.  2- Moving air to and fr...

‫فسلجة وتشريح‪ /‬الفصل الثاني عشر‬ ‫المرحلة الثانية‬ ‫مدرس المادة‪ :‬د‪.‬عباس فضال حمادي‬ ‫‪|Page1‬‬ 1-The respiratory system functions:-  1- Providing a large area for gas exchange between air and circulating blood.  2- Moving air to and from the gas-exchange surfaces of the lungs.  3- Protecting the respiratory surfaces from dehydration and defending against invading pathogens.  4- Producing sounds permitting speech, singing, and nonverbal auditory communication.  5- Providing olfactory sensations to the central nervous system for the sense of smell. The organization of the respiratory system:  The major anatomical structures of the respiratory system are:  -Nose (including the nasal cavity and paranasal sinuses).  -Pharynx (throat).  -Larynx (voice box).  -Trachea (wind-pipe).  -Bronchi.  -Lungs contain the bronchioles (conducting passageways).  -Alveoli (exchange surfaces). Respiratory tract: the airways that carry air to and from the exchange surfaces of the lungs, which can be divided into:  1- conducting portion: begins at the entrance to the nasal cavity and continues through the pharynx, larynx, trachea, bronchi, and the larger bronchioles. In addition to delivering air to the lungs, conducting passageways filter, warm, and humidify the air, thereby protecting the alveoli from debris, pathogens, and environmental extremes. By time inhaled air reaches the alveoli, most foreign particles and pathogens have been removed, and the humidity and temperature are within acceptable limits. |Page2  2- Respiratory portion: includes the smallest and most delicate bronchioles and the alveoli, which provide large blood-gas exchange surfaces.  The nose : air normally enters the respiratory system through the paired external nares, or nostrils, which opened into the nasal cavity. The nasal vestibule is the space enclosed within the flexible tissues of the nose. Here coarse hairs extend across the nostrils and guard the nasal cavity from large particles such as sand, dust, and even insects. The nasal cavity opens into nasopharynx at the internal nares.  The nose contain also paranasal sinuses (the frontal, sphenoid, ethmoid, and maxillary sinuses). |Page3  The nasal septum divides the nasal cavity into left and right sides.  The nasal cavity and much of the respiratory tract are lined by protective, mucous membrane, or respiratory mucosa. This membrane is made of respiratory epithelium, a ciliated columnar epithelium containing many goblet cells, and underlying loose connective tissue layer (the lamina propria) containing mucous glands. Cilia sweep that mucous and any trapped debris or microorganism toward pharynx, where they can be swallowed and exposed to the acids and enzymes of the stomach.  The pharynx: or throat, is a chamber shared by the digestive and respiratory systems. It extends between the internal nares and the entrances to the larynx and esophagus and consists of three subdivisions: the nasopharynx, the oropharynx, and the laryngopharynx. The last two regions are lined by a stratified squamous epithelium that can resist mechanical abrasion, chemical attack, and pathogenic invasion. |Page4  The larynx: or voice box, consists of nine cartilages stabilized by ligaments, skeletal muscles, or both. The glottis is a narrow opening for entry of inhaled air through larynx. Epiglottis projects above the glottis. During swallowing, the larynx is elevated and the elastic epiglottis folds back over the glottis, preventing the entry of liquids or solid food into the respiratory tract. The larynx contain the vocal cords for producing the voice. The voices ton related to the length, diameter, and the tension of the vocal cord. short, and thin cord vibrate more rapidly, producing high-pitched tone, while thick, and long cord vibrate more slowly producing a low pitched tone.  The trachea: or windpipe, is a tough, flexible tube that is about 2.5 cm in diameter and approximately 11 cm long. The trachea begins at the level of the sixth cervical vertebra, where it attaches to the cricoid cartilage of the larynx. It ends in the mediastinum, at the level of the fifth thoracic vertebra, where it branches to form the right and left primary bronchi.  The wall of the trachea are supported by 15-20 tracheal cartilages. These C-shape cartilages protect the airway; by stiffening the tracheal walls, they prevent trachea’s collapse or overexpansion as pressures change in the respiratory system. The open portion of the c-shaped tracheal cartilages face posteriorly, toward the esophagus, so the posterior tracheal wall can easily distort, allowing large masses of food to pass along the esophagus.  The ends of each tracheal cartilage are connected by an elastic ligament and the smooth tracheal muscle allowing the change of diameter of the trachea under autonomic control. Sympathetic stimulation increases the diameter of the trachea, making it easier to move large volumes of air along the respiratory passageways. |Page5  The bronchi: within the mediastinum the trachea branches into the right and left primary bronchi. The walls of the primary bronchi resemble that of the trachea, including a ciliated epithelium and C-shaped cartilaginous rings.  The right primary bronchus supplies the right lung, and the left supplies the left lung.  In each lung, the primary bronchi branch into smaller and smaller airways that form the bronchial tree which consist of secondary and tertiary bronchi. |Page6  The bronchioles: are the smallest airway in the bronchial tree with diameter about 1mm.  Bronchioles branch further into terminal bronchioles with diameter of 0.3-0.5mm. Each terminal bronchiole supplies air to a lobule of the lung. Within a lobule, a terminal bronchiole divides to form several respiratory bronchioles. these passages, the thinnest branches of the bronchial tree, deliver air to the gas-exchange surfaces of the lung.  The alveolar ducts and alveoli: respiratory bronchioles open into passageways called alveolar ducts. The ducts end at alveolar sacs, common chambers connected to multiple individual alveoli—the exchange surfaces of the lung (equal |Page7  approximately 140 square meters). Each lung contains about 150 million alveoli, and their abundance gives the lung an open, spongy appearance.  The alveolar epithelium primarily consists of an unusually thin simple Sequamous epithelium. Each alveoli contain alveolar macrophages (dust cell) patrol the epithelium, phagocytizing dust or debris that reached the alveolar surfaces. Also here present septal cells, which secrete onto the alveolar surfaces an oily secretion called surfactant to reduced surface tension to prevent collapse the delicate alveolar walls. |Page8 The respiratory membrane:  Gas exchange occurs across the respiratory membrane of the alveoli. The respiratory membrane consists of three components:  1- The sequamous alveolar epithelium.  2- The endothelial cells lining an adjacent capillary.  3- The fused basement membranes that lie between the alveolar and endothelial cells.  At the respiratory membrane, the distance separating alveolar air from blood can be as little as 0.1µm. Diffusion across the respiratory membrane proceeds very rapidly because the distance is very small and because both oxygen and carbon dioxide are lipid soluble. The membranes of the epithelial and endothelial cells, thus, do not pose a barrier to the movement of oxygen and carbon dioxide between blood and the alveolar air spaces. Circulation to the respiratory membrane:  The respiratory exchange surfaces receive blood from arteries of the pulmonary circuit. Each lobule receives an arteriole. And network of capillaries surrounds each alveolus directly beneath the alveolar epithelium. After passing through the capillaries and into venules, blood enters the pulmonary veins, which deliver it to the left atrium.  Blood pressure in the pulmonary circuit is usually relatively low, with systemic pressures of 30mmHg or less. The organization of the respiratory system:  The lung: each of the two lungs has distinct lobes that are separated by deep fissures. The right lung has three lobes (superior, middle, and inferior), and the left lung has two (superior, and inferior).  The lungs have a light and spongy consistency because most of the actual volume of each lung consists of air-filled passageways and alveoli. An abundance of elastic fibers gives the lungs the ability to tolerate the large changes in volume.  The pleural cavities: the thoracic cavity has the shape of a broad cone. Its wall are the rib cage, and its floor is the muscular diaphragm. Within the thoracic cavity, each lung occupies a single pleural cavity. Lined by a serous membrane called pleura. The |Page9  parietal pleura covers the inner surface of the body wall and extends over the diaphragm and mediastinum. The visceral pleura covers the outer surfaces of the lungs, extending into the fissures between the lobes. The two pleural cavities are separated by the mediastinum. Pleural cavity contain pleural fluid to reduce friction between the two layers of the pleural during respiration. Respiratory physiology:  The process of respiration involves three integrated steps: | P a g e 11   Step 1: pulmonary ventilation, or breathing, which involves the physical movement of air into and out of the lungs.  Step 2: gas exchange, which involves gas diffusion at two sites: across the respiratory membrane between alveolar air spaces and alveolar capillaries. And across capillary cell membranes between blood and other tissues.  Step 3: gas transport, which involves the transport of oxygen and carbon dioxide to and from the alveolar capillaries and the capillary beds in other tissues.  Abnormalities affecting any of these processes will ultimately affect the gas concentrations (hypoxia, or anoxia) of the interstitial fluids and, thus, cellular activities as well. Pulmonary ventilation:  Pulmonary ventilation is the physical movement of air into and out of the respiratory tract. A single breath, or respiratory cycle, consists of an inhalation (or inspiration) and exhalation (or expiration).  The respiratory rate is the number of breaths per minute. This rate in normal adults at rest ranges from 12 to 18 breath per minute. Children breathe more rapidly, about 18 to 20 breaths per minute.  Breathing functions to maintain adequate alveolar ventilation, the movement of air into and out of the alveoli. Alveolar ventilation prevents the buildup of carbon dioxide in the alveoli and ensures continuous supply of oxygen that keeps pace with absorption by the bloodstream.  Changes in the volume of the thoracic cavity result from movements of the diaphragm and rib cage. As the volume of the container (the lungs) increases, the pressure of the gas (air) decreases; as volume decreases, pressure increases.  