Nervous System Module 3 PDF

MODULE 3 Coordinated Functions of the ❖ Nervous System ❖ Endocrine System, and ❖ Reproductive System  The Nervous System Identify and describe the major divisions, parts and functions of the nervous system Describe the generalized functions of the system as a whole...

MODULE 3 Coordinated Functions of the ❖ Nervous System ❖ Endocrine System, and ❖ Reproductive System  The Nervous System Identify and describe the major divisions, parts and functions of the nervous system Describe the generalized functions of the system as a whole Describe major nervous system disorders  Divisions of the Nervous System Brain Rest & of Spine Body  Central Nervous System The CNS serves as the main processing center for the entire nervous system. It consists of two main components, namely the: Brain Spine  Central Nervous System Brain -This is an organ located within the skull that functions as organizer and distributor of information for the body. It has three main parts: Brain stem medulla, pons, midbrain - the part that connects the brain to the spinal cord and controls automatic functions such as breathing, digestion, heart rate, and blood pressure.  Central Nervous System It has three main parts: Cerebellum – the part under the cerebrum that controls posture, balance, and coordination. Cerebrum – large, upper part of the brain that controls activity and thought. ✧ Diencephalon thalamus & hypothalamus  Central Nervous System Spine Spinal Cord -This serves as a channel for signals between the brain and the rest of the body, and controls simple musculoskeletal reflexes without input from the brain.  Central Nervous System Brain Brain stem medulla, pons, midbrain Diencephalon thalamus & hypothalamus Cerebellum Cerebrum Spine Spinal Cord  Cerebrum Regions Lobes of the Cerebrum Frontal Parietal Temporal Occipital Special regions Broca’s area Wernicke’s area Limbic System  Peripheral Nervous System The PNS connects the central nervous system to the organs and limbs. It has two main divisions: Somatic Nervous System Autonomic Nervous System  Somatic Nervous System This system is associated with the voluntary control of body movements and has two main parts: Spinal nerves -the nerves that carry motor and sensory signals between the spinal cord and the body. 31 pair Attached to spinal cord  Somatic Nervous System Cranial nerves – the nerve fibers that carry information into and out of the brain stem 12 pair Attached to undersurface of brain Autonomic Nervous System This system is associated with the involuntary control of body movements and has two subdivisions: Sympathetic nervous system - it is activated when the body is in a dynamic role or stress. (e.g., increased heart rate and breathing, dilation of pupil, sweating, etc.) Emergency response Fight or flight Autonomic Nervous System Parasympathetic nervous system - it maintains body functions and restores the body to normal or relaxed mode. Normal everyday conditions Autonomic Nervous System  Neuron Basic functional cell of nervous system Transmits impulses Three types Sensory neurons – bring messages to CNS Motor neurons - carry messages from CNS Interneurons – between sensory & motor neurons in the CNS  Neuron/Nerv e Cell Basic functional cell of nervous system Also called nerve cells Transmits impulses Three types Sensory neurons – bring messages to CNS Motor neurons - carry messages from CNS Interneurons – between sensory & motor neurons in the CNS  Neuron/Nerv e Cell There are billions of neurons in the body. Some exist alone. Others are joined together to form organs like the brain and spinal cord. There are twelve to fourteen billions of neurons in one part of the brain alone.  Neuron Has Cell Body with nucleus – nucleus & most of cytoplasm Dendrite –receive stimulus and carries it impulses toward the cell body - A cell may have as many as 200 dendrites carrying impulses toward the cell body. A single dendrite can be over one meter long.  