P&a unit 4 nervous system


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P&a unit 4 nervous system

  1. 1. P&A Unit 4<br />Nervous System<br />
  2. 2. I. Intro – 2 parts to Nervous System<br />A. Central Nervous System – CNS<br />Brain and spinal cord<br />B. Peripheral Nervous System – PNS<br />All the nerves that connect to CNS and other body parts<br />
  3. 3. II. Nervous Tissue<br />A. Neurons<br />1. Def: Nerve cell – structural and functional unit of the nervous system<br />B. Neuron Structure<br />1. cell body<br />Main portion of neuron<br />Contains neurofibrils<br />Conatains NISSIL BODIES<br />Make protein<br />Contains nucleus<br />Mature neurons cannot reproduce<br />DESTROY THEM AND THEY ARE GONE!!<br />
  4. 4. 2. dendrites<br />Short, highly branched parts off of cell body<br />Each neuron may have many<br />F: main RECEPTIVE surface of neuron<br />Communicates with other neurons<br />**BRINGS IMPULSES IN<br />
  5. 5. 3. axon<br />An extension of the cell body which sends impulses AWAY from the neuron<br />Schwaan cells<br />Cells which surround axon<br />Make up myelin (lipoprotein) sheath<br />MS – makes impulse travel very quickly<br />A). Not all axons are myelinated<br />GRAY MATTER<br />Def: group of cells in NS which are unmyelinated<br />WHITE MATTER<br />Def: group of cells in NS which ARE myelinated<br />Nodes of Ranvier<br />Def: narrow gaps in myelin sheath b/n axon cells<br />
  6. 6.
  7. 7. III. Nerve Impulse Conduction<br />A. Nerve impulse<br />Def: the propagation (increase/transmission) of electrical charges along nerve cells<br />B. Process of Conduction<br />1. nerve fiber develops resting potential<br />Def: state in which a net POSITIVE charge is on the OUTSIDE of the cell membrane = POLARIZED<br />Cause: Na+ and K+ are key ions<br />3 Na+ ions diffuse outside the nerve fiber – low to high conc.<br />2 K+ ions diffuse inside the nerve fiber – low to high<br />What is the charge? POSITIVE on OUTSIDE = resting potential<br />
  8. 8. 2. Threshold stimulus is received<br />Minimal stimulus needed for a nerve to fire<br />Will be reached if a nerve is stimulated by:<br />Nearby nerve stimulus<br />Changes in light, temperature, pressure<br />Resting potential decreases – net positive charge on outside of membrane decreases<br />How?<br />Sodium/Potassium pump = active transport<br />Na+ channels open and Na+ starts flowing inside (L to H) cell membrane = DEPOLARIZED<br />If stimuli are strong enough, THRESHOLD STIMULUS is reached<br />
  9. 9. 3. Shortly after, K+ diffuses outside of cell (L to H) causing the cell to be REPOLARIZED<br />4. Action potential occurs<br />Def: rapid depolarization and repolarization of a nerve cell<br />Lasts 1/1000 of a second<br />Causes electric current to flow to next area of nerve cell<br />5. Wave of APs continue through nerve = IMPULSE<br />6. refractory period<br />Time when nerve is repolarizing and will not respond to another stimulus<br />http://people.eku.edu/ritchisong/301notes2.htm<br />
  10. 10. C. Impulse conduction<br />1. unmyelinated fibers<br />Impulses travel slowly<br />2. myelinated fibers<br />Impulses travel quickly<br />Jump from N of R to N of R<br />
  11. 11. D. all or none response<br />Nerve fiber ALWAYS responds completely when TS is reached<br />Impulse always travels through entire nerve<br />E. Synapse<br />Def: the junction where 2 neurons meet and interact<br />Sending neuron: PRESYNAPTIC NEURON<br />Receiving neuron: POSTSYNAPTIC NEURON<br />Synaptic cleft: space b/n pre and post neurons<br />** impulses jump this gap when traveling<br />
