SB14

Place in order the events of the propagation of an action potential in a myelinated axon. Start with the generation of an action potential.

An initial action potential is generated. Local currents are generated. Local currents flow to the next node of Ranvier. Local currents promote depolarization. Threshold is reached in the membrane. The next action potential is generated.

What type of potential is irreversible?

Action potential

Identify the ions that have a higher concentration in the extracellular fluid compared to the intracellular fluid. Select all that apply.

Ca++ Cl- Na+

_____ potentials are conducted in a decremental fashion, while ____ potentials are conducted with a constant magnitude.

Graded, action

The sodium-potassium pump is responsible for what portion of the resting membrane potential?

Less than 15mV

Which type of circuit is associated with complex neuronal processes, such as solving mathematical equations?

Parallel after-discharge

Large, negatively charged proteins inside the cell _____ readily diffuse across the neuron membrane.

cannot

Neurotransmitter receptors at the postsynaptic membrane act as ________ regulated ion gates.

chemical

A pathway in which one input nerve fiber synapses with multiple postsynaptic neurons is called a _______ pathway.

diverging

True or false: When a neurotransmitter binds to a receptor on a postsynaptic membrane, a depolarization will always occur.

false

The sodium-potassium pump plays a _____ role in maintaining resting membrane potential.

minor

Because of its repulsion to the negatively charged proteins within the neurons, Cl- diffuses ______.

out of the cell and accumulates in the extracellular fluid

The propagation of action potentials from one node of Ranvier to another along a myelinated axon is called ______ conduction.

saltatory

By definition, ______ occurs when multiple stimuli combine their effects on a cell to produce a response.

summation

When signals occur rapidly at just one synapse, it is ______ summation.

temporal

The intracellular fluid is considered to be electrically neutral because ______.

there are the same number of positively and negatively charged ions

Match the type of synapse with the correct description. Electrical synapse chemical synapse

A gap junction that allows an ionic current to flow between adjacent cells A synapse where one cell releases a neurotransmitter to communicate with another cell

Match the various stimuli that affect the frequency of action potentials with the correct definition. Subthreshold stimulus Threshold stimulus Maximal stimulus Submaximal stimulus

A stimulus not strong enough to produce a graded potential that reaches threshold A stimulus that is just strong enough to reach threshold and cause the production of a single action potential A stimulus just strong enough to produce a maximum frequency of action potentials A stimulus between threshold and maximal stimulus strength A stimulus stronger than maximal stimulus

What type of potential is non-decremental?

Action potential

Place the events of an electrical synapse in chronological order, starting with the first at the top.

An action potential occurs within the membrane of an initial cell. A local current is generated. The local current flows through a gap junction. This stimulates the production of an action potential in an adjacent cell.

Place the events of a chemical synapse in chronological order, starting with the first at the top.

An action potential reaches the presynaptic terminal. Voltage-gated Ca++ channels open. Ca++ diffuses into the presynaptic terminal. Neurotransmitters are released into the synaptic cleft. Neurotransmitters bind to receptors on the postsynaptic membrane. Depolarization or hyperpolarization of the postsynaptic membrane occurs.

Explain why Na+ has little effect on establishing the resting membrane potential?

At rest, the membrane is relatively impermeable to Na+ because there are few Na+ leak channels.

Identify the type of synapse that includes a presynaptic cell, synaptic cleft, and postsynaptic cell.

Chemical

Which common ion associated with neuron function diffuses out of the cell due to its repulsion to the large intracellular proteins?

Cl-

Identify the difference between EPSPs and IPSPs.

EPSPs promote a depolarization and IPSPs promote a hyperpolarization.

Place the events of the propagation of an action potential in a myelinated axon.

Generation of an initial action potential Generation of local currents Flow of local currents to the next node of Ranvier Depolarization results from the local currents. Threshold is reached in the membrane. Generation of the next action potential

Differentiate graded potentials and action potentials. Select all that apply.

Graded potentials are conducted in a decremental fashion and action potentials are conducted with a constant magnitude. The magnitude of graded potentials is variable and action potentials are all-or-none.

_____ occurs when the inside of the plasma membrane becomes more negative, and ______ occurs when the inside of the plasma membrane becomes less negative.

Hyperpolarization, depolarization

What is the nature of the signal that propagates along neurons that ultimately regulates and coordinates the functions of the body?

It is electrical.

What effect will a neurotransmitter have on the postsynaptic membrane?

It may produce a depolarization or a hyperpolarization.

Indicate the correct order of events that occur during a single action potential.

Local potential decreases membrane potential. Threshold is reached. Depolarization spike occurs. Repolarization occurs. Afterpotential occurs. Resting membrane potential re-established.

What is the name of the gaps found between segments of myelin along an axon?

