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35 Cards in this Set

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What are the main two ways to describe the nervous system?
1.Structural standpoint - Central/peripheral nervous systems
2.Functional standpoint - Somatic/visceral nervous systems
Describe the structural standpoint.
Central Nervous System - brain and spinal cord (both continuous with the foramen magnum at the base of the skull)
Peripheral Nervous System - 12 pairs of cranial nerves that exit the cranium, 31 pairs of spinal nerves that exit the spinal cord
Describe the functional standpoint.
Somatic nervous system - part of the nervous system that controls and supplies the body (other than the internal organs)
Visceral nervous system - nervous system that supplies the internal organs

Both nervous systems have a sensory and motor component.
What are neurons? What are the parts?
Structural and functional unit of the nervous system.

Parts are:
1.Body/soma - part of the cell with the nucleus in it
2.Dendrites - branch processes that stand off the cell body and conduct a nerve impulse toward the cell body
3.Single axon - part that leaves the cell body that conducts an impulse away from cell body (distally the axon will branch)
What is a synapse? What is the most common kind?
Junction where one neuron ends on another neuron.

Chemical synapse - presynaptic neuron releases a chemical neurotransmitter into the synaptic cleft which binds to receptor on post-synaptic neuron (inducing or prohibiting a response)
What is myelin sheath?
lipoprotein substance that surrounds the axon (imparts a whitish color to it) and increases conduction velocity of the axon
What is the conus medullaris?
Inferior end of the spinal cord that has a conical shape and it terminates between L1 and L2 vertebrae in adults.
Why is the spinal cord the whole length of the vertebral column initially and not so in adults?
During development the cord does not keep up its growth. There is a progressive shortening.
Where does the cord end at birth?
Around L3?
How many pairs of spinal nerves are there?
31 pairs
8 Cervical (although there are only 7 cervical vertebrae)
12 thoracic
5 lumbar nerves
5 sacral nerves
1 Coccygeal nerve
What is a spinal cord segment?
Area of the spinal cord where the nerves are attached
Compare the cervical nerves location to the rest of the spinal nerves.
First 7 cervical nerves emerge above (superior) to the respective vertebrae. 8th cervical nerve emerge between C7-T1 vertebrae. All other spinal nerves emerge below the respective vertebrae.
What is the Cauda Equina?
Leash-like bundles of nerve fibers that are formed from spinal nerve roots from the lumbosacral enlargement and medullary cone.
What is the internal filum terminale?
Delicate filament of non-nervous tissue made of pia mater that descends among the spinal nerve roots of the cauda equina
What is the purpose of the internal filum terminale?
It serves as an anchor for the end of the dural sac. It takes on layers of arachnoid and dura mater as it penetrates the inferior end of the dural sac to pass thru the sacral hiatus and attach to the coccyx.
What are the two enlargements of the spinal cord and why are they enlarge?
1.Cervical enlargement at spinal cord segments C4-T1
2.Lumbral-sacral enlargement at spinal cord segments L2-S3

These are areas where spinal nerves innervating either upper or lower limbs are attached.
Compare/contrast the gray and white matter of the spinal cord.
Gray matter - 'H' shaped, made up of cell bodies

White matter - surround the gray matter, have myelinated axons that give off a whitish appearance, axons are either ascending to higher levels of the brain or descending from brain to lower levels of cord.
Discuss the horns of the gray matter.
Ventral (Anterior) horn - contains motor neurons that supply the skeletal muscle

Dorsal (posterior) horn - has sensory neurons that receive impulses from spinal nerves sensory information coming in
What is the lateral horn and at levels of the spinal cord does this additional horn appear?
Lateral horn - contains cell bodies of autonomic motor neurons tha supply involuntary structures (smooth muscle, cardiac muscle, glands)

The lateral horn only appears at T1-L2 spinal cord levels and only at thes levels.
How are the dorsal and ventral roots connected to the spinal cord?
They are connected to the spinal cord via rootlets that unite
What does the dorsal root have that the ventral root does not?
Dorsal root ganglion - swelling of collection of dorsal neurons outside the CNS.
Compare/contrast dorsal and ventral roots.
Dorsal roots - spinal nerves tha are sensory and are conveying sensory info into the spinal cord

Ventral roots - spinal nerves that are motor carrying impulses away from the spinal cord.
What is a spinal nerve proper?
Very short part where the dorsal and ventral roots unite. NOW YOU HAVE A MIXED SPINAL NERVE (SENSORY AND MOTOR)
What happens after the roots combine to form the spinal nerve proper?
Spinal nerve exits the intervertebral foramen and then divides into two branches of rami that are mixed just like the nerve (one dorsal ramus and one ventral ramus)
What is a ganglion?
Collection of neurons outside the central nervous system
What is unique about the ventral ramus of the spinal nerves of T1-L2?
The ventral ramus is connected to the sympathetic ganglion by a white and gray rami communicantes.

If above T1 or below L2, there would only be gray ramus (communicantes?)
What are rami communicantes?
Little connection branches that connect the ventral rami from T1-L2 with the sympathetic ganglion.
What are the two kinds of ganglia?
Sensory (dorsal) and autonomic (ventral) ganglia
Discuss the autonomic ganglia.
Motor ganglia (doesn't matter if sympathetic or para sympathetic - all are motor) where cell bodies conduct impulse away to either smooth muscle, cardiac muscle or glands.

All autonomic ganglia have a synapse because it takes two neurons to get from CNS to effector organ with synapse in the ganglia.

Note there is no synapse in the dorsal root ganglia.
What is seen in a typical thoracic spinal nerve?
Spinal cord, dorsal and ventral roots, dividing into dorsal and ventral rami
What do the dorsal/ventral rami supply?
Dorsal - deep muscles of the back and skin of the back

Ventral - runs along the body wall to supply the muscles there, the skin (laterally by a lateral cutaneous branch or anteriorly thru an anterior cutaneous branch)
What is a plexus and name a few?
Plexus - combination of certain spinal nerves

Brachial plexus - lower cervical nerves and upper thoracic nerves

Lumbar-sacral plexuses - where lumbar and sacral nerves combine
What scheme is used to determine the function of individual nerve fibers?
Determine if nerve fiber is...
1.afferent (sensory) or efferent (motor)
2.Somatic (outer part of body wall) or visceral (internal organs)
3.General (distribute to tissues/structures with wide distribution in body) or specific (restricted tissue not widely distributed)
How many possible components are there?
Seven,not eight, because the SSE (special somatic efferent) category does not exist
Compare occurrance of special/general component.
Special - occur in some cranial nerves

General - occur in most cranial nerves and in all spinal nerves