  12. 12. F. Neurotransmitters<br />1. def: chemical substance released by presynaptic neuron which may cause impulses to be conducted to postsynaptic neuron<br />** if enough NT is released, TS in postsynaptic is reached and impulse travels<br />2. Types<br />A. excitatory NT<br />Cause impulse to quickly be transferred to postsynaptic neuron<br />Allows ions to quickly diffuse through membrane<br />B. inhibitory NT<br />Cause impulse to die<br />TS is raised because ions can’t diffuse<br />
  13. 13. Examples<br />Excitatory<br />Acetylcholine<br />Dopamine<br />Inhibitory<br />GABA – gamma amino butyric acid<br />Mood, control many other excitatory NT<br />Serotonin<br />Slow the brain down, reduce stress, relax, effect mood<br />
  14. 14. V. Types of Neurons/nerves<br />A. Multipolar neurons – many nerve fibers<br />Many dendrites/ 1 axon<br />Located: brain and spinal cord<br />B. bipolar neurons – 2 nerve fibers<br />1 axon/ 1 dendrite<br />Located: eyes, nose, ears<br />C. unipolar neuron – 1 nerve fiber, splits into A and D<br />1 dendrite/ 1 axon<br />Axon connected to brain/ spinal cord<br />Dendrite connected to peripheral body part<br />
  15. 15. D. Nerve types<br />Nerves: group of neurons held together by connective tissue<br />1. sensory nerves<br />Send messages to brain/SC<br />2. motor nerves<br />Send messages to muscles/glands<br />3. mixed nerves<br />Send messages to both<br />4. interneurons<br />Connect nerves in brain/SC<br />
  16. 16. VI. Nerve pathways<br />A. reflex arc<br />1. def: the simplest pathway an impulse may take<br />** never reaches the brain<br />Process:<br />1. Sensory receptor at end of sensory nerve fiber takes in stimulation<br />2. SNF takes it to reflex processing center in Spinal Cord<br />3. interneurons communicate in SC<br />4. motor neuron carries response to effector<br />5. effector does action – muscle, gland etc<br />
  17. 17. B. reflex behavior<br />1. def: automatic unconscious responses to changes occurring within or outside the body<br />2. controls: <br />Heart rate<br />Breathing rate<br />Blood pressure<br />Digestion<br />Sneezing<br />Coughing<br />Vomiting<br />
  18. 18. 3. example: knee jerk<br />A. sensory receptor sense touch to petallar ligament<br />B. sensory nerve fiber dendrite takes in info<br />C. impulse sent to SC where sensory axon meets an interneuron which connects to motor neuron dendrite<br />D. motor axon carries impulse to effector in quad<br />E. quad flexes <br />4. withdrawal reflex<br />Person touches something hot, pulls away body part<br />P. 214<br />
  19. 19. VII. Impulse processing<br />A. convergence<br />1. def: neuron impluses from 2 or more axons converge on 1 neuron<br />Allows NS to bring different information together<br />B. divergence<br />1. def: impulses leaving 1 axon pass into several other neurons<br />Allows impulse effect to be amplified<br />Ex: send message to all motor neurons in muscle so all contract<br />
  20. 20. VIII. Coverings of CNS<br />A. Intro<br />1. brain lies in: cranial cavity<br />2. SC lies in: vertebral canal<br />3. both surrounded by membranes called MENINGES<br />Between bone and nerve tissue<br />
  21. 21. B. meninges<br />3 layers<br />Dura mater<br />Arachnoid mater<br />Pia mater<br />1. dura mater<br />Outermost<br />Tough, white connective tissue<br />Many vessels & nerves<br />May extend into lobes of brain<br />
  22. 22. 2. arachnoid mater<br />Thin, weblike<br />Middle layer<br />No blood vessels<br />** Cerebrospinal fluid between arachnoid and pia mater – CSF<br />3. pia mater<br />Thin<br />Innermost<br />Many vessels to nourish brain and SC<br />
