Ch. 13 General Nervous System

The central nervous system (CNS) includes the _

Brain and spinal cord

The anatomical subdivisions of the nervous system are (the) ___

Autonomic and somatic nervous systems

Functions of the peripheral nervous system include ________.

providing sensory information to the CNS and carrying motor commands to the peripheral tissues and systems

Receptors may be classified as ________.

somatic and visceral

Muscle cells, gland cells, and specialized cells that respond to neural stimuli are called ________.

effectors

Cardiac muscle, smooth muscle, and glands are regulated by the ________.

autonomic nervous system

The nervous system and the ________ system share important structural and functional characteristics, such as relying upon some form of chemical communication with targeted tissues and organs.

endocrine

The ________ division of the PNS sends motor information to muscles and glands.

efferent

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

neural

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

detection of pain after a bee sting

If Julie is in a store deciding whether or not to buy a new purse, her decision-making thought process requires activity from which part of the nervous system?

central nervous system

It is possible for an axon to synapse with __________.

All of the listed responses are correct.

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.

The cells responsible for information processing and transfer are the ________.

neurons

The cell body usually has several branching ________, which are specialized to respond to specific stimuli in the extracellular environment.

dendrites

In what way are neurons different from neuroglia?

Neurons are excitable and conductive, whereas neuroglia are not.

Which of the following selections lists only types of neuroglial cells?

microglia, oligodendrocytes, and Schwann cells

Oligodendrocytes ________.

provide structural framework and myelinate the central nervous system (CNS) axons

Microglia are (the) ________.

smallest neuroglial cell

Which of the following neuroglia produce cerebrospinal fluid?

ependymal cells

Myelin is (a) ________.

made of phospholipids

Areas of a myelinated axon that are not covered by myelin are called ________.

nodes

Areas of the nervous system that are dominated by myelinated axons are referred to as ________.

white matter

Cerebrospinal fluid is produced by ________.

ependymal cells

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.

All of the listed responses are correct

Which cell monitors the composition of the CSF in the CNS?

ependymal cell

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

Myelin

plasma membranes of Schwann cells

The myelin sheath is functionally important because it __________.

increases the conduction speed of nerve impulses

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.

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

axon

The area in a multipolar neuron that connects the cell body to the initial segment of the axon is called the ________.

axon hillock

The structural classification of a neuron is based upon ________.

the number of processes that project from the cell body

The functional classifications of neurons include ________, which carry information toward the CNS.

sensory neurons

Interneurons ________.

can be classified as excitatory or inhibitory on the basis of their effects on the postsynaptic membranes of other neurons

are located between sensory and motor neurons

are located entirely within the brain and spinal cord

are responsible for the analysis of sensory inputs and the coordination of motor outputs

All of the answers are correct.

________ monitor the position and movement of skeletal muscles and joints.

Proprioceptors

Which type of neuron is found in the CNS and special sense organs and has NO distinguishable axon?

anaxonic neurons

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?

proprioceptors

Injured neurons can fully recover their functional capabilities if ________.

the oxygen and nutrient supplies are restored within a period of a few minutes

In the process known as Wallerian degeneration ________.

macrophages phagocytize the debris of damaged axons

Where do most action potentials originate?

Initial segment

What opens first in response to a threshold stimulus?

Voltage-gated Na⁺ channels

What characterizes depolarization, the first phase of the action potential

The membrane potential changes from a negative value to a positive value.

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.

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

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

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Resting membrane potential (RMP)

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

Leak channels

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

The inside surface of the plasma membrane is much more negatively charged than the outside surface.

The plasma membrane is much more permeable to K⁺ than to Na⁺. Why?

There are many more K⁺ leak channels than Na⁺ leak channels in the plasma membrane.

The resting membrane potential depends on two factors that influence the magnitude and direction of Na⁺ and K⁺ diffusion across the plasma membrane. Identify these two factors.

The presence of concentration gradients and leak channels

What prevents the Na⁺ and K⁺ gradients from dissipating?

Na⁺-K⁺ ATPase

Action potentials result from ________.

a change in the membrane potential of axons

When an action potential develops in one location of an axon, ________.

it will propagate along the length of the axon toward the axon terminals

The rate of conduction of a nerve impulse depends upon ________.

the presence or absence of a myelin sheath

________ is the ability of a plasma membrane to respond to an adequate stimulus.

Excitability

If an axon ________, the impulse will be conducted ________.

has a larger diameter; more rapidly

When an excitable membrane reaches threshold, what event occurs in the cell membrane?

The membrane changes its permeability to certain positive and negative ions.

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

the amount of neurotransmitter binding to the dendrites of the neuron

The small space between the sending neuron and the receiving neuron is the

synaptic cleft.

A molecule that carries information across a synaptic cleft is a

neurotransmitter.

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential.

Over 50 different neurotransmitters have been identified, but the best known is ________.

acetylcholine

In the case of somatic neuromuscular neurons, the arrival of a nerve impulse at the axon terminal immediately triggers ________.

the release of acetylcholine (ACh) at the presynaptic membrane

At a chemical synapse, the neurons communicate via ________.

neurotransmitters

Neurotransmitters are ________.

stored in synaptic vesicles in the presynaptic membrane

A neuron might be temporarily unable to transmit an impulse to another neuron or effector if ________.

its supply of neurotransmitters is exhausted

Which of the following is the correct sequence of events at a synapse?

(1) neurotransmitter release/diffusion

(2) generation of action potential in the postsynaptic cell membrane

(3) arrival of nerve impulse at an axon terminal in the presynaptic cell

4) removal of neurotransmitter molecules from receptors

(5) binding of neurotransmitter to receptors

3, 1, 5, 2, 4

To transmit a nerve impulse in chemical synapses, the neurotransmitter diffuses across the ________ and binds to receptors on the postsynaptic membrane.

synaptic cleft

A neurotransmitter travels across the synaptic cleft and binds to receptors on a postsynaptic cell. Provided that the neurotransmitter is inhibitory, which of the following is likely to occur?

No action potential will be generated.

In the PNS, the neuron cell bodies are found in clusters called ________.

ganglia