Action Potentials and Synapse Biology - MCAT Biological and Biochemical Foundations of Living Systems
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When a neuron is unable to produce another action potential no matter how much stimulation is provided, what period is the neuron said to be in?
When a neuron is unable to produce another action potential no matter how much stimulation is provided, what period is the neuron said to be in?
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During the absolute refractory period, no action potential can occur. In the relative refractory period, an action potential can occur with more stimulation than is normally required.
During the absolute refractory period, no action potential can occur. In the relative refractory period, an action potential can occur with more stimulation than is normally required.
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The heart contains autorhythmic cells, which can generate an action potential on their own. These cells then spread the action potential throughout the heart, resulting in a contraction. Which of the following mechanisms is an explanation for why these cells can spontaneously generate action potentials?
The heart contains autorhythmic cells, which can generate an action potential on their own. These cells then spread the action potential throughout the heart, resulting in a contraction. Which of the following mechanisms is an explanation for why these cells can spontaneously generate action potentials?
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Remember that an action potential starts with the diffusion of sodium into the cell. As more sodium enters the cell, more voltage gated sodium channels open up. This leads to depolarization of the cell. With a steady diffusion of sodium into the cell, the threshold stimulus will eventually be attained, and an action potential will be generated. It is the steady diffusion of sodium into the autorhythmic cells which results in an action potential.
Remember that an action potential starts with the diffusion of sodium into the cell. As more sodium enters the cell, more voltage gated sodium channels open up. This leads to depolarization of the cell. With a steady diffusion of sodium into the cell, the threshold stimulus will eventually be attained, and an action potential will be generated. It is the steady diffusion of sodium into the autorhythmic cells which results in an action potential.
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Which of the following correctly pairs neuron structure with function?
Which of the following correctly pairs neuron structure with function?
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Voltage-gated calcium channels do not cause depolarization in neurons, but are integral to depolarization in muscle. Voltage-gated sodium channels are responsible for neural depolarization; there are no sodium leaky channels in neurons, as these would disrupt the resting potential. Voltage-gated potassium channels actively import potassium, whereas the sodium-potassium pump actively exports potassium. There is no such thing a potassium-calcium pump.
Voltage-gated calcium channels do not cause depolarization in neurons, but are integral to depolarization in muscle. Voltage-gated sodium channels are responsible for neural depolarization; there are no sodium leaky channels in neurons, as these would disrupt the resting potential. Voltage-gated potassium channels actively import potassium, whereas the sodium-potassium pump actively exports potassium. There is no such thing a potassium-calcium pump.
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During an action potential, depolarization is associated with which of the following?
During an action potential, depolarization is associated with which of the following?
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During depolarization, voltage-gated sodium channels open and allow a rapid influx of sodium ions. The membrane voltage rises from its resting potential of -70 mV to 35 mV. Depolarization is not associated with endocytosis of neurotransmitters.
During depolarization, voltage-gated sodium channels open and allow a rapid influx of sodium ions. The membrane voltage rises from its resting potential of -70 mV to 35 mV. Depolarization is not associated with endocytosis of neurotransmitters.
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Which of the following refers to the process by which action potentials jump from one node of Ranvier to another?
Which of the following refers to the process by which action potentials jump from one node of Ranvier to another?
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The answer is saltatory conduction. Saltatory conduction is the term used to define the process of action potential jumping described in the question. The other possbilities, while involved in the nervous system and its function, do not adaquately describe the process in question.
The answer is saltatory conduction. Saltatory conduction is the term used to define the process of action potential jumping described in the question. The other possbilities, while involved in the nervous system and its function, do not adaquately describe the process in question.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A scientist shows that the protein labeled "1" has a voltage gate, as well as an inactivation gate, while proteins 2 and 3 lack this dual gate architecture. What ion is most likely to be controlled by protein 1?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A scientist shows that the protein labeled "1" has a voltage gate, as well as an inactivation gate, while proteins 2 and 3 lack this dual gate architecture. What ion is most likely to be controlled by protein 1?
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Sodium channels have an inactivation gate, as well as a voltage gate. This allows the sodium channels to be turned off, even while voltage changes persist, thereby facilitating repolarization. This dual gate structure also causes the refractory period.
Sodium channels have an inactivation gate, as well as a voltage gate. This allows the sodium channels to be turned off, even while voltage changes persist, thereby facilitating repolarization. This dual gate structure also causes the refractory period.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The protein labeled "2" in the diagram facilitates repolarization following the peak of an action potential. What ion is most likely to be controlled by this protein channel?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The protein labeled "2" in the diagram facilitates repolarization following the peak of an action potential. What ion is most likely to be controlled by this protein channel?
