Chapter 13 Check Points

One of the first somatic reflexes to develop is the suckling reflex. Which type of reflex is this?

The suckling reflex is an innate reflex.

Define reflex.

are rapid, automatic responses to specific stimuli. It is an important mechanism for maintaining homeostasis

After injuring her back, Tina exhibits a positive Babinski reflex. What does this imply about Tina's injury?

positive Babinski reflex is abnormal in adults; it indicates possible damage of descending tracts in the spinal cord.

Define spinal reflex.

rapid, automatic responses triggered by specific stimuli

Name the components of the CNS and of the PNS.

CNS is the brain and spinal cord PNS is the cranial nerves and spinal nerves

Damage to which root of a spinal nerve would interfere with motor function?

Damage to the ventral root of a spinal nerve, which is composed of both visceral and somatic motor fibers, would interfere with motor function

List the five circuit patterns found in neuronal pools

Divergence Convergence Serial processing Parallel processing Reverberation

Identify the three spinal meninges.

Dura Mater, Arachnoid mater, and Pia mater

Where is the cerebrospinal fluid that surrounds the spinal cord located?

The cerebrospinal fluid that surrounds the spinal cord is located in the subarachnoid space, which lies beneath the epithelium of the arachnoid mater and superficial to the pia mater.

What is the minimum number of neurons in a reflex arc?

The minimum number of neurons required for a reflex arc is two. one must be a sensory neuron that brings impulses to the CNS, and the other a motor neuron that transmits a response to the effector.

A person with polio has lost the use of his leg muscles. In which area of his spinal cord. would you expect the virus-infected motor neurons to be?

The poliovirus infected neurons would be in the anterior gray horns of the spinal cord, where the cell bodies of somatic motor neurons are located.

An anesthetic blocks the function of the dorsal rami of the cervical spinal nerves. Which areas of the body will be affected?

a anesthetic that blocks the function of the dorsal rami of the cervical spinal nerves would affect the skin and muscles of the back of the neck and of the shoulder

A disease that damages myelin sheaths would affect which portion of the spinal cord?

a disease that damages myelin sheaths would affect the columns in the white matter of the spinal cord, because the columns are composed of bundles of myelinated axons.

Identify the basic characteristics of polysynaptic reflexes.

all polysynaptic reflexes involve pools of interneurons, are intersegmental in distribution, and involve reciprocal inhibition.

Compression of which nerve produces the sensation that your leg has "fallen asleep"?

compression of the sciatic nerve produces the sensation that your leg has "fallen asleep"

Injury to which of the nerve plexuses would interfere with the ability to breathe?

damage to the cervical plexus or more specifically to the phrenic nerves, which originate in this plexus and innervate the diaphragm-would greatly interfere with the ability to breathe and might even be fatal.

During a withdrawal reflex of the foot, what happens to the limb on the side opposite the stimulus? What is this response called?

during a withdrawal reflex, the limb on the opposite side is extended. This response is called a crossed extensor reflex.

Define neuronal pool.

functional groups of interconnected neurons within the CNS

Define reinforcement as it pertains to spinal reflexes.

reinforcement is an enhancement of spinal reflexes; it occurs when the postsynaptic neuron enters a state of generalized facilitation caused by chronically active excitatory synapses.

Differentiate between sensory nuclei and motor nuclei.

sensory nuclei receive and relay sensory information from peripheral receptors. Motor nuclei issue motor commands to peripheral effectors.

Identify the major networks of nerves known as plexuses.

the major plexuses are the cervical, brachial, lumbar, sacral, and coccygeal.

A weight lifter is straining to lift a 200-kg barbell above his head. Shortly after he lifts it to chest height, his muscles appear to relax and he drops the barbell. Which reflex has occurred?

this response is the tendon reflex.

For the patellar reflex, how would the stimulation of the muscle spindle by gamma motor neurons affect the speed of the reflex?

when intrafusal fibers are stimulated by gamma motor neurons, the muscle spindles become more sensitive. As a result, little if any stretching stimulus would be needed to stimulate the contraction of the quadriceps muscles in the patellar reflex. Thus, the reflex response is the tendon reflex.