At the start of a breath, pressures inside and outside the lungs are identical, and there is no movement of air (figure15-10b).  When the diaphragm contracts and the movement of respiratory muscles enlarges the thoracic cavity, the pleural cavities and lungs expand to fill the additional space, so the pressure inside the lungs decreases. Air now enters the respiratory passageways because the pressure inside the lungs (Pi) is lower than the atmospheric pressure (pressure outside, or Po) (figure15-10c). | P a g e 11   Downward movement of the diaphragm during exhalation reverse the process and reduce the volume of the lungs. Pressure inside the lungs now exceeds atmospheric pressure, and air moves out of the lungs (figure15-10d). Modes of breathing:  The respiratory muscles are used in various combinations, depending on the volume of air that must be moved into or out of the system. Respiratory movements are classified as quiet breathing or forced breathing.  Quiet breathing, inhalation involves muscular contractions, but exhalation is passive. Inhalation involves the contraction of the diaphragm muscles (75% of air) and the external intercostal muscles (25% of air). | P a g e 12  forced breathing, both inhalation and exhalation are active. Forced breathing involves the accessory muscles during inhalation and the internal intercostal muscles and abdominal muscles during exhalation.  As noted earlier, A respiratory cycle is a single cycle of inhalation and exhalation.  Tidal volume (VT): the amount of air moved into or out of the lungs during a single respiratory cycle, the average VT is 500ml.  Expiratory reserve volume (ERV): is the amount of air that could be voluntarily expelled at the end of a respiratory cycle, it is about 1000ml.  Inspiratory reserve volume (IRV): is the amount of air that can be taken in over and above the resting tidal volume. Because the lungs of the males are larger than those of females. The IRV of males averages 3300ml versus 1900ml in females.  Vital capacity: the sum of the ERV and IRV and VT. It is the maximum amount of air that can be moved into and out of the respiratory system in a single respiratory cycle.  Residual volume: is the amount of air that remains in the lung even after maximal exhalation, it average about 1200ml in males and 1100ml in females.  Minimal volume: is the amount of air that remains in the respiratory system after penetration of the chest cavity (pneumothorax), it about (30-120ml).  Anatomic dead space: is the total volume of respiratory passageways of the lungs, it average about 150ml which not take part in gas exchange with the blood. | P a g e 13 Gas exchange:  During pulmonary ventilation, the alveoli are supplied with oxygen, and carbon dioxide is removed from the bloodstream. The actual process of gas exchange with the external environment occurs between the blood and alveolar air across the respiratory membrane. This process depends on:  1- The partial pressures of the gases involved (the pressure contributed by single gas), for oxygen Po2159mmHg in the atmospheric air. Each gas contributes to the total pressure in proportion to its relative abundance.  2- The diffusion of molecules between the gas and a liquid. Partial pressures within the circulatory system:  The process of gas exchange may be divided into external respiration and external respiration. | P a g e 14  External respiration: is the diffusion of gases between the blood and alveolar air across the respiratory membrane.  Internal respiration: is the diffusion of gases between the blood and interstitial fluid across the endothelial cells of capillary walls.  The deoxygenated blood delivered by the pulmonary arteries has lower Po 2 and a higher Pco2 than does alveolar air.  Diffusion between the alveolar air and the pulmonary capillaries, thus, elevates the Po2 of the blood while lowering its Pco2. By the time it enters the pulmonary venules, the oxygenated blood has reached equilibrium with the alveolar air, so it departs the alveoli with a Po2 of about 100 mmHg and a Pco2 of roughly 40mmHg.  Normal interstitial fluid has a Po2 of 40mmHg and a Pco2 45mmHg. As a result, oxygen diffuses out of the capillaries, and carbon dioxide diffuses in, until the capillary partial pressures are the same as those in the adjacent tissues. | P a g e 15  When the blood return to the alveolar capillaries, external respiration will replace the oxygen released into the tissues at the same time that excess CO2 is lost.  Oxygen and carbon dioxide have limited solubilities in blood plasma. So little amount dissolved in the plasma and the large part transported by red blood cells.  Oxygen: only 1.5% of O2 transported by plasma and the rest bind to the hemoglobin molecules, specifically, to the iron ions in the center of heme units (Hb + O2 HbO2). The amount of oxygen bound or released by hemoglobin depends primarily on the Po2, pH, and temperature in its surrounding.  Carbon dioxide: 3 ways for CO2 transportation present:  1- 7% dissolve in plasma.  2- 23% bind to the “globin” portions of hemoglobin molecules, forming carbaminohemoglobin.  70% be converted to a molecule of carbonic acid (CO2 + H2O H2CO3 H + HCO3- ). + | P a g e 16 The control of respiration:  The equilibrium of normal Po2 and Pco2 is restored through homeostatic mechanisms that involve:  1- changes in blood flow and oxygen delivery under local control.  2- changes in depth and rate of respiration under the control of the brain’s respiratory centers.  1- both the rate of oxygen delivery at each tissue and the efficiency of oxygen pickup at the lungs are regulated by the local level. If a peripheral tissue becomes more active, the interstitial Po2 falls and the Pco2 rises. These changes increase the difference between partial pressures in the tissue and arriving blood, so more oxygen is delivered and more carbon dioxide is carried away. In addition, rising Pco 2 levels cause the relaxation of smooth muscles in the walls of arterioles in the area, increasing blood flow. Local adjustment in blood flow, or of the flow of air into alveoli, also improve the efficiency of gas transport. As blood flow to pulmonary capillaries, it is directed to pulmonary lobules in which Po2 is relatively high.  2- control by the respiratory centers of the brain: respiratory control has both involuntary and voluntary components. | P a g e 17  The brain’s involuntary respiratory centers (in the medulla oblongata and pons, they are three pairs nuclei, and each center can be subdivided into a dorsal respiratory group(DRG), which contains an inspiratory center and it is active in any respiratory cycle, and a ventral respiratory group(VRG), which contains an expiratory center and it is active only in forced breathing) regulate the respiratory muscles and control the frequency (respiratory rate) and depth of the breathing. They do so in response to sensory information arriving from the lungs and other portions of respiratory tract, as well as from the variety of other sites.  The voluntary control of respiration reflects activity in the cerebral cortex that affects the output of the respiratory centers or of motor neurons that control respiratory muscles in response to sensory stimuli, emotional states, or speech patterns.  The respiratory receptors activities are modified by the sensory information from mechanoreceptors (respond to stretch of lung tissue and the change in blood pressure) and chemoreceptors (respond to chemical changes in the blood and cerebrospinal fluid as pH, Pco2, Po2). | P a g e 18 | P a g e 19    ‫الفسلجة والتشريح‪ /‬الفصل العاشر‬ ‫المرحلة الثانية‬ ‫مدرس المادة‪ :‬د‪.‬عباس فضال حمادي‬ ‫‪1‬‬  endocrine system — The nervous system and the endocrine system are the two main coordinating and controlling systems of the body. There are several differences between these two systems. Nervous system Endocrine system 1- Acts by mean of electric impulses 1-Acts by mean of chemical stimuli and chemical stimuli. only. 2- Has an immediate and short-term 2- Has more widespread, slower and effect on muscles and glands. longer lasting effect. 3- Has relatively localized effects. 3- Has more generalized effects on such activities as (growth, metabolism, reproduction) — 1- Hormones: — They are chemicals messengers released by glands of endocrine system directly into the blood stream. Every hormone has specific cell receptor and target tissue:- -Receptor:- it’s the site at which the hormones attach on the affected cells. -Target tissue:- it’s the tissue that responding to the effect of hormones. — 1-1- hormones chemistry:- — Hormones fall chemically into two categories:- A- protein hormones:- its composed of amino acids, all hormones are protein except those of adrenal cortex and sex glands. B- steroid hormones:- its derived from lipids and produced by the adrenal cortex and sex glands. — -2-1- Hormones action: — A- most protein hormones do not enter the target cell, instead, they attach to the surface and activate another substance “second messenger” that alter the cell activity. — B- steroid hormones:- can pass through the cell membrane and enter the target cell, then they combine with receptors and enter 2  the nucleus; here they have direct effect on the DNA, thus altering the activity of the cell. — In general, the effect of hormones is to change the rate of protein manufacture in the cytoplasm. — -3-1- Hormones regulation: — The release of hormones is controlled by:- — 1- negative feedback system:- a stimulus triggers the production of a hormone whose direct or indirect effects reduce the intensity of the stimulus. The endocrine activity may be controlled by changes in the composition of the extracellular fluid, for example, the control of blood calcium levels by two hormones, parathyroid hormone and calcitonin. When calcium levels in the blood decline, parathyroid hormone is released, and the responses of target cells elevate blood calcium levels. When calcium levels in the blood rise, calcitonin is released, and the responses of the target cells lower blood calcium levels. — 2- hormonal stimuli:- by changes in the levels of circulating hormones. Such control may involve one or more intermediary steps and two or more hormones, e.g. by releasing hormones from hypothalamus it control the activity of endocrine organs. — 3- neural stimulation:- resulting from the arrival of neurotransmitter at a neuroglandular junction as the activity of the hypothalamus on the adrenal medullae causes the release of epinephrine. — -2- The endocrine system: — It consist of ductless glands which secrete hormones directly in the bloodstream. These glands are made of epithelial tissue with extensive blood vessels network. — -3- The endocrine glands and their hormone: — -3-1- The pituitary gland" hypophesis ‫سيدة‬,‫"(الغدة النخامية‬ ‫الغدد‬ 3  — Is a small gland about the size of a cherry located in a saddle-like depression of the sphenoid bone(‫ )العظم اإلسفيني‬just behind the point at which the optic nerves cross. — The pituitary gland is often called the master gland because it releases hormones that affect the working of other glands, such as “thyroid, adrenal, gonads glands”. — — Their secretion is controlled by hypothalamus which secrete “releasing factors or hormones”, through portal system to control secretion of anterior pituitary gland, while posterior pituitary gland control by direct nerve impulse from hypothalamus. 