Neuron Axon – fiber which carries impulses away from cell body - pass impulses to the dendrites of other neurons or cell body of muscle cells. Axons can be grouped together into cable-like bundles called nerves. Schwann Cells- cells which produce myelin or fat layer Myelin sheath – lipid layer around the axon Node of Ranvier – gaps or nodes in the myelin sheath Impulses travel from dendrite to cell body to axon  Nerve Impulses Impulse Self propagating Mechanism – Na+ K+ pump Synapse Junction between neurons Neurotransmitters Synapse Junction between neurons The neurons do not actually tough at the synapse Neurotransmitters used to restart impulse in dendrite of 2nd neuron  Neurotransmitters Chemicals in the junction which allow impulses to be started in the second neuron Reflex Arch  SENSE ORGANS The nervous system is assisted by five sense organs - the eyes, ears, nose, tongue, and skin. These sense organs are constantly receiving information from the environment and sending messages to the brain. These senses aid in the survival of human beings. A stimulus (plural: stimuli) is any factor in the environment that may trigger a nerve impulse. A response is a reaction to a stimulus. A stimulus is received by the body and a response is made. An organism must be able to respond to a stimulus in order to survive.  Sense Receptors receive input generate receptor potentials and with enough summation generate action potentials in the neurons they are part of or synapse with  5 Types of Sensory Receptors Based on the type of stimuli they detect: Mechanoreceptors - pressure receptors, stretch receptors, and specialized mechanoreceptors involved in movement and balance. Thermoreceptors - skin and viscera, respond to both external and internal temperature Pain receptors - stimulated by lack of O2, chemicals released from damaged cells and inflammatory cells Chemoreceptors - detect changes in levels of O2, CO2, and H+ ions (pH) as well as chemicals that stimulate taste and smell receptors Photoreceptors - stimulated by light  Distribution of Receptors in the body Special Senses mediated by relatively complex sense organs of the head, innervated by cranial nerves eg. vision, hearing, equilibrium, taste and smell General (somesthetic, somatosensory) receptors widely distributed in skin, muscles, tendons, joints, and viscera they detect touch, pressure, stretch, heat, cold and pain, blood pressure and chemistry  The Senses ∙ Special senses ∙ Smell- chemoreceptors (chemicals) ∙ Taste- chemoreceptors ∙ Sight- photoreceptors (light) ∙ Hearing- mechanoreceptors ∙ Equilibrium- (balance) mechanoreceptors ∙ General senses ∙ touch (tactile) ∙ Temperature- thermoreceptors (heat) ∙ Pressure- mechanoreceptors (movement) ∙ Pain- mechanoreceptors  Major Sense Organs Vision – Eye Hearing – Ear Taste – Taste receptors (new) Smell – Olfactory system Skin – Hot, cold, pressure, pain Eye  Images Cornea and the lens help to produce the image Images are upside down and backwards when they reach the retina Visual Pathway Ear Taste Buds Chemical Receptors Sweet Sour Bitter Salty MSG Olfactory Receptors Chemical Receptors Top of nasal cavity Extremely sensitive Easily fatigued Much of “taste” involves smell  General Senses Skin receptors – touch, pressure, heat, cold, pain Proprioceptors – Stretch receptors in joints, ligaments, and tendons Pain receptors – skin, skeletal muscle and visceral  Senses in Skin Heat Cold Light pressure Heavy Pressure Pain  General Senses Skin receptors – touch, pressure, heat, cold, pain Proprioceptors – Stretch receptors in joints, ligaments, and tendons Pain receptors – skin, skeletal muscle and visceral  Proprioceptors Maintain some degree of continuous contraction (partial sustained contraction) or muscle tone Muscle spindles – modified muscle fibers with sensory nerve endings wrapped around the middle (and also found at the ends) Detect stretch and stimulate a reflex contraction  Pain Receptors Somatic nociceptors - from skin and skeletal muscle Visceral nociceptors - receptors that help maintain internal homeostasis Respond to stretch, lack of O , chemicals released 2 from damaged cells and inflammatory cells. Referred pain – visceral pain afferents travel along the same pathways as somatic pain afferents, so sometimes the brain interprets the visceral pain as the more common somatic pain. Example – Often pain from the heart felt during a heart attack is perceived as a pain that originates in the left arm.  