The Nervous System

Introduction to the Nervous System

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The Nervous System
Made up of two components the
Central Nervous System- the brain and the spinal cord.
Peripheral Nervous System which is made up of
i. Afferent nerves (Sensory)- carry signals to the
CNS.
ii. Efferent nerves (motor) carry signals away from
the CNS.
I. Somatic Nervous System (voluntary)- for voluntary control of skeletal muscle.
II. Autonomic Nervous System (in-voluntary)- regulates smooth and cardiac muscles and glands.
Cells of the Nervous System
Neurones- conduct electrical impulses, last a lifetime, are amiotic, have high metabolic rates, sensitive to O2 and
glucose levels.
Neuron Structure
Cell body- most are in the CNS, In the PNS cell
bodies cluster as ganglia.
Dendrites- receptive regions, carry impulse away
from the cell body.
Axon Terminals- found at the end on axone.
Supporting Cells
Astrocytes- in the CNS, regulate chemical environment and assist capillary exchange.
Microglia- in the CNS, have defense functions.
Ependymal Cells- in the CNS, help circulate cerebrospinal fluid.
Oligodendrocytes- in the CNS, form myelin sheaths around nerve fibres.
Satellite Cells- in the PNS, surround cell bodies in the ganglia.
Schwann Cells- in the PNS form myelin sheaths around nerve fibres. Gaps between schwann cells form the
Nodes of Ranvier.
Spinal Nerves
31 pairs, each nerve has a dorsal root and a ventral root. Each spinal nerve divides into three branches. The dorsal
ramus, ventral ramus and meningeal branch.
Cranial Nerves
12 pairs of cranial nerves related to structrues in the head:
Oldfactory-smell
Optic-vision
Ocularmotor-vision
Trochlear-eye movement
Trigeminal-sensory nerves of the face
Abductens-eye movement
Facial-facial movement
Vestibulocochlear-hearing and balance

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Glossopharyngeal- tongue and pharynx
Vagus- lungs and abdominal organs
Accessory-movement of the head and neck
Hypoglossal-tongue
Reflex Arc
Receptor- A
Sensory Neuron-B
Intergration Centre-C
Motor Neuron- D
Effector- E
Neuron Classification
I. Unipolar- one process extending from the cell body.
II. Bi-polar- axon and dendrite extend from opposite sides of the cell body.
III. Multi-polar- have three or more processes extending from the cell body.
Words and Meanings
I. Somatic Nervous System- voluntary nervous system, a division of the PNS: innervates skeletal muscle.
II.…read more

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