4 — 1-1-3- Hormones of the anterior lobe: — 1- growth hormone(GH) or somatotropic hormone which promotes growth of all body tissues. — 2- thyroid-stimulating hormone(TSH), or thyrotropic hormone which stimulates thyroid gland to produce thyroid hormones. — 3- adrenocorticotropic hormones(ACTH), which stimulates adrenal cortex to produce cortical hormones; aids in protecting body in stress situations (injury, pain). — 4-Gonadotropic hormones: exist two hormones; — A- follicle-stimulating hormone (FSH), which stimulates growth and hormone activity of ovarian follicles in female; stimulates growth of testes. Promotes development of sperm cells. — B- luteinizing hormone (LH), called in male interstitial cell- stimulating hormone(ICSH), which causes development of corpus luteum at site of ruptured ovarian follicle in female; stimulates secretion of testosterone in male. 5 — 5- Prolactin (PRL), which stimulates secretion of milk by mammary gland — — 3-1-2 hormones of the posterior lobe: — 1- antidiuretic hormone; vasopresin(ADH), which promotes reabsorption of water in kidney tubules; stimulates smooth muscle tissue of blood vessels to constrict. — 2- oxytocin, which causes contraction of muscle of uterus; causes ejection of milk from mammary glands. — — — — 6  3-2- The thyroid gland: — — The largest gland in the body located in the front of the neck; have to lateral lobes connected by narrow band called isthmus. Thyroid gland secretes two hormones:-1 — 1- thyroxine (T4) and tri-iodothyronine(T3)hormone; which increases metabolic rate, influencing both physical and mental activities; required for normal growth. — 2- Calcitonin: decreases calcium level in blood. — — 3-3- Parathyroid glands: — parathyroid glands are two tiny pairs embedded in the posterior surfaces of the thyroid gland. The chief cells secretes parathyroid hormones, which regulates exchange of calcium between blood and bones; increases calcium level in the blood. 7 — — -4-3- The Adrenal glands: — They are a yellow, pyramid-shaped adrenal gland, or suprarenal gland, sits on the superior border of each kidney. Each adrenal gland has two parts: — A- an outer adrenal cortex. — B-an inner adrenal medulla. — A – adrenal cortex:- produces steroid hormones called adrenocortical steroids, or simply corticosteroids as; — 1- mineralocorticoids(MCs) mainly Aldestorone (95%) produces from the outer zone of the adrenal cortex , aids in regulating electrolytes and water balance. 8 — 2-glucocorticoids(GCs) mainly cortisol(95%) produces from the middle zone of the adrenal cortex , aids in metabolism of carbohydrate, proteins, and fats; active during stress. — 3- androgens(sex hormones) produces from the inner zone of the adrenal cortex , may influence secondary sexual characteristics in male. — B- adrenal medulla contain two populations of secretory cells, one producing epinephrine(E) or adrenaline, and the other norepinephrine(NE) or noradrenaline , both increase blood pressure and heart rate; activates cells influenced by the sympathetic nervous system plus many not affected by sympathetic nerves. — — 9 — 5-3- The pancreas: — The pancreas lies in the J-shaped loop between the stomach and proximal portion of the small intestine. — It is a slender, pale organ with a nodular consistency, and it contains both exocrine and endocrine cells. The exocrine produce digestive enzymes, while the endocrine cells produce two hormones, glucagon and insulin from pancreatic islets, or the islets of langerhans; contain alpha cells, which produce the hormone glucagon, and beta cells, which secrete insulin. — -insulin: aids transport of glucose into cells; required for cellular metabolism of foods, especially glucose; decrease blood sugar. 11 — -glucagon: stimulate liver to release glucose, thereby increasing blood sugar levels — -6-3- The gonads: — Tests :- are male sex endocrine glands produce testosterone hormone, which stimulates growth and development of sexual organs(testes, penis, others) plus development of secondary sexual characteristics such as hair growth on the body and face and deepening of voice; stimulates maturation of sperm cells. — Ovaries:- are female sex endocrine glands produce estrogen and progesterone hormones: 11 — -estrogens stimulate growth of primary sexual organs(uterus, tubes, etc) and development of secondary sexual organs such as breasts, plus changes in pelvis to avoid. Broader shape. - progesterone stimulates development of secretory parts of mammary glands; prepares uterine lining for implantation of fertilized ovum; aids in maintaining pregnancy. 12  3-7- The thymus: — The thymus is located in the Mediastinum, just posterior to the sternum. — It produces thymosins hormone which important in development of T-lymphocytes needed for immunity and early development of lymphoid tissue. — — 8-3- The pineal gland: — the pineal gland lies in the posterior potion of the third ventricle of the brain contain secretory cells secrete melatonin hormone(melatonin production is lowest during daylight hours and highest at night), which may regulate activity of gonads in response to light. 13  ‫الفصل التاسع ‪ /‬الفسلجة والتشريح‬ ‫المرحلة الثانية‬ ‫مدرس المادة‪ :‬د‪.‬عباس فضال حمادي‬ ‫‪1‬‬   sense and sensory system  The sensory system serves to protect the individual by detecting changes in the environment. The sensory system consist of general and special sense organs. A- The special sensory system: are localized in special sense organs those for light, sound, and chemicals; where from this organs stimuli travels for specific area for each stimuli. B- The general sensory system: The receptors of this sensory system are widely distributed throughout the body, as those receptors for pain, touch, and temperature, from these receptors the stimuli travel by sensory afferent nerves to the CNS to the sensory area at parietal lobe where interpreted as sensation.  A- The specific senses: 1- the vision and the eye:  The eye is a delicate organ which exist in eye cavities in the front of the skull protected by “eye protection”:-  1- the skull bones form the eye orbit “cavity”.  2- the led and eyelashes protected eye anteriorly;  3- tears wash away small foreign object that enter the eye.  4- a sac lined with an epithelial membrane, aids in the destruction of some pathogenic bacteria.  1-1- coats of the eye  The eyeball has three separate coats, or tunics:-  1- sclera: is the outermost layer, is made of tough connective tissue to protect inner layers of the eye and also called the white of the eye.  2- choroid: is the second layer composed of delicate network of connective tissue with many blood vessels, this layer contain much dark pigment serve as the dull black lining of a camera to prevent incoming light rays from scattering and reflecting of the inner surface of the eye.  3- retina: is the innermost layer, is made of ten layers of nerve cells sensitive to light “photoreceptor”.  One of these cells are called Rods (‫ قضبان‬,‫)عصي‬, are very light- sensitive enable us to see in dimly lit rooms. 2  And the others are Cons (‫ )مخاريط‬provide us with color vision “sensitive for red, green, and blue light”. So person who completely lack of Cones are totally color blind(In males only).  Rods and Cons functions by means of pigments that are sensitive to light, manufacturing of this pigment requires vitamin A, in case of lack of vitamin A, person developed night blindness. 3  1-1-1- vision pathway  The light rays come through cornea and lens stimulate the Rods and Cons to produce nerve signals that conducted by optic nerve(N II) to be interpreted by the cortex of occipital lobe at visual area. 4  2- the hearing and the ear  The ear is the sense organ related to both hearing and equilibrium “balance”. It may be divided into three main sections:  2-1-The external ear: it contain the auricle, the external auditory canal “meatus”, and the tympanic membrane (‫)غشاء الطبلة‬.  Their function is to collect sound wave and directed them to middle ear. 5  2-2- the middle ear:  It is a small, flattened space that contains air(air enters the cavity from the pharynx through the Eustachian tube) and three small bones or ossicles “malleus ‫المطرقة‬incus ‫السندان‬, stapes ‫”العظم الركابي‬ there connection as follow:-  Tympanic membrane malleus incus stapes the membrane of the oval window.  Middle ear function:- to amplify the sound waves that received by tympanic membrane and then transmit the sound to the fluid in the internal ear. 6  2-3- the inner ear:  It’s the most complicated and important part of the ear. Its consist of :-  1- Bony labyrinth(‫)المتاهة العظمية‬, which divided in three parts “ vestibule(‫)الدهليز‬, cochlea(‫)القوقعة‬, and the semicircular canals( ‫القنوات‬ ‫)النصف دائرية‬. Its filled with fluid, called perilymph.  2- Membranous labyrinth(‫)المتاهة الغشائية‬, are localized inside the Bony labyrinth(Bony labyrinth surrounds and protects it), its filled with a fluid called endolymph.  Both vestibule and semicircular canals have receptors which provide sensation of gravity, linear acceleration, and equilibrium. They are stimulated by rotation of head. 7  The cochlea contain receptors for hearing by organ of Corti which stimulated by sound wave that conduct by ossicles of middle ear to the internal ear, which creates pressure waves within perilymph; this pressure waves will stimulates receptors of hearing to send electrical signal through the fibers of sensory neuron of the internal ear, these fibers form the vestibulocochlear nerve.  vestibulocochlear nerve conduct sensation of equilibrium to the vestibular nuclei in the brain stem, and hearing sensation to the cortex of temporal lobe “auditory cortex” where these sound signal interpreted as hearing sensation. 8 9  3- sense of taste:  The sense of taste involves receptors in the tongue, by two different nerves carry impulses to the brain, “ anterior 2/3 of the tongue by facial nerve, and the posterior 1/3 of the tongue by glossopharyngeal nerve.  