Multiple Choice

Opiate drugs derived from poppies relieve pain in humans because the human nervous system has

receptors for endogenous opiates.

Migraine results from

release of calcitonin gene-related peptide from the trigeminal nerves at the base of the brain, in response to a spreading wave of excitation followed by lack of response from the cortex.

This figure illustrates __________ conduction along an axon.

saltatory

Dendrites on unipolar neurons are parts of

sensory neurons.

A neuron in the aorta detects oxygen content in the blood and relays this information to the brain. This neuron is a __________ of the __________ pathway.

sensory receptor; afferent

The most rapid conduction of an impulse along an axon occurs on a fiber that is

thick and myelinated.

Each neuron in the CNS may receive input from

thousands of axons.

A neuron is stimulated, which changes membrane potential to the point where voltage-gated Na+ channels open and begin depolarizing the cell. The neuron has reached

threshold.

Summation of EPSPs and IPSPs occurs at the __________ of the neuron.

trigger zone

In __________ axons, impulse conduction is uninterrupted along the entire axon; while in __________ axons, action potentials only occur at nodes of Ranvier.

unmyelinated; myelinated

A myelinated nerve fiber is __________, whereas an unmyelinated nerve fiber is __________.

white, and composing the white matter of the brain and spinal cord; gray, and composing the gray matter of the brain and spinal cord

Masses of myelinated nerve fibers appear

white.

An excitatory postsynaptic potential lasts for about

15 milliseconds.

What is the correct sequence of events along an axon that follows a membrane reaching threshold potential?1. The membrane depolarizes.2. Sodium channels open and sodium ions diffuse inward.3. The membrane repolarizes.4. Potassium channels open and potassium ions diffuse outward.

2, 1, 4, 3

What does the sodium/potassium (Na+/K+) pump transport?

3 sodium ions out of the cell and 2 potassium ions into the cell

What type of electrical signal is an all-or-none response?

Action potential

A positive feedback loop occurs when the outcome of an event causes the event to continue occurring and amplifies its effects. Which of the following aspects of an action potential constitutes a positive feedback loop?

An initial flow of sodium ions into the neuron opens voltage-gated sodium channels, rapidly causing more sodium to enter.

Hillocks, collaterals, and terminals are associated with what part of a neuron?

Axon

Organize the following list of nervous system elements by their classifications as CNS or PNS elements: oligodendrocytes, thermoreceptors (nerves that sense temperature), interneurons, satellite cells, brain, motor neurons.

CNS brain, oligodendrocytes, interneurons; PNS thermoreceptors, satellite cells, motor neurons

Synaptic potentials are due to the opening of what type of channels?

Chemically-gated ion channels

Which of the following is unique to neurons?

Chromatophilic substance

What structure of a neuron is a short, highly branched process that helps receive input from other neurons?

Dendrites

An action potential is triggered if

EPSPs overpower IPSPs.

What are muscles and glands whose activities are controlled by nervous activity called?

Effectors

What results from the decomposition of neurotransmitter molecules or the reuptake of neurotransmitters from a synaptic cleft?

End of synaptic transmission

Which of the following molecules is responsible for "runner's high," a good feeling that accompanies long-distance running?

Endorphin

The class of neurotransmitters called neuropeptides include which neurotransmitter(s)?

Enkephalins and substance P

The disease called multiple sclerosis involves an immune response against myelin of the central nervous system, causing scar formation (sclerosis) within the neural tissue. How would this affect nerve impulse conduction?

Impulses are blocked or interrupted.

The fastest impulse conduction would occur in a what type of axon?

Large-diameter myelinated axon

In Guillain-Barre syndrome, the immune system attacks and degrades the myelin sheath of PNS axons. Predict the effect this will have on nerve impulse and motor function.

Lost insulation from myelin will cause neurons of the PNS to lose saltatory conduction, resulting in poor muscle function.

What structure supports the axon from within?

Neurofibrils.

What is a group of interneurons called that synapse with each other, receiving input and generating output, and performing a common function?

Neuronal pool

What is the effect of the binding of neurotransmitters to their receptors on the postsynaptic cell membrane?

Neurotransmitters are sometimes excitatory and sometimes inhibitory.

A test organism develops a genetic mutation that causes neurons to develop without synaptic knobs. How will this impact neuronal function?

No neurotransmitters will be released into the synapse to signal the postsynaptic neuron, as the synaptic knob is where they are stored.

The myelin sheath along an axon is not continuous. What are the gaps between Schwann cells called?

Nodes of Ranvier

The cell membrane of a neuron has both gated and non-gated ion channels. Which type of non-gated channel is more abundant?

Non-gated potassium channels

What neurotransmitter is classified as a monoamine?

Norepinephrine

Which cells produce myelin in the brain and spinal cord?

Oligodendrocytes

In a nerve cell at rest, the cell membrane is more permeable to which ion?

Potassium

The resting cell membrane is more permeable to which ion?

Potassium

A neuron is exposed to a drug that completely blocks voltage-gated potassium channels, but has no effect on non-gated channels or the sodium-potassium pump. Which of the following describes the effect on action potential generation?

Repolarization will still occur, but at an inefficiently slow rate.

Which of the following neuroglia are not part of the CNS?

Satellite cells

Which of the following cells is found only in the PNS?

Schwann cell

What neuroglia produces the myelin in the peripheral nervous system?

Schwann cells

What functions to detect changes inside and outside of the body?

Sensory receptors

Why is saltatory conduction along a myelinated axon faster than continuous conduction along an unmyelinated axon?

