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Understanding Nervous Tissue and Spinal Cord Divisions

Explore the central and peripheral nervous systems, the functions of sensory and motor neurons, neuron classification, neuroglia roles, synapses, myelin function, spinal cord organization, plexuses, and reflexes. Delve into neuron organelles and the intricacies of neural circuits.

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Understanding Nervous Tissue and Spinal Cord Divisions

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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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