The taste receptors, known as taste buds(‫)براعم ذوقية‬, are located along the edges of small depressed area called fissures(‫)شقوق‬. Taste buds are stimulated only if the substance to be tasted is in solution. Taste can be divided into four kinds:-  1- sweet tastes: present at the tip of the tongue.  2- sour tastes: present at the side of the tongue.  3- salty tastes: present at the tip of the tongue.  4- bitter tastes: present at the back part of the tongue.  The impulses of the taste are interpreted by the front portion of the brain. 11  4- sense of smell:  The receptors of smell are located in the olfactory epithelium containing olfactory receptor cells, neurons are sensitive to chemicals dissolved in the overlying mucosa.  Approximately 10-20 million olfactory receptors cells are packed into an area of roughly 5 cm2. The information from these receptors are interpreted by the brain as sensation of smell at olfactory cortex in the temporal lobe.  The general sense:  Receptors for general senses are scattered throughout of the body and are relatively simple in structure. These receptors are classified according to the nature of the stimulus that excites them, these are:  1- receptors sensitive to pain “nociceptors”.  2- receptors sensitive to temperature “ thermoreceptors”. 11  3-Receptors sensitive to touch, pressure, and body position “mechanoreceptor”.  4- receptor sensitive to chemicals stimuli “ chemoreceptors”.  All these stimuli are carried by sensory neuron through spinal cord to sensory area in the cortex of parietal lobe to be interpreted as sensation according to the type of stimuli. 12 13  ‫المرحلة الثانية‬ ‫هندسة تقنيات األجهزة الطبية‬ ‫مدرس المادة ‪ /‬د‪.‬عباس فضال حمادي‬ ‫‪1‬‬   Chemistry: - Is the science that investigates matter and its interaction0.  Matter: - Is anything that takes up space and has mass. All matter is composed of substances called elements.  Elements: - Cannot be changed or broken down into simpler substances.  Atoms: - The smallest stable unit of matter. Structure of an atom:  Atoms contain three major types of subatomic particles:- 1- Neutron neutral electrical charge ] mass ] number 2- Proton (p+) positive electrical charge ] ] atomic 3- Electron (E-) Negative electrical charge ] number “Electron mass 1/1836 as massive as proton” - Isotopes: - Are atoms of element that differ in the number of neutrons in the nucleus. Some of isotopes are unstable. Unstable isotopes are radioactive. They spontaneously emit subatomic particles or radiation. - Atomic weight: - Is the average mass of elements atoms which takes account the mass of the subatomic particles and the relative proportions of any isotopes. - Electrons and electron shells: - The number of electrons in an atoms outer shell determines the chemical properties of that element. Chemical bonds:-  Chemical bonds and chemical compounds: by chemical bonds living organism can create new molecules, combination of atoms of two or more elements produce compounds. 2  Types of chemical bonds:-  1- Ionic bonds: - this type of bonds creates when one atom loses while the other gain electron. Atoms or molecules that have an electric charge are called ions those ions with positive charge(+) are cations, and those with a negative charge(-) are anions so ionic bonds are chemical bonds created by the electric attraction between anions and cations.  2- Covalent bonds: - are chemical bonds created by sharing electrons with other atoms. If the sharing of one pair of electron creates a single covalent bond “as in H 2” but sharing two pairs of electrons forming a double covalent bond “as in O2”. Covalent bonds are very strong because the shared electrons tie the atoms together.  If the electrons are shared equally such bonds are called nonpolar covalent bond “as in H2, O2”. But an unequal sharing between atoms of different electrons creates a polar covalent bond “as in H2O” molecule. The oxygen atom has a much stronger attraction for the shared electrons than do the hydrogen atoms, therefore the oxygen atom develops a slight negative charge, at the same time, and the hydrogen atoms develop a slight positive charge because their electrons are away part of the time. 3  3- Hydrogen bonds: - is the attraction between a slight positive charge on the hydrogen atoms of one polar covalent bond and a weak negative charge on an oxygen or nitrogen atoms of another polar covalent bond. Hydrogen bond are too weak to create molecules, but they can alter molecular shapes or pull molecules together, for example, the attraction between water molecules at a free surface is important because it : (1) slows the rate of evaporation and (2) creates the phenomenon known as surface tension which acts as a barrier that keep small objects from entering the water, it’s a reason that a layer of watery tears keeps small dust particles from touching the surface of the eye. 4  Chemical reactions:-  Cells remain alive by controlling chemical reactions. It means, new chemical bonds form between atoms or existing bonds between atoms are broken by process called metabolism.  1- Basic energy concept:- living organism can get its own energy by metabolism, to perform their normal functions.  Work:- is movement or change in the physical structure of matter, for example, walking, the conversion of liquid water to water vapor(evaporation)  Energy: - is the capacity to perform work. There are two major types of energy:-  A- Kinetic energy: - is the energy of motion.  B- Potential energy: - is stored energy “ex. The position of protein filaments inside skeletal muscles and the covalent bonds between molecules adenosine triphosphate (ATP) inside the cell. Potential energy is converted into kinetic energy and heat is released, ex. During muscle contraction. 5 Types of chemical reaction:-  There are three important type of reaction :-  1- Decomposition reaction:- breaks molecule into smaller fragments as in digestion ex. AB → A + B.  A- hydrolysis:- is decomposition reaction when one of the bonds in complex molecule is broken, and the components of water molecule(H and OH) are added to the resulting fragments: ex. A-B-C-D-E-F +H2O → A-B-C--H + HO—D-E-F.  B- catabolism: - is a decomposition reaction of complex molecules within cells to release energy.  2- Synthesis reaction:- assembles larger molecules from smaller components, ex. A + B → AB.  A- Dehydration synthesis: - “condensation” is the formation of a complex molecule by the removal of water: “it’s the opposite of hydrolysis”, ex. A-B-C—H + HO—D-E → A-B-C-D-E + H2O.  B- Anabolism:- is the synthesis of the new component in the body. It takes energy. It’s the opposite of catabolism.  C- Exchange reaction: - the component of reactions and products are present in different combinations. Ex. AB + CD → AD + CB.  3- Reversible reaction: - the equation is: A + B ↔ AB. The two reaction occur simultaneously, one a synthesis (A + B → AB) and the other a decomposition (AB → A + B) at equilibrium, the rate of the two reaction are in balance. Enzymes and chemical reactions:-  Many reactions need enough energy to activate reactants before the reaction can proceed. The amount of energy required to start a reaction is called the activation energy. So enzymes is a protein molecules called catalysts promote chemical reactions by lowering the activation energy as shown in figure (1). 6 figure (1). Activation energy Inorganic compounds:-  Nutrients: are the essential elements and molecules obtained from diet.  Metabolites: includes all of the molecules synthesized or broken down by chemical reactions inside our body.  Inorganic compounds: are small molecules that not contain carbon and hydrogen atoms.  Organic compounds: are primarily composed of carbon and hydrogen atoms, and they can be much larger and more complex than inorganic compounds. 7  The most important inorganic compounds in the human body are carbon dioxide, oxygen, water, inorganic acids and bases, and salts.  1- Carbon dioxide and oxygen: are gases, carbon dioxide (CO2) is produce by cell through normal metabolic activity. It is transported in the blood and released into the air in the lungs. Oxygen (O2), an atmospheric gas, is absorbed at the lungs, then transported in the blood, and consumed by cells throughout the body.  2- Water and it’s properties: water is important constituent of the body, accounting for almost 2/3 of total body weight. Water properties:  A- Water is an excellent solvent. Water dissolves a remarkable variety of inorganic and organic compounds.  B- Water has a very high heat capacity. Heat capacity is the ability to absorb and retain heat. This feature is important in the cooling effect on the skin by perspiration.  C- Water is an essential reactant in the chemical reactions of living systems.  3- Inorganic acids and bases: Acid: is any substance that breaks apart (dissociate) in solution to release hydrogen ions. Ex. Hydrochloric acid (HCI) in stomach. Base: is a substance that removes hydrogen ions from solution. Strong acids and bases dissociate completely in solution, while weak acids and bases dissociate in completely in solution. The human body contains weak bases that are important in counteracting acids produced during cellular metabolism.  Hydrogen ions and pH:- hydrogen ions in excessive numbers lead to:  1- They will break chemical bond.  2- Change the shape of complex molecule.  3- Disrupt cell and tissue functions. Therefore, these hydrogen ions concentration must be precisely regulate.  pH:- is the concentration of hydrogen ions of the solution. The pH value is a number between (0 – 14). Normal pH of the blood and body fluids is between (7.35 – 7.45), a pH below (7) called acid, and above (7) called base.  Buffers and pH:- are compounds that stabilize pH by either remove or replacing hydrogen atoms. Ex. NaHCO3. 8  4- salts:- is an ionic compound consisting of any cation except a hydrogen ion and any anions except a hydroxide ion. Salts are held together by ionic bonds, and in water they dissociate, releasing cations and anions. Salts are conducting an electrical current in solution which is important in cells function. Ex. Na+, K+, Ca+2, Cl-1. Organic compounds:-  Organic compounds always contain the elements carbon and hydrogen and oxygen, and less nitrogen, phosphorus, sulfur, and iron. Many organic molecules are made up of long chains of carbon atoms linked by covalent bonds.  The four major classes of large organic molecules: carbohydrates, lipids, proteins, and nucleic acids.  1- Carbohydrate:- is an organic molecules that contains carbon, hydrogen, and oxygen in a ratio near 1:2:1. Its account for less than 3% of total body weight. Carbohydrates are the most important as sources of energy. The three major types of carbohydrates are monosaccharides, disaccharides, and polysaccharide.  