Disorders of the Nervous System Epilepsy, Seizures, Alzheimer’s Disease Multiple Sclerosis Parkinson’s Disease, Shingles (herpes zoster), Cerebral palsy, Glaucoma, Pink eye (conjunctivitis) Symptoms of disorders Treatments and prevention  Effects of Drugs Effects of drugs on the nervous system Alcohol Caffeine Nicotine Marijuana ENDOCRINE SYSTEM The endocrine system is composed of glands that secrete different types of hormones that affect almost every cell, organ, and function of our body. It is essential in regulating growth and development, metabolism, as well as reproductive processes and mood. Nervous System vs. Endocrine System Nervous System Endocrine System Chemical Messenger neurotransmitters hormones Location of message synapses target cells Effects rapid & short-lasting slower & longer lasting Controls muscles & glands activities of cells  Endocrine System Major Endocrine Organs Hypothalamus Pituitary gland Pineal gland Thyroid gland Parathyroid gland Thymus Adrenal gland Pancreas Ovaries Testes  GLAND TYPES A. Exocrine gland Ducts Lumen and surfaces B. Endocrine gland Chemical messengers Blood stream  ENDOCRINE SYSTEM AND HOMEOSTASIS Homeostasis Feedback Mechanisms Stimulus change in homeostatic environment signal sent to CNS Response signal sent from CNS produce effect body returns to homeostasis  Hormones Chemical messenger Secreted by endocrine gland Specific to target Activate cellular change Of 4 different chemical types  Hormones specific chemical compound produced by a specific tissue of the body released in the body fluids carried to a distant target tissue affects a pre-existing mechanism effective is small amounts.  Control of Endocrine Function A. Positive B. or Negative Feedback mechanisms Self-regulating system  STIMULUS Hypothalamus Releasing Hormone (Release-Inhibiting Hormone) Pituitary Stimulating Hormone Gland Target Hormone  Positive Feedback Not common Classic example: Action of OXYTOCIN on uterine muscle during birth. Positive Feedback Baby pushes on cervix Nervous signal to Hypothalamus Hypothal. manufactures OXY OXY transported to POSTERIOR PITUITARY & released OXY stimulates uterine contraction Loop stops when baby leaves birth canal  Negative Feedback Most common control mechanism Level of hormone in blood or body’s return to homeostasis shuts off loop at hypothalamus and pituitary Negative Feedback: Thyroid  Basic Structure of Feedback Loop Environmental Stimulus Stimulates Control Center (Brain-hypothalamus) Hypothalamic hormones stimulate Pituitary Pituitary hormone stimulate Target area Target area produces change Change acts negatively or positively on the cycle.  Endocrine System Major Endocrine Organs Pituitary gland Hypothalamus Pineal gland Thyroid gland Parathyroid gland Thymus Adrenal gland Pancreas Ovaries Testes  Hypothalamus Connection to pituitary Also part of the brain, attached to the posterior pituitary gland Its function is to synchronize the information from the brain and the secretions of hormones Neurosecretory cells – specialized neurons that synthesize & secrete hormones The hypothalamus controls the secretions of the pituitary gland through nervous stimulation (posterior pituitary) and releasing hormones secreted to the anterior pituitary Neuronal to POSTERIOR PITUITARY Endocrine to ANTERIOR PITUITARY RH = Pituitary releasing hormones RIH = Pituitary release inhibiting hormones  Neurosecretory Cells 1. Specialized neurons Synthesize and secrete hormones 2. Extend from HYPOTHALAMUS to POSTERIOR PITUITARY  Hypothalamic Hormones Release Inhibiting Hormones Somatostatin Prolactin release inhibiting hormone-PIH Releasing Hormones Thyrotropin releasing hormone-TRH Growth hormone releasing hormone-GHRH  Pituitary gland Located at the base of the brain and is no larger than the size of a pea. Considered the most important part of the endocrine system and is often called the “master gland ”. Controls many other endocrine system glands. The pituitary gland helps control body and tissue growth. Also secretes endorphins, chemicals that reduce sensitivity to pain. Divided into anterior and posterior sections Anterior & Posterior Pituitary  Anterior Pituitary Hormones HORMONE TARGET FUNCTION Thyroid (TSH) Thyroid gland TH synthesis & Stimulating release Growth (GH) Many tissues growth Adrenocortico- Adrenal cortex Cortisol release Tropin (ACTH) (androgens) Prolactin (Prl) Breast Milk production Follicle (FSH) Gonads Egg/sperm prod. Luteinizing (LH) Gonads Sex hormones  Posterior