A&P Ch 13

The number of neurons in a descending pathway is .

2

Click and drag on elements in order How many spinal nerves are there in order from superior to inferior? Instructions

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

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

Which structure is indicated by the arrow?

Anterior root

Which nerve tract is indicated in the figure?

Anterolateral system

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

Where do signals ascending through the spinocerebellar tract terminate?

Cerebellum

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

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

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

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

Descending

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

Which connective tissue layer is indicated by the arrow?

Epineurium

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

False

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

Fascicles

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

First

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

First order

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

Lateral

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

Lower

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

Mixed

Which type of reflex arc consists of only an afferent neuron and an efferent neuron?

Monosynaptic

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

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

The spinoreticular tract carries what type of signals?

Pain

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

Perineurium

What is a reflex involving one or more interneurons called?

Polysynaptic

Which structure is indicated by the arrow?

Posterior root ganglion

Which nerve tract is indicated by the black arrow in the figure?

Posterior spinocerebellar tract

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

Reticular formation

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

Roots

Select all that apply Which are nerve plexuses of the body?

Sacral Lumbar Brachial Cervical

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

Sensory

The somas of which neurons are found within the posterior root ganglion?

Sensory

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.

The tract indicated by the letter A is the posterior tract.

Spinocerebellar

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

Tendon

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

Thalamus

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

In a sensory pathway, which neurons run from the thalamus to the sensory cerebral cortex?

Third-order

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

Three

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

Upper

What is the source of the sensory signals carried by the cuneate fasciculus?

Upper limbs and chest

The structure indicated by the arrow is the root.

anterior

The spinothalamic 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

tract carries signals for precise, finely coordinated limb movements.

corticospinal

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

crossed

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 structure indicated by the arrow is called the root.

dorsal

The bundle between the arrows labeled A is a(n) and contains several nerve fibers.

fascicle

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

first

What structure marks the superior end of the spinal cord?

foramen magnum

The structure indicated by the arrow is called the posterior root .

ganglion

The tract indicated in the figure by the letter A is the fasciculus.

gracile or cuneate (depends on pic)

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

intervertebral

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

ipsilateral

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

Spinal nerves are described as nerves because they carry both afferent and efferent signals.

mixed

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

monosynaptic

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

nerve

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

A is a rapid, involuntary response to a stimulus. Listen to the complete question

reflex

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

reflex

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

roots

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

second

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

spinocerebellar

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

tendon

How many neurons are found in a descending tract?

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

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

white