Biol 2022 Nervous System

Each neuron in the CNS may receive input from

thousands of axons.

A stimulus great enough to change the membrane potential and propagate an action potential is said to have reached _________.

threshold

Masses of myelinated nerve fibers appear

white.

Match each description with the correct part of a neuron: Release neurotransmitter molecules

Synaptic knobs

What happens next, after an action potential arrives at a synaptic knob, opening calcium channels and allowing calcium to enter the cell?

Synaptic vesicles migrate to the plasma membrane and release acetylcholine.

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

Match the description of the neuroglia with the correct cell type: Found between neurons and blood vessels (blood-brain barrier); regulate ion concentration in nervous tissue

Astrocytes

Match the description with the correct type of neuron: Cell body with a process arising from each end; one dendrite and one axon

Bipolar neuron

Match each description with the correct part of a neuron: Rough endoplasmic reticulum with neuron cell body

Chromatophilic substance

Match each description with the correct part of a neuron: Branches of an axon

Collaterals

Match the description of the neuroglia with the correct cell type: Covers the choroid plexus; lines space in the brain (ventricles)

Ependymal cells

Acetylcholine is actively transported across the synaptic cleft.

False

Match the description with each functional aspect of the nervous system: Detects stimulus/informs CNS

Integrative function

Match the description with the correct classification of neuron: Relay impulses between neurons in CNS

Interneurons

Match the description with the correct type of neuron: Cell body with many processes; one axon and many dendrites

Multipolar neuron

When a nerve fiber is polarized, the concentration(s) of

Na+ is higher on the outside of the membrane and K+ is higher on the inside.

Match each description with the correct part of a neuron: Provide support for axon hillock and axon

Neurofibrils

_________ support the axon from within.

Neurofibrils.

Match the description of the neuroglia with the correct cell type: Form myelin in CNS

Oligodendrocytes

Which cells produce myelin in the brain and spinal cord?

Oligodendrocytes

Which of the following ions cross neuron cell membranes most readily?

Potassium

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

Satellite cells

In the peripheral nervous system, myelin is formed by cells called __________ ______.

Schwann cells

Match the description with each functional aspect of the nervous system: Decides response

Sensory function

During an action potential, what change occurs at the cell membrane?

The area inside the neuron cell membrane becomes positively charged compared to the outside.

If the postsynaptic membrane potential reaches threshold level, an action potential will be produced.

True

Match the description with the correct type of neuron: Cell body has single process that divides into two branches

Unipolar neuron

An action potential traveling down the presynaptic neuron reaches the synaptic knob. What initially occurs at the synaptic knob when that action potential arrives?

Voltage-gated calcium ion channels open, and calcium ions diffuse into the synaptic knob.

Every neuron has

a cell body.

The _______ refractory period occurs first. It is a time period when a stimulus will not produce a new action potential. The ion channels are unresponsive.

absolute

The neurotransmitter that controls skeletal muscle contraction is

acetylcholine.

A drug that functions as an agonist

activates a receptor, helping a neurotransmitter bind or triggering an action potential in some other way.

The refractory period for an area of cell membrane occurs _______ an action potential occurs.

after

The nervous system

all of the above.

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.

Myelin

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

Diverging axons amplify an impulse by

contacting many neurons.

An action potential generates local currents that cause _____ of the membrane immediately adjacent to the action potential.

depolarization

If the membrane potential becomes less negative than the resting membrane potential, the membrane is _______.

depolarized

A neurotransmitter that causes the opening of sodium channels is an ______ neurotransmitter while one that causes the opening of potassium channels is an _______ neurotransmitter.

excitatory; inhibitory

If a neuron receives a series of stimuli whose effect is excitatory but subthreshold, the neuron is more excitable to incoming stimulation than before and is said to be

facilitated

If the membrane potential becomes more negative than the resting membrane potential, the membrane is __________.

hyperpolarized

If a resting potential becomes more negative, the membrane is

hyperpolarized.

The occurrence of the refractory periods ensure that action potential propagation occurs ____ _____ ________.

in one direction

Saltatory conduction

is faster than conduction on an unmyelinated fiber.

Neurons that conduct impulses from the CNS to muscles or glands are

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

The two types of cells of the nervous system are

neurons and neuroglia.

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.

The cell membrane of a resting neuron is described as being ________.

polarized

During the next phase, the ______ refractory period, only a strong stimulus will trigger an action potential.

relative

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

thick and myelinated.

The occurrence of the refractory period allows an action potential to propagate in both directions along the axon.

False

Describe the effect of acetylcholine on the postsynaptic neuron.

Ligand (chemically)-gated sodium channels open, and sodium diffuses into the postsynaptic neuron.

Match the description of the neuroglia with the correct cell type: Phagocytes; supportive function

Microglia

Match the description with each functional aspect of the nervous system: Response

Motor function

Match the description with the correct classification of neuron: Carry impulses from the CNS to effectors

Motor neurons

Match the description with the correct classification of neuron: Carry impulses from receptors to CNS

Sensory neurons

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

clinical depression.

Neurotransmitters that are modified amino acids are

dopamine, serotonin, epinephrine, and norepinephrine.

The neurotransmitter most likely produced when a person uses a drug that creates a sense of well-being is

dopamine.

In the central nervous system, myelin is formed by cells called ________.

oligodendrocytes

A neuron may have

one axon and many dendrites.