CH 13

SPINAL CORD

What is the epidural space?

A cushion of fat and connective tissue that helps protect the spinal cord.

Where is the epidural space located?

Between the dura mater and the vertebral wall.

What are the three meninges?

Dura mater, Arachnoid mater, Pia mater.

What is the Dura mater?

The most superficial layer, thick and strong, composed of dense irregular connective tissue.

What is the Arachnoid mater?

A thin covering composed of collagen and elastic fibers, avascular.

What is the Pia mater?

The innermost layer that adheres to the surface of the spinal cord and brain, composed of thin squamous to cuboidal cells.

What is the subarachnoid space?

The space filled with cerebrospinal fluid located below the arachnoid layer between the arachnoid and pia mater.

From which part of the brain stem does the spinal cord extend?

from the medulla oblongata, the lowest part of the brainstem.

How far down the vertebrae does the spinal cord extend?

To the superior border of the second lumbar vertebra.

Are the spinal cord and vertebral column the same length?

No, the spinal cord is shorter than the vertebral column.

What are the two spinal cord enlargements?

Cervical enlargement and lumbar enlargement.

Where do the nerves from the cervical enlargement arise?

To and from the upper limbs. • Extends from C4 to T1

Where do the nerves from the lumbar enlargement arise?

To and from the lower limbs. extends from L2-S3

What is the conus medullaris?

The tapered, conical structure where the spinal cord terminates, ending between L1 and L2.

What is the filum terminale?

An extension of the pia mater that anchors the spinal cord to the coccyx.

How many pairs of cervical nerves are there?

8 pairs.

How many pairs of thoracic nerves are there?

12 pairs.

How many pairs of lumbar nerves are there?

5 pairs.

How many pairs of sacral nerves are there?

5 pairs.

How many pairs of coccygeal nerves are there?

1 pair.

What are roots?

Bundles of axons that connect each spinal nerve to a segment of the cord.

What are rootlets?

Even smaller bundles of axons that make up the roots.

What type of neuron does the posterior dorsal gray horn receive information from?

Sensory neurons.

What type of neuron do spinal nerves leaving the anterior ventral gray horn consist of?

Motor neurons.

What information is regulated in the lateral gray horns?

Autonomic motor neurons that regulate cardiac and smooth muscles and glands.

How is white matter in the spinal cord arranged?

In columns, containing spinal tracts that carry information up and down the spinal cord.

What are sensory tracts?

Axons that conduct nerve impulses toward the brain. ASENDING TRACTS

What are motor tracts?

Axons that carry nerve impulses from the brain. DESCENDING TRACTS

Where is the gray matter of the spinal cord found in the largest amount?

In the cervical and lumbar segments.

Where is white matter found in the largest amount in the spinal cord?

In the cervical segment.

What does the endoneurium cover?

Wraps axons within a nerve.

What does the perineurium cover?

Wraps fascicles within a nerve.

What does the epineurium cover?

Covers the entire nerve.

How many pairs of spinal nerves are there?

31 pairs.

What nerves does the cervical plexus supply?

Skin and muscles of the head, neck, and upper part of the shoulder.formed by roots of C1-C5)

What does the brachial plexus supply?

Nerves that supply the upper limbs and neck and shoulder muscles. Roots of spinal nerves C5-T1

What does the lumbar plexus supply?

Nerves that supply the abdominal wall, external genitals, and lower limbs. roots of spinal nerves L1-L4)

What does the sacral plexus supply?

Nerves that supply the buttocks and lower limbs.

What does the coccygeal plexus supply?

Nerves that supply the skin of the coccygeal region.

What does the phrenic nerve innervate?

The diaphragm.

What does the sciatic nerve innervate?

The lower limbs, specifically the thigh hamstring muscles and adductors.

How many spine segments of the spinal cord are there?

31 segments.

What is a reflex?

A fast, predictable sequence of involuntary actions in response to environmental changes.

What is a spinal reflex?

A reflex with integration taking place in the spinal cord gray matter.

What is a cranial reflex?

A reflex with integration occurring in the brain stem.

What is a reflex arc?

The pathway followed by nerve impulses that produce a reflex.

What is a tendon reflex?

A reflex that controls muscle tension by causing muscle relaxation before muscle force becomes excessive.

Controls muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might tear.

• Instead of resulting in a contraction

What is a flexor reflex?

A polysynaptic reflex arc that results in withdrawal from a painful stimulus.

Polysynaptic reflex arc

a. Polysynaptic reflex arc-more than 1 CNS

b. synapse and more than 2 different neurons are involved

withdrawal reflex”

Which reflex is a monosynaptic reflex?

The stretch reflex (patellar reflex).

Which reflex is a polysynaptic reflex?

The flexor reflex (withdrawal reflex).

What does the stretch reflex cause?

Causes contraction of skeletal muscle in response to stretching.