A- monosaccharides: - is a carbohydrate containing three to seven carbon atoms, such as glucose, fructose.  B- disaccharides: - is formed by joining together two monosaccharides by dehydration synthesis. Glucose + fructose ↔dehydration sucrose + H2O hydrolysis 9  C- Polysaccharide:- it’s the larger carbohydrate molecule they result when repeated dehydration synthesis reactions add additional mono or disaccharides. Ex. Starches:- are glucose-based polysaccharides important in our diet “plant starches”, while glycogen is an “animal starches”, liver and muscles tissues make and store glycogen. 2- Lipids:-  Contain carbon, hydrogen, and oxygen but because they have relatively less oxygen than do carbohydrates, the ratio does not approximate 1:2:1, lipid may contain small quantities of other elements, including phosphorus, nitrogen, or sulfur. Lipids form: 1- essential structural components of all cells 2- lipid deposit are important as energy reserves.  Lipids normally account for 12 – 18% of total body weight of adult man and for woman 18 – 24%. The major types are fatty acids, fats, steroids, and phospholipids.  A- Fatty acids:- are long chains of carbon atoms with attached hydrogen atoms that end in carboxylic acid group. Carboxylic end soluble in water while carbon chain “hydrocarbon tail” is relatively insoluble. Fatty acids serve as energy reserve. Saturated fatty acid each carbon atom has 4 single covalent bond with neighboring carbon atoms and two hydrogen atoms. Its bring danger of heart disease. Unsaturated fatty acid, it mean present double covalent bond between C= C atoms.  B- Fats:- (ex. Triglyceride) consist of glycerol which attached to three fatty acids. Triglyceride is most common fats in the body. Fats function is: 1- Serving as a random energy reserve. 2- Fat deposit under the skin serves as insulation. 3- Mass of fat around a delicate organ such as kidney provides a protective cushion. Glycerol + 3 fatty acid ↔dehydration synthesis triglyceride + H2O hydrolysis  C- steroids:- are large lipid molecules composed of four connected rings of carbon atoms. They differ in the carbon chains that are attached to his basic structure. Cholesterol is well known steroid, its function: 1- To maintain cell membranes. 2- Manufacture steroid hormone derived from cholesterol. 10  D- phospholipids: consist of glycerol and two fatty acids linked to non lipid group by a phosphate group. The non lipid portion is soluble in water, whereas the fatty acid portion is relatively insoluble in water. Phospholipids are the most abundant lipid component of cell membranes. 11 3- Protein:-  Proteins: are the most abundant organic components of the human body and the in many ways the most important. They account for about 20% of the total body weight. All proteins contain carbon, hydrogen, nitrogen, and smaller quantities of sulfur may also be present.  A- protein function:- proteins perform a variety of functions such as:  1- support: structural proteins create a three-dimensional of framework for the body, providing strength organization, and support for cells, tissues, and organs.  2- Movement: contractile proteins are responsible for contraction.  3- Transport: transport proteins responsible for transportation insoluble lipids, respiratory gases, minerals such as iron and several hormones.  4- Buffering: proteins provide a considerable buffering action, helping to prevent potentially dangerous changes in pH in cells and tissues.  5- Metabolic regulation: enzymes accelerate chemical reaction in living cells.  6- Coordination, communication, and control: protein hormones can influence the metabolic activities of every cell in the body.  7- Defense: the tough, water proof proteins of the skin, hair, and nails protect the body from environment hazards. Antibodies proteins protect us from disease; clotting proteins restrict bleeding following an injury to the cardiovascular system. B- Protein structure:-  Proteins are long chains of organic molecules called amino acids, there are 20 amino acids serve as building blocks of protein (typical protein has 1000 – 100000 amino acids). A- Amino acid consist of:  1- Central carbon atom bonded to hydrogen atom.  2- Amino group.  3- Carboxylic group. 12  4- Variable group or side chain(may be present as straight chain or rings atoms(R), the different R groups distinguish one amino acid from another, giving each its own chemical properties.  - Peptide bond: this is a bond between the carboxylic acid of one amino acid attached to the amino group of another amino acid.  - Peptides: are molecules made up of amino acids held together by peptide bonds. Depeptide means 2 amino acids, polypeptide are long chain of amino acids. Polypeptides with 100 amino acid and more called proteins.  Single changes in one amino acid sequences of complex proteins may lead to several cancers and sickle cell anemia.  Denaturation: is a change in the three dimensional shape of proteins due to high temperature (over 43 C0) or changes of pH of its surroundings. 13 D- Enzyme function:-  Enzymes are very important proteins that catalyze the reaction that sustain life.  The reactants in an enzymatic reaction called substrates which interact to form a specific product. The substrates must bind to a special region of the enzyme called the active site. This binding depends on the complementary shapes of the two molecules. Much as a key fits into a lock. So this specificity make each enzyme catalyzes only one type of reaction. Figure (2) shows a simple model of enzyme function. 14 4- Nucleic acid (N.A):-  N.A is large organic molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus. N.A have very important function:-  1- N.A stored and process information at molecular level inside cells.  2- The DNA in our cells determines our inherited characteristic. Ex. hair, eye color.  3- The DNA molecules encode the information needed to build proteins.  There are two classes of N.A deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). A- structure of nucleic acid:- A nucleic acid is made up subunits called nucleotides. Each single nucleotide has three components:- 1- Sugar always a five carbon sugar. Either ribose in RNA or deoxyribose in DNA. 2-Phosphate group (PO4-3). 3- Nitrogenous base: A- adenine (A), guanine (G), cytosine(C), thymine (T), in DNA. B- Adenine (A), guanine (G), cytosine(C), uracil (U), in RNA. A molecule of RNA consists of a single chain of nucleotides. A DNA molecule consist of two nucleotides chains held together by weak hydrogen bonds between the opposing nitrogenous bases (adenine can bond with thymine, and cytosine with guanine) known as complementary base pairs. Figure 3. 15 5- High-energy compounds:-  The energy that powers a cell is obtained by the breakdown “catabolism” of organic molecules such as glucose. To be useful. That energy must be transferred from molecule to molecule or from one part of the cell to another.  The usual method of energy transfer involves the creation of high-energy bonds by enzymes within cells.  A high energy bond is a covalent bond that stores an unusually large amount of energy. When that bond is later broken, the energy is released under controlled conditions. 16  Most high-energy compounds are derived from nucleotides; the most important high- energy compound in the body is adenosine triphosphate (ATP).  ATP is composed of the nucleotide adenosine monophosphate (AMP) and two phosphate groups. The addition of two phosphate groups requires a significant amount of energy.  The arrangement can be summarized as:(figure 4) ADP + 2 phosphate groups + energy → ATP + H2O 17  ‫المرحلة الثانية‬ ‫هندسة تقنيات األجهزة الطبية‬ ‫مدرس المادة ‪ /‬د‪.‬عباس فضال حمادي‬ ‫‪-1-‬‬ Definition Anatomy: - Is the study of internal and external structure and the physical relationship between body parts. Physiology: - Is the study of how the living organisms perform their vital functions. The basic function of all living things: Responsiveness: - organism responds to changes in their immediate environment. Growth: - Over a life time, organisms increase in size through the growth of cells, the simplest unit of life. Reproduction: - Organisms reproduce, creating subsequent generation of similar organisms. Movement: - Organisms are capable of producing movement, which may be internal (transporting food, blood, and waste product) or external (movement through the environment). Metabolism: - Is complex chemical reaction to provide the energy required for Responsiveness, Growth, Reproduction, and movement. Levels of organization: To understand the human body, we must examine its organization at several different levels, from submicroscopic to the macroscopic. Chemical (or molecular) level: - Atoms, the smallest stable units of matter, combine to form molecules with complex shape. Cellular level: - Different molecules can interact to form larger structures to form cells. Tissue level: - Similar cells working together to perform a specific function of specific tissue. (Heart muscle tissue). Organ level: - Tow or more different tissues working together to perform specific function of specific organ (heart). -2-  Organ system level: - Many organs interact together to produce function of specific system as cardiovascular system consist of heart, blood, blood vessels. Organism level: - All of the organ systems of the body work together to maintain life and health. Homeostatic regulation : Homeostasis: - Is the existence of a stable internal environment. Homeostatic regulation: - Is the adjustment in physiological systems that preserve homeostasis. Homeostatic regulation involves:- 1- Receptor: - That is sensitive to a particular environment change or stimulus. 2- Control center: - (or integration center), which receives and processes information from receptor. -3- 3- Effector: - which responds to the commands of the control center and whose activity opposes or reinforces the stimulus. Tow method of homeostatic regulation are present in the human body:- 1- Negative feedback: - Variation outside normal limits triggers an automatic response that corrects the situation. 