Since action potentials do not occur at the axonal membrane surrounded by myelin, less membrane surface (only at nodes of Ranvier) has to conduct the impulse.

This figure shows a membrane at rest, during depolarization, and during repolarization. Note the pink and purple circles. These represent ions involved in the depolarization/repolarization process. What ion is represented by the purple circles?

Sodium

What occurs during depolarization of an axon?

Sodium channels open and sodium diffuses into the cell.

Organize the following list of bodily functions and actions according to whether they are controlled by the somatic nervous system or autonomic nervous system: heart rate, walking, looking to the left, digestion, vasoconstriction, biceps femoris contraction.

Somatic walking, looking to the left, biceps femoris contraction; Autonomic heart rate, digestion, vasoconstriction

A physiologist testing signal transduction rates in two different nerves notices that one fiber conducts signals much faster than the other. Which is the most likely difference between the two?

The faster nerve fiber is myelinated and the slower one is not.

What is the role of monoamine oxidase and acetylcholinesterase in the nervous system?

To breakdown neurotransmitter molecules

What is the role of neural pools in the CNS?

To process information

Every Neuron Has

a cell body.

In reuptake

a neurotransmitter that has already been released into the synaptic cleft is taken back into the synaptic knob of the presynaptic neuron.

Convergence refers to

axons from neurons in different parts of the nervous system contacting the same neuron.

A reason that the axons in the CNS and PNS differ in their ability to regenerate after injury is that

axons of the CNS lack neurilemmae.

Synaptic knobs are at the ends of

axons.

In order for a severed peripheral nerve to regenerate and recover its original function, nerve fibers must sprout and enter tubes formed by

basement membranes and connective tissues.

When an action potential passes over the surface of a synaptic knob, the contents of the vesicles are released in response to the presence of

calcium ions.

The brain and the spinal cord make up the __________ nervous system.

central

Drugs that increase the actions of norepinephrine and/or serotonin by keeping them in synapses longer are most likely used to treat

clinical depression.

Myelin

consists of layers of lipids and proteins that wrap around an axon.

Diverging axons amplify an impulse by

contacting many neurons.

The nervous system

controls the movement of muscles.

The cytoplasmic extensions that, together with the cell body, provide the main receptive surfaces for neurons are

dendrites

Sensory receptors

detect changes in and outside the body.

Neurotransmitters that are modified amino acids are

dopamine, serotonin, epinephrine, and norepinephrine.

Presynaptic neurons release neurotransmitters by _________.

exocytosis

A neuron receives a series of stimuli that increases the membrane permeability of Na+, but not enough to cause membrane potential to surpass -55mV. This neuron is said to be

facilitated.

Clusters of neuron cell bodies in the PNS are called _________.

ganglia

If a resting potential becomes more negative, the membrane is

hyperpolarized.

Transmitting an impulse from one neuron to another involves a(n)

impulse stimulating a presynaptic axon to release a neurotransmitter into a synaptic cleft.

The dendrites of a neuron interact with several different axon terminals. Some of them are sending excitatory signals, while others are sending inhibitory signals. Over the course of the effects of these signals, the neuronal membrane potential reaches around -90mV. This means, overall, that the neuron will be

inhibited from generating action potentials.

A neuron receives a stimulation that causes Cl- channels to open, resulting in a hyperpolarization of the neuronal membrane. This situation is an example of a(n)

inhibitory postsynaptic potential.

Three general functions of the nervous system are

integrative, motor, and sensory.

The types of neurons that are organized into neuronal pools are

interneurons.

Saltatory conduction

is faster than conduction on an unmyelinated fiber.

Drugs that decrease membrane permeability to sodium

lessen pain.

Myelin is rich in __________.

lipids

Synaptic potentials are __________ potentials resulting from opening or closing __________-gated ion channels.

local; chemically

The oculomotor nerve is a cranial nerve containing nerve fibers that innervate eye muscles and control eye movement. These fibers are examples of

motor neurons.

An immune response that affects the myelin coating on axons throughout the spinal cord and brain, triggering inflammation and leaving scars, is

multiple sclerosis.

Most of the neurons in the brain and spinal cord are

multipolar.

In a resting neuron, the area just inside of the cell membrane is more __________ than the area just outside of the cell membrane.

negative

Neural stem cells can be harvested from autopsies and stored, alive, in banks, whereas neurons cannot, because

neural stem cells have lower oxygen and energy requirements than neurons.

Viagra is a drug used to treat erectile dysfunction by dilating arteries in the penis. The neurotransmitter that Viagra affects is

nitric oxide.

A neuron may have

one axon and many dendrites.

The negative charge across a resting membrane is due to the more __________ ions diffusing out of the cell than __________ ions diffusing into the cell.

potassium; sodium

At a synapse, the neuron that releases the neurotransmitter (sends the signal) is the __________ and the neuron that responds to the neurotransmitter (receives the signal) is the __________.

presynaptic neuron; postsynaptic neuron

Action potentials are related to impulses conducted along an axon in that

propagation of a series of action potentials along a nerve fiber constitutes an impulse.

What would happen if there were no Schwann cells?

Muscles would not be able to contract and the body would be paralyzed.

In what type of axon does saltatory conduction occur?

Myelinated

A nerve cell membrane becomes depolarized as a result of

Na+ ion channels being opened and Na+ ions diffusing into the cell.

The neurotransmitter that controls skeletal muscle contraction is

acetylcholine.

Drugs that inhibit the enzyme monoamine oxidase

allow increased activity of norepinephrine.

The branch of the peripheral nervous system that controls cardiac muscle, smooth muscle, and glands is called the __________ nervous system.

autonomic