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Potassium is the major species that repolarizes a neuron following depolarization. After sodium has entered the cell to create depolarization, repolarization is driven by potassium ion efflux.
Potassium is the major species that repolarizes a neuron following depolarization. After sodium has entered the cell to create depolarization, repolarization is driven by potassium ion efflux.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
Before any of the voltage-sensitive channels in a neuron open in response to adjacent depolarization, what is true of the the resting membrane potential?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
Before any of the voltage-sensitive channels in a neuron open in response to adjacent depolarization, what is true of the the resting membrane potential?
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The presence of potassium leak channels in the membrane allows potassium to drive the resting cell membrane potential nearer to its equilibrium potential than to sodium's.
The equilibrium potential is the electric potential that would exaclty balance the competing forces of concentration and electrical gradients. High potassium concentration in the cytosol drives potassium out of leak channels in the membrane, toward the extracellular space, but the inside develops a negative charge as a result. When this negative charge pulling positive potassium ions back in is enough to exactly cancel the concentration forces pushing potassium out, the equilibrium potential has been reached.
The presence of potassium leak channels in the membrane allows potassium to drive the resting cell membrane potential nearer to its equilibrium potential than to sodium's.
The equilibrium potential is the electric potential that would exaclty balance the competing forces of concentration and electrical gradients. High potassium concentration in the cytosol drives potassium out of leak channels in the membrane, toward the extracellular space, but the inside develops a negative charge as a result. When this negative charge pulling positive potassium ions back in is enough to exactly cancel the concentration forces pushing potassium out, the equilibrium potential has been reached.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The protein labeled "3" is an active transport pump that restores the normal balance of sodium and potassium every time an action potential travels through the region of the axon. What is this pump most likely to transport?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The protein labeled "3" is an active transport pump that restores the normal balance of sodium and potassium every time an action potential travels through the region of the axon. What is this pump most likely to transport?
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The sodium-potassium pump, or Na/K ATPase, is what restores ionic concentrations back to normal after an action potential. This pump is electrogenic, and active, using ATP to pump three sodium out of the cell, and two potassium into the cell. Along wtih the potassium leak channels, this keeps the potassium concentration in a cell high, and sodium concentration low.
The sodium-potassium pump, or Na/K ATPase, is what restores ionic concentrations back to normal after an action potential. This pump is electrogenic, and active, using ATP to pump three sodium out of the cell, and two potassium into the cell. Along wtih the potassium leak channels, this keeps the potassium concentration in a cell high, and sodium concentration low.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The refractory period is the period of time after action potential that a neuron is unable to "refire" if another stimulus is present.
If protein 1 is a voltage-gated sodium channel, protein 2 is a voltage-gated potassium channel, and protein 3 is a leak channel, which channel contributes most to the absolute refractory period?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The refractory period is the period of time after action potential that a neuron is unable to "refire" if another stimulus is present.
If protein 1 is a voltage-gated sodium channel, protein 2 is a voltage-gated potassium channel, and protein 3 is a leak channel, which channel contributes most to the absolute refractory period?
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The sodium channel being inactivated, via its inactivation gate, prevents a stimulus from initiating an action potential immediately after a previous stimulus.
During the absolute refractory period, this is a fact regardless of how strong the stimulus is. During the relative refractory period the neuron can be stimulated, but only by a very large stimulus.
The sodium channel being inactivated, via its inactivation gate, prevents a stimulus from initiating an action potential immediately after a previous stimulus.
During the absolute refractory period, this is a fact regardless of how strong the stimulus is. During the relative refractory period the neuron can be stimulated, but only by a very large stimulus.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A scientist is studying the nerve cell depicted in the above figure. He notices that proteins like 1, 2, and 3 are only located a certain regions along the length of the axon. What are these regions most likely to be called?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A scientist is studying the nerve cell depicted in the above figure. He notices that proteins like 1, 2, and 3 are only located a certain regions along the length of the axon. What are these regions most likely to be called?
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The proteins responsible for allowing ionic flow into and out of axons are most likely to be found at Nodes of Ranvier, where there is no myelin and ions can move freely. Action potentials travel via saltatory conduction, meaning that the ion channels are only stimulated a certain points on the membrane. The majority of the impulse is conducted through the interior of the axon without further external stimulation.