  23. 23. VIII. Spinal Cord<br />A. Intro<br />Cord begins at foramen magnum and end at intervertebral disk b/n 1st and 2nd lumber vertebrae<br />B. structure<br />1. 31 segments, each with a pair of nerves that branches off peripherally<br />Spinal nerves<br />8 cervical<br />12 thoracic<br />5 lumbar<br />5 sacral<br />1 coccygeal<br />CAUDA EQUINA – last group of nerves, taillike<br />
  24. 24. 2. Cross Section<br />
  25. 25. 3. Functions of SC<br />1. to conduct nerve impulses to and from Brain<br />Involves only white matter<br />A. ascending tract<br />Carry impulses TO brain<br />B. descending tract<br />Carry impulses FROM brain to muscles/glands<br />2. to be the center of the reflex arc<br />Involves grey matter<br />
  26. 26. IX. Brain<br />A. Intro<br />100 billion multipolar neurons<br />3 major portions:<br />1. cerebrum<br />Largest<br />Nerve centers for sensory and motor functions<br />Memory and reasoning centers here<br />2. cerebellum<br />Posterior/dorsal region<br />Coordinates complex skeletal voluntary muscle movements<br />Maintains posture<br />Position of body parts<br />3. brain stem<br />Connects nerve pathways that connect many nerves between SC and brain<br />Regulate many organ activities<br />
  27. 27. B. Cerebrum<br />1. Structure<br />A. cerebral hemispheres (2)<br />2 equal halves of cerebrum<br />B. corpus callosum<br />Bridge of nerve fibers that connects cerebral hemisheres<br />Allows R and L sides to communicate<br />C. convolutions<br />Ridges of cerebrum<br />D. sulcus<br />Groves b/w convolutions<br />E. fissures<br />DEEP groves b/n parts of the brain<br />
  28. 28. F. frontal lobe<br />G. parietal lobe<br />H. occipital lobe<br />I. Temporal lobe<br />J. cerebral cortex<br />Thin layer of grey matter over cerebrum<br />Covers convolutions, sucli, and fissures<br />Contains nearly 75% of all neuron cell bodies<br />Just beneath is a mass of White Matter that makes up cerebrum<br />
  29. 29. 2. functions<br />A. frontal lobe<br />1. motor speech area – Broca’s Area<br />Moves mouth, tongue, pharynx, larynx<br />2. frontal eye field<br />Controls voluntary movements of eyes and eyelids<br />3. Concentration, planning, problem solving area<br />4. emotions and reasoning<br />5. motor areas which control voluntary muscles<br />
  30. 30. B. parietal lobe<br />Sensory areas involved with sensations of skin<br />Understanding speech, using words<br />C. occipital lobe<br />Visual area<br />Combines visual images from L and R eyes<br />Recognition<br />D. temporal lobe<br />Interpretation of sensory experiences<br />Memory of visual and audio patterns<br />E. general interpretive area<br />Overlaps all lobes<br />Primary in complex thought and processing<br />F. hemisphere dominance<br />L= verbal, analytical, computational, detailed<br />R= musical, visual, creative, <br />
  31. 31. C. cerebrospinal fluid – CSF<br />1. structure<br />A clear liquid that is secreted by CHOROID PLEXUS in pia mater<br />Tiny flowerlike masses<br />Circulates around the brain and down central canal of SC – eventually reaches blood to deliver wastes etc<br />2. function<br />Surrounds brain and SC for support/protection<br />Provide path to blood for waste<br />** always stays at same pressure b/c it is continually made and reabsorbed<br />** it not, pressure on the brain<br />
  32. 32. D. cerebellum<br />1. located below occipital lobe<br />2. mostly white matter<br />3. covered by CEREBELLAR CORTEX – grey matter<br />4. involved in:<br />Planning<br />Personality<br />Intelligence<br />Interprets desired movements and causes body to do them<br />5. damage = :<br />Tremors<br />Loss of muscle tone<br />Uncoordinated walk<br />Loss of equilibrium<br />
