HTHS 1110 Unit 01 Textbook PDF

1 Introduction to Anatomy & Physiology Objective 1 Objective 5 The Framework of Homeostasis Anatomy & Physiology Objective 6 Objective 2 Disease | A Disruption Levels of Organization of Homeostasis Objective 3...

1 Introduction to Anatomy & Physiology Objective 1 Objective 5 The Framework of Homeostasis Anatomy & Physiology Objective 6 Objective 2 Disease | A Disruption Levels of Organization of Homeostasis Objective 3 Objective 7 Naming Anatomical Measurement Systems Planes & Directional & Dimensional Analysis Terminology Objective 4 Recognizing Major Organs & Structures of the Body N 1-1  Objective 1: The Framework of Anatomy & Physiology 1 State and compare the definitions of anatomy and physiology. Compare and contrast anatomical and physiological approaches to the study of the human body. Give examples of the interrelationship between anatomy and physiology. Describe the subdivisions of anatomy and physiology and recognize the types of study and level of analysis that characterize each subdivision. In this objective, we will define and compare the terms anatomy and physiology. You should be able to recognize the definitions of anatomy and physiology. You should be able to compare their respective approaches to the study of the human body, specifically relating to structure and function. Anatomy and physiology have several subdivisions and you should be able to recognize their focus of study. Science is divided into different disciplines of study, such as physics, chemistry, biology, geology, among others. Anatomy and physiology are biological sciences. This is a human anatomy and physiology course so we will narrow their focus to the study of the human body. Structure Anatomy (Greek: anatomē, “dissection”) is the study of the structure of the human body. Anatomy is the study of the organization of body systems. Function Physiology is the study of processes that keep body systems in balance (homeostasis). Physiology (Greek: physis, “nature, origin”, and –logia, “study of”) is the study of the function of the human body. The most important branch of physiology is the study of homeostasis, which is the condition of equilibrium (balance) in the body’s internal environment due to the constant interaction of the body’s many regulatory processes. We will examine homeostasis in a later objective. 1-1 The primary reason we teach anatomy and physiology together, in a single two- semester course, is that anatomy (structure) and physiology (function) are so intimately interrelated. But which leads to the other? Does structure determine function? Or does function determine structure? Short answer: Yes. Longer answer: Each influences the other. Structure determines function, as in how bone structure allows the skeletal and muscular systems to perform the functions of support and movement. Likewise, function determines structure, as in how the functional need for cells to pass signals to each other determines there are structures to do just that. The structure and function of lung alveoli can help with this concept. When we breath in air, it eventually ends up in the alveoli of the lung. The alveolar walls are structurally very thin, being composed of only one cell layer. The thin structure is important because we want to exchange oxygen, among other gases, across that wall to and from the capillary so we can deliver that oxygen to the vital organs of the body. If this wall was very thick, it would be difficult for alveoli to perform their function. For the lungs, as in other human organs, structure and function are inter-related and cannot be separated. 1-2 Anatomy Anatomy is the study of the structure of the human body. Cell biologists and histologists study the microscopic anatomy of cells and tissues, respectively. Systemic anatomists study the human body at the level of systems (e.g. digestive system). Gross anatomists are concerned with internal and external structures that can be seen without a microscope. Regional anatomists study internal and external anatomic interrelationships in a body region (e.g. thorax or head/neck) and surface anatomists never look inside. Radiographic anatomy is the study of body structure using penetrating energy (x-rays, sound waves, and magnetic resonance). Understanding how structures develop over time is the job of embryologists and developmental biologists. Studying structural changes in illness is a concern for pathological anatomists. 1-3  You will be tested on your knowledge of the subdivisions of anatomy listed in this table. Subdivisions of Anatomy Study/Focus Embryology The first 8 weeks of development Developmental Biology All stages of development Cell Biology Cell structure and function Histology Microscopic structure of tissues Surface markings of the body, observed through Surface Anatomy visualization and palpation (perception by touch) Gross Anatomy Structures viewed without a microscope System Anatomy Structures of specific systems Regional Anatomy Structure of specific regions of the body Radiographic Anatomy Body structures visualized with X-ray, CT, or MRI Pathological Anatomy Structural changes with disease 1-4 Physiology Physiology is the study of the function of the human body. There are many different functional systems in a human body, including the nervous system, endocrine system, cardiovascular system, immunologic (defense) system, respiratory system, and renal (urinary) system. Exercise physiologists study how exercise affects the human body. In another course, Introductory Pathophysiology (HTHS 2230, which many of you will take), we study functional changes caused by disease. 1-5 Subdivisions of Physiology Study/Focus Neurophysiology Functional properties of nerve cells Endocrinology Hormones and how they control body functions Cardiovascular Physiology Function of the heart and blood vessels How the body defends against disease-causing Immunology agents and identifies "self" Functions of the air passageways, lungs and gas Respiratory Physiology exchange Renal Physiology Functions of the kidney Changes in cell and organ function as a Exercise Physiology result of muscular activity Functional changes associated with Pathophysiology disease and aging You will be tested on your knowledge of the subdivisions of anatomy listed in this table. 