Explain what happens when an action potential reaches the axon terminus (terminal) by activating the receptors on the postsynaptic membrane. Explanation addressing the question above When an action potential, or nerve impulse, arrives at the axon terminal, it activates voltage-gated calcium channels in the cell membrane. Which is present at a much higher concentration outside the neuron than inside, rushes into the cell. The Ca2+ allows synaptic vesicles to fuse with the axon terminal membrane, releasing neurotransmitters into the synaptic cleft. The molecules of neurotransmitters diffuse across the synaptic cleft and bind to receptor proteins on the postsynaptic cell. Activation of postsynaptic receptors leads to the opening or closing of ion channels in the cell membrane. This may be depolarizing, making the inside of the cell more positive, or hyperpolarizing making the inside more negative depending on the ions involved. The excitatory and inhibitory postsynaptic potentials When a neurotransmitter binds to its receptor on a receiving cell, it causes ion channels to open or close. This can produce a localized change in the membrane potential voltage across the membrane. An EPSP is depolarizing. It makes the inside of the cell more positive, bringing the membrane potential closer to its threshold for firing an action potential. Sometimes, a single EPSP isn't large enough to bring the neuron to the threshold, but it can sum together with other EPSPs to trigger an action potential. IPSPs have the opposite effect. They tend to keep the membrane potential of the postsynaptic neuron below the threshold for firing an action potential. IPSPs are essential because they can counteract or cancel out the excitatory effect of EPSPs. Anything that interferes with the processes that terminate the synaptic signal can have significant physiological effects. Question: Respond to the explanation post above about what happens when an action potential reaches the axon terminus (terminal) by activating the receptors on the postsynaptic membrane.
Explain what happens when an action potential reaches the axon terminus (terminal) by activating the receptors on the postsynaptic membrane.
Explanation addressing the question above
When an action potential, or nerve impulse, arrives at the axon terminal, it activates voltage-gated calcium channels in the cell membrane. Which is present at a much higher concentration outside the neuron than inside, rushes into the cell. The Ca2+ allows synaptic vesicles to fuse with the axon terminal membrane, releasing neurotransmitters into the synaptic cleft. The molecules of neurotransmitters diffuse across the synaptic cleft and bind to receptor proteins on the postsynaptic cell. Activation of postsynaptic receptors leads to the opening or closing of ion channels in the cell membrane. This may be depolarizing, making the inside of the cell more positive, or hyperpolarizing making the inside more negative depending on the ions involved. The excitatory and inhibitory postsynaptic potentials When a neurotransmitter binds to its receptor on a receiving cell, it causes ion channels to open or close. This can produce a localized change in the membrane potential voltage across the membrane. An EPSP is depolarizing. It makes the inside of the cell more positive, bringing the membrane potential closer to its threshold for firing an action potential. Sometimes, a single EPSP isn't large enough to bring the neuron to the threshold, but it can sum together with other EPSPs to trigger an action potential. IPSPs have the opposite effect. They tend to keep the membrane potential of the postsynaptic neuron below the threshold for firing an action potential. IPSPs are essential because they can counteract or cancel out the excitatory effect of EPSPs. Anything that interferes with the processes that terminate the synaptic signal can have significant physiological effects.
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