2- Positive feedback: - The initial stimulus produces a response that reinforces that stimulus. Negative feedback: Negative feedback:- Variation outside normal limits triggers an automatic response that corrects the situation. Regardless of whether the stimulus (such as temperature) rises or falls at the receptor. Most homeostatic mechanisms in the body involve negative feedback. For example, consider the control of body temperature, a process called thermoregulation. -4-  Thermoregulation involves altering the relationship between heat loss, which occurs primarily at the body surface, and heat production, which occurs in all active tissues. In the human body, skeletal muscles are the most important generators of body heat. The cell of the thermoregulatory control center is located in the brain. Temperature receptors are located in the skin and in cells in the control center. The thermoregulatory center has a normal set point near 370C. If the body temperature rises above 37.20C, activity in the control center targets to effectors: 1- smooth muscles in the walls of the blood vessels supplying the skin and 2- sweat gland. The muscle tissue relaxes and the blood vessels widen. Or dilate, increasing blood flow at the body surface, and the sweat glands accelerate their secretion. The skin thin acts like a radiator, losing heat to the environment, and the evaporation of sweat speeds the process. When body temperature returns to normal, the control center becomes inactive and superficial blood flow and sweat gland activity decrease to normal resting levels. -5-  If temperature at the control center falls below 36.70C, the control center targets the same two effectors and skeletal muscles. This time, blood flow to the skin declines, and sweat gland activity decreases. This combination reduces the rate of heat loss to the environment. Because heat production continues, body temperature gradually rises; once the set point has been reached, the thermoregulatory center turns itself “off”, and both blood flow and sweat gland activity in the skin increase to normal resting levels. Additional heat may be generated by shivering, which is caused by random contractions of skeletal muscles. -6-  Positive feedback:- The initial stimulus produces a response that reinforces that stimulus. In the body, positive feedback loops are involved in the regulation of a potentially dangerous or stressful process that must be completed quickly. For the example, the immediate danger from a severe cut is blood loss, which can lower blood pressure and reduce the pumping efficiency of the heart. Damage to the cells in the cut blood vessel wall releases chemicals that begin the multistep process of blood clotting. As clotting gets under way, each step releases chemicals that accelerate the process until formation of the blood clot, which patches the vessel wall and stops the bleeding. Labor and delivery, another example of positive feedback in action. -7- The language of the anatomy: 1- Surface anatomy: a- Anatomical land marks; - Anatomical position supine (face up), Prone (face down) b- Anatomical region; - Abdominopelvic quadrants (4) - Abdominopelvic regions (9) -8- C- Anatomical direction; - Anterior Frontal Ventral - Posterior Back Dorsal - Lateral External - Medial Internal - Proximal Toward an attached base - Distal Away from an attached base - Superior Above - Inferior Below -9- 2- Sectional Anatomy:- a- Planes and sections; 1- Transverse plane: divided the body to superior (up) and inferior (dawn) parts. 2- Frontal plane: (coronal plane) divided the body to anterior and posterior parts. 3- Sagital plane: divided the body to right and left parts. b- Body cavities; are a specific space in the body contain specific organs. Function of body cavities:- 1- They protect delicate organ "brain, heart, lung”. 2- They permit significant changes in size and shape of internal organ. The type of body cavities:- The major body cavity in the body is a ventral body cavity, which is divided by diaphragm to:- 1- Thoracic cavity: - a- Pleural cavity (lung) b- Pericardial cavity (heart) c- Mediastinum cavity (aorta) 2- Abdominopelvic cavity; a- Peritoneal (abdominal) cavity (gastrointestinal tract (GIT), liver, kidney) b- Pelvic cavity (Genital organ) - 10 - body cavities covered:- All body cavities are covered by serous moist membrane, those which lines organs “viscera” called the visceral layers, and the opposing layer that lines the inner surface or the body wall or chamber is called the parietal layer, and these layers usually takes the name of it’s cavities. The function of these layers is:- 1- They permit expansion and limited movement. 2- Preventing friction. - 11 -  ‫الفسلجة والتشريح‪ /‬الفصل الحادي عشر‬ ‫المرحلة الثانية‬ ‫مدرس المادة‪ :‬د‪.‬عباس فضال حمادي‬ ‫‪1‬‬ The cardiovascular system: consists of the heart, blood vessels, and blood. —1- The heart: — is a muscular pump consisting of four chambers; two atria and two ventricles. — 1-1-Right and left atria:- the two atria are separated from each other by the interatrial septum. They receive blood from veins “R.atria” from vena cava superior and inferior, and the “left atria” from the four pulmonary arteries. — 1-1-1-The atrial functions: — 1- primarily as reservoirs, where the blood returning from veins collects before it enters the ventricles. — 2- contraction of the atria forces blood into the ventricles to complete ventricular filling. 2 — 1-2- the right and left ventricles: they are the major pumping chambers of the heart. They eject they blood into arteries “ R.ventricle into pulmonary trunk to pulmonary circulation, and left ventricle into aorta to systemic circulation throughout all the body”. The two ventricles are separated from each other by the muscular interventricular septum. The wall of the L.ventricle is thicker than the wall of R. ventricle because it does more work than the R.ventricle “ the pressure approximately 120 mmHg in the L.ventricle, while in the R.ventricle reach only to one fourth of the pressure in the L.ventricle during systole”. 3 1-3-The heart valves: — 1-3-1- atrioventricular valves: They are located between R. atrium and R. ventricle, and L. atrium and L. ventricle. Their function to allow blood to flow from the atria into ventricles but prevent the backflow of blood from ventricles into the atria. — 1- The valve between the R.A. and R.V. have three flaps, or cusps of fibrous tissue known as the tricuspid valve. 4 — 2- the valve between L.A. and L.V. has only two flaps, or cusps known as bicuspid or mitral valve. — Each ventricle contains cone-shaped muscular pillars called papillary muscles, which attached by thin, strong connective tissue fibers called chordae tendineae to the cusps of A.V. valves. their function to prevent the valves from opening into the atria so much by pulling on the chordae tendineae. — 1-3-2- aortic and pulmonary semilunar valves: each valve consists of three pocketlike semilunar cusps “half moon-shaped”. Blood flowing out the ventricles pushing against each valve; forcing it open. When blood flow back toward ventricles; it enter the pockets of the cusps, causing them to meet in the center of the Aorta and the pulmonary trunk and closing them to prevent the 5  backflow of blood from the Aorta into L. ventricles. And from the pulmonary trunk into R. ventricles. — 1-4- Connective tissue of the heart: — A-The connective tissue of the heart include abundant collagen and elastic fibers that wrap around each cardiac muscle cell and tie together adjacent cells. These fibers: — 1- provide support for the cardiac muscle fibers, blood vessels, and nerves of the myocardium. — 2- add strength and prevent overexpansion of the heart. — 3- help the heart to return to normal shape after contraction. 6  — B- Connective tissue also forms the fibrous skeleton of the heart as a plate of fibrous connective tissue rings around the atrioventricular and semilunar valves, its functions: — 1- provide a solid support for the valves. — 2- serves as electrical insulation between the atria and ventricles. — 3- provide a rigid site of attachment for cardiac muscle, so it called the skeleton of the heart. 1-5- conducting system of the heart: — These are specialized cardiac muscle cells in the wall of the heart that form the conducting system of the heart. It consists of: — 1-5-1-Sinoatrial node(SA):- it is the pacemaker of the heart; located in the upper posterior wall of the right atrium, which 7  initiates the contraction cycle activity of the heart by origination the action potentials in the SA node and spread it over the R. & L. atria and the rest of conducting system. Pacemaker cells depolarized rapidly and spontaneously, generating 70-80 action potentials per minute. This results in a heart rate or 70 -80 beats per minute(bpm). — After the stimulus for a contraction is generated at SA node, it must be distributed so that; — 1- the atria contract together, before the ventricles. — 2- the ventricles contract together, in a wave that begins at the apex and spreads toward the base. When the ventricles contract in this way, blood is pushed toward the base of the heart into Aorta and pulmonary trunk. 8 — 1-5-2- Atrioventricular(AV) node: it is located in the lower portion of the R. Atrium. The action potential spread slowly through the AV node (with 100 msec delay time) to allows the atria to complete their contraction before action potentials are delivered to the ventricles. AV node generate only 40-60 action potentials per minute spontaneously. — 1-5-3- Atrioventricular bundle or bundle of His: it receives action potentials from AV node, and divided into two branches of conducting tissues :- — 1- 5-4- right and left bundle branches: at the tips of these branches forms many small bundles; 9 — 1-5-5- purkinje fibers: they extend to the cardiac muscle cells of the both ventricles wall. — Conducting system spread action potentials more rapidly than cardiac muscle fibers; within 225 msec the action potentials travels from the AV node to purkinje fibers, and the contraction cycle then be completed. 11 1-6-The electrocardiogram(ECG or EKG): — Action potentials conducted through the heart during the cardiac cycle produce electric current that can be measured at the surface of the body. Electrodes placed on the surface of the body and attached to a recording system, which can detect the small electric changes resulting from the action potentials in all of the cardiac muscles cells. The record of these electrical events is an electrocardiogram. — The normal ECG consists of a P wave, QRS complex, and T wave. — the P wave results from atrial depolarization, which precedes the onset of atrial contraction. — The QRS complex consists of three individual waves the Q, R, and S waves. It results from ventricular depolarization which precedes ventricular contraction. — The T wave represents ventricular repolarization which precedes ventricular relaxation. — A wave represents atrial repolarization which cannot be seen because it occur during QRX complex. 