Lab 1: Spinal Cord and Spinal Nerves

descending pathways

The systems of neurons that bring motor information from the brain down to the appropriate spinal level. Signals travel along two neurons. An example is the corticospinal tract.

sympathetic chain

Distributes neurons of the communicating rami and sends branches towards the thoracic and abdominal cavities. Runs parallel to the spinal cord.

visceral sensory

From the viscera to the dorsal horn.

somatic motor

To skeletal muscles from the ventral horn.

visceral motor

To smooth muscle and glands from the lateral horn.

vertebral foramen

A hole within the vertebra through which the spinal cord passes.

dorsal root ganglion

A large collection of cell bodies. Forms due to the unique structure of the unipolar sensory neurons in which the cell body is in the middle of the course of the axon.

stretch reflex

A monosynaptic reflex. An example is the patellar (or knee-jerk) reflex.

plexus

A network of nerves formed by the joining of the spinal nerve's ventral rami.

intercostal nerves

A pattern of ventral rami along the inferior surface of teh ribs that send small branches to nearby muscles, bones, and skin.

polysynaptic reflex

A reflex invovling one or several interneurons.

vertebral canal

A tube formed from successive vertebral foramina that houses the spinal cord.

withdrawal reflex

An example of a polysynaptic reflex.

spinal cord

Begins as the medulla oblongata exits the skull and enters the vertebral foramen of the first cervical vertebra.

dorsal ramus

Branch off of spinal nerve that carries somatic motor information to and somatic sensory information from the posterior body wall.

ventral ramus

Branch off of the spinal nerve that carries somatic motor information to and somatic sensory information from the lateral and anterior body wall.

communicating rami

Branch off of the spinal nerve that carries visceral motor and visceral sensory neurons to and from the viscera. Can be myelinated or unmyelinated.

sympathetic chain ganglia

Bulges on the sympathetic chain composed of neuronal cell bodies.

cauda equina

Bundle of spinal nerves beyond the conus medularis that resembles a horse's tail.

ventral root

Carries motor information with their cell bodies in the ventral and lateral horns of the spinal cord.

dorsal root

Carries sensory information to the dorsal horn of the spinal cord.

spinal nerves

Exit the vertebral column through the intervertebral foramina. They supply structures in the body with innervation at regular intervals and are numbered according to the vertebral level from which they take their exit from the vertebral canal. They form from the joining of two major tributaries, the dorsal and ventral roots.

filum terminale

Extension of the pia mater that lies within the cauda equina. It is a thin thread that anchors the end of the spinal cord to the sacrum.

brachial plexus

Formed of C5-T1 spinal nerve rami. Supplies the upper limb.

lumbosacral plexus

Formed of L2-S2 rami. Supplies the lower limb.

somatic sensory

From skin, skeletal muscles, and joints to the dorsal horn.

spinal reflexes

Involuntary circuits in which the brain is not involved in the response to the stimulus.

monosynaptic reflexes

Involve a sensory neuron and its synapse with a motor neuron. An example is the stretch reflex.

central canal

Located at the center of the spinal cord and is continuous with the ventricles of the brain.

lumbar enlargement

Located in the spinal cord in the region of the lower limb. This structure results from many more neurons sending and receiving information to and from the limbs.

cervical enlargement

Located in the spinal cord in the region of the upper limb. This structure results from many more neurons sending and receiving information to and from the limbs.

pia mater of the spinal cord

Menix that is in direct contact with the spinal cord.

visceral

Refers to the interior cavities of the body (digestive, respiratory, cardiovascular systems).

somatic

Refers to the outer body (bones, skeletal muscles, skin)

denticulate ligaments

Specializations of the pia mater that anchor the spinal cord to the dura mater and limit the movement of the cord.

meninges

Structures that cover and protect the brain as well as the spinal cord.

epidural space

Surrounds the dura mater of the spinal cord (but not the dura of the brain). It is a space filled with fat and is a common site for the injection of anesthetic during labor.

conus medularis

The cone-shaped termination of the spinal cord.

gray matter

The inner region of the spinal cord that contains the unmyelinated neurons of the CNS. These include the interneurons as well as portions of sensory and motor neurons. It is organized into three columns: the dorsal horn, the ventral horn, and the lateral horn.

Epineurium

The outer most layer of a nerve.

white matter

The outer region of the spinal cord that consists of myelinated axons that are oriented vertically to communicate with higher or lower regions of the CNS. The white matter is roughly grouped into 3 columns on each side of the sagittal plane.

dura mater of the spinal cord

The outermost and toughest layer menix covering the spinal cord.

ascending pathways

The systems of neurons that bring information up to the brain. Signals travel along three neurons. An example is the spinothalamic tract.

anterior median fissure

a small division on the anterior side of the spinal cord (different from the central canal)

dermatome

the region of your skin that is innervated by a particular pair of spinal nerves

decussation

to cross the midsagittal plane to the contralateral side.