1-6  Objective 2: Levels of Organization 2 Identify and give an example of each level of organization of the human body. Arrange the levels in the correct order, from smallest to largest. In this objective, you will be introduced to the various levels of organization. You should be able to identify the levels in the correct order (smallest to largest) and give examples of each level. Levels of Organization The subdivisions of anatomy Chemical smallest reflect the different levels of ᵒ Atomic organization of the human ᵒ Molecular body. The smallest level of Cellular organization is the chemical Tissue level; the largest is the entire Organ body (organism). System largest Organism The chemical level of organization consists of the atoms and molecules of the human body. For example, there are gases dissolved in the blood, so those dissolved gases (oxygen, carbon dioxide, nitrogen) are part of the chemical level. Molecules such as deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and proteins carry out essential functions at a microscopic level. All living things are made up of cells. There are many different types of cells, but they all have three things in common: 1) they are surrounded by a fatty two-part layer (lipid bilayer) called the plasma membrane; 2) the lipid bilayer surrounds a complex chemical “soup” called the cytoplasm, where essential cell functions are carried out; 3) they have a control center or information repository called a nucleus where instructions encoded in nucleic acids (DNA and RNA) are stored and manipulated. 1-7 Cells gather together in groups for the third level of organization, the tissue. A tissue is made up of cells of a certain type. For example, connective tissue holds the structure of the body; nervous tissue collects, uses, and sends out information. An organ is a collection of tissues that perform a function needed for the human body to survive. For example, the kidney is an organ which filters and removes wastes from the blood to make urine. A system is a group of organs which carry out a more complete set of functions. After being created by the kidney, urine moves through a pair of tubes called the ureters and is stored by the urinary bladder until it is expelled from the body through another tube called the urethra. Together, the kidneys, ureters, bladder and urethra make up the urinary system. The 11 body systems work together to form the organism, the human body. 1-8 Our course outline follows the levels of organization. Units 2-6 are focused on the atomic and cellular levels of organization. Unit 7 will cover tissues. Units 8-20 focus on the individual body systems. Level Examples Course Unit(s) Hydrogen, Carbon, Sulfur, Nitrogen, Chemical: Atomic Oxygen, Sodium, Chlorine, Potassium, Unit 2 Calcium, Iron, Iodine Carbohydrates, Lipids (fats), Proteins, Chemical: Molecular Unit 3 Nucleic Acids, Vitamins Plasma membrane, cytoplasm, Cellular Units 4–6 organelles Epithelial tissue Connective tissue Tissue Unit 7 Muscular tissue Nervous tissue Brain, thyroid gland, heart, lungs, Organ See systems stomach, liver, kidney, ovaries, testes Integumentary (skin) Unit 8 Skeletal Unit 9 Muscular Unit 10 Nervous Unit 11–13 Endocrine Unit 14 Organ System Blood, Lymphatic & Immune Unit 15 Cardiovascular Unit 16 Respiratory Unit 17 Digestive Unit 18 Urinary Unit 19 Reproductive Unit 20 Organism 1-9 Objective 3: Naming Anatomical Planes & Directional Terminology 3 Describe the human anatomical position and identify the major regions of the human body. Define and identify the directional terms used in human anatomy. Identify and describe the three cardinal planes used to section the body. Locate the major body cavities and demonstrate an understanding of the three-dimensional relationship between the body cavities. Identify the four abdominopelvic quadrants and the nine abdominopelvic regions, and the major organs that occupy them. In this objective, you will be introduced to the terminology used to describe body position, the body cavities, and directional terms. You should be able to describe the anatomical position. You should be able to identify the major body regions, the abdominopelvic regions and quadrants, and the major body cavities on a diagram or photograph. You should be able to describe and identify directional terms and the cardinal planes. We will cover multiple topics in this objective: 1. Anatomical position 2. Directional terms 3. Planes of section 4. Body cavitites 5. Abdominopelvic quadrants and regions 6. Regional anatomy Anatomical Position We need to define a single position for the human body so we can describe the relationship between various structures. For example, we use the term superior to mean “above” or “on top of”. You can put your hand on top of your head, but no one would say the hand is superior to the head. It’s the other way around. 1-10 We then define a “normal” position so that we can say where one structure is in relationship to another. We call it the human anatomical position. In the anatomical position the subjects stands erect, facing the observer with the head level, the eyes facing forward, feet flat on the floor, feet directed forward, and the arms at their sides with the palms facing forward. Now that we’ve defined a standard position, we’ll add words to describe specific locations on the outside surface of the human body. These are the terms commonly used in surface anatomy. We will also see all of these names again as we learn specific organ systems. Directional Terms Directional terms are pairs of words defining the two ends of an imaginary, two-headed arrow, like north and south; east and west. Before we use them, we have to imagine the human body in anatomical position. 1-11 Directional terms can relate to the structures on the body surface and to structures inside the body. Superficial means toward the surface. Deep means towards the core. Most organs inside cavities are covered with a double-layered membrane. Parietal is the membrane surface closest to the cavity wall. Visceral is the membrane surface closest to the organ inside the cavity. See the table for definitions of all of the directional terms we will study. Let’s go through a few examples: ꞏ The heart is superior to the bladder. The bladder is inferior to the heart. ꞏ The nose is medial to the eye orbits. The ears are lateral to the nose. ꞏ The sternum is anterior to the heart. The spinal column is posterior to the trachea. ꞏ The right arm is contralateral to the left arm. The right arm is ipsilateral to the right leg. The right arm is contralateral to the left leg. ꞏ The skin is superficial to the muscles. The muscle is deep to the skin. ꞏ The visceral and parietal pleural membranes are examples of these terms. We will study them in depth in unit 17. The visceral pleura is the membrane that lines the surface of the lungs while the parietal pleura lines the wall of the thoracic cavity. For all the structures named in this unit, you should be familiar