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Example Questions
Example Question #1 : Help With Action Potential Physiology
What part of the action potential results in the depolarization of the cell?
Closing of voltage-gated sodium channels
Opening of voltage-gated sodium channels
Closing of voltage-gated potassium channels
Opening of voltage-gated potassium channels
Opening of voltage-gated sodium channels
When at rest, the neuron initially has a negative membrane potential. At the beginning of an action potential, voltage-gated sodium channels open, allowing sodium ions to enter the cell. This causes the cell to become positively charged compared to the outside of the cell. This process is called depolarization.
After depolarization occurs, the sodium channels close, initiating the absolute refractory period. Voltage-gated potassium channels then open and potassium ions exit the cell. This results in hyperpolarization and the relative refractory period. The potassium channels then close and the sodium-potassium pump returns the cell to its resting potential by removing sodium and collecting potassium.
Example Question #2 : Help With Action Potential Physiology
Which of the following does NOT take place during an action potential?
Repolarization
Hyperpolarization
Depolarization
Potentialization
Potentialization
An action potential across a cell membrane has five phases:
1. The resting membrane potential is a negative membrane potential established by the sodium-potassium pump and maintained by potassium leak channels.
2. Depolarization involves opening of voltage-gated sodium channels and results in a rapid influx of positively-charged sodium ions into the cell, creating a positive membrane potential.
3. Overshoot occurs during the maximal value (peak) of the action potential.
4. Hyperpolarization occurs when sodium channels close and potassium channels open, allowing potassium to leak out the cell, and establishing a negative membrane potential below the resting potential.
5. Repolarization occurs when voltage-gated potassium channels eventually close and the membrane potential returns to the resting value via action of the sodium-potassium pump.
Potentiation refers to the phenomenon when nerves become more effective at transmitting signals due to extensive use of the same pathway.
Example Question #2 : Help With Action Potential Physiology
Which of the following statements is true concerning the absolute refractory period?
The action potential will proceed, but will take place in the opposite direction, re-stimulating previously stimulated neurons
A larger than normal stimulus is needed in order to create an action potential during this time
Even the smallest stimulus will create an action potential during this time
Sodium channels are still open from a pervious stimulus
No stimulus can result in an action potential during this time
No stimulus can result in an action potential during this time
Once an action potential has been created, the membrane has a period of time during which it cannot be stimulated to create another action potential. The absolute refractory period occurs when the voltage-gated sodium channels initially close. The first gating mechanism of these channels cannot be overcome by an electrical stimulus, and the sodium channels will remain closed even if a large electrical stimulus is present. During this period, even a very large stimulus cannot result in neural depolarization.
Following this, the secondary gating mechanism for the channel becomes active. This mechanism is sensitive to electrical stimuli, but keeps the channels closed when the neuron is at rest. The relative refractory period results when sodium channels are capable of opening, but the cell is hyperpolarized, making it very difficult to initiate a stimulus that reaches the action potential threshold.
Example Question #4 : Help With Action Potential Physiology
What are the two gates of the voltage-gated channels along the axonal plasma membrane?
and
Activation and reactivation
Activation and inactivation
Positive and negative
Activation and inactivation
The voltage-gated channels along the axonal plasma membrane open and close in response to changes in voltage, and may exist in three distinct states: deactivated, activated, and inactivated. While the axon is at rest, these channels are said to be deactivated; they are impermeable to sodium ions since their activation gates are closed. Once the neuron gets depolarized to the threshold of the voltage-gated sodium channels, the activation gates open, allowing the influx of sodium down its concentration gradient into the cell. During this time the channels are in their activated state. At the peak of the action potential the activation gates are still open, but the inactivation gates close, stopping the flow of sodium through the channels. The channels are in the inactivated state due to the cell becoming depolarized. Once the membrane potential drops back down towards resting, the inactivation gates open, and the activation gates close, thereby deactivating the channels again, until another action potential depolarizes the membrane.
Example Question #4 : Help With Action Potential Physiology
Which of the following are in the correct order regarding action potentials?