Pituitary Hormones Manufactured in Hypothalamus, & released from Posterior Pituitary Oxytocin Target = smooth ms. Uterus and Breast (&brain) Function = labor and delivery, milk ejection,(pair bonding) ADH (Vasopressin AVP) Target = kidneys Function = water reabsorption  Pineal Gland The pineal gland is located in the brain It secretes melatonin, which regulates our internal clocks and any rhythmic activities It plays a large role in our sleep and wake cycles  Thyroid It wraps around the trachea at the base of the neck Secretes a hormone called thyroxine Thyroxine regulates the metabolic rates of almost all the cells in the body As the thyroxine levels in the blood increase so does the rate of cellular respiration The thyroid gland needs iodine to create thyroxine, that is why salt is iodized now  Thyroid Hormone ↓ T3 & T4 stim. Or environmental stim. Hypothalamus TRH stim. Anterior Pituitary TSH stim. Thyroid ↑ T3 & T4 shuts off TRH and TSH production  Parathyroid These four little glands are embedded in the thyroid gland They secrete parathyroid hormone which regulates the amount of calcium in the blood and its absorption by bones  Thymus Located below the thyroid between the right and left lung Secretes thymosin which stimulates T-cell (that is a type of white blood cell) production in children. This gland shrinks with age as we are exposed to more germs and build up our stores of antibodies  Adrenal There are two located on top of the kidneys Medulla secretes epinephrine (adrenaline) and norepinephrine which regulate our fight or flight response at times of extreme stress Cortex secretes aldesterone which regulates reabsorption of nutrients from the kidney It also secretes cortisol which controls the rate of metabolism of carbohydrates, fats, and proteins  Pancreas Located behind the right side of the stomach Secretes insulin which tells the liver and muscles to remove sugar from the blood and store it as fat Also secretes glucagon which tells the liver to break down fat stores and release sugar back into the blood  Ovaries (females) Secrete estrogen and progesterone which regulate the female menstrual cycle Endometrium in the uterus also secretes a female hormone when a fertilized egg binds to it to stop the menstrual cycle from progressing to menstruation  Testicles (Males) Secretes male steroid hormones such as testosterone. Testosterone controls development of male characteristics such as formation of male sex organs in the womb, sperm development, and secondary sex characteristics at puberty (deep voice, facial hair, chest and armpit hair, etc.)  Endocrine Disorders Hypersecretion disorders are caused by too much hormone – these are much harder to treat Hyposecretion disorders are caused by too little hormone – they can be treated by addition of the hormone Target cell insensitivity produces symptoms similar to hyposecretion  Examples of the Endocrine System Disorders Diabetes – increased levels of glucose in blood Hypoglycemia - low blood sugar Graves Disease – overactive thyroid Goiter – enlarged thyroid gland  Mechanism of Hormone Action  Protein/Peptide Hormones Hydrophilic Large Can't fit through membrane Second messenger mechanism of action Most hormones Example: Insulin  peptide and amines Protein hormones (1st messengers) - bind to receptor on target cell triggering 2nd messenger to affect cell’s activity hormone (1st messenger) does not enter the cell but binds to receptor on the plasma membrane receptors hormone-receptor complex activates G protein generates chemical signal (2nd messenger) – most common is cAMP and IP3 2nd messenger chemical signal activates other intracellular chemicals to produce response in target cell Steroid Hormones Small Hydrophobic/Lipophilic Travel in blood w/carrier Cytoplasmic or nuclear receptors change protein synthesis Example: estradiol  Steroid Hormones Steroid hormones - bind to receptors within target cell and influence cell activity by acting on specific genes hormone diffuses freely into cell where cytoplasmic and/ or nuclear proteins serve as receptors hormone binds to receptor (hormone-receptor complex) complex bonds to steroid response element (sections of DNA receptive to the hormone-receptor complex hormone-receptor complex acts as transcription factor to turn target genes “on” or “off”