Nodes of Ranvier

Describe characteristics of receptors at the synapses. Select all that apply.

Only specific molecules are able to bind to the receptors They are ligand activated receptors

Which type of circuit involves neurons stimulating other neurons in parallel and resulting in a common output cell?

Parallel after-discharge

Identify the correct sequence of information in a chemical synapse.

Presynaptic terminal, synaptic cleft, postsynaptic membrane

Identify the characteristics of graded potentials.

Reversible Graded Decremental

Explain why the propagation of action potentials occurs in one direction.

The absolute refractory period prevents the generation of an action potential in the reverse direction.

Identify how neurotransmitters are removed from the synaptic cleft.

The neurotransmitter is broken down by an enzyme. The neurotransmitter diffuses away from the synapse. The neurotransmitter is transported into the presynaptic terminal.

Identify characteristics that are responsible for establishing the resting membrane potential.

The plasma membrane is impermeable to large, intracellular anions. K+ concentration is higher in the intracellular fluid and Na+ concentration is higher in the extracellular fluid.

If both IPSP's and EPSP's stimulate the same postsynaptic cell, which of the following is true?

The response of the postsynaptic cell depends on which type of graded potential has a larger effect.

Identify the statement that best describes the magnitude of a graded potential.

The size of a graded potential is proportional to the strength of the stimulus.

Identify the similarity between EPSPs and IPSPs. Select all that apply.

The size of the EPSP or the IPSP is proportional to the strength of the stimulus. They are conducted in a decremental fashion. They are both graded potentials.

What factors are in equilibrium that contribute to the resting membrane potential?

The tendency for K+ to diffuse out and its attraction to the negative interior of the cell.

Identify the characteristics of action potentials.

They are all-or-none. The strength of the stimulus determines the frequency of the action potentials. They are propagated in a non-decremental fashion.

Identify the statements that are true regarding the nature of the large proteins found within neurons.

They are negatively charged. They do not readily diffuse through the membrane. They are synthesized inside the cell.

Identify why the membrane becomes hyperpolarized following the repolarization phase of an action potential.

Voltage-gated K+ channels remain open for a short period of time after reaching RMP; allowing K+ to diffuse out of the cell.

A period of time when a cell cannot respond again to an electrical stimulus is the __ refractory period.

absolute

After a nerve cell responds to a stimulus, the period of time when the cell cannot respond again, regardless of the strength of stimulus, is called the _________ refractory period.

absolute

Electrical signals that are propagated along axons in a non-decremental fashion are called _____ potentials

action potentials

The electrical signals that are propagated along axons, regulating and coordinating body activities, are known as _____.

action potentials

Within a chemical synapse, the receptors _____.

bind to very specific ligands

A molecule such as a neurotransmitter or a hormone that _____ is called a(n) ligand.

binds to a receptor

Entry of ______ ions into the synaptic knob triggers exocytosis of neurotransmitters.

calcium

Synapses in which neurotransmitters are released are called ______ synapses.

chemical

In the region of the plasma membrane immediately adjacent to the area where the last action potential occurred, the entry of positive ions stimulates a new action potential. This kind of conduction is known as ______ conduction.

continous

The type of action potential conduction in an unmyelinated axon is ______ conduction.

continuous

A pathway in which several input nerve fibers synapse with fewer postsynaptic neurons is called a ______ pathway.

converging

When several input nerve fibers synapse with fewer postsynaptic neurons, this is called a _______ pathway.

converging

Neurotransmitter X has an excitatory effect on cell A. It also has an effect on cell B. The effect on cell B ______.

could be excitatory or inhibitory

During an action potential, an increase in membrane permeability to Na+ leads to a(n) _______ followed by an increase in permeability to K+ that leads to a(n) ______ of the membrane and a slight afterhyperpolarization.

depolarization, repolarization

A ______ pathway allows one part of the nervous system to affect several other parts of the nervous system.

diverging

Local currents flow through gap junctions between adjacent cells in a(n) _____ synapse.

electrical

Gap junctions allow direct communication or ionic flow between adjacent cells for a(n) ______ synapse, while synapses that use neurotransmitters to signal from the presynaptic to postsynaptic cell are called _______ synapses.

electrical, chemical

The resting membrane potential is a(n) ______ that is established when the tendency for K+ to diffuse out of the cells is equal to the tendency for K+ to be attracted to the negatively charged proteins within the cell.

equilibrium

A postsynaptic cell may receive both inhibitory and _______ postsynaptic potentials.

excitatory

The entry of calcium into the synaptic knob triggers ______.

exocytosis of neurotransmitter

True or false: Na+ has the greatest influence on resting membrane potential due to its high permeability in the membrane.

false

True or false: The magnitude of an action potential is important in relaying information about the strength of a stimulus.

false

Neuron communication about the strength of a stimulus is conveyed by the _______ of action potentials.

