Chapter 13: The Spinal C13: The Spinal Cord and Nerves and Reflexes

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

3

How many spinal nerves are there in order from superior (top) to inferior (bottom)?

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

Where does the spinal cord arise from the medulla oblongata?

At the foramen magnum

What is the white matter of the spinal cord?

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

Choose all that are nerve plexuses of the body.

Cervical Lumbar Sacral Brachial

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

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

Contralateral

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

Place the meninges in order from superficial (at the top) to deep (at the bottom).

Dura Mater Arachnoid Mater Pia mater

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

False

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

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

In descending pathways, the upper motor neurons synapse with which motor neurons in the brainstem or spinal cord?

Lower

Which are a series of fibrous connective tissue membranes covering the central nervous system?

Meninges

A reflex arc that consists of only one synapse between two neurons is called a(n) ______________ reflex arc.

Monosynaptic

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

Monosynaptic

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

Motor

What is a reflex involving one or more interneurons called?

Polysynaptic

Choose all that are functions of the spinal cord.

Reflexes Locomotion Conduction

A reflex that occurs in response to excessive tension on a tendon is called a(n) _________ reflex.

Tendon

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

A reflex involving one or more interneurons is a monosynaptic reflex.

false

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

first

Which nerve tracts do not decussate?

ipsilateral

Fibers from the cuneate fasciculus end on the which side of the medulla oblongata?

isplateral

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

motor

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

nerve

What does contralateral mean?

on the opposite side of the body

What does ipsilateral mean?

on the same side of the body

Which pathways are made up of three neurons?

sensory

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

tendon

How many neurons are found in a descending tract?

two

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

upper

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

white