Anatomy Chapter 13

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

What is a reflex?

A stereotyped, involuntary response to a stimulus

What is a muscle spindle?

A type of stretch receptor embedded in skeletal muscle

In which disease does sclerosis of the lateral spinal cord occur, with destruction of motor neurons?

Amyotrophic lateral sclerosis

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

Anterior and lateral

Within the spinal cord, which tracts carry information up to the brain?

Ascending

A nerve fiber refers to which part of a neuron?

Axon

What is the white matter of the spinal cord?

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

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?

Conduction

Which are functions of the spinal cord?

Conduction Neural Integration Locomotion Reflexes

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

A reflex in which a contralateral extensor muscle is contracted is called a ________ extension reflex.

Crossed

In which reflex does a contralateral extensor muscle contract?

Crossed extension

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

What factor accounts for the fact that the right side of the brain communicates with the left side of the body, and vice versa?

Decussation

What is an area of skin innervated by a spinal nerve called?

Dermatome

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

Dura mater, arachnoid mater, pia mater

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

False

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

First order

What structure marks the superior end of the spinal cord?

Foramen magnum

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

From vertebra T6 and up

The nerve fibers of the gracile fascicules terminate at the _________ nucleus of the medulla oblongata.

Gracile

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

Which tract will have its origin and destination on the same side of the body?

Ipsilateral

In an adult, the spinal cord ends at which vertebra?

L1

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

Lower

The ________ motor neurons (which are the motor neurons connecting the brainstem and spinal cord to muscle fibers) of the descending pathway innervate skeletal muscle.

Lower

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

Monosynaptic

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

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

Nerve

What is a reflex involving one or more interneurons called?

Polysynaptic

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

Reticular formation

In the spinothalamic tract, the ________ -order neurons decussate from the posterior horn of the spinal cord.

Second

In a sensory pathway, which neurons run from the spinal cord or brainstem to the thalamus?

Second-order

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.

A ________ reflex occurs in response to excessive tension on a tendon.

Tendon

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

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

Three

The number of neurons in a descending pathway is

Two

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 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