The proteins responsible for allowing ionic flow into and out of axons are most likely to be found at Nodes of Ranvier, where there is no myelin and ions can move freely. Action potentials travel via saltatory conduction, meaning that the ion channels are only stimulated a certain points on the membrane. The majority of the impulse is conducted through the interior of the axon without further external stimulation.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A dendrite carries an electrical signal to the nerve cell body associated with the axon in Figure 1. If this signal is inhibitory (an inhibitory post synaptic potential), which of the following is likely true of the impact of this signal on the cell?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A dendrite carries an electrical signal to the nerve cell body associated with the axon in Figure 1. If this signal is inhibitory (an inhibitory post synaptic potential), which of the following is likely true of the impact of this signal on the cell?
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An inhibitory post synaptic potential (IPSP) drives the post synaptic cell membrane toward hyperpolarization, and thus away from the threshold necessary to fire an action potential. As a result, the axon requires more stimuli in order to fire an action potential.
An inhibitory post synaptic potential (IPSP) drives the post synaptic cell membrane toward hyperpolarization, and thus away from the threshold necessary to fire an action potential. As a result, the axon requires more stimuli in order to fire an action potential.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
At the distal end of the axon shown in Figure 1, what process directly drives the fusion of synaptic vesicles to discharge neurotransmitter into the synaptic cleft?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
At the distal end of the axon shown in Figure 1, what process directly drives the fusion of synaptic vesicles to discharge neurotransmitter into the synaptic cleft?
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Calcium is a very common vehicle that drives membrane fusion, including the fusion of synaptic vesicles with the synaptic cell membrane. This allows the ejection of neurotransmitter into the synaptic cleft.
Calcium is a very common vehicle that drives membrane fusion, including the fusion of synaptic vesicles with the synaptic cell membrane. This allows the ejection of neurotransmitter into the synaptic cleft.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The cell body associated with the axon in Figure 1 is actively taking in electrical inputs from neighboring cells. Which of the following properties is the major difference between post-synaptic potentials from neighboring neurons and pre-synaptic action potentials?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The cell body associated with the axon in Figure 1 is actively taking in electrical inputs from neighboring cells. Which of the following properties is the major difference between post-synaptic potentials from neighboring neurons and pre-synaptic action potentials?
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Post-synaptic potentials are graded, while action potentials are "all-or-nothing". This means that the farther from the point of integration in a nerve cell an electrical input enters, the weaker its corresponding post-synaptic potential will be when it reaches the distant integration site.
In this way, post-synaptic potentials can be summed as a function of intensity and distance, while action potentials are always the same amplitude no matter from how far they travel.
Post-synaptic potentials are graded, while action potentials are "all-or-nothing". This means that the farther from the point of integration in a nerve cell an electrical input enters, the weaker its corresponding post-synaptic potential will be when it reaches the distant integration site.
In this way, post-synaptic potentials can be summed as a function of intensity and distance, while action potentials are always the same amplitude no matter from how far they travel.
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Immediately after an action potential, there is a fraction of time when the neuron can only be stimulated if there is a stronger than normal stimulus. What is this fraction of time called?
Immediately after an action potential, there is a fraction of time when the neuron can only be stimulated if there is a stronger than normal stimulus. What is this fraction of time called?
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The relative refractory period is the moment directly after an action potential when the neuron can only be stimulated to fire another action potential if there is a larger than normal stimulus. During an action potential, voltage-gated sodium channels open. After the action potential, the channels are gated and cannot be re-stimulated. This period is the absolute refractory period. The secondary gating is released, making the sodium-channels functional again, but the neuron has not been fully restored to resting potential. Release of potassium through voltage-gated potassium channels leads to hyperpolarization until the sodium-potassium pump is able to restore ion balance. This restoration takes longer than the un-gating of sodium channels, creating a period when the cell is hyperpolarized, but the voltage-gated sodium channels are capable of stimulation. If a large enough stimulus overcomes the cell hyperpolarization and reaches threshold, and action potential can still occur. This period is the relative refractory period.
The relative refractory period is the moment directly after an action potential when the neuron can only be stimulated to fire another action potential if there is a larger than normal stimulus. During an action potential, voltage-gated sodium channels open. After the action potential, the channels are gated and cannot be re-stimulated. This period is the absolute refractory period. The secondary gating is released, making the sodium-channels functional again, but the neuron has not been fully restored to resting potential. Release of potassium through voltage-gated potassium channels leads to hyperpolarization until the sodium-potassium pump is able to restore ion balance. This restoration takes longer than the un-gating of sodium channels, creating a period when the cell is hyperpolarized, but the voltage-gated sodium channels are capable of stimulation. If a large enough stimulus overcomes the cell hyperpolarization and reaches threshold, and action potential can still occur. This period is the relative refractory period.
