1. Fundamentals of the Nervous System and Nervous Tissue11
P A R T A
Fundamentals of the Nervous System and Nervous Tissue

2. Structural units of the nervous system
Neurons (Nerve Cells)
Structural units of the nervous system
Composed of a body, axon, and dendrites
Long-lived, _ _ _ _ _ _ _ _, and have a high metabolic rate
Their plasma membrane functions in:
Electrical signaling
amitotic
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3. Neuron Classification
Functional:
Sensory (afferent) — transmit impulses toward the CNS
Motor (efferent) — carry impulses away from the CNS
_ _ _ _ _ _ _ _ _ _ _ _ (association neurons) — shuttle signals through CNS
interneurons

4. Neuron Classification/Components Reflex Arc

5. Neurons (Nerve Cells)
Figure 11.4b

6. Contains an axon hillock – cone-shaped area from which axons arise
Nerve Cell Body (Soma)
Contains the nucleus
Contains an axon hillock – cone-shaped area from which axons arise
Concentrations of cell bodies termed _ _ _ _ _ _ in the CNS and _ _ _ _ _ _ _ in the PNS
Nuclei ganglia

7. Armlike extensions for signal conduction
Processes
Armlike extensions for signal conduction
Called _ _ _ _ _ _ in the CNS and _ _ _ _ _ _ in the PNS
There are two types: axons and dendrites
tracts nerves

8. Short, branched group of processes
Dendrites
Short, branched group of processes
They are the receptive, or _ _ _ _ _ regions of the neuron
Electrical signals here are conveyed as graded potentials (not action potentials)
input

9. Axons: Structure
Slender process of uniform diameter arising from the hillock
Usually there is only one axon per neuron
Axonal terminal – ending of an axon

10. Generate and transmit electrical signals (action potentials)
Axons: Function
Generate and transmit electrical signals (action potentials)
Secrete _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ from the terminals
neurotransmitters

11. Whitish, fatty, segmented sheath around most long axons
Myelin
Whitish, fatty, segmented sheath around most long axons
It functions to:
Protect the axon
Electrically insulate fibers from one another
Increase the _ _ _ _ _ of nerve impulse transmission
speed

12. Formed by Schwann cells in the PNS A Schwann cell:
Myelin Formation
Formed by Schwann cells in the PNS
A Schwann cell:
Envelopes an axon in a trough
Encloses the axon with its plasma membrane
Forms concentric layers that make up the myelin sheath (jelly roll)

13. Myelin Sheath: Formation
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Figure 11.5a–c

14. _ _ _ _ in the myelin sheath between adjacent Schwann cells
Nodes of Ranvier
_ _ _ _ in the myelin sheath between adjacent Schwann cells
Ion gates are concentrated here (important in development of action potential)
gaps
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15. Conduction Velocities of Axons
Conduction velocities vary widely among neurons
Rate of impulse propagation is determined by:
Axon diameter – the larger the diameter, the faster the impulse
Presence of a myelin sheath – myelination dramatically increases impulse speed (saltatory conduction)
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16. Saltatory Conduction
Electrical current passes through a myelinated axon only at the nodes of Ranvier
Voltage-gated Na+ channels are concentrated at these nodes
Action potentials are triggered only at the nodes and jump from one node to the next
Much faster than conduction along unmyelinated axons

17. Saltatory Conduction
Figure 11.16

18. Regions of the Brain and Spinal Cord
White matter – dense collections of myelinated fibers
Gray matter – mostly cell bodies and unmyelinated fibers
BRAIN SPINAL CORD

19. Pathology: Multiple Sclerosis (MS)
An autoimmune disease that mainly affects young adults
Symptoms: visual disturbances (blindness), weakness, and loss of muscular control (paralysis)
Myelin sheaths in the CNS become nonfunctional due to hardened lesions (scleroses)
Shunting and short-circuiting of nerve impulses occurs

20. Pathology: Adrenoleukodystrophy (ALD)
An X-Linked genetic disorder that affects males
Myelin sheaths in the CNS are degraded due to build-up of VLCFAs
Progressive disease leading to coma and death