ORGANIZATION OF THE NERVOUS SYSTEM

1. ORGANIZATION OF THE NERVOUS SYSTEM

2. FUNCTIONS • SENSORY • MOTOR • COGNITIVE

3. ANATOMICAL ORGANIZATION of the NERVOUS SYSTEM

4. Central Nervous System (CNS) • Unpaired, bilaterally symmetrical structures extending along the longitudinal axis of the midsagittal plane of the body. • Structures arising directly from the neural tube. • Includes: Brain Spinal cord

5. Peripheral Nervous System • (PNS) • Made up of transmission pathways carrying information between the CNS and external/internal environments. • Afferent (sensory) pathways: Carry information to the CNS. • Efferent (motor) pathways: Carry information from the CNS.

6. Peripheral Nervous System • Includes: Cranial nerves (12 pairs) Spinal nerves (31 pairs) • Also includes sensory receptors in skin and wall of gut tube as well as in tendons and skeletal muscles. • Also includes motor end plates between motor neurons and skeletal muscle fibers.

7. Autonomic Nervous System • May be considered a subdivision of the PNS. • Entirely motor. • Innervates smooth muscle and glands (viscera)

8. ANS Subdivisions • Sympathetic system (fight or flight) Also called thoracolumbar • Parasympathetic system (feed and breed) Also called craniosacral

10. Parts of a Neuron • Cell body: Trophic unit Perikaryon • Dendrites: Receptive unit • Axon: Conductive unit

12. Cell Body • That part of a neuron that encloses the nucleus and other organelles necessary to maintain and repair neuron.

13. Cell Body Organelles • Nucleus • Golgi apparatus • RER Ribosomes =Nissl substance

15. Dendrites • Branches off the cell body that carry information to the cell body. • Usually several to many. • Relatively short. • Often branched. • Have receptors for neurotransmitters. • Conduct local potentials.

16. Axon • That part of the neuron that carries information to another neuron or muscle cell. • Usually relatively long. • Single. • Conducts action potential (nerve impulse)

17. Axon • Ends in short branched processes called: Telodendria: Give off endings called terminal boutons. Terminal boutons contain synaptic vesicles of neurotransmitters. • May have collateral branches.

19. Axon • Cell membrane is called the axolemma. • Cytoplasm is called the axoplasm.

20. Axon • Contains: Mitochondria Neurofilaments Neurotubules

21. Axonal Transport • Anterograde • Retrograde • Slow transport • Fast transport

22. Axon • Covered by neurolemma: Made up of Schwann cells. • Often myelinated: Myelin is formed by Schwann cells. • Note: axon is only part of neuron that is ever myelinated.

23. General Terminology • Nucleus: Aggregation of dendrites and nerve cell bodies in the CNS. • Ganglion: Aggregation of dendrites and nerve cell bodies in the PNS.

24. General Terminology • Nerve: Bundle of fibers (axons) in the PNS. • Tract: Bundle of fibers (axons) in the CNS. • Commissure: Tract in the CNS that crosses from one side to the other.

25. General Terminology • White matter: Areas of myelinated axons. • Gray matter: Areas of unmyelinated axons, cell bodies, and dendrites.

26. Functions of the CNS • Refer to p. 63 in syllabus

27. Spinal Nerve Branches • Dorsal primary ramus • Ventral primary ramus • Ramus recurrens • White ramus communicans • Gray ramus communicans

28. Spinal Nerve Branches • Paravertebral ganglion • Splanchnic nerve • Prevertebral ganglion

29. Reflex Arc • Afferent (sensory) pathways: Somatic. Visceral (splanchnic). • Efferent (motor) pathways: Somatic. Visceral (splanchnic). • Association neurons (interneurons).

30. Synapse • Components: Presynaptic membrane: With synaptic vesicles filled with neurotransmitters. Synaptic cleft: Postsynaptic membrane: With receptors for neurotransmitters. • Monosynaptic pathways. • Polysynaptic pathways.