11 — P-Q or P-R interval represents the time between the beginning of the P wave and the beginning of the QRS complex, during this time atria contract and begin to relax. — Q-T interval extends from the beginning of the QRS complex to the end of the T wave and represents the length of time required for ventricular depolarization “contraction” and repolarization “relaxation” 12 1-7- The heart sounds and murmurs: — The heart sounds and murmurs can be detect by simple instrument called stethoscope, which is used to listen for heart sounds. The normal heart sounds are usually describe by the syllables lubb - dupp. — Lubb: is the first heart (systolic) sound, is longer, lower pitched sound, which produced as AV valves close and the semilunar valves open. It marks of ventricular systole ‘V contraction’. — Dupp: is the second heart sound, is shorter and sharper. Occurs at the beginning of ventricular diastole, when the semilunar valves close. 13 — Third and fourth heart sounds are very faint and seldom detectable in healthy adults. These sounds are associated with atrial contraction and blood flowing into the ventricles rather than with valve action. — Murmurs: is an abnormal sounds due to faulty action of the valves( because of the narrowing or dilatation of the valves) or congenital defect as septal defect. — Clinically; ventricular systole occurs between the first and the second heart sounds, while the ventricular diastole occurs between the second heart sound and the first heart sound of the next beat. 14 1-8- control of the heart rate: — The heart rate originated spontaneously within the heart itself by the Sinoatrial node. The heart rate can be influence by the following factors: — Sympathetic nervous system stimulation increases HR lead to tachycardia (HR over 100 beat/minute). — Parasympathetic nervous system stimulation decreases HR lead to bradycardia (HR less than 60 beat/minute). — Other factors as hormones “epinephrine increase HR”. Ions and drug. — Arrhythmia: is a regular or irregular variation in heart beat due to changes in the rate. — Premature beats: also called extrasystoles are beats that come in before the expected normal beats. 1-9- Heart dynamics: — The term heart dynamics refers to movements and forces generated during cardiac contractions. Each time the heart beats, the two ventricles eject equal amounts of blood. — Stroke volume (SV): the amount of blood ejected by a ventricle during a single beat (average 80 ml/beat). — Cardiac output (CO): the amount of blood pumped by each ventricle in one minute. — Cardiac output can be calculated by multiplying the average stroke volume by the heart rate (HR). — CO = SV X HR, for example. If the average SV is 80ml/beat and the heart rate is 70 bpm, the CO will be: — CO = 80ml/beat x 70bpm = 5600 ml/min (5.6 L/min). 15 2- Blood vessels: — The blood vessels, together with for heart chambers form a closed system for the flow of blood. On the basis of function; the blood vessels may be divided into three groups; — Arteries: carry blood from the ventricles of the heart out to the capillaries in organs and tissues. The smallest arteries are called arterioles. — Veins: drain capillaries in the tissues and organs and return the blood on the heart. The smallest veins are the venules. — Capillaries: allow for exchanges between the blood and body cells, or between the blood and air in the lung tissues. The capillaries connect the arterioles and venules. — All vessels together may be subdivided into two groups of circuits: pulmonary and systemic circuits. — 1- Pulmonary circuit: these vessels carry blood to and from the lungs. This circuit functions to eliminate carbon dioxide from the blood and replenish its supply of oxygen. — 2- systemic circuit: transports blood to and from the rest of the body. 2-1- The structure of blood vessels: — A- The arteries and veins: have three coats(tunics) but arteries have thicker wall than veins because they must receive blood pumped under high pressure from the ventricles of the heart. The coats are: — 1- endothelium: is a flat epithelial cells making up the internal smooth surface over which the blood may easily move. 16 — 2- middle layer: more bulky layer is made of smooth involuntary muscle combined elastic connective tissue. In veins this layer is relatively thin, therefore, veins are easily collapsed. In addition to this, most veins have one-way valves that permit blood to flow in only one direction; toward the heart. — 3- An outer tunic: is made of a supporting connective tissue. — B- capillary walls: have the thinnest walls of any vessels; have only one cell layer “endothelium. 17 2-2- Names of the systemic arteries: — The aorta and its parts: aorta is the largest artery, is about 2.5cm in diameter. It extends from the left ventricle. Aorta is one continuous artery, but it may be divided into sections: 18 — 1- The ascending aorta(‫)الصاعد‬, is near the heart and give left and right coronary arteries to the heart muscle. — 2- the aortic arch(‫)قوس األورطي‬, is a curves from the right to the left also extends backward; gives off three large branches: — A- the brachiocephalic trunk (supply the right upper extremity and the right side of the head). — B- left common carotid artery(‫ الوداجي‬supply left side of the head). — C- left subclavian artery "supply the left upper extremity. — 3- the thoracic aorta, lies in front of thoracic vertebral column “supply the chest organ and thoracic wall”. — 4- the abdominal aorta, lies in the abdominal cavity and supply the abdominal part of the body and both lower extremities. 19 21 2-3- Anastomoses: — Is a communication between two arteries, so blood reaches vital organs by more than one route. For example: — 1- the circle of Willis; receives blood from the two internal carotid arteries as well as from the basilar artery, which is formed by the union of two vertebral arteries. This arterial circle lies just under the center of the brain and send branches to the cerebrum and other parts of the brain. — 2- the volar arch; is formed between radial and ulnar arteries in the hand it send branches to the hand and fingers. 2-4- Names of systemic veins: — 1- superficial veins: these veins are found near the surface under the skin, as those in the extremities. 21  — 3- deep veins: the deep veins tend to parallel arteries and usually have the same names as the corresponding arteries as femoral vein. — 3- superior vena cava: it collect blood from head, neck, upper extremities, and the chest; then goes to the heart. — 4- inferior vena cava: it is much longer than the superior vena cava. It collect blood from the part of the body below the diaphragm and goes to the heart. — 5- venous sinuses: is a large channel that drains deoxygenated blood but does not have the usual tubular structure of the veins. Such as coronary sinus which receives of most of the blood from the veins of the heart. 3- The physiology of circulation: 22  — 3-1- How capillaries work: the blood flows through capillaries surrounding the air sacs in the lungs, it picks up oxygen and unloads carbon dioxide; later when this oxygenated blood is pumped to capillaries in other parts of the body, it unloads the oxygen and picks up carbon dioxide as well as other substances resulting from cellular activities. — 3-2- Vasoconstriction and vasodilatation: Vasoconstriction; refers to a decrease in the diameter of a blood vessel. -vasodilatation; refers to an increase in the diameter of a blood vessel. 3-3- Regulation of blood pressure: — Many factors includes in regulation of blood pressure: — 1- Vasomotor activities: serve in part to regulate blood pressure — 2- total blood volume. — 3- cardiac output. — 4- blood viscosity. — 5- peripheral resistance. — When blood vessels dilate; blood pressure decrease, and when vessels constrict; blood pressure increase. 3-4- Blood distribution: — Vasomotor activities regulate the amount of blood that flows to various parts of the body. Some organs, such as brain, liver, and kidneys, event at rest require large quantities of blood. Other organs, such as skeletal muscles and digestive organ need an increased supply of blood during increased activity( the blood flow in muscle can increase 20 times during exercise). — This done by vasomotor changes, particularly by vasodilatation of arterioles which allows delivery of more blood to the tissues,while it decrease by vasoconstriction. 23  — 3-5- Return of blood to the heart: — The blood return to the heart is done by two mechanism: — By skeletal muscles contraction which squeeze the blood in the veins forward to the heart through the veins’ valves, which prevent blood from flowing backward. — During inspiration the chest expand, and the pressure in the chest cavity drops(negative pressure), causing the large veins in the chest “vena cava inferior and superior” to expand and draw blood back toward the heart. 24 3-5- Pulse and blood pressure: — 3-5-1-Pulse: is the force of ventricular contraction starts a wave of increased pressure that begins at the heart and travels along the arteries. It’s about 70-80 times per minute. It can be felt in any artery that is relatively close to the surface; such as radial(‫)كعبري‬, carotid(‫)سباتي‬, and dorsalis pedis (‫)ظهر القدم‬arteries. It is important to measure: — 1- strength., 2- the regularity, 3- the rate. 25 3-5-2- blood pressure and its determination: — Blood pressure: is the force that the blood produced against the blood vessels wall. It measured by instrument called a sphygmomanometer. — Two variables are measured: — 1- systolic pressure: occurs during heart muscle contraction; average around 120 mmHg and is expressed in millimeter of mercury. — 2- diastolic pressure: occurs during relaxation of the heart muscle; average around 80mmHg — Procedure method: the sphygmomanometer is essentially a graduated column of mercury connect to an inflatable cuff. The 26 cuff is wrapped around the patient’s arm above of the right or left elbow joint; and then inflated it with air by hand bulbe until the brachial artery is compressed and the blood flow cutoff. Then, listening with stethoscope placed over the artery distal to the cuff; slowly lets air out of the cuff by opening the valve on the bulbe until the first pulsation are heard, at this time the pressure is equal to the systolic pressure, and this pressure is read off the mercury column. Then, more air is let out until the pulse’s sound become characteristic muffled or disappears, at this point it indicates diastolic pressure. The distinctive sounds heard during this test are called sounds of korotkoff. When the blood pressure is recorded, systolic and diastolic pressures are usually separated by a slash, as in “120/80”(read "one twenty over eighty”) 27  ‫ الفصل الثامن‬/ ‫الفسلجت والتشزيح‬ ‫المزحلت الثانيت‬ ‫عباس فضال حمادي‬.