with their relationship with each other. Example: “The brain is superior to the kidneys.” Common Directional Terms Superior: top or above Inferior: bottom or below Caudal: toward the buttocks (cauda, Cranial: toward the head Latin, "tail") Medial: toward the midline Lateral: away from the midline Proximal: closer to the point of origin or Distal: further away from the point of attachment origin or attachment Anterior (ventral): toward the front Posterior (dorsal): toward the back Ipsilateral: same side of midline Contralateral: opposite side of midline Superficial: toward the surface Deep: toward the core Parietal: membrane surface closest to Visceral: membrane surface closest to cavity wall organ inside the cavity 1-12 Body Planes Next we will explore cardinal planes. There are three cardinal planes used to define sections through the human body. 1) sagittal: divides right from left sides of body. 2) transverse (also called horizontal): divides superior from inferior 1-13  3) frontal (also called coronal): divides anterior from posterior (dorsal from ventral) Note the importance of anatomical position in these descriptions. The transverse (horizontal) plane is parallel to the ground, which is how it gets its name. Yet, if you’re lying down on your back, the frontal plane is parallel to the ground. We still call it the frontal plane. Technically, the sagittal plane is any section that divides left from right, but most anatomists use two more related terms: midsagittal (dividing the body into two equal, mirror-image halves) and parasagittal (all other sagittal planes). Sagittal and parasagittal are the same thing. An oblique plane is any plane or section that does not fit the above descriptions. Because of the variations in cuts and the number of analyses, the number of possible sections in each of these planes is infinite. 1-14 In a sagittal cut, we can identify anterior and posterior, superior and inferior, but not right and left. We have divided the right from the left so we lose that information. In a frontal cut, we can identify superior and inferior, left and right, but not anterior and posterior. We have divided the anterior from the posterior, so we lose that information. In a transverse cut, we can identify anterior and posterior, left and right, but not superior and inferior. We have divided the superior from the inferior, so we lose that information. In each case, structures that are not seen in a surface view become visible. You can also view organs in sections based on the cardinal planes. Notice how the shape of the section changes. 1-15 That’s the power of sectioning, as is done in many radiological studies such as magnetic resonance imaging (MRI) or computed tomography (CT) scans. In fact, “computed tomography” means using the computer to make slices from a series of low-dosage conventional X-rays. Body Cavities There are two main body cavities 1. Dorsal (cranial and vertebral); 2. Ventral (thoracic and abdominopelvic). 1-16 Each of these is subdivided into smaller cavities. The cranial cavity is in the skull; a hole in the bottom of the skull leads into the vertebral canal which is defined by the bony vertebrae. The thoracic cavity contains the pleural cavities, pericardial cavity, and the mediastinum. The mediastinum contains the pericardial cavity, which in turn contains the heart. The pleural cavities contain the lungs. The thoracic cavity is divided from the abdominopelvic cavity by the diaphragm. An imaginary line separates the abdominal and pelvic cavities within the abdominopelvic cavity. The thoracic and abdominopelvic cavities are together called the ventral cavity. They are the adult derivatives of an embryonic cavity called the coelom (pronounced “seal-um”). 1-17  Body Cavity Information Cranial cavity Contains brain, formed by cranial bones Dorsal Vertebral canal Contains spinal cord, formed by vertebral column Thoracic cavity Chest cavity Pleural cavity Space between layers of pleura that surround the lungs Pericardial cavity Space between layers of pericardium that surround the heart Mediastinum Central portion of thoracic cavity between lungs, contains heart, thymus, trachea, large Ventral vessels that enter the heart Abdominopelvic cavity Abdominal cavity Contains liver, pancreas, gallbladder, spleen, serious membrane is peritoneum, kidney is retroperitoneal (behind the peritoneum) Pelvic cavity Contains internal reproductive organs, urinary bladder You should spend a lot of time thinking about these cavities, how they relate to each other, and how they relate to the body as a whole. For example, the thoracic cavity (chest) has a medial mediastinal cavity and two lateral pleural cavities. The heart is within the pericardial cavity and the pericardial cavity is within the mediastinum. The lungs are within the pleural cavities. The pericardial cavity is therefore medial to the pleural cavities, and the pleural cavities are lateral to the pericardial cavity. 1-18 Abdominopelvic Quadrants & Regions The abdominopelvic cavity is divided into either four quadrants or nine regions using surface features.To divide the surface of the abdomen into four quadrants, vertical and horizontal lines are drawn through the umbilicus (“belly button”) when the human body is in the anatomical position. Abdominopelvic Quadrant Major Organ(s) Examples Liver Right Upper Quadrant (RUQ) Gallbladder Stomach Left Upper Quadrant (LUQ) Spleen Kidney (left) Cecum (where small meets large intestine) Right Lower Quadrant (RLQ) Appendix Left Lower Quadrant (LLQ) Ovary (left) – if female 1-19 To divide the surface of the abdomen into nine regions, a “tic-tac-toe” pattern is centered on the umbilicus. The vertical lines are drawn through the middle of the clavicles (collarbones) and the horizontal lines are drawn at 1/3 and 2/3 of the distance between the diaphragm and the pelvic bone. Abdominopelvic Regions Right hypochondriac region Epigastric region Left hypochondriac region Hypochondriac = “under the ribs” Epigastric = “on top of stomach” Hypochondriac = “under the ribs” Right lumbar region Umbilical region Left lumbar region Lumbar = “lower back” Centered on the umbilicus Lumbar = “lower back” Right inguinal region Hypogastric Region Left inguinal region (right iliac region) (left iliac region) (pubic region) Inguinal = “groin” Inguinal = “groin” Hypogastric = “under the stomach” Iliac = “flank” Iliac = “flank” 1-20 Regional Anatomy The last topic of this objective is regional anatomy. Here is a list of the major regions of the human body and a graphic to match their location. You should be able to identify these regions on a graphic or photograph. (Note: