ANATOMY CH. 13-16

Some axons within the peripheral nervous system are unmyelinated. What relationship do these neurons have with Schwann cells?

Schwann cells have multiple superficial grooves, each of which accommodates a single unmyelinated axon.

Which of the following statements about oligodendrocytes and/or Schwann cells is correct?

Schwann cells provide a framework for growth when an axon has been cut and is in the process of regenerating.

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value. The plasma membrane, which was polarized to a negative value at the RMP, depolarizes to a positive value.

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

What do the cervical and brachial plexuses have in common?

Both plexuses receive fibers from the ventral rami of spinal nerve C5

Extension at the knee depends on signals sent by which of the following nerves of the lumbar plexus?

Femoral nerve

The sciatic nerve is the largest nerve in the human body. If it were severed, the patient would lose which of the following functions?

Flexion of the knee and plantar flexion at the ankle

Satellite cells surround the cell bodies of peripheral neurons, which can be found in (the) ________.

Ganglia

Fibers from L4 and L5 join together to form the __________, which later joins with fibers from S1-S3.

Lumbosacral trunk

The portion of a neuron that carries information in the form of a nerve impulse (action potential) is called the

Axon

Neuroglia in the nervous system function to

act as phagocytes

What would you NOT be able to find in a section of gray matter from the CNS?

axon bundles that transmit messages to the upper and lower limbs WOULD FIND: nuclei that process respiration and heart rate neuron cell bodies that handle memory formation higher-order centers for abstract reasoning

Which does NOT affect the speed of an action potential along an axon?

the amount of neurotransmitter binding to the dendrites of the neuron

Motor fibers travel in the ________ of the spinal cord.

descending tracts

Which of the following is an activity of the nervous system?

detection of pain after a bee sting

Caudally, the spinal dura mater blends with components of the ________ to form the coccygeal ligament.

filum terminale

The myelin sheath is functionally important because it __________.

increases the conduction speed of nerve impulses

Where do most action potentials originate?

initial segment

A nerve plexus __________.

is a tangled bundle of spinal nerves formed by the fusion of multiple ventral rami

When a stimulus is applied to the axon, it produces a temporary change in the ________ of the axolemma in a localized area of the axon

permeability

Damage to which nerve(s) of the cervical plexus would directly affect the ability to breathe?

phrenic nerve

The myelin sheath is an important structure surrounding the axons that make up white matter in the nervous system. In the peripheral nervous system, this myelin sheath is formed by the __________.

plasma membranes of Schwann cells

If Adam is walking through his yard barefoot and steps on a nail, he will withdraw his injured foot yet also extend his other leg so as not to fall. This kind of reflex could be called __________.

polysynaptic

Lynn is taking a yoga class and closes her eyes while transitioning from one pose to another. Which of the following instructs her brain to tell her whether or not she is in the correct position for the new pose?

proprioreceptors

What do the spinal meninges do?

protect the cord from injury that would be caused by rubbing against a vertebral foramen isolate the spinal cord from surrounding tissue absorb shock transmitted up the body when walking, running, or other vigorous motions occur

The denticulate ligaments of the pia mater __________.

protect the spinal cord from side-to-side motion that might damage the cord

Receptors may be classified as

somatic and visceral

Neurotransmitters are

stored in synaptic vesicles in the presynaptic membrane

Rick feels a cramping pain deep in his abdomen. What kind of receptor is giving him this sensation?

visceral interoreceptor

Involuntary cardiac muscle fibers of the heart are innervated by

visceral motor fibers

Which of the following occurs in the afferent division of the peripheral nervous system?

A neuron carries information from the stomach area to the brain.

If Rachel takes a medication that is designed to regulate her heart rate but should NOT affect her nervous system, what cells keep the chemical in the medication from penetrating the brain tissue?

Astrocytes

The neuromuscular synapse is a chemical synapse that releases the neurotransmitter

Ach

The nervous system includes all of the ______ tissue in the body.

Neural

If a disease erodes away the myelin sheath on a PNS axon, what structure will have been removed?

Neurilemma

Which of the following statements accurately compare(s) neuroglia to neurons?

Neuroglia act more as structural components of the CNS. Neuroglia have a greater ability to phagocytize foreign particles. Neuroglia have a greater ability to block the movement of materials out of the blood vessels.

Which of the following is FALSE regarding chemical synapses?

None are false, ALL TRUE The change in cell activity is short-lived, so multiple action potentials must occur to cause more neurotransmitter to be released. The synapses are filled with vesicles containing neurotransmitters. Neurotransmitters are sent from one cell to another to initiate change in a cell's activity.

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV. The plasma membrane was depolarized to a positive value at the peak of the first phase of the action potential. Thus, it must repolarize back to a negative value.

What is true of all of the axons within a particular tract?

They carry either sensory or motor information. They are of approximately the same diameter. They carry information to approximately the same location.

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels The activation gates of voltage-gated Na+ channels open, and Na+ diffuses into the cytoplasm.

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na+ channels change shape, and their activation gates open

A neuronal pool is ________.

a group of interconnected neurons with specific functions

It is possible for an axon to synapse with

another neuron a muscle cell, such as skeletal muscle a glandular cell

The epidural space contains areolar and adipose tissue, in addition to ________.

blood vessels

In electrical synapses, nerve impulse transmission occurs between cells of the CNS and PNS without any delay due to

communicating junctions that permit the passage of ions between the cells

The lateral gray horns __________.

contain the nuclei for visceral motor nerves

Which of the following are most closely involved with somatic sensory neurons?

exteroceptors

Functions of the nervous system include which of the following?

seat of higher functions, such as intelligence, memory, learning, and emotions receives sensory input; coordinates sensory input and motor output regulates smooth muscle, cardiac muscle, and glandular activities integrating and processing data

The rate of conduction of a nerve impulse depends upon

the presence or absence of a myelin sheath

In a reflex arc, which step follows the activation of a motor neuron?

the response by the effector