A&P Ch. 13

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

3

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 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 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 meninx is just below (deep to) the dura mater?

Arachnoid mater

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

Ascending

A nerve fiber refers to which part of a neuron?

Axon

Which are nerve plexuses of the body?

Brachial Lumbar Cervical Sacral

What is the white matter of the spinal cord?

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

The first cervical spinal nerve emerges above vertebrae ______.

C1

What does the central canal of the spinal cord contain?

CSF

The anterior rami of spinal nerves form which nerve plexuses?

Cervical, lumbar, sacral

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

Functions of the spinal cord include which of the following?

Conduction, locomotion, reflexes

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

Contralateral

The nerve fibers of which tract form ridges called pyramids on the anterior surface of the medulla?

Corticospinal

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

Corticospinal

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 the dural sheath around the spinal cord made of?

Dura mater

Place the meninges in order from superficial to deep.

Dura, arachnoid, pia

What is the loose connective tissue surrounding an individual nerve fiber called?

Endoneurium

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

Epineurium

True or false: Reflex pathways always involve the cerebral cortex.

False

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

Fascicles

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

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 which structure to emerge from the vertebral column?

Intervertebral foramen

Which nerve tracts do not decussate?

Ipsilateral

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

L1

In which column of the spinal cord is the anterior spinocerebellar tract found?

Lateral

What are the three funiculi of white matter found in the spinal cord?

Lateral funiculus Ventral funiculus Posterior funiculus

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

Motor

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

Motor

What do muscle spindles monitor?

Muscle length and body movements

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

Muscles and tendons

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

Perineurium

Which viral disease results in the destruction of motor neurons?

Poliomyelitis

Which spinal nerve roots carry sensory nerve signals?

Posterior

What type of signal does the spinocerebellar tract carry?

Proprioception

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

Reticular formation

Nerve fibers of peripheral nerves are encased in which cells?

Schwann

What are the four components of a monosynaptic somatic reflex arc?

Skeletal muscle Receptor in skin, muscle or tendon Afferent nerve fiber Efferent nerve fiber

Where are the receptors for somatic reflexes found?

Skin, muscle, and tendons

A somatic fiber innervates which of the following?

Skin, skeletal muscles, bones, and joints

The first cervical spinal nerve emerges between which two structures?

Skull and vertebra C1

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

Some sensation may remain.

__________ fibers are nerve fibers that innervate more localized organs in the head (eyes, ears, olfactory and taste receptors, etc.).

Special

Signals for proprioception are carried by the anterior and posterior ________tract.

Spinocerebellar

Where is the white matter in the spinal cord?

Superficial to the gray matter

Where do the third-order neurons of the spinoreticular tract run from the pons to?

Thalamus

What is the subarachnoid space?

The space between the arachnoid mater and pia mater

______ fibers are nerve fibers that innervate blood vessels, glands, and internal organs.

Visceral

A general fiber innervates which of the following?

Widespread organs such as muscles, skin, glands, viscera, and blood vessels

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

anterolateral

The middle layer of the meninges is the ______ mater.

arachnoid

The mater is just below (deep to) the dura mater.

archnoid

In the spinal cord, the ________ canal is lined with ependymal cells and contains cerebrospinal fluid.

central

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

contralateral

The nerve fibers of the _________tract form ridges called pyramids on the anterior surface of the medulla.

corticospinal

___________tract is also called the pyramidal tract.

corticospinal

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

The dural sheath around the spinal cord is formed from the

dura matter

External to the neurilemma of a nerve fiber is the layer of loose connective tissue that surrounds a nerve fiber called a(n)

endoneurium

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

false

In a sensory pathway,_________ order neuron detects the stimulus and transmits the signal to the spinal cord or brainstem.

first

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

first

Which order neurons of the spinocerebellar tract originate at muscles and tendons?

first

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

gracile

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

ipsilateral

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

The ______ are a series of fibrous connective tissue membranes covering the central nervous system.

meninges

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

mixed

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

motor

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

nerve

The spinoreticular tract carries what type of signals?

pain

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

pons

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

posterior

Which ramus of a spinal nerve innervates the local muscles, joints, and skin of the back?

posterior

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

reflex

The second-order neurons of the spinoreticular tract terminate in the ________formation of the brainstem.

reticular

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

roots

What does ipsilateral mean?

same side

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

The posterior root of a spinal nerve carries what type of nerve fibers?

sensory

Which pathways are made up of three neurons?

sensory

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

true

How many neurons are found in a descending tract?

two

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