Both the English term and the Greek or Latin term are given for each region; be familiar with both.) Head (cephalic) Upper Extremity Skull (cranial) Armpit (axillary) Base of skull (occipital) Arm (brachial) Face (facial) Front of elbow (antecubital) Forehead (frontal) Back of elbow (olecranal, cubital) Temple (temporal) Forearm (antebrachial) Eye (orbital, ocular) Wrist (carpal) Ear (otic) Hand (manual) Cheek (buccal) Thumb (pollux) Nose (nasal) Palm (palmar, volar) Mouth (oral) Back of hand (dorsum) Chin (mental) Fingers (digital, phalangeal) Neck (cervical) Lower extremity Thigh (femoral) Knee Spinal column (vertebral) Knee Anterior surface (patellar) Trunk Posterior surface (popliteal) Chest (thoracic) Leg (crural) Breastbone (sternal) Calf (sural) Breast (mammary) Foot (pedal) Shoulder blade (scapular) Ankle (tarsal) Back (dorsal) Sole (plantar) Abdomen (abdominal) Top of foot (dorsum) Navel (umbilical) Heel (calcaneal) Hip (coxal) Toes (digital, phalangeal) Loin (lumbar) Great toe (hallux) Between hips (sacral) Pelvis (pelvic) Groin (inguinal) Pubis (pubic) Buttock (gluteal) Perineal 1-21 1-22 Objective 4: Recognizing Major Organs & Structures of the Body 4 Identify and describe the basic function of the 11 organ systems. Identify the major organs/structures of the body and the major body cavity they occupy. Locate the major bones of the body. In this objective, you will be introduced to the 11 organ systems and their functions and the major organs and structures of the body. You should be able to describe the basic function of each body system and recognize the major organs and structures of the body and the body cavities they occupy. Body systems are made up of cooperating organs which, together, perform common functions. We will briefly explore each body system and provide examples of their structure and function. 1-23 Integumentary (Skin) (Unit 8) Functions: Protects the body, helps regulate body temperature, eliminates some wastes, helps make vitamin D, detects sensations such as touch, pain, warmth, and cold. Organs/Structures to know: none for unit 1 Skeletal (Unit 9) Functions: Supports and protects the body, provides a surface area for muscle attachments, aids body movements, houses cells that produce blood cells, stores minerals and lipids (fats). Organs/Structures to know: It is important to learn a few of the “landmark” bones in the human body. You should be able to identify each of the bones listed. 1-24 Identify these Major Bones on the Diagram: Skull Radius Patella Vertebral column Ulna Tibia Sternum Carpals Fibula Ribs Metacarpals Tarsals Clavicle Phalanges Metatarsals Scapula Pelvis Phalanges Humerus Femur 1-25 Muscular (Unit 10) Functions: Produces body movements (such as walking), stabilizes body position (posture), generates heat, and stores and moves substances within the body (bladder, gut, lymph, peristalsis). Organs/Structures to know: none for unit 1 Nervous (Units 11–9) Functions: Generates action potentials (nerve impulses) to regulate body activities, detects changes in the body’s internal and external environments, interprets the changes, and responds by causing muscular contractions or glandular secretions, or interfacing with other neurons. Organs/ Structures to know: Brain (cerebrum + cerebellum), spinal cord 1-26 Endocrine (Unit 14) Functions: Regulates body activities by releasing hormones, which are chemical messengers transported in the blood from an endocrine gland or tissue to a target organ. Organs/Structures to know: Hypothalamus, thyroid gland, thymus gland, adrenal glands, pancreas, testes (♂), ovaries (♀). Lymphatic (Unit 15) Functions: Returns proteins and fluid to blood. The lymphatic system includes structures where lymphocytes mature and proliferate. Lymphocytes are a type of white blood cell that protect against disease-causing microbes. Organs/Structures to know: Thymus gland, spleen, appendix 1-27 Cardiovascular (Units 15–16) Functions: Heart pumps blood through blood vessels; blood carries oxygen and nutrients to cells and carbon dioxide and waste products away from cells and helps regulate acid-base balance, temperature, and water content of body fluids; blood components help defend against disease and repair damaged blood vessels. Organs/Structures to know: Superior vena cava, inferior vena cava, heart, right and left atrium, right and left ventricle. Respiratory (Unit 17) Functions: Transfers oxygen from inhaled air to blood and carbon dioxide from blood to exhaled air; helps regulate acid-base balance of body fluids; air flowing out of lungs through vocal cords produces sounds. Organs/Structures to know: Nostrils/nasal cavity, oral cavity, larynx, trachea, lungs, diaphragm 1-28 Digestive (Unit 18) Functions: Achieves physical and chemical breakdown of food, absorbs nutrients and water, eliminates solid wastes. Organs/Structures to know: Mouth/tongue, esophagus, stomach, small intestine, large intestine, cecum, appendix, liver, gallbladder, spleen, pancreas Urinary (Unit 19) Functions: Produces, stores, and eliminates urine, eliminates wastes and regulates volume and chemical composition of blood, helps maintain the acid-base balance of body fluids, maintains body’s mineral balance, helps regulate production of red blood cells. Organs/Structures to know: Kidney, ureter, urinary bladder, urethra 1-29 Reproductive (Unit 20) Functions: Gonads (ovaries and testes) produce gametes (sperm or oocytes) that unite to form a new organism; gonads also release hormones that regulate reproduction and other body processes; associated organs transport and store gametes. This is the only organ system which is completely different between the two sexes, male and female. For this reason, differences in these two systems are called the primary sexual characteristics. Organs/Structures to know: Ovary (♀), uterus (♀), cervix (♀), vagina (♀), testicle (♂), penis (♂) 1-30 At the organismal level, the highest level of organization, the various body systems must be integrated. These systems are responsible for balance in all body systems, a process called homeostasis. We will study homeostasis in detail in the next objective. Now think about what you know about anatomy (the study of structure) and physiology (the study of function). Structure depends on function, and function depends on structure. Anatomy and physiology are intimately related and the intertwining of these two once-separate fields is a major theme which runs throughout this course. Think about how the chemical, cellular, tissue, organ and system levels of organization are integrated into an entire organism. Small changes in the balance of each of these, at any level, can cause major problems in the organism, a process called disease, which we will discuss in objective 6. For example, your blood is normally almost 100% saturated with oxygen. If your blood is only 80% saturated with oxygen, you feel quite ill and may die. Next, we will explore the major organs and structures of the body. The table below is an organized list of the organs/structures you will need to know for this unit. These organs/ structures were listed with each organ system and noted by the images. This table provides more depth regarding the body cavities that they occupy. You should be able to identify these organs and structures and the major body cavity that they occupy. 