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Chapter 16: Spinal Cord and Spinal Nerves
Spinal Cord and Spinal Nerves
15
Anatomy
Undergraduate 1
11/09/2011

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Term
2 Functions of Spinal Cord
Definition

1) pathway for sensory and motor impulses

2) cord and nerves responsible for reflexes (quickest reactions to stimuli)

Term
Why is the spinal cord shorter than the vertebral canal?
Definition
Because the growth of the vertebrae continues longer than the growth of the spinal cord
Term
Name the Spinal Cord nerves
Definition

31 total

8 Cervical C1-C8

12 Thoracic T1-T12

5 Lumbar L1-L5

5 Sacral S1-S5

1 Coccygeal Co

Term
Define Ipsolateral
Definition

When the receptor and effector organ of the reflex are on the same side of the spinal cord

Ex. left arm contracts to pull left hand away from stove

Term
Define Contralateral
Definition

When the sensory impuses from a receptor organ cross over through the spinal cord to activate effector organs in the opposite limb

Ex. step on sharp object with left foot and contract right leg muscle to maintain balance.

Term
Define reflex
Definition
rapid, automatic involuntary reaction of muslces or glands to a stimulus
Term
Reflex Arc
Definition
neural wiring of a single reflex. Begins with receptors in PNS, communicates with CNS and ends at a peripheral effector (muscle or gland cell)
Term
Monosynaptic reflex
Definition
Sensory axons synapse directly on motor neurons whose axons project to the effector.
Term
Polysynaptic
Definition

more complex pathways that exhibit a number of synapses involving interneurons within the reflex arc.

Ex. withdraw your foot from painful stimulus, contraction of extensor muscles in limb enables you to maintain balance. 

Term
What are the nerve plexuses
Definition
network of interweaving anterior rami of spinal nerves. Brain, cervical, lumbar, and sacral
Term
What is the cervical plexus
Definition
innervates head, neck, and shoulder
Phrenic nerve - travels through thoracic cavity to innervate diaphragm.
Term
What is the Sacral plexus
Definition
Innvervates gluteal region, pelvis, posterior thigh and leg and foot. houses sciatic nerve - largest and longest nerve in the body.
Term
What is a reflex
Definition
rapid, automatic involuntary reactions of muscles or glands to stimulus. 2 types monosynaptic and polysynaptic
Term
What is a monosynaptic reflex
Definition
sensory axon synapse directly on motor neuron whose axon projects to effector. No interneuron
Term
What is a polysynaptic reflex
Definition
more complex pathways that exhibit a number of synpases involving interneurons within the reflex arc.
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