QUESTION 26 Place the events in the correct order during an action potential. A graded potential on the dendrites and cell body depolarizes the neuron to threshold (-55 mV) Potassium ions leave the axon causing repolarization Sodium ions enter the axon causing depolarization Sodium-potassium pumps reposition the ions moving the axon back to resting potential The axon hyperpolarizes (-90 mV) Voltage gated potassium channels close (-70 mV) Voltage gated sodium channels close (+35 mV) Voltage gated sodium channels open quickly, and voltage gated potassium channels open slowly
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The action potential is a transient change in the resting membrane potential from -70 mV to +30 mV, then back to -70 mV. This change is caused by the opening of first _ then voltage-gated channels. Na+ then K+ What area(s) of the neuron first generate signals that open the voltage-gated channels in the first part of the axon? The axon hillock, Axon collaterals, Dendrites and cell body. As the axon hillock depolarizes, Voltage-gated Na+ channels open and Na+ moves (into or out of) the cell causing further (depolarization or repolarization). out of; depolarization into; repolarization out of; repolarization into; depolarization If depolarization reaches -55 mV, an action potential will be generated. What is this -55 mV trigger point called? Threshold At the end of the depolarization phase, what voltage-gated channels open to help restore the resting membrane potential? Voltage-gated K+ channels. Repolarization is caused by the movement of what ion (sodium or potassium), in what direction (into or out of the cell)? potassium; out of the cell sodium; into the cell After an action potential, the membrane becomes more negative than -70 mV. This period is called hyperpolarization.
Sri K.
Question 29 (2 points) For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in depolarization of the neuron, making an action potential more likely. hyperpolarization of the neuron, making an action potential more likely. depolarization of the neuron, making an action potential less likely. hyperpolarization of the neuron, making an action potential less likely. a release of neurotransmitters from the synapse Question 30 (2 points) What is the direct cause of an action potential occurring in a pre-synaptic neuron? the sodium-potassium pump increases activity release of neurotransmitters opening Ca++ channels and the movement of anions opening voltage-gated Na+ channels closing voltage-gated K+ channels Question 31 (2 points) A "resting" motor neuron __________. releases acetylcholine. has a high permeability to sodium ions. is equally permeable to sodium and potassium ions. has a resting potential that is more negative than the "threshold" potential. has a higher concentration of sodium ions on the inside the cell than on the outside.
Lochan U.
In a neuron, where is the greatest concentration of voltage-gated sodium and voltage-gated potassium channels? axon terminal soma dendrites axon hillock axon Question 46 The all-or-none principle, associated with the action potential, states that once membrane potential reaches threshold, an action potential will be generated and that action potential will always be the same magnitude. the positive feedback loop for the sodium channel is terminated by the inactivation gate. following an action potential, the membrane will be repolarized by the opening of a potassium channel. all of the action potentials will be generated from the axon hillock. there is a positive feedback loop for sodium channels that results in a rapid membrane depolarization.
Sulav P.
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