1-31 Organ/Structure Body Cavity Subdivision(s) of Body Cavity (if applicable) Brain Cerebrum Cranial Cavity Dorsal Cerebellum Spinal Cord Vertebral Canal (cavity) Nostrils Nasal Cavity Tongue Oral Cavity Thyroid (in neck) Larynx Trachea Thymus Esophagus Mediastinum Aorta Ventral Thoracic Superior Vena Cava Inferior Vena Cava Heart Mediastinum Pericardial Lungs Pleural Diaphragm (divides thoracic & abdominopelvic cavitites) Stomach Liver Gallbladder Spleen Peritoneal Small Intestine Large Intestine Abdominal Pancreas Cecum, Appendix Kidneys Adrenal Glands Ventral Abdominopelvic Retroperitoneal Ureters Urinary Bladder Urethra Anus Ovaries (♀) Pelvic Uterine tubes (♀) Uterus (♀) Cervix (♀) Vagina (♀) Testicles (testes) (♂) in scrotal sac and penis are outside the abdominopelvic cavity 1-32  Objective 5: Homeostasis 5 Characterize homeostasis. Provide specific examples of organ systems maintaining homeostasis. List the components of a homeostatic feedback loop and explain the function of each. Explain how different organ systems relate to one another to maintain homeostasis. Give an example of positive and negative feedback loops in homeostasis. Describe the specific structures included in the feedback loops. In this objective, you will need to define homeostasis. You should be able to provide specific examples of how negative and positive feedback loops maintain homeostasis. Physiology is mostly the study of homeostasis. Homeostasis is the condition of equilibrium in the body’s internal environment due to the constant interaction of the body’s many regulatory processes. Break this definition down into its parts and try to understand it fully. What is equilibrium? What is meant by the internal environment? What sort of form will the interaction between regulatory processes take, and what exactly is meant by " regulatory processes?" Homeostatic Feedback Loops We accomplish homeostasis by utilizing feedback loops. Each feedback loop consists of a receptor, a control center, and an effector. The receptor is what perceives the stimulus. The receptor sends that information to the control center. The control center makes the decision ("what do I change to bring this system back into balance?"), then sends a command to the effector to cause that change.. 1-33 The easiest way to approach the study of homeostasis is to study specific examples, remembering that they reflect general principles that we will re-visit many times. All body systems must maintain some sort of equilibrium. We thirst, and we drink; we hunger, and we eat. In these (apparently) simple examples, there are many embedded, interacting, and complex feedback loops. What we call “thirst” may be triggered by an imbalance, such as an increase in the sodium concentration of the blood to higher than normal limits. The sodium concentration of the blood is monitored by receptors, a kind of molecular sensor that sends a signal to the control center in the brain. The “thirst center” of the brain, in turn, sends a signal to other areas of the brain that are responsible for driving us to find, and then drink, water. This loop continues operating until homeostasis (in this case normal blood sodium levels) is restored. Ahh! So refreshing to My blood osmolarity decrease my blood is too high! osmolarity! “Osmolarity” is the salt concentration in the blood. Diluting the salt with water decreases the blood osmolarity. ꞏ Variable: Change in blood osmolarity ꞏ Receptor: Senses change in blood osmolarity ꞏ Control center: Determines blood osmolarity is higher than the setpoint, and makes the decision to lower it by drinking water ꞏ Effector: Thirst response 1-34 You should be familiar with examples of receptors, control centers, and effectors for many different homeostatic loops. We will study a few now, and add many more as the course progresses. All feedback loops in the human body can be classified as either negative feedback loops or positive feedback loops. If the response reverses the stimulus, a system is operating by negative feedback. Homeostasis: Negative Feedback Loops Negative feedback loops are by far the most common kind of homeostatic circuit. This is because they are self-controlling; they cannot spin out of control if they are over- stimulated. For example, imagine you are outside on a cold day and your body temperature begins to lower. You have receptors that sense that decrease in body temperature. That signal is sent to the temperature regulatory center in the brain. In an effort to increase body temperature the control center will send a signal to cause muscles to shiver and blood vessels to constrict, to increase heat production and conservation. Thus, increasing body temperature and reversing the initial stimulus (decreased body temperature). ꞏ Variable: Body temperature ꞏ Receptor: A thermoreceptor senses the change in body temperature ꞏ Control center: The hypothalamus determines the body temperature is lower than the setpoint (37°C), and makes the decision to raise it by activating shivering and blood vessel constriction ꞏ Effector: Muscles shiver; blood vessels constrict (shrink) 1-35 The opposite effect happens if the temperature increases. You will respond to the increase in temperature by ꞏ Variable: Body temperature ꞏ Receptor: A thermoreceptor senses the change in body temperature ꞏ Control center: The hypothalamus determines the body temperature is higher than the setpoint (37°C), and makes the decision to lower it by activating sweating and blood vessel dilation ꞏ Effector: Sweat glands secrete sweat; blood vessels dilate (enlarge) 1-36 Another familiar example is blood sugar (glucose) control. Something happens to increase your blood glucose (e.g. you eat a bowl of Cap’n Crunch). Receptors in the beta cells of the pancreas detect the increase in blood glucose. The beta cells (also a control center) release insulin. Insulin increases glucose uptake into cells. As glucose is moved out of the blood and into