chapter 39 ~ neurons Flashcards by Nicole Rashidi

Cells in the nervous system that send and receive electrical signals are called….

Neurons

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Which component of a neural signaling pathway sorts and interprets messages?

Integration

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Which sequence of the neural signaling pathway is correctly arranged from the earliest to the latest event as it occurs in the nervous system?

Reception, transmission, integration, transmission, response

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Which cells serve as electrical insulators in the central nervous system?

Oligodendrocytes

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Which type of neuron directly stimulates a muscle or gland?

Efferent neurons only

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A frog sees a fly and immediately sticks his tongue out to catch it. Which type of cell transmitted the visual signal from his eye to his brain?

Afferent neuron

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A trapeze artist loses her grip and falls off the trapeze, causing her heart rate to increase in response to the rear of falling (despite the net below to prevent injury). Which type of neurons is directly responsible for this increase in heart rate?

Efferent neuron

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In humans, and some primates, the most abundant neurons are the…

Interneurons

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Which part of the neuron conducts the electrical signals away from the cell body of a neuron?

Axon

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Which gilal cell(s) is/are only found in the peripheral nervous system?

Schwann cells

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In the context of the nervous system, what does the term “nucleus” mean?

A cluster of neurons in the CNS with a related function

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Where is a ganglion found?

Peripheral nervous system

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Which cells assist and nourish neurons that transmit electrical signals?

Glial cells

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Which category of organic macromolecule allows myelinated sheaths to act as electrical insulators?

Lipids

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Otto Loewi demonstrated that neurons transmit signals across synapse by _______.

Chemical signals

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Which process is responsible for the release of neurotransmitters from the presynaptic neurons into the synapse?

Exocytosis

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Electrical synapses are most common in the….

Retina

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If a drug inhibits the uptake of an excitatory neurotransmitter after it has been released into the synaptic cleft, what is the most likely result?

An increased number of EPSPs

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If a drug binds irreversibly to a postsynaptic receptor to prevent the binding of an excitatory neurotransmitter, what is the most likely result?

A decreased number of EPSPs

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If a drug binds to a receptor, which normally triggers the opening of a Na+ channel, causing it to open in the absence of neurotransmitter release, what is the most likely result?

An increased number of EPSPs

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In an effort to determine the mechanism of neuronal signaling, Otto Loewi isolated_____.

Frog brains

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For a neuron at rest, there is a higher concentration of ______ outside the cell than inside.

Na+

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When measuring membrane potential, the tip of a microelectrode is inserted into a(n) _______.

Axon

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What is the typical resting potential of an isolated neuron?

-70 mv

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The nernst equation is used to calculate the _______.

Equilibrium potential

Calculate the ENa for a neuron that has an extracellular concentration of Na + of 78 mM and an intracellular concentration of Na+ of 6 mM

68.0 mv

An abrupt and transient change in membrane potential is called a(n)

Action potential

When a neuron membrane potential becomes less negative, it is said to be_______.

Depolarized

The minimum level of depolarization required to initiate an action potential in an excitable cell is called the ____ potential.

Threshold

When a neuron membrane potential goes below its resting value it becomes______.

Hyperpolarized

The refractory period of a neuronal plasma membrane is important because it _______.

Ensures that an impulse will travel in a one-way direction.

During an action potential, the membrane potential can reach as high as______.

+30 mv

When threshold potential is reached______.

The activation gates of Na+ channels open

As the action potential peaks….

The inactivation gates of Na+ channels close

If the K + channels of an excitable plasma membrane were blocked by the action of a drug, which process(es) would be disrupted?

Repolarization and hyper polarization

Depolarization of the neuronal plasma membrane occurs due to…

The diffusion of Na+ into the cell

At which point in this action potential diagram are Na+ inactivation gates opening?

Answer the question using the accompanying figure. At which point in this action potential diagram are many Na+ activation gates open and K + activation gates closed?

Answer the question using the accompanying figure. At which point in this action potential diagram does the onset of Na+ channel inactivation stop the inward flow of Na+?

Answer the question using the accompanying figure. At which point in this action potential diagram does the K+ channel close to stabilize the membrane potential?

An action potential is propagated down an unmyelinated neuronal plasma membrane because it stimulates voltage-gated ____ channels adjacent to it. (Choose the most accurate answer)

Na+

Action potentials are propagated in a one-way direction down a neuronal plasma membrane because _____.

The adjacent channels upstream from the action potential are in a refractory period.

The magnitude of an action potential _____ as it is propagated down an excitable membrane due to the ____ principle.

Remains constant, all or nothing principle

The intensity of an electrical impulse is reflected in the _____ of action potentials

Frequency

The duration of an action potential is approximately five _____.

Milliseconds

Action potential propagation is the fastest in….

A myelinated axon with a large diameter

The spaces between adjacent Schwann cells are called ________.

Nodes of ranvier

Jean-Luc Eiselé and his coworkers used_____ receptors in their research on neurotransmitter receptor function.

Artificial

The neurotransmitter receptor research of Jean-Luc Eiselé and his coworkers showed that…

The parts of a receptor binding a neurotransmitter and conducting ions function independently

Place the events in chemical synapse transmission in the correct order.

Action potential reaches axon terminal of presynaptic neuron Ca2+ enters axon terminal Neurotransmitter released by exocytosis Neurotransmitter binds to postsynaptic receptor Ligand-gated ion channels open in postsynaptic membrane 4,1,5,3,2

What removes Ca 2+ from the inside of an axon terminal of a chemical synapse after an electrical impulse has passed?

