1. NERVOUS SYSTEM Lecture 1 OVERVIEWandNEUROHISTOLOGY

2. ANATOMICAL ORGANIZATION of the NERVOUS SYSTEM Nervous System CNS BRAIN SPINAL CORD PNS CRANIAL NERVES SPINAL NERVES ANS SYMPATHETIC PARA- SYMPATHETIC

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

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

5. Peripheral Nervous System (PNS) Includes: Includes: Cranial nerves (12 pairs). Spinal nerves (31 pairs).

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

7. ANS Subdivisions Sympathetic system (fight or flight): Sympathetic system (fight or flight): Also called thoracolumbar. Parasympathetic system (feed or breed): Parasympathetic system (feed or breed): Also called craniosacral.

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

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

10. Cell Body Organelles Nucleus Nucleus Golgi apparatus Golgi apparatus RER RER Ribosomes (=Nissl substance)

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

12. Axon Characteristics Carries information to another neuron or muscle cell. Carries information to another neuron or muscle cell. Often relatively long. Often relatively long. Single (one per neuron). Single (one per neuron). Conducts action potential Conducts action potential

13. Axon Characteristics Ends in short branched processes called telodendria. Ends in short branched processes called telodendria. May have collateral branches. May have collateral branches. Cell membrane (= axolemma). Cell membrane (= axolemma). Cytoplasm = (axoplasm). Cytoplasm = (axoplasm).

14. Axon Characteristics Covered by neurolemma: Covered by neurolemma: Made up of Schwann cells. Often myelinated: Often myelinated: Myelin is formed by Schwann cells. Note: axon is the only part of a neuron that is ever myelinated. Note: axon is the only part of a neuron that is ever myelinated.

15. Axon Organelles Mitochondria Mitochondria Neurofilaments Neurofilaments Neurotubules Neurotubules

16. Axonal Transport Anterograde: Anterograde: Transports vesicles from cell body to end of axon. Kinesin Retrograde: Retrograde: Transports vesicles from end of axon toward cell body. Cytoplasmic dynein

17. Axonal Transport Slow transport: Slow transport: 1-5 mm/day Fast transport: Fast transport: 200-400 mm/day

18. General Terminology Nerve: Nerve: Bundle of fibers in the PNS. Tract: Tract: Bundle of fibers in the CNS. Commissure: Commissure: Tract in the CNS that crosses from one side to the other.

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

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

21. Synapse Definition: Definition: Composite structure that allows two neurons or a neuron and a muscle cell to “talk” to each other. Composite structure that allows two neurons or a neuron and a muscle cell to “talk” to each other.

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

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

24. Neuroglial Cells Schwann cells Schwann cells Astrocytes Astrocytes Microglial cells Microglial cells Oligodendrocytes Oligodendrocytes Ependymal cells Ependymal cells

25. Schwann Cells Derived from neural crest cells. Derived from neural crest cells. Myelinate axons in the PNS. Myelinate axons in the PNS.

26. Astrocytes Derived from neural crest cells. Derived from neural crest cells. Function to physically support neurons. Function to physically support neurons. Channel materials between capillaries and neurons (= Blood-brain barrier). Channel materials between capillaries and neurons (= Blood-brain barrier). Support and guide neurons during embryonic building of cerebral cortex. Support and guide neurons during embryonic building of cerebral cortex. Act as sinks for ions (i.e., K + ). Act as sinks for ions (i.e., K + ). Remove neuroactive and potentially toxic substances. Remove neuroactive and potentially toxic substances.

27. Microglial Cells Derived from embryonic mesenchyme. Derived from embryonic mesenchyme. May transform into phagocytes within CNS. May transform into phagocytes within CNS.

28. Oligodendrocytes Derived from neural crest cells. Derived from neural crest cells. Function to myelinate axons within CNS. Function to myelinate axons within CNS.

29. Ependymal cells Derived from neural crest cells. Derived from neural crest cells. Line ventricles of brain. Line ventricles of brain.