frequency

A protein channel that opens or closes in response to a stimulus would be classified as a ______ channel.

gated

Some protein channels in a cellular membrane are able to open or close in response to stimuli; because of this characteristic, these channels are called ______ channels.

gated

Binding of chemical signals to receptors, changes in membrane voltage, mechanical stimulation, temperature changes and spontaneous membrane changes can all cause ______ potentials.

graded

The slow closing of voltage-gated potassium channels is the cause of ______.

hyperpolarization

At rest, the neuron plasma membrane is relatively ______ to Na+; therefore, Na+ does not influence the resting membrane potential very much.

impermeable

As the strength of a stimulus increases, the magnitude of a graded potential will ______.

increase

K+ concentration is higher in the ______ fluid.

intracellular

K+ concentration is higher in the ______ fluid and Na+ concentration is higher in the ______ fluid

intracellular, extracellular

Electrically excitable cells use the difference of ______ across the cell membrane to carry out their functions.

ions

Action potentials are conducted more rapidly along an axon with a _____ diameter.

larger

When a neuron is at rest, ______ channels are open.

leak

Ion channels that are always open are called ______.

leak channels

A specific molecule binds to a membrane receptor. This molecule is called a ______.

ligand

Decremental potentials along a dendrite or the cell body are called ______ potentials.

local

In an unmyelinated axon, an action potential generates a local current flow that stimulates an action potential in the ______.

membrane immediately adjacent to the previous action potential

Action potentials are conducted more rapidly along ______ axons.

myelinated

When the resting membrane potential becomes more _____ the condition is referred to as hyperpolarization.

negative

Ligand-gated ion channels bind ______ that have diffused across a synaptic cleft.

neurotransmitters

The intracellular fluid has essentially the same number of positive and negative charges and is therefore electrically ______ .

neutral

The gaps found between Schwann cells forming the myelin are referred to as the _______ of __________.

nodes ranvier

The plasma membrane has opposite charges arranged across the membrane and is thus said to be ______ .

polarized

When opposite charges are arranged on opposing sides of a membrane, the membrane is said to be ______.

polarized

At a synapse, the neuron that responds to the neurotransmitter is the ______ neuron.

postsynaptic

The second neuron at a synapse (where the neurotransmitter binds) would be the _____ neuron.

postsynaptic

______ is the electrolyte that has the greatest influence on resting membrane potential due to the greater permeability of the plasma membrane to this electrolyte.

potassium

At a synapse, the neuron that releases a neurotransmitter referred to as ______.

presynaptic

The first neuron at a synapse (the end of an axon that releases neurotransmitter) would be the ______ neuron.

presynaptic

The purpose of the absolute refractory period is to _____.

prevent action potentials from being generated in reverse direction

A nerve cell can only respond to an unusually strong stimulus during the ______ refractory period.

relative

After a nerve cell responds to a stimulus, the period of time when the cell cannot respond again except to an unusually strong stimulus is called the ____ refractory period.

relative

Diffusion, degradation, and re-uptake all describe the mechanisms of ______.

removing neurotransmitters from the synaptic cleft

A ______ circuit has a chain of neurons that makes a positive-feedback loop.

reverberating

A ______ occurs when neurons are arranged in a circular fashion and produce action potentials more than once.

reverberating circuit

Propagation of an action potential down a myelinated axon requires that the action potential "jumps" from node to node in a process called ______ conduction.

saltatory

An axon with a smaller diameter will conduct action potentials more _______ than an axon with a larger diameter

slowly

An unmyelinated axon will conduct action potentials more ______ than a myelinated axon.

slowly

When threshold is reached due to signals arriving at multiple synapses, _________ summation has occurred.

spatial

Graded potentials may be caused by ______.

spontaneous changes (not caused by a specific stimulus) mechanical stimulation chemical signals binding to receptors temperature changes changes in voltage across the plasma membrane

A stimulus that is not strong enough to produce a graded potential that reaches threshold is called a(n) ______ stimulus.

subthreshold

When multiple graded potentials combine their effects on a cell to produce a response, the process is called ______.

summation

When the effect of one graded potential is added to the effect of another, ______ occurs.

summation

When the effect of one graded potential is added to the effect of another, this is referred to as ______ .

summation

When the effect of one graded potential is added to the effect of another, this is referred to as ________.

summation

Excitable cells operate through the movement of ions across _____.

the plasma membrane

In order for an action potential to occur, a minimum membrane potential called the ______ must be reached.

threshold

In order for local potentials to trigger an action potential, the membrane must reach a level called the ______.

threshold

True or false: A neurotransmitter can have excitatory effects on one cell and inhibitory effects on another cell.

true

An action potential is initiated immediately adjacent to where the last action potential terminated in ______ axons.

unmyelinated