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An action potential travels down a neuronal axon. Which of the following is occurring during depolarization of the neuron?
An action potential travels down a neuronal axon. Which of the following is occurring during depolarization of the neuron?
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It is important to recognize that sodium is flowing into the neuron during depolarization. The area outside of the neuron is electrically positive relative to the area inside of the neuron, resulting in the negative resting membrane potential of the cell. This potential allows positively charged sodium ions to flow from a high concentration of positive charge, towards the negative charge in the cell interior. Because the sodium travels from a region of relatively positive charge to a region of relatively negative charge, it is flowing down its electrical gradient.
Due to action by the sodium-potassium pump, there is also a large concentration of sodium ions outside of the cell, relative to the small sodium ion concentration inside the cell. This imbalance creates a chemical gradient across the axon membrane. The opening of the voltage-gated sodium channels during depolarization allows sodium to flow down chemical gradient from high ion concentration to low ion concentration.
It is important to recognize that sodium is flowing into the neuron during depolarization. The area outside of the neuron is electrically positive relative to the area inside of the neuron, resulting in the negative resting membrane potential of the cell. This potential allows positively charged sodium ions to flow from a high concentration of positive charge, towards the negative charge in the cell interior. Because the sodium travels from a region of relatively positive charge to a region of relatively negative charge, it is flowing down its electrical gradient.
Due to action by the sodium-potassium pump, there is also a large concentration of sodium ions outside of the cell, relative to the small sodium ion concentration inside the cell. This imbalance creates a chemical gradient across the axon membrane. The opening of the voltage-gated sodium channels during depolarization allows sodium to flow down chemical gradient from high ion concentration to low ion concentration.
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Which of the following ions plays a direct role in the release of neurotransmitters from the pre-synaptic terminal?
Which of the following ions plays a direct role in the release of neurotransmitters from the pre-synaptic terminal?
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While sodium and potassium maintain important functions in the conduction of action potentials along the axon of the neuron, it is calcium that is responsible for the binding of vesicles containing neurotransmitters to the pre-synaptic membrane. A severe lack of calcium would inhibit the release of neurotransmitters into the synaptic cleft. When the action potential reaches the axon terminal, it stimulates the opening of voltage-gated calcium channels. The resulting influx of calcium binds to synaptic vesicles, initiating the process to release their neurotransmitter contents into the synaptic cleft.
While sodium and potassium maintain important functions in the conduction of action potentials along the axon of the neuron, it is calcium that is responsible for the binding of vesicles containing neurotransmitters to the pre-synaptic membrane. A severe lack of calcium would inhibit the release of neurotransmitters into the synaptic cleft. When the action potential reaches the axon terminal, it stimulates the opening of voltage-gated calcium channels. The resulting influx of calcium binds to synaptic vesicles, initiating the process to release their neurotransmitter contents into the synaptic cleft.
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What is the process by which action potentials are able to "jump" from one node of Ranvier to the next?
What is the process by which action potentials are able to "jump" from one node of Ranvier to the next?
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Saltatory conduction is the property that allows an action potential to jump from one node to the next along a neural axon. This is accomplished by the presence of myelin, a non-conducting sheath around the axon. Myelin interrupts the flow of current down the membrane, forcing it to skip from one region of membrane to the next, rather than fluidly traveling down the entire axon length.
Depolarization is the stage of action potential transmission in which sodium channels are opened, and sodium rushes into the cell down its concentration gradient. The resting potential of the neural membrane is roughly 
. The rapid influx of positive sodium ions causes this potential in increase to 
at the action potential peak.
Repolarization is the stage of action potential transmission in which potassium channels of a cell are opened, and potassium moves out of the cell. This event re-establishes the negative resting membrane potential.
The refractory period is the obligatory temporal gap between action potentials. After an action potential, the primary gating mechanism of the voltage-gated sodium channels causes the channels to close and deactivate. This constitutes the absolute refractory period, during which no stimulus is capable of producing an action potential. The relative refractory period follows, during the cell repolarization, when potassium efflux causes the membrane potential to drop below the resting potential. This state of hyperpolarization means that a greater stimulus is required to reach threshold, and constitutes the relative refractory period.
Saltatory conduction is the property that allows an action potential to jump from one node to the next along a neural axon. This is accomplished by the presence of myelin, a non-conducting sheath around the axon. Myelin interrupts the flow of current down the membrane, forcing it to skip from one region of membrane to the next, rather than fluidly traveling down the entire axon length.
