Chapter 13 spinal cord, nerve, and reflexes

What is a reflex?

A quick, stereotyped, involuntary response to a stimulus

The anterior rami of spinal nerves form which nerve plexuses?

Cervical, lumbar, sacral

Functions of the spinal cord include which of the following?

Conduction, locomotion, reflexes

In a sensory pathway, which neuron detects the stimulus and transmits the signal to the spinal cord or brainstem?

First order

In descending pathways, the upper motor neurons synapse with ______ motor neurons in the brainstem or spinal cord.

Lower

In descending tracts, which motor neuron innervates the target organ?

Lower

The poliovirus destroys which neurons in the brainstem and anterior horn of the spinal cord?

Motor

Within the spinal cord, what type of information do the descending tracts carry?

Motor

Which is a type of stretch receptor embedded in skeletal muscle?

Muscle spindle

Where do the first-order neurons of the spinocerebellar tract originate?

Muscles and tendons

A is a cordlike organ composed of numerous nerve fibers (fascicles) bound together by connective tissue.

Nerves

Within a nerve, each fascicle is wrapped in which layer?

Perineurium

Which viral disease results in the destruction of motor neurons?

Poliomyelitis

What is a reflex involving one or more interneurons called?

Polysynaptic

What type of signal does the spinocerebellar tract carry?

Proprioception

Where do the second-order neurons of the spinoreticular tract terminate?

Reticular formation

Moving peripherally from the spinal cord, the anterior and posterior _____ form the spinal nerve.

Roots

Moving peripherally from the spinal cord, which anterior and posterior structures form a spinal nerve?

Roots

Which reflex occurs in response to excessive tension on a tendon?

Tendon

What does contralateral mean?

That two points are on opposite sides of the body.

What does ipsilateral mean?

That two points are on the same side of the body

Conduction

The spinal cord contains ascending and descending nerve fibers that send information between the CNS and the periphery. This illustrates which function of the spinal cord?

The number of neurons in a descending pathway is

Two

The spinothalamic tract is part of the ______ system in the anterior and lateral columns.

anterolateral

Fibers from the cuneate fasciculus end on the ______ side of the medulla oblongata.

ipsilateral

The third-order neurons of the spinoreticular tract runs from the __ to the __.

pons and thalamus

The cuneate fasciculus is located in the ______ column of the spinal cord.

posterior

Signals for proprioception are carried by the anterior and posterior______ tract.

spinocerebellar

How many spinal nerves are there in order from superior to inferior?

8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

How many spinal nerves are in each region of the spinal cord in order from superior to inferior?

8,12,5,5,1

What is a nerve?

A cord of nerve fiber bundles bound together by connective tissue

The spinoreticular tract is found in which columns of the spinal cord?

Anterior and lateral

The spinothalamic tract is found in which columns of the spinal cord?

Anterior and lateral

Which are nerve plexuses of the body?

Brachial Sacral Cervical Lumbar

What is the white matter of the spinal cord?

Bundles of myelinated and unmyelinated axons found superficial to the gray matter

Since the corticospinal tracts decussate, they will innervate which muscles?

Contralateral

Which tract will have its origin and destination of opposite sides of the body?

Contralateral

In the spinoreticular tract, the second order neurons decussate to where?

Contralateral anterolateral system

Which tract carries signals for precise, finely coordinated limb movements?

Corticospinal

In which reflex does a contralateral extensor muscle contract?

Crossed extension reflex

What is the order of the meninges from superficial to deep?

Dura mater, arachnoid mater, pia mater

What is the dense irregular connective tissue layer enclosing an entire nerve called?

Epineurium

True or false: A reflex involving one or more interneurons is a monosynaptic reflex.

False

True or false: Severing a sensory nerve root will completely deaden sensation from a dermatome.

False

Within a nerve, nerve fibers are gathered into bundles called what?

Fascicles

Which order neuron of the spinothalamic tract ends in the posterior horn at the point of entry to the spinal cord?

First

Nerve signals carried from the midthoracic and lower parts of the body are carried by which ascending tract?

Gracile fasciculus

Where do the nerve fibers of the gracile fasciculus terminate in the medulla oblongata?

Gracile nucleus

Where does the first-order neuron of the spinothalamic tracts end?

In the posterior horn at the point of entry

All spinal nerves except C1 pass through a(n) ________ foramen to emerge from the vertebral column.

Intervertebral

All spinal nerves except C1 pass through which structure to emerge from the vertebral column?

Intervertebral foramen

Which nerve tracts do not decussate?

Ipsilateral

Based on the presence of both efferent and afferent fibers, spinal nerves are classified as which of the following?

Mixed

A _____ reflex arc consists of only one synapse between two neurons.

Monosynaptic

The anterior root of a spinal nerve contain axons of which neurons?

Motor

Muscle spindles are classified as what type of receptor?

Proprioceptor

What is a quick, involuntary, stereotyped response to a stimulus is called?

Reflex

Which pathways are made up of three neurons?

Sensory

What effect does severing a sensory root that innervates a dermatome have?

Some sensation may remain.

How many neurons are typically found in an ascending pathway between the receptor and the brain?

Three

True or false: Muscle spindles sense changes in muscle length and are therefore proprioceptors.

True

Consider the two motor neurons that form descending pathways. The neurons called the _____ motor neurons have their somas in the cerebral cortex or brainstem.

Upper

In descending pathways, which motor neurons have their somas in the cerebral cortex or brainstem?

Upper

matter is composed of myelinated and unmyelinated axons and is superficial to the gray matter of the spinal cord.

White

The spinothamalic tract is part of the ______ system in the anterior and lateral columns.

anterolateral

Since the corticospinal tracts decussate, innervation to the muscles will be across the body or _______

contralateral

Because the nerve tracts of the spinal cord undergo ___, the right side of the brain communicates with the left side of the body, and vice versa.

decussation

Within the spinal cord, which tracts carry motor signals down from the brain?

descending

Where does the spinal cord arise from the medulla oblongata?

foramen magnum

The nerve fibers of the gracile fasciculus terminate at the ______ of the medulla oblongata.

gracile

A is a rapid, involuntary response to a stimulus.

reflex

Where is the origin of sensory signals carried by the cuneate fasciculus?

vertebra T6 and up