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Nervous System

Learn about the components and functions of the central and peripheral nervous systems, including the role of neurotransmitters, reflex arcs, and the protection of the CNS. Explore how the CNS integrates and processes information, and the crucial functions of the spinal cord. Understand the structure of reflex arcs and the barrier mechanisms safeguarding the CNS.

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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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