Chapter 12

Which muscle group is innervated primarily by the median nerve?

Flexor muscles in the forearm

Which of the following correctly describes a difference between the gray and white rami communicantes of a spinal nerve?

The white ramus contains myelinated fibers, and the gray ramus does not.

In a ________ neuronal pool, one neuron synapses on several postsynaptic neurons.

diverging

The layer of the meninges in direct contact with the spinal cord is the

pia mater.

Each of the following nerves originates in the lumbar plexus except the ________ nerve.

sciatic

The posterior horns of the spinal cord contain mainly

sensory nuclei.

Compared to the vertebral column, the spinal cord is

shorter.

The nerve that innervates the flexor muscles located in the arm (brachium) is the __________. This nerve is a branch of the __________ cord.

Musculocutaneous nerve; lateral

Identify the word grouping that is correct.

Posterior division, axillary nerve, deltoid

A typical spinal cord has how many pairs of spinal nerves, and where does the spinal cord end? (Module 12.2A)

31 pairs; lumbar vertebra 1 or 2

The spinal cord continues to elongate until about age

4 years.

What is a reflex? (Module 12.1B)

A reflex is a rapid, automatic response triggered by specific stimuli.

What are common characteristics of reflexes? (Module 12.12A)

All reflexes are rapid, unconscious patterned responses to stimuli that restore or maintain homeostasis.

In which of the following would the delay between stimulus and response be greater?

a polysynaptic contralateral reflex

Suppose that you feel something brushing against your abdomen. The sensory information would be carried to the spinal cord over a ________ ramus.

anterior

The ________ plexus supplies innervation to the diaphragm.

cervical

When the humerus is broken mid-shaft, injury to the radial nerve can often result. Following healing of the broken bone, what muscular deficits would be apparent if the radial nerve had been injured at the area of fracture?

Weakness or loss of extension of the wrist

Reflexes that activate muscles on the opposite side of the body as the stimulus are called

contralateral

The ________ reflex complements the flexor reflex by activating contralateral muscles.

crossed extensor

Which kind of neural circuit processes information in a stepwise fashion, one neuron to another? (Module 12.11B)

serial processing

In the condition ________, a virus infects posterior root ganglia, causing a painful rash whose distribution corresponds to that of the affected sensory nerves as seen in their dermatomes.

shingles

What is the significance of the cauda equina? (Module 12.2E)

It is made up of extensions of the posterior and anterior roots of spinal segments L2 to S5. It forms as the vertebral column continues to elongate after growth of the spinal cord ceases at about age 4.

The outermost connective-tissue covering of nerves is the

epineurium.

The ________ is a strand of fibrous tissue that provides longitudinal support as a component of the coccygeal ligament.

filum terminale

The specialized membranes that surround the spinal cord are termed the

spinal meninges.

A posterior and anterior root of each spinal segment unite to form a

spinal nerve.

Samples of CSF for diagnostic purposes are normally obtained by placing the tip of a needle in the

subarachnoid space.

The nerve crucial for breathing that originates within the cervical plexus is called the ________ nerve.

phrenic

Damage to which nerve of the cervical plexus would interfere with the ability to breathe? (Module 12.8A)

phrenic nerve

Through which root of a spinal nerve does visceral sensory information arrive? (Module 12.6B)

posterior root

Which nerve divides into the tibial nerve and common fibular nerve? (Module 12.10C)

sciatic

Sweat glands receive instructions through the anterior and posterior rami of spinal nerves. The neurons carrying these messages are _____ motor fibers, and their cell bodies are found in the __________.

visceral; sympathetic ganglion

All of the following terms refer to ways that reflexes can be classified except

voluntary.

Reflexes can be classified according to all of the following except

whether they are sensory or motor.

Each peripheral nerve provides ________ innervation to peripheral structures.

both motor and sensory

The stretch reflex

is important in regulating muscle length.

The myotatic reflex is also known as the ________ reflex.

stretch

Define reinforcement as it pertains to spinal reflexes. (Module 12.15A)

Reinforcement is an enhancement of a spinal reflex through the facilitation of motor neurons involved in reflexes.

Differentiate between sensory nuclei and motor nuclei. (Module 12.4A)

Sensory nuclei receive and relay sensory information from peripheral receptors; motor nuclei issue motor commands to peripheral receptors.

Describe the brachial plexus. (Module 12.9A)

The brachial plexus is a network of nerves formed by branches of spinal nerve segments C5-T1.

In the patellar reflex, how does stimulation of the muscle spindle by gamma motor neurons affect sensitivity and reaction time? (Module 12.13C)

The muscle spindles become more sensitive and the reflex response occurs more quickly.

Sensory input from interoceptors of the body walls and limbs is carried to the spinal nerve via the

anterior rami.

Of the spinal meninges, the middle one is the ________ mater.

arachnoid

The ventral rami of spinal nerves C4 to T1 contribute fibers to the ________ plexus.

brachial

Which of the following is not true about a positive Babinski reflex?

causes you to close your eyes when you sneeze

The posterior root ganglia mainly contain

cell bodies of sensory neurons.

The outward projections from the central gray matter of the spinal cord are called

horns

There are five steps in the typical reflex arc. Which of the following best describes the activity of the third step?

information processing within the CNS

A viral disease that destroys the neuronal cell bodies of the anterior gray horn will

lead to muscle weakness or paralysis.

Spinal nerves from the sacral region of the cord innervate the ________ muscles.

leg

Reflexes, controlled by the spinal cord, act by

motor output over spinal nerves to effectors.

Jim was in a car accident and suffered damage to the posterior ramus of several spinal nerves in his lumbar region. What problems might he experience as a result?

muscle weakness or paralysis loss of sensation from affected areas decreased sympathetic response All of the listed responses are correct.

The white matter of the spinal cord is mainly

myelinated axons.

The anterior rami form four major plexuses, including all of the following except the ________ plexus.

nuchal