‫ د‬:‫مدرس المادة‬ — The nervous system: — The nervous system can be divided according to anatomic (or structural) and functional classification. — 1- Anatomic classification: - -Central nervous system(CNS): includes the brain and spinal cord. 1 - -Peripheral nervous system(PNS):includes all the neural tissue outside the CNS (cranial and spinal nerves). - 2- Functional classification: PNS can be divided into:- - Afferent division which brings sensory information to the CNS. - Efferent division, which carries motor commands to muscles, glands, and fat cells. The efferent division includes: - somatic nervous system(SNS) produce voluntary control over skeletal muscle contractions. - autonomic nervous system(ANS) produce automatic, involuntary regulation of smooth muscle, cardiac muscle, glandular activity, and adipose tissue. 2 — The nervous system functions: — 1- monitors the internal and external environments. — 2- integrates sensory information. — 3- coordinates voluntary and involuntary responses of many other organ systems. — 1- nerve cell and their function:The nerve cell is called neuron, which composed of cell body contain big nucleus and nerve fiber dendrites and axon. — Dendrites: conduct impulses to the cell body. — Axon: conduct impulses away from the cell body. Based on the relationship of the dendrites to the cell body and axon, neurons are classified into three types: 3 — 1- A Multipolar neuron has two or more dendrites and single axon. These are the most common neurons in the CNS. All of the motor neurons that control skeletal muscles are multipolar. — 2- A Unipolar neuron the dendrites and axon are continuous, and the cell body lies off to one side. The action potential begins at the base of the dendrites, and the rest of the process is considered an axon. Most sensory neurons of the PNS are unipolar. — 3- A Bipolar neurons have to processes-one dendrites and one axon-with the cell body between them. They are rare but occur in special sense organs, where they relay information about light, smell, or hearing from receptor cells to other neurons. — — Axon in CNS & PNS are covered with fatty insulating material called myelin by special cells that wrap around the axon forming a sheath with small spaces that 4  remain between the cells, called node, are important in the conduction of nerve impulse. These axons called white fiber and are found in the white matter of brain and spinal cord. — The fibers and cell bodies that not covered with myelin are found in gray matter. — 2- The nerve impulse — At rest the nerve cell membrane carries an electric charge, positive charge from outside and negative charge from inside membrane, due to different in ion concentration on either side of the membrane, — A nerve impulse: is a local reversal in the charge on the cell membrane, which spreads along the membrane like an electric current. This sudden electric change is called an action potential(depolarization). — A stimulus: is any force that can initiate an action potential, 5 — — The electric change results from rapid shifts in sodium and potassium ions across the cell membrane. The reversal occurs rapidly in less than 1/1000 of a second and is followed by a rapid return of the membrane to its original state so that it can be stimulated again(repolarization). 6 — A myelinated nerve fiber conducts impulses more rapidly than an unmyelinated fiber of the same size because the electric impulse “jumps” from space to space (node) in the myelin sheath instead of traveling continuously along the fiber. — 7 — — 3- the synapse: — Each neuron is a separate unit, and there is no anatomic connection between neurons. — Synapses: are points of junction for the transmission of nerve impulses by neurotransmitters. — Neurotransmitters: are chemical substances, released from the nerve fiber endings through vesicular transport mechanism to enable impulses to leap the synaptic junction; such as; 8 — - epinephrine- (adrenaline) — - norepinephrine-(noradrenaline)- both of them release in the brain and ANS by adrenergic synapses. They are inactivated by enzyme called monoamine oxidase enzyme present in synaptic cleft. — - acetylcholine(ACh)- release at the neuromuscular junctions by cholinergic synapses. Inactivated by acetylcholinesterase enzyme present in synaptic cleft. — Above mention neurotransmitters have excitatory effects, while dopamine, gamma aminobutyric acid, and serotonin neurotransmitters have inhibitory effects. — There are at least 50 other neurotransmitters whose functions are not well understood — — 4- Nerve and neuron: — Nerves could be:- — The nerve, is a bundle of nerve fibers located outside the CNS. — Tracts, are bundles of nerve fiber within the CNS. — Neurons could be: — Afferent neurons(sensory), conduct nerve impulses to the brain and spinal cord. — Efferent neurons(motor), conduct nerve impulses from CNS to the muscles and glands. — Most nerve contain both types of fibers so called mixed nerves. 9 — — 5- The central nervous system(CNS) — CNS can be divided to:- — 1- the brain: the main parts of the brain are; — A – the cerebrum, which is divided by central fissure into two hemispheres(right, and left). — B- the diencephalon, is the area between the cerebral hemispheres and the brain stem. — 2 – the brain stem, connect cerebrum to the spinal cord, and contain: — A – midbrain is the upper portion. — B – the Pons is the middle portion. — C – the medulla oblongata is the lower portion. — 3- the cerebellum. Is smaller than cerebrum and also contain two hemispheres. 11 — — 5-A- the cerebrum(cerebral hemispheres) — The largest region of the brain, is the site where conscious thought and intellectual functions originate. Much of the cerebrum is involved in receiving somatic sensory information and then exerting voluntary and involuntary control over somatic motor neuron. It contains: — 1-Gray matter „cerebral cortex”, has gyri(‫ )تالفيف‬and sulci(central and lateral sulcus‫)أخاديد‬, its superficial tissue. — 2- white matter (internal tissue) contain few islands of gray matter. — Each cerebral hemisphere is divide into four visible lobes named from the overlying cranial bones. They are frontal, parietal, temporal(insula fifth lobe), and occipital lobes. — 5-A-1- function of the cerebral cortex(lobes) 11  — 1- frontal lobes: lies in front of the central sulcus, it is relatively larger in human being than in any other organism. The lobe contain the motor cortex, which directs actions; the left side of the brain governs the right side of the body, and the right side of the brain governs the left side of the body. Also contain two areas important in speech “ motor speech and written speech”. — 2- the parietal lobe: occupies the upper part of the each hemisphere and lies just behind the central sulcus. It contains the sensory control area “touch, pain, temperature”, also determination of distance, sizes and shapes of objects take place here. — — 3- the temporal lobe: lies below the lateral sulcus and folds under the hemisphere on each side. It contains the auditory area and olfactory area, which is located in the medial part of the temporal lobe, concerned with sense of hearing and smell respectively. — 4- the occipital lobe: lies behind the parietal lobe and extends over cerebellum. It contains the visual area for interpreting vision. — 5-Insula: is the fifth lobe located deeply within the lateral sulcus. Not much known about this lobe — 5-A-1- function of the white matter of cerebral cortex(lobes) 12 — Its located under the gray matter of the cerebral cortex and consist of myelinated nerve fiber such as a- corpus callosum(‫ )الجسم الجاسئ‬which located at the bottom or the longitudinal fissure and serve as: — 1- bridge between the right and the left hemispheres, which permits impulses to cross from one side of the brain to the other. — 2-Connects the cortical areas with each other and with other parts or the nervous system. — B-The — B-The internal capsule is a crowded strips of white matter composed of many myelinated nerve fiber “forming tracts) — Basal — Basal nuclei “gangly”, are masses of gray matter located deeply within each cerebral hemisphere. These groups of neurons help in regulation of body movement and facial expressions communicated with the cerebral cortex. The neurotransmitter dopamine is secreted by the neurons of basal nuclei. — 5-A-2- communication area: — The development and use of these areas are closely connected with the process of learning. These areas are:- — 1-The auditory areas: are located in the temporal lobe. In one area of these areas sound impulses are detected, while in the surrounding area(auditory speech center) the sounds are interpreted and understood. — 2- the motor areas: for talking and writing are located in front of the lowest part of the motor cortex in frontal lobe. So speech center lies in front of frontal motor cortex for head and neck which control the muscles of speech in the tongue, the soft palate and the larynx. — 3- the visual areas: it receives visual impulses from eyes to the occipital lobe. These images are interpreted as words in the visual interpretation area that lies in front of the visual receiving area. The ability to read with understanding is also developed in this area. — 5-A-3- memory and the learning process. — Memory: is the mental faculty(ability) for recalling ideas. We have short-term and long- term. — Short-term memory: refers to the retention of bits of information for a few seconds or may be a few minutes. — Long-term memory: refers to the storage of information that can be recalled at a later time. 13  — Organization of information: brain is able to organize information so that new ideas are stored in the same areas in which similar ones have been stored. — 5-B- the diencephalon “interbrain” ‫(الدماغ الداخلي‬ — It is a mass of gray matter. It includes the thalamus and the hypothalamus. It lies inter the brain and the function of the them are; — Thalamus: is sort out the sensory impulses and direct them to particular areas of the cerebral cortex. — The hypothalamus: is located in the midline area below the thalamus, and contain cells for controlling body temperature, water balance, sleep, appetite, and some emotions, such as fear and pleasure. Also controls autonomic nervous system(sympathetic and parasympathetic NS) and pituitary gland; thus, it influences the heart beat, the contraction and relaxation of the walls of blood vessels, hormone secretion, and other vital body functions. — — 5-2- The brain stem(‫)جذع الدماغ‬ 14 — It contain midbrain, pons, and medulla oblongata. It connect the cerebrum with spinal cord. — The midbrain: located just below the center of the cerebrum, forms the forward part of the brain stem. It contains:- — 1- four rounded mass of gray matter, which form the upper part of midbrain; and act as relay centers for certain eye and ear reflexes. — 2- the white matter at the front of the midbrain conducts impulses between the higher centers of the cerebrum and the lower centers of the pons, medulla, cerebellum, and spinal cord. — 3- cran