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41 Cards in this Set

  • Front
  • Back
What makes up the nervous system?
1) central nervous system

2) peripheral nervous system
central nervous system (CNS)
consisting of the brain and spinal cord,
peripheral nervous system (PNS)
made up of peripheral nerves (spinal and cranial nerves). Peripheral nerves extend away from the spinal cord or brain to the rest of the body (periphery). The slide shows the nerves supplying the body wall and limbs. Note the high concentration of nerves going to the upper and lower limbs.
The brain and spinal cord are enclosed in what?
The brain and spinal cord are enclosed in bones forming the skull and vertebral column. Note the cervical and lumbosacral enlargements of the spinal cord. These contain nerve cell bodies for motor nerve fibers going to the limbs.
What what is the name of the nerves and vertabrae called and how many are there of each
There are 31 pairs of spinal nerves, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal
Relation of spinal nerves to vertebral levels: Cervical Region
1)Spinal nerve emerges above its correspondingly-numbered vertebra

-C8 emerges above vertebra T1
Thoracic, lumbar, sacral, and coccygeal regions: Relation of spinal nerves to vertebral levels
Spinal nerve emerges below its correspondingly-numbered vertebra
Gray matter
contains cell bodies of neurons
White matter
contains nerve processes carrying information to and from the brain; most of these processes run vertically in the anatomical position (standing up) and their cross-sections look like small circles in a cross-section of the spinal cord.
White matter
contains nerve processes carrying information to and from the brain; most of these processes run vertically in the anatomical position (standing up) and their cross-sections look like small circles in a cross-section of the spinal cord.
what are the different types of peripheral nervous system?
motor and sensory nerves
motor neuron
the cell body has many short dendrites and one long axon that goes peripherally to a muscle
sensory neuron
is pseudounipolar; the cell body is located at the side of its process. One end of the process goes peripherally to the area being sensed. The other end of the same process goes centrally to the spinal cord, where it may synapse locally or go all the way to the brain. Individual processes are too small to be seen without a microscope.
What does the Ventral roots arise from
roots arise from the ventral horn and dorsal roots arise from the dorsal horn.
dorsal root ganglion
is a bulge found on the dorsal root that contains the cell bodies for sensory neurons.
What nerves form the spinal nerves
Dorsal and ventral roots are grouped together to form spinal nerves.
What is the spinal nerve divided into
into dorsal and ventral primary rami
What layer protects the spinal chord?
Within the vertebral column, several protective layers called the meninges surround the spinal cord
What are the different layers of the meninges
1)dura mater- outer layer(tough)

2) arachnoid- Just inside the dura is the arachnoid (spider-web), a thinner layer

3) sub-arachnoid space: The space deep to the arachnoid is the sub-arachnoid space, which contains cerebrospinal fluid (CSF).

4)pia: is the pia, a thin transparent layer tightly applied to the spinal cord; it makes the surface of the spinal cord look shiny. The pia also tightly covers the nerve rootlets and roots.

*these layers surround the brain too.
intervertebral foramen
The spinal nerve leaves the vertebral column via a gap between adjacent vertebrae called an intervertebral foramen. This is important because damage to the disc separating two vertebrae can lead to pinching of the nerve and neurological symptoms. This is especially likely at L4-L5, L5-S1, or C-7-C8, C8-T1.
Function of Motor nerves
Motor nerves go to skeletal muscles and control contraction of these muscles. Motor nerves are also called efferent nerves (e = away): they carry information outward (away from the spinal cord) to the periphery
What must the muscles be integrated with in order to work correctly?
1)In order to work correctly, muscles must be innervated by a motor nerve, but also have sensory feedback as to their position and strength of contraction. Part of this sensory input comes from muscle spindles. These are microscopic, so you won’t see them on dissection, but you should realize they are present and that a nerve to a muscle contains sensory as well as motor fibers.

2)Sensory nerves supplying the muscle spindles send back information as to strength of contraction and rate of movement of the muscle. Sensory nerves are afferent (a = toward, think affection); they carry information inward toward the spinal cord.
What nerves allow skin to seen touch, temp and pressure
1)Additional sensory nerve endings are found in the skin, where they sense touch, temperature and pressure.

2) Sensory nerves with these endings are found in nerves going to the skin, which are called cutaneous nerves.