cells the blood glucose levels are lowered. ꞏ Variable: Blood sugar level (blood glucose) is raised by absorption of digested Cap’n Crunch from the intestines ꞏ Receptor: Beta cells in pancreas sense high glucose ꞏ Control center: Pancreas determines blood glucose is above setpoint and releases a chemical signal (the hormone insulin) into the bloodstream ꞏ Effector: Insulin binds to receptors on the surface of body cells. The cells receiving the signal increase their glucose uptake 1-37 Homeostasis: Positive Feedback Loops If the response enhances or intensifies the stimulus, a system is operating by positive feedback. Only rarely are positive feedback loops used in the human body. They cannot be controlled as they move forward; rather, they only shut down when the system is depleted or the problem is corrected. Still, when your body needs a strong, rapid and ongoing response, such as in blood clotting or childbirth, a positive feedback loop is the best choice. When the baby is forced into the cervix, the cervix stretches, and the signal is sent to the brain. The brain releases oxytocin, a hormone that travels through the bloodstream to increase contractions in the uterus. These contractions force the baby further into the birth canal, which stretches the cervix even more, and the cycle continues, increasing in intensity and frequency, until the baby is born. ꞏ Variable: Diameter of cervix ꞏ Receptor: Stretch receptors sense stretch in the ring of muscle around the cervix ꞏ Control center: The hypothalamus responds to cervical stretch by releasing a chemical signal (the hormone oxytocin) from the posterior pituitary gland into the bloodstream ꞏ Effector: Smooth muscle in the uterine wall contracts more forcefully, pushing the baby further into the cervix 1-38 The suckling response is also a positive feedback loop. Baby suckles mother’s nipple. Receptors detect the tug from the baby and relay that information to the control center. The control center in the hypothalamus interprets the signal and releases a hormone (oxytocin — yes the same one) which ejects milk from milk glands in the breast. The baby responds to milk by tugging more. This positive loop only stops when baby is sated. ꞏ Variable: Milk release ꞏ Receptor: Touch receptors in the mother’s nipple sense the touch of baby’s lips ꞏ Control center: The hypothalamus responds to the baby’s lips touching the mother’s nipple by releasing a chemical signal (again, the hormone oxytocin) from the posterior pituitary gland into the bloodstream ꞏ Effector: Smooth muscle in the milk ducts relax, releasing the gland contents (breast milk) so the baby can drink 1-39 A third example of a positive feedback loop is blood clotting. Blood leaking from an injured vessel causes platelets to rub each other. Receptors on the surface of platelets detect this friction and the platelets become activated. Activated platelets set a cascade into motion which results in the formation of a sticky protein (fibrin) which rubs platelets together more. This only stops when the blood (locally) runs out of fibrin. ꞏ Variable: Platelet “stickiness” ꞏ Receptor: Platelets bang into each other as they are forced out of blood vessels ꞏ Control center: Platelets release a chemical signal which makes nearby platelets “stickier” ꞏ Effector: Platelets stick together and form platelet plug 1-40 The last positive feedback loop example we'll cover here is severe blood loss. A final positive feedback loop example (for our current discussion) is severe blood loss. This example is a bit more complex. Significant blood loss results in a decrease in blood pressure. Blood pressure is a regulated variable. Receptors in the major vessels leading away from the heart detect a decrease in pressure. The control centers in the brainstem and spinal cord direct the heart to beat more quickly in an attempt to increase the amount of blood in the circuit. This places increased metabolic demands on the heart which can only be met by more blood but the blood is on the floor of the Emergency Department and not available to the heart. Tissues also undergo hypoxia (low oxygen available) which leads to vasodilation (in an attempt to bring in more blood) but this vasodilation leads to more blood loss. Heart damage decreases heart efficiency and less blood is pumped, reducing blood pressure...and the positive feedback loop continues until death occurs. Because events controlled by positive feedback are more difficult to control and are more complex, they are not used very often. The only thing that stops them is some outside mechanism: the elements needed to clot blood are depleted; the child is born; the child stops suckling or milk is depleted; severe blood loss is halted. 1-41 Negative feedback loops are much more common and are used for all sorts of “housekeeping” functions. Negative feedback loops are self-regulating: there is some pre-existing set-point (normal body temperature, normal blood glucose, etc.) and when the system returns to that normal range, the feedback loop is shut down without further intervention. Positive Feedback Characteristics Negative Feedback Characteristics Strengthen or reinforce the stimulus Reverse the stimulus (change) in a (change) controlled condition Action stops automatically when set-point Action continues until it is interrupted is reached. Reinforces conditions that do not Regulate conditions that remain fairly happen very often stable over long periods Positive Feedback Examples Negative Feedback Examples Suckling Body temperature Childbirth Blood glucose Blood clotting Water balance Massive blood loss Many, many others 1-42  Objective 6: Disease | A Disruption of Homeostasis 6 Explain how disruptions in homeostasis may lead to disease. Define the terms “signs” and “symptoms” relative to disease states. Define syndrome. In this objective, you will be introduced to the disease terminology. You should be able to explain how disruptions in homeostasis may lead to disease. You should also be able to define the terms signs, symptoms, and syndrome. Diseases result from a disruption in homeostasis. Most diseases are recognized by their signs and symptoms. Signs result from the health care provider observing the patient. Signs of disease include such things as swelling, redness, rashes, pus formation, fever, vomiting, the results of laboratory tests. Symptoms result from an internal state or “feeling” and therefore can only be relayed by the patient. They may include nausea, pain, shortness of breath, headache and generalized malaise. 