Anatomy and Physiology Outline

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Spinal Cord, Spinal Nerves, Somatic Reflexes-Chapter 13

Reflexes- they are involuntary stereotyped responses to stimuli, they involve the brain, spinal cord, and peripheral nerves

Spinal cord- cylinder nervous tissue that begins at the foramen magnum and passes through the vertebral canal as far as the inferior margin of the first lumbar vertebrae (L1), 18 inches long and ½ inches wide

Anterior Median Fissure- in the front, deeper

Posterior Median Sulcus- in the back, shallow

▪Two Enlargements for Limbs: (up and down below)

1. Cervical Enlargement- in the inferior cervical region, the spinal cord gives rise to the nerves of the upper limbs, up

2. Lumbar Enlargement- in the lumbosacral region there are nerves to the pelvic region and lower limbs arise, below

Medullary Cone- the spinal cord becomes more tapered

▪Meninges- the spinal cord and brain are enclosed in three fibrous membranes, specialized membranes that surround the spinal cord

A. shock absorption

B. physical stability

C. blood vessels that branch within these layers to provide oxygen and nutrients

1. Dura Mater- outer most layer, forms a loose fitting sleeve called the dural sheath around the spinal cord, though and fiborous, it will fuse with the periosteum of the occipital bone around the formamus magnum

Coccygeal Ligament- inferiorly the dura mater will blend with the filum terminal, longitudinal support

-horizontally there is stability by fusing with connective tissue of the spinal nerve such that the dura mater will extend out of the IVF

Epidural Space- the space between the sheath and the vertebrae bone, the space between the dura and the wall of the vertebral canal, it has loose connective tissue, blood vessels and adipose tissue

2. Arachnoid Mater- adheres to the dural sheath, it consists of a simple squamous epithelium, the arachnoid membrane

Subarchnoid Space- a loose mesh of collagenous and elastic fibers spanning the gap between the arachnoid membrane and the pia mater, it's filled with cerebrospinal fluid (CSF), a clear liquid

Pia Mater- inner most; a delicate, translucent membrane that closely follows the contours of the spinal cord

Filum Terminal- this continues beyond the medullary cone and is a fibrous strand

3. Cauda Equina- surrounded by CSF, the lumbar enlargement and medullary cone give rise to a bundle of nerve roots that occupy the canal of the vertebrae L2 to S5 (segments), it has a resemblance to a horse tail and it innervates the pelvic organs and lower limbs, region inferior to the L1 and L2, consists of dorsal and ventral roots

-31 pairs of spinal nerves

-8 cervical nerves (C1-C8)

-12 thoracic (T1-T12)

-5 lumbar (L1-L5)

-5 sacral (S1-S5)

-1 coccygeal (Co)

Ganglia- the cell bodies of sensory neurons that are located at each segment

Dorsal Root Ganglia- (toward the back, spinal) they lie between the pedicles of the adjacent vertebrae, the axons that are appropriated to the dorsal root ganglia are the dorsal roots and send sensory information to the CNS

Ventral Roots- axons of motor neurons, they both pass through the intervertebral foramen (IVF)

-they are distal to the ganglion

-dorsal and ventral roots are formed together and this forms the spinal nerves which are also called mixed nerves

*dorsal is posterior and you have information coming in; sensory

*anterior is ventral and you information going away (to); motor commands

-the spinal cord will grow until age four

-the spinal column will continue growing

-there is loose correlation between the segment and the nerve

-spinal nerves elongate and the sacral segments of the spinal cord are located at the C1 and L2 area

Denticulate Ligaments- extend from the pia mater to the dura mater and are on both sides and prevents lateral movement

Anterior/Posterior Median Fissure- mark the left and right sides of the spinal cord

White Mater- mylinated axons, more...
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