ANAT 215 Lecture Notes - Lecture 8: Cardiac Muscle, Dorsal Root Ganglion, Occipital Bone

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PERIPHERAL NERVOUS SYSTEM
(Reading material: Chapter 13: page 347-349; Chapter 14: pages 375-388; Chapter 16:
pages 436-446; Supplemental reading for interested students Chapter 15).
-Represents part of the nervous system outside of the CNS
-Consists mainly of nerves extending to/
-from the brain and spinal cord
-SPINAL NERVES: carry information to & from spinal cord
-CRANIAL NERVES: carry information to & from brain
There are two functional subdivisions
1. Sensory/ Afferent division
Afferent: carrying info towards the central nervous system
a) Somatic afferent: spinal nerves carrying information from skin, skeletal
muscles, and joints
b) Visceral afferent: spinal nerves carrying information from the organs with in
the ventral body cavity
2. Motor/ efferent division
Efferent: carrying info away from the CNS towards effector organs
Nerves carrying information away from the CNS towards effector target
organs – like muscles and glands
a) Somatic nervous system: nerves that conduct info from the CNS to our
skeletal muscles – voluntary- we consciously control the activity of our
skeletal muscles
b) Autonomic nervous system: division that regulates smooth muscle, cardiac
muscles and glands – “involuntary nervous system”
Spinal nerves
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How is a spinal nerve formed?
Each spinal nerve is formed by the combination of nerve fibers from the dorsal and
ventral roots of the spinal cord (Figure 0). The dorsal roots carry afferent sensory
axons, while the ventral roots carry efferent motor axons. The spinal nerve
emerges from the spinal column through an opening (intervertebral foramen)
(Figure 1) between adjacent vertebrae. This is true for all spinal nerves except for
the first spinal nerve pair, which emerges between the occipital bone and the atlas
(the first vertebra). Thus the cervical nerves are numbered by the vertebra below,
except C8, which exists below C7 and above T1. The thoracic, lumbar, and sacral
nerves are then numbered by the vertebra above. In the case of a lumbarized S1
vertebra (aka L6) or a sacralized L5 vertebra, the nerves are typically still counted
to L5 and the next nerve is S1.
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How is it formed?
˃31 pairs, each containing 10 000’s of nerve axons arise from the spinal cord
that supply all parts of the body except the head and few small areas of the
neck
˃Named according to point of issue from spinal cord
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