1-43 For example, if a person is experiencing hypotension (low blood pressure), they may present with the following signs: pale skin, sweating, diarrhea, or vomiting. They may also present with some of the following symptoms: dizziness, thirst, or shortness of breath. Again, signs are things you can observe while symptoms are what they tell you they are feeling. There is a homeostatic feedback loop controlling blood pressure. If something disrupts either the receptors, or the control center, or the effectors, then the “set-point” of homeostasis can be set inaccurately. The set-point of blood pressure should be 120/80 (both numbers are measured in millimeters of mercury, or mmHg). If the set-point of systolic blood pressure (the higher number) moves from 120 mmHg to 150 mmHg, then we say the patient has high blood pressure or hypertension. If the set-point for fats (also called lipids, and consisting of cholesterol and related compounds) is abnormal, we call this dyslipidemia. If the set-point for body weight relative to height is abnormally high, this is obesity. If the homeostatic loop for the pancreatic hormone insulin (receptors and control center), or the cells that respond to it (effector), is abnormal, which causes blood sugar levels to be abnormal, the disease is called diabetes mellitus (the two most common types are called “type 1” and “type 2”). A syndrome is a group of signs and/or symptoms that commonly occur together. The combination of three or more of the following conditions — hypertension, dyslipidemia, obesity and type 2 diabetes — is called metabolic syndrome. When three or four of these occur together, it is defined as a syndrome. 1-44  Objective 7: Measurement System & Dimensional Analysis 7 State the meaning of the following as prefixes to SI units: giga, mega, kilo, deci, centi, milli, micro, nano, and pico. Apply dimensional analysis to solve problems involving changes in units. In this objective, you will be introduced to the metric system and the prefixes used to describe the basic units of measure. You should be able to recognize the meaning of metric system units and prefixes. Specific prefixes include: giga, mega, kilo, deci, centi, milli, micro, nano, and pico. You will also be introduced to dimensional analysis and should be able to perform simple unit conversions. The United States is one of only three countries in the world (along with Liberia and Myanmar) that still use inches and feet as measurements. These units of length, along with others listed in the table below, constitute the US customary system (aka Imperial system) of weights and measures. This system is problematic for several reasons, but the most significant issue is simply that medicine, as other scientific pursuits, is an international discipline and demands a common language. That is why the metric system (known officially by its French name, Système International d’Unités, or the abbreviation SI) is the international measurement language of science. US Customary System vs Metric System (SI) US Customary Unit(s) Quantity Metric (SI) Unit inch, foot, yard, rod, fathom, length meter furlong, mile, league (or sea depth) ounce, pound, stone, ton mass gram teaspoon, tablespoon, ounce, volume liter cup, pint, quart, gallon second, minute, hour time second degree Fahrenheit temperature degree Celsius couple, few, several, dozen amount of matter mole 1-45 Remembering how many inches are in a foot, how many feet are in a yard or a mile, or the relationships between seven different units of volume can be confusing if you’re from the US, and downright impossible if you’re not. The metric system has just one unit each for length, mass, volume, time, temperature, and amount of matter. You must become familiar with the base units of the metric system; they are meter, gram, liter, second, degree Celsius, and mole. Metric System (SI) Base Units Unit Quantity Symbol meter length m gram mass g liter volume L second time s degree Celsius temperature °C mole amount of matter mol It is common to deal with very small and very large numbers in human biology and medicine. Consider mass (weight) in grams. At the atomic level, a single hydrogen (H) atom weighs about 0.0000000000000000000000017 g; a very small number. At the organism level, the average Japanese sumo wrestler weighs about 180,000 g; a rather large number. Both of these numbers are written in standard notation and, because it’s a drag to write all those zeroes, we rarely write them that way. Instead, using exponential notation (scientific notation), we write the mass of a single hydrogen atom as 1.7 x 10-24 g and the mass of an average sumo wrestler as 1.8 x 105 g. The key to moving back and forth between standard notation and exponential notation is rather simple. If the standard notation number is smaller than 1 (begins with “zero point something,” i.e., 0.0…, 0.1…, 0.2…, …0.9…), the exponent (superscript number) will always be negative (e.g. 10-5). If the standard notation number is 1, the exponent will be 0 (1 = 100). If the standard notation number is larger than 1, the exponent will always be positive (e.g. 105). To determine the numeric value of the exponent, just count how many places you move the decimal point. 1-46 For example, let’s assume you need to write 0.0000052 in exponential notation. First, note it is smaller than 1, which means the exponent will be negative. Second, note where the decimal is and count how many places it must move to end up after the “5”… Next, maybe you need to write 63,000,000 in exponential notation. First, note it is larger than 1, so the exponent will be positive. Second, note where the decimal is (after the last zero) and count how many places it must move to end up after the “6”… Finally, you need to write 7.6 x 109 in standard notation. The exponent is positive, so the number is larger than 1. Note where the decimal is and move it 9 places… Let’s go back to the small and large mass examples. A hydrogen atom has a mass of 1.7 x 10-24 g and a large sumo wrestler has a mass of 1.8 x 105 g. I don’t know about you, but I struggle to wrap my mind around how much is 1.7 x 10-24 g, and 1.8 x 105 g doesn’t make much sense to me either. By combining exponential notation with the metric system, it becomes even easier to express those numbers. 