1. The neuron has a resting potential.
2. Sodium ions exit the cell and hyperpolarize the membrane potential.
3. The membrane potential then reaches the threshold level.
4. An action potential is fired, which means that the hyperpolarization spreads down the neuron's axon.
1. The neuron has a resting potential.
2. Sodium ions enter the cell and alter the membrane potential.
3. The membrane potential depolarizes all the way up to the threshold level.
4. An action potential is fired, which means that the depolarization spreads down the neuron's axon.
1. The neuron has a resting potential.
2. Sodium ions enter the cell and alter the membrane potential.
3. The membrane potential hyperpolarizes beyond the threshold level.
4. An action potential is fired, which means that the depolarization spreads down the neuron's axon.
1. The neuron has a resting potential.
2. The membrane potential depolarizes all the way up to the threshold level.
3. Sodium ions enter the cell and alter the membrane potential.
4. An action potential is fired, which means that the depolarization spreads down the neuron's axon.
1. The neuron has a resting potential.
2. Sodium ions enter the cell and alter the membrane potential.
3. The membrane potential depolarizes all the way up to the threshold level.
4. An action potential is fired, which means that the depolarization spreads down the neuron's axon.
The neuron has a resting potential. In its resting state, the neuron has a resting potential with a slightly negative interior compared to the exterior. Sodium ions enter the cell and alter the membrane potential. Through voltage-gated channels, enters and makes the interior less negative therefore decreasing the membrane potential difference, which is known as depolarization. The membrane potential depolarizes all the way up to the threshold level. After enough enters, the threshold membrane potential is reached. This opens more channels. An action potential is fired, which means that the depolarization spreads down the neuron's axon. This travels down the entire axon, eventually reaching the dendrite and signaling to other neurons.
Example Question #5 : Help With Action Potential Physiology
Which type of signal is transmitted along a neuron?
Hormonal
Osmosis
Chemical
Mechanical
Electrical
Electrical
To support the general function of the nervous system, neurons must communicate within the cell (intracellular signaling) and between other cells (intercellular signaling). In order to achieve long distance and rapid communication, neurons have special abilities for sending electrical signals (action potentials) along axons. This mechanism is called conduction, and it is how the neuron's cell body communicates with its own terminals via the axon. Communication between neurons is achieved at synapses by the process of neurotransmission.
Example Question #3 : Help With Action Potential Physiology
When an action potential occurs, the permeability of __________ across the cell membrane becomes much greater.
Sodium
Calcium
Magnesium
Potassium
Chloride
Sodium
At resting potential, the cell membrane is about 25 times more permeable to potassium ions than it is to sodium ions. During an action potential, the membrane becomes much more permeable to sodium ions than potassium ions, causing the membrane potential to become more positive, as sodium flows down its concentration gradient into the cell. Note that this concentration gradient is largely set up by the action of the sodium-potassium ATPase, which pumps three sodium ions out of the cell in exchange for two potassium ions into the cell.
Example Question #4 : Neural Physiology
The junction between the transmitting and receiving neuron is called a(n) __________.
action potential
node of Ranvier
neurotransmitter
synapse
myelin sheath
synapse
A synapse is a specialized junction between cells. It is involved in the integration and converging of signals between neurons. At a synaptic junction, the membranes of the pre- and post- synaptic neurons are separated by a gap called a synaptic cleft, which is the site of neurotransmitter release.
Example Question #4 : General Neuron Physiology
Which of the following is responsible for opening sodium channels in the plasma membrane of the receiving neuron, leading to an action potential or more excitable neuron?
Glutamate
GABA (gamma-aminobutyric acid)
Calcium
Chloride
Norepinephrine
Glutamate
Glutamate opens sodium channels in the plasma membrane of the receiving neuron, moving the action potential towards (depolarize) the sodium Nernst potential (81mV). GABA is an inhibitory neurotransmitter which opens chloride channels in the plasma membrane of the receiving neuron, making the neuron more difficult to excite (hyperpolarized).
Example Question #3 : General Neuron Physiology
The resting membrane potential (RMP) is primarily determined by which ion?
Sodium
Calcium
Chloride
Potassium
Magnesium
Potassium
The resting membrane potential is based on the difference in electrical charges of the ions that flow through the membrane. The membrane potential has a greater permeability to potassium when at rest which causes a shift in its potential. Thus, potassium has the strongest affect on the RMP and causes it to be closer to potassium's reversal potential. Side note: This potential is strongly held by the sodium potassium pump.
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