  33. 33. E. brain stem<br />Def: bundle of nerve tissue that connects cerebrum to spinal cord<br />Several masses of grey matter<br />1. Parts:<br />A. diencephalon<br />b/w cerebral hemispheres<br />1) infundibulum here<br />A piece which hangs down and attaches to pituitary gland<br />2) thalamus here<br />Receives all sensory impulses and relays them to appropriate region of cortex for interpretation<br />
  34. 34. 3) hypothalamus here<br />Regulates heart rate, blood pressure, body temp, hunger, release of hormones, regulates sleep<br />4)limbic system here<br />Combination of many areas<br />Involved in emotional expression<br />Fear, anger, pleasure, sorrow<br />Recognizes things that threaten life – “fight or flight” <br />
  35. 35. B. midbrain<br />Below diencephalon<br />Much grey matter as a reflex center<br />Visual reflex = eyeballs move when head moves<br />Auditory reflex = ears move close to sound<br />C. pons<br />Below midbrain – round bulge<br />Relay impulses all over brain<br />Ex: relays breathing rhythms to medulla oblongata<br />D. medulla oblongata<br />Extends from pons<br />Controls:<br />Cardiac center: speed or lower heart rate<br />Vasomotor center: constrict/dilate blood vessels<br />Respiratory center: rate/rhythm of breathing<br />
  36. 36. X. Peripheral Nervous System - PNS<br />A. def: nerves that branch out from the brain and SC<br />SOMATIC NS: consists of cranial and spinal nerves that connect to skin and skeletal muscle<br />AUTONOMIC NS: nerves that connect to organs/glands<br />
  37. 37. B. Cranial nerves – 12 pair<br />* go in order from front to back<br />1. olfactory nerves (I)<br />Sensory nerves<br />Transmit smell impulses<br />2. optic nerves (II)<br />Sensory nerves<br />Transmit vision impulses<br />3. oculomotor(III)<br />Mostly motor nerves<br />Transmit impulses to: adjust lens, adjust pupil, move eyelid, move eye<br />
  38. 38. 4. trochlear (IV)<br />Mostly motor nerves<br />Transmit eye movement impulses<br />5. trigeminal (V)<br />Mixed<br />Sensory: <br />Transmit impulses from: tear glands, scalp, forehead, upper eyelids, teeth, lips, skin of face<br />Motor:<br />Transmit impulses of chewing<br />
  39. 39. 6. Abducens (VI)<br />Mostly motor<br />Transmit impulses of eye movement<br />7. facial (VII)<br />Mixed<br />Sensory:<br />Transmit impulses of tongue/taste<br />Motor:<br />Facial expression, tear glands, salivary glands<br />8. vestibulocochlear (VIII)<br />Sensory nerves<br />Transmit impulses for equilibrium and hearing<br />
  40. 40. 9. glossopharyngeal (IX)<br />Mixed<br />Sensory:<br />Pharynx, tonsils, tongue, neck artery<br />Motor:<br />Swallowing, salivary<br />10. vagus (X)<br />Mixed<br />Sensory:<br />Pharynx, larynx, esophagus, organs<br />Motor:<br />Speech, swallowing, heart, glands<br />
  41. 41. 11. accessory (XI)<br />Mostly motor<br />Pharynx, larynx, neck, back<br />12. hypoglossal (XII)<br />Mostly motor<br />Muscles that move tongue<br />
  42. 42. D. Spinal Nerves<br />31 pair<br />Communicate impulses from spinal cord and arms, legs, neck, trunk<br />
  43. 43. D. Autonomic Nervous System<br />Regulates heart rate, BP, breathing rate, body temp<br />Respond to emotional stress and strenuous physical activity<br />1. sympathetic division <br />Prepares body for emergency situations<br />Initiates activation and secretion of adrenaline<br />2. Parasympathetic division<br />Active during ordinary conditions<br />Restores body back to normal after stress<br />
  44. 44. XI. Clinical Terms<br />