1-47 In the metric system, different powers of ten (exponents) have their own name, and those names are used as prefixes to the base units (meters, grams, liters, etc). Instead of expressing a sumo wrestler’s mass in grams (g), it makes more sense to use kilograms (kg). There are 1000 grams in one kilogram, so a sumo wrestler’s mass is about 180 kg (180,000 g = 180 kg). The prefix kilo- means 103 (1000). Likewise, it makes more sense to use picograms (pg) for the mass of a hydrogen atom. There are 1,000,000,000,000 (1012 or 1 trillion) picograms in one gram, so a hydrogen atom has a mass of 1.7 x 10-12 pg (1.7 x 10-24 g = 1.7 x 10-12 pg). The prefix pico- means 10-12. The prefixes are listed in this table. Notice there is not a prefix for every possible exponent (eg, none for 104, 105, 107, 108, etc). For exponents from 10–3 through 103 (10-3, 10-2, 10-1, 101, 102, 103), each exponent has a prefix. Outside that range, each third exponent has a prefix (10–12, 10–9, 10–6, 10–3; 10 3, 10 6, 10 9, 10 12). Metric System (SI) Prefixes Prefix Multiplier Symbol tera- 1012 = 1,000,000,000,000 T giga- 109 = 1,000,000,000 G mega- 106 = 1,000,000 M kilo- 103 = 1,000 k hecto- 102 = 100 h deca- 101 = 10 da deci- 10-1 = 0.1 d centi- 10-2 = 0.01 c milli- 10-3 = 0.001 m micro- 10-6 = 0.000001 µ nano- 10-9 = 0.000000001 n pico 10-12 = 0.000000000001 p 1-48 At the atomic level, a hydrogen atom is about 50 pm (picometers) in diameter. At the cellular level, a red blood cell is 8 µm (micrometers) in diameter, or 160,000 (1.6 x 105) times larger than a hydrogen atom. At the organism level, a typical human is 1.6 m (meters) tall, or the height of 200,000 (2 x 105) red blood cells. When we need to make a calculation that involves converting one unit to another (say, grams to picograms, or miles to kilometers), it is relatively easy to do so by applying a method called dimensional analysis or the factor-label method (or, as Mr. Fore, my high school chemistry teacher, called it, “using conversion factors"). If we have a starting number with units, the units we want to end up with, and an appropriate conversion factor, we can apply dimensional analysis to easily make the conversion. The examples below show how to apply dimensional analysis. We’ll start with a very simple problem to demonstrate how it works, and then show you a more complex example. You will have an opportunity to practice this in Lab 1. Example 1. Imagine you have a ruler with a label indicating it is 1.5 meters long but without any other markings, and you need to know its length in millimeters. How many millimeters are in 1.5 meters? Although you may be able to quickly solve this in your head, it’s a good example of how to use dimensional analysis. First, and this is very important, anything divided by itself equals 1......and that doesn't apply only to numbers. The goal in dimensional analysis is to convert a measurement in one unit into an equivalent measurement in a different unit. We do that do that by multiplying by 1. Multiplying by 1 is always “legal” — it doesn’t change the value, but it does allow us to convert the units. Let’s continue with Example 1 to illustrate this process. 1.5 m (meters) is equivalent to how many mm (millimeters)? Starting units = m, ending units = mm. All we need is a conversion factor. 1-49 What is the relationship between meters and millimeters? From the previous table we know that milli- means 10-3. So…...or... Our conversion factor, then, is 1 m = 1000 mm. Notice it contains our starting units (m) and our ending units (mm). In order to use it in our calculation, we need to write it as either… …both of which are equal to 1. Now let’s lay out the calculation. Start with what you know (1.5 m), multiply by the conversion factor, and end with the converted number in the units you want (mm). Insert the conversion factor (I suggest you always write this out on scratch paper). Notice, as you look at the whole equation, we have m (meters) as a unit above the line (1.5 m) and below the line (1 m). We have already demonstrated that meters divided by meters equals 1. In other words the two meters units “cancel each other out” (you might remember this terminology from a past math class…), leaving mm (millimeters) as the only unit in the equation. Now, just do the math. 1-50 Remember, from above, there were two ways to write the conversion factor. Don’t fret too much about which one to use. If you choose the correct version, your calculation will be successful; you’ll cancel out units you want to be rid of and end up with only the units you want. If you choose the wrong one, units won’t cancel out and you’ll end up with some funky units that make no sense. To illustrate, let’s try Example 1 with the other version of the conversion factor… I don’t know about you, but I have no idea what to do with units of “square meters per millimeter…” Example 2. Let’s apply this to a common situation — child birth. When a woman goes into labor, the goal is always that she be “dilated to a 10” before a vaginal delivery. That means the woman’s cervix, which is usually either tightly closed or open only enough to allow passage of menstrual flow or sperm, has opened (dilated) much wider and now measures 10 cm (centimeters) across (diameter). If you’re not really familiar with the metric system and centimeters sounds a bit foreign, dimensional analysis can help quickly discover — 10 cm is equal to how many inches? We will need a conversion factor that takes us from metric units of length to US customary units of length. Sometime in junior high or high school, I remember learning… To use this as a conversion factor, we write it as either… Next, lay out the calculation. Starting units = cm, ending units = in (inches). Plug in the conversion factor… 1-51 Make sure the starting units cancel out and the ending units remain… Then do the math... A standard softball is 3.5 inches in diameter. Its no wonder epidurals are popular. One final example, to illustrate how useful dimensional analysis can be. Example 3. From my driveway in Pleasant View, Utah, to my son’s driveway in Pleasant Grove, Utah, is exactly 70 miles. Suppose, for whatever reason, I need to know that distance in kilometers. It’s not hard to find a conversion factor for miles to kilometers, but what if I can’t find one and don’t remember one? What if the only metric to US customary length conversion factor I can remember is the one I mentioned above, 1 inch = 2.54 cm, that I learned years ago? Thankfully, I can use dimensional analysis to solve the problem. (Note: We will not ask you to do anything this involved.) 1-52 Starting units = miles, ending units = kilometers, and 1 inch = 2.54 cm. What else do I know? Well… You can chain together more than one conversion factor, if needed. The key is to ensure all unwanted units cancel, leaving only the units you want, then do the math... Notice that miles, feet, inches, centimeters, and meters all cancel, leaving just kilometers, the unit we need. For those unfamiliar with serial multiplication, punch the above equation into your calculator as follows: 1-53