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Chapter 12, 13

Chapter 12, 13. Nervous Tissue, Spinal Cord. Divisions of NS. CNS-central nervous system Brain Spinal Cord PNS-peripheral nervous system- primarily nerves of body A. Spinal nerves- 31 pairs B. Cranial nerves- 12 pairs. Divisions of PNS. a. Somatic- controls skeletal muscle, skin

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Chapter 12, 13

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  1. Chapter 12, 13 Nervous Tissue, Spinal Cord

  2. Divisions of NS • CNS-central nervous system • Brain • Spinal Cord • PNS-peripheral nervous system- primarily nerves of body A. Spinal nerves- 31 pairs B. Cranial nerves- 12 pairs

  3. Divisions of PNS a. Somatic- controls skeletal muscle, skin b. Autonomic-controls smooth, cardiac muscle 1. Sympathetic- fight/flight, emergencies 2. Parasympathetic-relaxation, “vegetative” reflexes

  4. 3 Basic Functions • Sensory (afferent) Receptors send impulses to CNS • Motor (efferent) CNS sends impulses to effectors (muscles or glands) 3. Integrated Functions- intelligence, creativity, personality, etc.

  5. Organelles in a neuron • Nucleus • Granular ER(Nissl bodies) • Mitochondria • Neurofibrils(microtubules) • No centrioles -

  6. Classification of Neurons • P365 • Anaxonic- located in brain, special sense organs • Bipolar-special sense organs • Unipolar-sensory neurons of PNS • Multipolar- most common

  7. Neuroglia 2. Neuroglia in PNS A. Satellite Cells- similar to astrocytes B. Schwann Cells- similar to oligodenedrocytes, produce myelin sheath in PNS

  8. Neuroglia 1.Neuroglia in CNS A. Astrocyte- function in creating blood-brain barrier, provide structure B. Oligodendocyte- produce myelin sheath C. Microglia- immune cells of CNS, similar to macrophages D. Ependymal- found in ventricles of brain, produce cerebrospinal fluid

  9. Synapse • A specialized site where neurons communicate with one another • http://faculty.washington.edu/chudler/synapse.html

  10. Myelin • Acts like electrical insulation • Nodes of ranvier-gaps between schwann cells on axon; allows nerve impulse to jump between nodes; leads to high conduction speeds= 100m/s • Locations- A. All motor neurons B. All spinal nerves C. 99% of brain

  11. Unmyelinated • Slow conductions speed, .5 m/s • Located A. In autonomic nervous system

  12. Length= 18”, width=.5” Extends from base(foramen magnum) of skull to 2nd lumbar vertebra “carrot shaped” Ends @ conus medullaris- many nerves exit and form cauda equina 2 enlargements=cervical and lumbar- where more nerves enter and leave the cord Spinal Cord- Chapter 13

  13. # of spinal nerves-31 • Cervical- 8 • Thoracic-12 • Lumbar-6 • Sacral-5

  14. Organization • White matter- myelinated sections on outermost parts • can be ascending- going to brain -carry sensory info -called afferent • Can be descending- coming from brain - carry motor info - called efferent

  15. Root- where nerve enters or exits cord dorsal root=sensory/afferent ventral root= motor/efferent ** In back door out front door**

  16. Organization • Gray matter- unmyelinated sections forming H pattern in the interior • posterior horns- contain afferent neurons • anterior horns- contain efferent neurons • “cross bar”=commissure

  17. Plexuses • Plexus- interwoven network of nerves • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus

  18. Reflexes • Rapid automatic response to a specific stimuli • Work through a reflex arc- a simple neural pathway • reception • transmission via sensory neuron • integration • transmission via motor neuron • response

  19. Classifying Reflexes p 424 • By response A. Somatic reflex- involves skin, skeletal muscle, function in protection • Visceral reflex- involves cardiac, smooth muscle, glands, bl.v, function in homeostasis

  20. By development A. Innate- w/drwal fr. pain, suckling, tracking objects w/ eye B. Acquired- driving, sports

  21. 3. By processing site • Spinal- patellar reflex • Cranial- sudden noise, bright light, respiration 4.Complexity of circuit • Monosynaptic- • Polysynaptic

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