Ch 13 Spinal Cord, Spinal Nerves & Spinal Reflexes

Dorsal root ganglia

- contain cell bodies of unipolar, sensory neurons - Lump on dorsal nerve root

Somatic motor nuclei

-(anterior) innervate skeletal muscle -the anterior horns of the spinal cord contain?

motor nuclei

-The cell bodies of neurons that issue commands to peripheral effectors are called - gray matter - anterior horns

sensory nuclei

-The cell bodies of neurons that receive and relay information from peripheral receptors are called - gray matter - posterior horn

Somatic and visceral sensory nuclei

-The posterior horns of the spinal cord contain

What is reciprocal inhibition?

-When antagonist relaxes due to contraction by agonist. - stimulate one set of muscles and inhibit the antagonist of another set of muscles

Mixed nerves

-contain both afferent (sensory) and efferent (motor) fibers -All spinal nerves are mixed nerves!

List the five steps involved in a neural reflex

1. Arrival of stimulus and activation of receptor 2. Activation of sensory neuron 3. Information processing in the CNS 4. Activation of motor neuron 5. Response of peripheral effector

Spinal nerve

A dorsal and ventral root of each spinal segment unite to form a

reflex

A predictable response to stimulus

Significance of a dermatome

A problem to a dermatome may indícate damage to an area of a specific nerve and can pinpoint injury to the area of the spinal cord

descending tracts

Axons convey motor commands down into the spinal cord by way of

ascending tracts

Axons that carry sensory information toward the brain

General Characteristics of Polysynaptic Reflexes

1. Involve pools of interneurons that inhibit and excite 2. Are intersegmental in distribution 3. Involve reciprocal inhibition 4. Have reverberating circuits Which prolong reflexive motor response 5. Several reflexes cooperate To produce coordinated, controlled response ———————- 1. Involve pools of interneurons that can inhibit and excite 2. Intersegmental 3. Reciprocal Inhibition 4. Reverberating Circuits 5. Reflexes may cooperate

What are the five parts of a neural reflex

1. Receptor 2. Sensory neuron 3. Integrating center 4. Motor neuron 5. Effector

What are the four pairs of plexuses?

Cervical plexus Brachial plexus Lumbar plexus Sacral plexus (includes coccygeal)

Myotome

Group of muscles innervated by a single spinal nerve Stroke evaluation

Visceral motor nuclei

Lateral horns located only in the thoracic and lumbar segments contains

subarachnoid space

Space between arachnoid & pia mater contains cerebrospinal fluid CSF

denticulate ligaments

Strands that help anchor the cord, coming out of the pia mater

pia mater

The blood vessels servicing the spinal cord run along the surface of the? -clear, innermost layer -attached to the spinal cord

Perineurium

The connective tissue partition that separates adjacent bundles of nerve fibers in a peripheral nerve is referred to as the

reflex arc

The crossed extensor reflex involves a contralateral reflex arc (contra, opposite), because the motor response occurs on the side opposite the stimulus.

cauda equina

The nerves that collectively radiate from the conus medullaris are known as the

spinal meninges

The specialized protective membrane that surrounds the spinal cord is the

dermatome

The specific bilateral region of the skin surfaced monitored by a single pair of spinal nerves is known as the a region of body surface innervated by a single spinal nerve

reflex arc

The stretch, tendon, and withdrawal reflexes involve ipsilateral (ipsi, same + lateral, side) reflex arcs: The sensory stimulus and the motor response occur on the same side of the body.

plexus

complex network formed by ventral rami of most spinal nerves - not T2-T12

Endoneurium

covers the individual axon

conus medullaris

end of spinal cord at L1/L2

subdural space

space between dura mater and arachnoid mater Contains serous fluid

epidural space

space between the dura mater and inside the bony covering of spinal cord

Perineurium

surrounds bundles of axons (fascicles)

Epineurium

surrounds entire nerve (bunch of fascicles)

dura mater

thick, white, strong, shiny, fibrous outermost layer of the meninges surrounding and protecting the brain and spinal cord -Does not stretch

filum terminale

thin thread of fibrous tissue at end of conus medullaris, attaches to coccygeal ligament

arachnoid mater

weblike, delicate, middle layer of the three meninges