Chapter 2: Resting membrane and action potentials Flashcards
Why is the resting membrane negative?
At rest, K+ ions are inside the cell and the sodium ion channels are closed, leading to a negative resting membrane
What is the sodium-potassium pump?
this pump actively transports Na+ ions out of the neuron and K+ ions into the neuron against their concentration gradients, maintaining the balance of a negative membrane
What happens when there is a change in action potential?
voltage-gated Na+ channels open, allowing Na+ ions to rapidly enter the neuron, further depolarizing the membrane potential.
Once the membrane potential reaches a certain level, voltage-gated K+ channels open, allowing K+ ions to move out of the neuron, repolarizing the membrane potential and restoring the resting membrane potential.
How is an action potential triggered?
An action potential is triggered when the membrane potential of a neuron is depolarized to a threshold level, typically around -55mV.
This depolarization occurs due to the opening of voltage-gated ion channels in response to a stimulus.
What are the key ions involved in an action potential?
sodium (Na+) & potassium (K+)
What is depolarization?
Depolarization: The process by which the membrane potential of a neuron becomes less negative (i.e., moves toward zero or becomes positive).
This occurs when positively charged ions, such as sodium (Na+) or calcium (Ca2+), enter the neuron, causing the membrane potential to become less negative.
What is hyperpolarization?
Hyperpolarization: The process by which the membrane potential of a neuron becomes more negative (i.e., moves away from zero or becomes more negative).
This occurs when negatively charged ions, such as chloride (Cl-) or potassium (K+), enter or positively charged ions exit the neuron, causing the membrane potential to become more negative.
What are EPSPs?
EPSPs are postsynaptic potentials that depolarize the neuron and increase the likelihood of an action potential
What are IPSPs?
IPSPs hyperpolarize the neuron and decrease the likelihood of an action potential.
What is Spatial and temporal summation?
Spatial summation occurs when multiple EPSPs or IPSPs are generated at different synapses on the same neuron.
Temporal summation occurs when multiple EPSPs or IPSPs are generated at the same synapse in rapid succession.
Both spatial and temporal summation play important roles in determining whether a neuron will fire an action potential or not.
How is an action potential conducted down the axon?
a) After an action potential is triggered, it moves down the axon toward the axon terminals.
b) As the action potential depolarizes the membrane of the axon, it triggers the opening of voltage-gated Na+ channels
c) This causes Na+ ions to flow into the axon, depolarizing the membrane and triggering the opening of more voltage-gated Na+ channels
d) This process repeats, with the action potential moving rapidly down the axon.
What is the refractory period?
the inability of the neuron to generate another action potential.
This refractory period is due to the inactivation of voltage-gated Na+ channels that opened during the action potential. These channels cannot be immediately opened again, and it takes some time for them to recover from inactivation and become available for opening again.
