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Why do not action potentials occur during the repolarization phase?
It has to do with what types of channels are open during this phase. In the repolarization phase the number of potassium channels are increased and the number of sodium channels are decreased. This allows for action potentials to not occur. Otherwise, the action potentials would add up and produce tetany.
Which cell must have action potentials to produce one or more action potentials in the postsynaptic cell?
A neuron (nerve cell) receives dendritic input in order to generate action potentials to transmit signals of the same. After the action potential triggers release of neurotransmitters in the axonal terminal of that neuron, those neurotransmitters propagate the signal forward to the next neuron, and so forth.
Why is the cardiac action potential longer?
The reason why cardiac muscle has a longer action potential is to extend the absolute refractory period to prevent another action potential. If too many action potentials stimulate the cardiac muscle it can get into tetanus which keeps the heart continuously contracted without relaxation.
How does an action potential differ from a graded potential?
Action potentials also known as spikes, differ from graded potentials in that they do not diminish in strength as they travel through the neuron.
Where do most action potentials originate?
initial segment
What is the sa node?
The SA node is the "pacemaker" of the heart. Cells in the SA node are called "pacemaker" cells and they direct the contraction rate of the entire heart by generating action potentials.
What are pacemaker potentials and the action potential they trigger?
Pacemaker potentials are automatic potentials generated and are exclusively seen in the heart. They arise from the natural "leakiness" of the membrane that pacemaker cells have, resulting in passive movement of both Na+ and Ca2+ across the membrane, rising the membrane potential to about -40mV. This results in a spontaneous depolarization of the muscle that has a rise in the curve that is nowhere near as steep as the action potential of other cells. Upon depolarization, the cell will return back to its resting membrane voltage, and continue the potential again.
How does a drug that increases the length of time required for the repolarization of pacemaker cells affect the heat rate?
would decrease the heart rate, because the pacemaker cells would generate fewer action potentials per minute
Why do not action potentials occur during the repolarization phase?
It has to do with what types of channels are open during this phase. In the repolarization phase the number of potassium channels are increased and the number of sodium channels are decreased. This allows for action potentials to not occur. Otherwise, the action potentials would add up and produce tetany.
Which cell must have action potentials to produce one or more action potentials in the postsynaptic cell?
A neuron (nerve cell) receives dendritic input in order to generate action potentials to transmit signals of the same. After the action potential triggers release of neurotransmitters in the axonal terminal of that neuron, those neurotransmitters propagate the signal forward to the next neuron, and so forth.
Do action potentials become weaker with distance?
action potentials are non-decremental and do not get weaker with distance.
The all or none principle states that?
all stimuli great enough to bring the membrane to threshold will produce identical action potentials. :)
Why is the cardiac action potential longer?
The reason why cardiac muscle has a longer action potential is to extend the absolute refractory period to prevent another action potential. If too many action potentials stimulate the cardiac muscle it can get into tetanus which keeps the heart continuously contracted without relaxation.
What do intercalated discs transfer from cell to cell?
action potentials, ionic currents, the force of contraction and ionic currents and action potentials only
What you mean by autorhythmicity?
The pacemaker is known as the SA node (sinotrial) and it generates action potentials to the AV node and then to the bundle of his down to the purkinje fibers. The branching of cardiac muscle tissue and the intercalated discs allow action potentials to propagate to other cardiac mt cells. The autorhythmicity of the heart is attributed to the fact that it creates its own action potentials from the SA node and can be generated independently from the rest of the body. The heart's autorhythmicity also prevents it from reaching tetanus (like a skeletal muscle does), because myocardial tissue only allows a certain amount of action potentials through before it reaches its absolute refractory period when it comes to a plateau and after the wave drops again and gets hit with another action potential it has already rested.
How does an action potential differ from a graded potential?
Action potentials also known as spikes, differ from graded potentials in that they do not diminish in strength as they travel through the neuron.
Communication in the nervous system depends on?
action potentials