3) Note that skin does not have skeletal muscle fibers, so cutaneous nerves don’t have motor fibers in them.

4) Skin does have smooth muscle fibers, however; these are supplied by sympathetic nerves.
cutaneous nerves
Sensory nerves with these endings are found in nerves going to the skin
Describe
This diagram of a cross section through the spinal cord shows the nerve roots covered by pia and lying in the subarachnoid space. The nerve roots are bundles of individual nerve fibers. The cell bodies of motor and sensory fibers are in different locations
What are the locations of the cell bodies of motor and sensory fibers are in different location?
A. The cell bodies of sensory nerve fibers are located in the dorsal root ganglion.
1. From the cell body one portion of a nerve fiber goes centrally through the dorsal root and into the dorsal horn of the spinal cord.
2. Another part of the nerve fiber goes peripherally through the spinal nerve and into a dorsal or ventral primary ramus.
3. The complete fiber brings sensory information from the periphery into the spinal cord.

B. Cell bodies of motor nerves are located in the ventral horn of the spinal cord itself. A motor nerve fiber goes laterally through the ventral root and spinal nerve, then into a dorsal or ventral primary ramus.
somites
1)During embryonic development, a series of somites forms

2)They are a regular progression of segments that contain forerunners of nerves, muscles, and skin

3) A nerve associated with a particular somite will continue to supply muscles and skin derived from that somite, thus innervation is segmental.
What happens to the nerve fibers when skin or muscles migrate out onto a limb?
1)A portion of skin or muscle that migrates, e.g. out onto a limb, will keep the nerve supply of its place of origin; the nerve just grows longer.

2)An interesting example is the diaphragm. It originally formed just underneath the chin and keeps its nerve supply from C3, 4, and 5 as it migrates to its position between thorax and abdomen.
dermatome
defined as that area of skin innervated by branches of the two spinal nerves (left and right) found at one vertebral level; this includes branches of both dorsal and ventral primary rami.
A diagram of dermatomes
Note how certain dermatomes are drawn out onto the limbs, and that the limbs have axial lines, where adjacent skin is supplied by nerves that are not from adjacent vertebral levels. Loss of sensation in a nerve on one side of an axial line will be much more apparent, because there is little or no overlap in innervation between the regions. Branches of dorsal primary rami only supply skin in a narrow strip down the back and the true back muscles that lie deep to this area of skin (darker colored in slide).
The somatic nervous system
controls skeletal muscles of the body wall and limbs, the “outside”. The parasympathetic system controls smooth muscles in the walls of the viscera, “inside”. For the G.I. tract, this control is via the enteric nervous system. The sympathetic system controls smooth muscle of blood vessels in both the body wall and in the viscera. There is no parasympathetic supply to the body wall or the limbs. Both the sympathetic and parasympathetic systems act on the heart.
. Sympathetic fibers
supply the hair erecting muscles and glands in the skin, but this is much less important than controlling smooth muscle tone in the walls of blood vessels, since that in turn controls blood flow through the vessels.
Sympathetic vs Parasympathetic
all spinal nerves exit where?
the the spinal nerve exits below the vertebra with the same number, e.g. spinal nerve T1 exits below vertebra T1 and so on down.

Exeception: Nerve C1 exits the vertebral canal between the atlas and the occipital bone of the skull. Therefore, spinal nerve C1 exits above C1 vertebra. This continues down the cervical region. Spinal nerve C7 exits above vertebra C7
Where does the spinal cord (nerve) end at?
The spinal cord ends at L2; the tapering portion is the conus medullaris.
conus medullaris
the tepering portion at the end of the spinal nerve
cauda equina
nerve roots leave the spinal cord (looks like a horse’s tail
Dorsal roots contain only what fibers
sensory fibers
ventral roots contain only what fibers
motor fibers
spinal nerves and primary rami contain what fibers
sensory and motor fibers
The motor portion is made up of how many motor neurons?
1)sympathetic system is a chain of two motor neurons.

2)The cell body of the first neuron lies in the lateral horn of the spinal cord; its axon leaves the spinal cord between levels T1 and L2. The axon travels within a ventral root, spinal nerve and ventral primary ramus to a white ramus communicans.
-White rami communicantes are found only where the first axons leave the spinal cord, between T1 and L2
- axon travels in white ramus communicans to a sympathetic ganglion and synapses with a second motor neuron.