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Nervous System

Nervous System. Compare the functions of the CNS & PNS. Objectives. Identify the principle parts of the nervous system Describe the cells that make up the nervous system Describe what starts and stops a nerve impulse (action potential) The role of neurotransmitters

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Nervous System

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  1. Nervous System Compare the functions of the CNS & PNS

  2. Objectives • Identify the principle parts of the nervous system • Describe the cells that make up the nervous system • Describe what starts and stops a nerve impulse (action potential) • The role of neurotransmitters • Compare the functions of the CNS & PNS • Identify the principle parts of the brain

  3. Components of the Nervous System - Somatic

  4. CNS = spinal cord & brain • PNS = nerves carry (tissue) impulses to and from brain • Motor Output side of chart has 2 divisions: somatic and autonomic • Focus Somatic 1st then Autonomic

  5. Somatic division/Motor/PNS • Requires only one neuron system: CNS to cell • 12 pairs cranial nerves • From brain’s underside/brain stem • Brain to muscles, glands, head, neck, thorax, abdomen • 31 pairs spinal nerves • Originate from spinal cord • Dorsal root ganglia– sensory incoming AP from tissues to cord • Ventral root ganglia– motor outgoing AP away from cord to body • Connects CNS to body parts

  6. Reflexes • Spinal Reflexes – require no conscious thought – processes @ spinal cord only • E.g. flexor reflex – withdrawal of foot from something sharp • Knee-jerk reflex (check up) – tap below patella causes contraction of thigh and upward movement of foot and leg • Stretch (quadriceps) reflex – posture maintenance – stand and move w/out having to think about it

  7. Components of the Nervous System-autonomic

  8. Autonomic Division • Sympathetic – stress / high activity • Parasympathetic – resting, homeostasis • 2 neuron system to transmit impulses to target cells • 1st neuron - preganglionic in CNS • 2nd neuron – postganglionic outside CNS & extending to the far reaches of the body (glands/organs) • Sympathetic & Parasympathetic oppose each other – work antagonistically for homeostasis

  9. Sympathetic vs. Parasympathetic • Neurotransmitters • Sympathetic – norepinephrine (adrenalin) - stress • Parasympathetic – acetylcholine - relax

  10. Somatic and Autonomic Divisions of the PNS

  11. Components of the Nervous System

  12. Brain & Spinal Cord • Central location & action • Integrating & processing of information • Info in  CNS  Complex Output

  13. “Billions of action potentials travelling in millions of neurons all come together as a conscious thought”

  14. Could this be what stress looks like? • Normal thoughts Dark thoughts

  15. Comic thoughts…

  16. Assignment 3.23 • Reflexes and the reflex arc – terms 142-143 • Learning Target #5 (Nervous System) p 135: Describe the structure of a reflex arc and the function of a reflex

  17. Protection of CNS • Bone, meninges & blood-brain barrier • Bone: skull & hollow vertebrae • Meninges: CNS enclosed by 3 membranous layers • Out  In • Dura matter – arachnoid matter – pia matter

  18. Figure 11.14ab

  19. CNF (cerebrospinal fluid) CNS is bathed in cerebrospinal fluid • Fills the space between the arachnoid matter & pia matter • Functions as a liquid shock absorber • Isolates the CNS from infection (meningitis: bacterial or viral infection of meninges can spread to CNS)

  20. More about CSF • CSF is like the interstitial fluid that bathes all cells but it does not exchange substances as freely with blood • Capillaries in this area are “tight” = not leaky & substances must pass through the actual capillary cells (vs. slipping between narrow slits of adjacent capillary cells) to get from blood to the brain

  21. Blood-brain barrier • Lipid soluble substances pass easily (O & CO2) • Glucose requires active transport • Larger molecules: proteins, viruses, bacteria kept out • What can pass through BBB? • Alcohol • Caffeine • Nicotine • Cocaine • Anesthetics

  22. Spinal cord • Information super highway for APs between the brain and the body • Recall – spinal reflexes don’t involve brain and therefore are considered “unconscious” • Size – about the diameter of your thumb • Location – runs from the base of your skull to the area of the 2nd lumbar vertebra ~ 17 inches

  23. Figure 11.13b

  24. Figure 11.10

  25. Inside the spine • Outer portions of the cord consist of bundles of axons = nerve tracts that are mylenated = white matter – ascending sensory nerves & descending motor nerves • Inner portions consist of cell bodies, dendrites, neuroglial cells that are unmylenated = gray matter – here sensory & motor neurons synapse & transmit to the brain…

  26. Figure 11.14

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