PHYSIOLOGY
NEUROTRANSMISSION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Sodium and potassium ions are moving across the membrane, creating an action potential.
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The neuron is becoming hyperpolarized.
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The neuron is taking a pause called the refractory period.
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Neurotransmitter molecules are being released across the synaptic gap (synapse).
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Detailed explanation-1: -As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon. In response to a signal from another neuron, sodium-(Na+) and potassium-(K+)–gated ion channels open and close as the membrane reaches its threshold potential.
Detailed explanation-2: -To reestablish the appropriate balance of ions, an ATP-driven pump (Na/K-ATPase) induces movement of sodium ions out of the cell and potassium ions into the cell.
Detailed explanation-3: -The neuron cell membrane is partially permeable to sodium ions, so sodium atoms slowly leak into the neuron through sodium leakage channels. The cell wants to maintain a negative resting membrane potential, so it has a pump that pumps potassium back into the cell and pumps sodium out of the cell at the same time.
Detailed explanation-4: -Once the sodium channels open, the neuron completely depolarizes to a membrane potential of about +40 mV. Action potentials are considered an “all-or nothing” event, in that, once the threshold potential is reached, the neuron always completely depolarizes.
Detailed explanation-5: -The activity of the Na+/K+-pump also influences the membrane potential directly by generating an outward sodium current that is larger when the Na+/K+-pump activity is greater.