2. The Nervous System Introduction, Spinal Cord, and Spinal Nerves
Chapter 10
The Nervous System
Introduction, Spinal Cord, and Spinal Nerves

3. Introduction Control center and communication network
Directs functions of body’s organs and systems
Interprets external environment
Determines reaction to change

4. Introduction (cont’d.)
Homeostasis: balanced internal environment
Controlled by nervous and endocrine systems

5. Organization

6. Organization (cont’d.)
Central nervous system: brain and spinal cord
Peripheral nervous system
Afferent peripheral system
Sensory neurons
Efferent peripheral system
Somatic
Autonomic: sympathetic and parasympathetic

7. Organization (cont’d.)

8. Classification of Nerve Cells

9. Neuroglia Cells Astrocytes: support, connection, blood-brain barrier
Oligodendroglia: support, myelin sheath formation
Microglial: phagocytosis
Ependymal: line the ventricles of the brain
Schwann: myelin sheaths in peripheral nervous system

10. The Structure of a Neuron
Cell body
Dendrites: receptive areas
Axon: extension of cell body
Schwann cells
Nodes of Ranvier

11. The Structure of a Neuron (cont’d.)
Needs Fig 10-2

12. The Structure of a Neuron (cont’d.)
Multipolar: several dendrites coming off cell body
Bipolar: one dendrite and one axon
Unipolar: one process extending from cell body

13. The Structure of a Neuron (cont’d.)
Receptors: detect environmental stimuli
Sensory: receive impulse from receptor site
Internuncial: transmit impulse for interpretation and processing
Motor: reaction to the stimulus

14. The Physiology of the Nerve Impulse

15. The Physiology of the Nerve Impulse (cont’d.)
Nerve cell fiber resting potential
Na+ concentration higher on outside
K+ concentration higher on inside
Negative charge on inside
Positive charge on outside

16. The Physiology of the Nerve Impulse (cont’d.)
Depolarization: Na+ rush inside cell
Repolarization: K+ rush out to restore balance
Depolarization: Repolarization moves in one direction
Myelinated vs. unmyelinated
All-or-none law

17. The Synaptic Transmission

18. The Synaptic Transmission (cont’d.)
Synapse: axon terminal branches close to next dendrites
Impulse reaches axon terminals
Triggers neurotransmitter release into synaptic cleft

19. The Synaptic Transmission (cont’d.)
Neurotransmitters
Acetylcholine
Most common
Epinephrine
Norepinephrine
Serotonin
Dopamine
Endorphins

20. The Synaptic Transmission (cont’d.)

21. The Reflex Arc

22. The Reflex Arc (cont’d.)
Knee-jerk reflex
Maintain homeostasis
Heartbeat/breathing rates
Digestion
Coughing
Sneezing
Swallowing
Vomiting

23. The Reflex Arc (cont’d.)
Involuntary reaction to external stimulus

24. Grouping of Neural Tissue

25. Grouping of Neural Tissue (cont’d.)
White matter
Groups of myelinated axons
Forms nerve tracts in CNS
Gray matter
Nerve cell bodies and dendrites
Unmyelinated axon bundles
Cortex: gray matter on surface of brain

26. Grouping of Neural Tissue (cont’d.)
Nerve: bundle of fibers outside CNS
Ganglia: nerve cell bodies outside CNS
Tract: bundle of fibers inside CNS
Nucleus: nerve cell bodies and dendrites inside CNS
Horns: areas of gray matter in spinal cord

27. The Spinal Cord

28. Introduction Continuation of medulla oblongata
31 segments each with a pair of spinal nerves
Protected by meninges
Dura mater
Arachnoid
Pia mater

30. Functions of the Spinal Cord
Conveys sensory impulses to the brain
Integrates reflexes
Spinal nerves connect at roots
Dorsal root: sensory
Ventral root: motor

31. The Spinal Nerves

32. The Spinal Nerves (cont’d.)
All 31 pairs arise from union of dorsal and ventral roots
Mixed nerves consisting of motor and sensory fibers
Most exit vertebral column between vertebrae

33. The Spinal Nerves (cont’d.)
Named and numbered according to region and level of spinal cord
Cervical: 8 pairs
Thoracic: 12 pairs
Lumbar: 5 pairs
Sacral: 5 pairs
Coccygeal: 1 pair

34. Summary Named the major division of the nervous system
Classified neurons and neuroglial cells
Discussed the physiology of the nerve impulse and transmission at synapses
Named the different types of neural tissue
Discussed the structure of the spinal cord
Named the spinal nerves