Active transport pumps

When an action potential reaches the axon terminal, the ___ channels are activated to trigger synaptic vesicle release.

Voltage-gated Ca2+ channels

What will be the effect of a drug that prevents the release of intracellular calcium?

Decreased neurotransmitter release

The binding of a neurotransmitter to ligand-gated K + channels will cause ____ in the postsynaptic membrane.

Hyperpolarization

The binding of a neurotransmitter to ligand-gated Cl- channels will cause ___ in the postsynaptic membrane.

Hyperpolarization

The binding of a neurotransmitter to ligand-gated Na+ channels will cause _____ in the postsynaptic membrane.

Depolarization only

In vertebrates, the neurotransmitter acetylcholine ____

Can act as a direct neurotransmitter between neurons and muscle cells

Neuropeptide neurotransmitters…

Can act as pain reducers and initiate euphoria

When a fish clenches to grasp a pencil, which neurotransmitter is most likely involved?

Acetylcholine

Which neurotransmitter is most likely to be inhibitory?

GABA

After burning your hand on a hot burner, which neurotransmitter will most likely be released from the pain receptors?

Substance P

To which class of neurotransmitters does glutamate belong?

Amino acids

To which class of neurotransmitters does substance p belong?

Neuropeptides

To which class of neurotransmitters does dopamine belong?

Monoamines

A graded, subthreshold change in the postsynaptic membrane potential that moves it toward threshold is called a(n)

EPSP

At which neuronal structure does summation occur?

Axon hillock

Which neuronal structure has the greatest density of voltage-gated Na + channels, resulting in the lowest threshold potential along a neuron?

Axon hillock

Assume a neuron receives EPSPs and IPSPs from several adjacent neurons. How might that neurons threshold potential be reached, causing it to produce its own action potential?

If EPSPs outnumber IPSPs

Approximately how many neurons comprise the human brain?

86,000,000,000

Despite recent advances, ____ is/are needed to revolutionize the field of neuroscience and allow for better understanding of neural networking

Computational simulations

Axon terminal of presynaptic cell

Plasma membrane of postsynaptic cell

Receptors

Synaptic cleft

Synaptic vesicles

An IPSP, for example

C, hyperpolarization

An EPSP, for example

A, depolarization

Occurs in a postsynaptic membrane when ligand-gated Cl- channels open.

C , hyperpolarization

Occurs due to the diffusion of Na+

A, depolarization

Causes a neuron membrane potential to become more negative, allowing it to approach its resting potential

B, repolarization

Occurs in a postsynaptic membrane when ligand-gated Na+ channels open

A, depolarization

The phase of an action potential when the membrane potential becomes more positive

A, depolarization

Begins when Na+ channel inactivation gates close and K+ activation gates open

B, repolarization

Describes the change in resting membrane potential that causes it to approach threshold potential

A, depolarization

Occurs when a membrane potential becomes more negative than its resting membrane potential

C, hyperpolarization

Explain how the resting membrane potential and resting ion distributions are established in a neuron

A resting membrane potential of -70 mV is established due to the unequal distribution of ions across the neuron plasma membrane. Na+/K+ pumps accumulate Na+ outside the plasma membrane and K+ inside the plasma membrane, while the presence of negatively charged anions inside the cell give the inside of the plasma membrane an overall negative charge relative to the outside.

Explain how neuron action potential propagation rate can be increased

Neuron action potential propagation can be increased in two ways 1. By increasing axonal diameter 2. Myelinating the axon. Increased axonal diameter reduces electrical resistance to current flow. Myelination causes an electrical current to “jump” from one node of ranvier to the next by saltatory conduction, which is more rapid than conduction in an unmyelinated neuron

A toxin interferes with the opening Na+ channels in the postsynaptic membrane so they open more slowly when bound to a neurotransmitter, what effect would there be on action potential formation in the postsynaptic membrane?

This would cause a postsynaptic membrane action potential to form more slowly (if at all), as well as slow action potential propagation speed.

Valium is a drug that causes voltage-gated Cl- channels to open. What effects would this cause in a postsynaptic membrane?

Valium would cause hyperpolarization in the postsynaptic membrane. Thus, it would take more frequent, or a greater number, of EPSPs to generate an action potential in a postsynaptic membrane

In terms of changes in membrane potential, compare and contrast action potentials and graded potentials

Action potentials are all or none phenomena that form when a membrane potential of an excitable cell reaches threshold potential. Graded potentials are additive sub-threshold changes in the membrane potential of an excitable cell. The net effect of graded potentials may cause a membrane potential to move closer to, or further away from, threshold potential

Afferent neurons carry electric impulse directly to muscles and glands.

False- efferent neurons

Oligodendrocytes are responsible for myelinating central nervous system axons

True

Neurotransmitters are stored in vesicles located within axon terminals

True

If the equilibrium potential is close to the resting membrane potential, the net ionic movement across the membrane fill be very small

True

Depolarization occurs due to the diffusion of K+ across a neuron plasma membrane

False Na+

Saltatory conduction is the slowest form of action potential propagation

False- fastest

Neurotransmitters that bind to G-protein coupled receptors act more rapidly than those ionotropic receptors

False- less

Whether a neurotransmitter is inhibitory or excitatory depends on the type of receptor it binds to on the postsynaptic neuron

True

The additive effect of one neuron sending many EPSPs to another neuron over a brief period of time is called spatial summation

False- temporal summation

EPSPs can form due to the diffusion of Na+ across a neuron plasma membrane

True