Depolarization is the stage of action potential transmission in which sodium channels are opened, and sodium rushes into the cell down its concentration gradient. The resting potential of the neural membrane is roughly
Repolarization is the stage of action potential transmission in which potassium channels of a cell are opened, and potassium moves out of the cell. This event re-establishes the negative resting membrane potential.
The refractory period is the obligatory temporal gap between action potentials. After an action potential, the primary gating mechanism of the voltage-gated sodium channels causes the channels to close and deactivate. This constitutes the absolute refractory period, during which no stimulus is capable of producing an action potential. The relative refractory period follows, during the cell repolarization, when potassium efflux causes the membrane potential to drop below the resting potential. This state of hyperpolarization means that a greater stimulus is required to reach threshold, and constitutes the relative refractory period.
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In saltatory conduction displayed by neurons containing myelinated axons, ion flow takes place at which region of the axon?
In saltatory conduction displayed by neurons containing myelinated axons, ion flow takes place at which region of the axon?
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Saltatory conduction is defined as the method by which action potentials are propagated along axons in myelinated neurons. The method by which they do this is by the generation of action potentials at each node of Ranvier. The only places along the myelinated axon that display ion flow are the nodes of Ranvier. The myelinated portions do not display ion flow, allowing the electrical stimulus to rapidly jump down the axon from one node to the next rather than slowly flow down the full axon length.
Schwann cells are types of cell that make up the myelin coated sheath for select neurons.
Saltatory conduction is defined as the method by which action potentials are propagated along axons in myelinated neurons. The method by which they do this is by the generation of action potentials at each node of Ranvier. The only places along the myelinated axon that display ion flow are the nodes of Ranvier. The myelinated portions do not display ion flow, allowing the electrical stimulus to rapidly jump down the axon from one node to the next rather than slowly flow down the full axon length.
Schwann cells are types of cell that make up the myelin coated sheath for select neurons.
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Which of the following is false regarding synapses?
Which of the following is false regarding synapses?
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There are two types of synapses: the chemical synapse and the electrical synapse. Chemical synapses are more common than electrical synapses, and use neurotransmitters (chemicals) to propagate action potentials. Electrical synapses have tunnels between cells, called gap junctions, that quickly transmit signals from one cell to the other. Electrical synapses are found extensively in the heart, since it is essential to have quick signal transmission between cardiac cells.
In chemical synapses an action potential reaches the end of a presynaptic neuron, which causes neurotransmitters to be released from the presynaptic neuron. These neurotransmitters bind to receptors on the postsynaptic neuron and initiate a signal transduction pathway in the postsynaptic neuron. The space between the presynaptic and postsynaptic neuron is called the synaptic cleft. Synaptic clefts are important regions where neurotransmitters are released and regulated.
Calcium ions play an important role in chemical synapses. Once an action potential arrives at the presynaptic neuron terminal, calcium ion channels on the presynaptic neuron become permeable to calcium ions. This facilitates the movement of calcium ions into the presynaptic neuron. Influx of calcium ions signals the presynaptic neuron to release neurotransmitters into the synaptic cleft, which eventually bind to receptors on the postsynaptic neuron. The calcium ions do not enter the postsynaptic neuron at the synapse.
There are two types of synapses: the chemical synapse and the electrical synapse. Chemical synapses are more common than electrical synapses, and use neurotransmitters (chemicals) to propagate action potentials. Electrical synapses have tunnels between cells, called gap junctions, that quickly transmit signals from one cell to the other. Electrical synapses are found extensively in the heart, since it is essential to have quick signal transmission between cardiac cells.
In chemical synapses an action potential reaches the end of a presynaptic neuron, which causes neurotransmitters to be released from the presynaptic neuron. These neurotransmitters bind to receptors on the postsynaptic neuron and initiate a signal transduction pathway in the postsynaptic neuron. The space between the presynaptic and postsynaptic neuron is called the synaptic cleft. Synaptic clefts are important regions where neurotransmitters are released and regulated.
Calcium ions play an important role in chemical synapses. Once an action potential arrives at the presynaptic neuron terminal, calcium ion channels on the presynaptic neuron become permeable to calcium ions. This facilitates the movement of calcium ions into the presynaptic neuron. Influx of calcium ions signals the presynaptic neuron to release neurotransmitters into the synaptic cleft, which eventually bind to receptors on the postsynaptic neuron. The calcium ions do not enter the postsynaptic neuron at the synapse.
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