INP_4.29.2024 Flashcards
What is the membrane potential at which enough voltage-gated sodium channels open?
Threshold
Threshold favors sodium over potassium permeability.
What occurs during the rising phase of an action potential?
Sodium rushes into the cell, causing rapid depolarization.
What is the membrane potential during the overshoot phase of an action potential?
Close to E Na, which is greater than 0 mV.
What is the main cause of the falling phase of an action potential?
Inactivation of sodium channels and opening of potassium channels.
What happens during the undershoot phase of an action potential?
Hyperpolarization occurs as potassium channels remain open.
What is the absolute refractory period?
Period when sodium channels are inactivated and cannot generate another action potential.
What is the relative refractory period?
Period when the membrane potential is hyperpolarized and requires more depolarizing current to reach threshold.
What happens if injected current does not depolarize the membrane to threshold?
No action potentials will be generated.
What is the effect of injecting current that depolarizes the membrane beyond threshold?
Action potentials will be generated.
What is passive conduction in neurons?
Potential change that decays with distance from the site of current injection.
What distinguishes active conduction from passive conduction?
Active conduction maintains a constant amplitude of action potentials along the axon.
What is saltatory conduction?
Current flows by jumping from one node of Ranvier to the next.
What are the primary functions of oligodendroglial and Schwann cells?
Providing layers of membrane that insulate axons.
What is the spike-initiation zone?
The region where action potentials are generated, typically at the axon hillock.
How did Otto Loewi contribute to the understanding of synaptic transmission?
Demonstrated that chemical release from stimulated axons affects heart rate.
What are electrical synapses?
Connections that allow direct transfer of ionic current between cells.
What are gap junctions?
Specialized sites where electrical synapses occur, allowing ionic current to pass directly.
What is an excitatory postsynaptic potential (EPSP)?
Depolarization of the postsynaptic membrane due to neurotransmitter binding and sodium influx.
What is an inhibitory postsynaptic potential (IPSP)?
Hyperpolarization of the postsynaptic membrane due to neurotransmitter binding and chloride influx.
What is spatial summation of EPSPs?
When two or more presynaptic inputs activate simultaneously, their EPSPs add together.
What is temporal summation of EPSPs?
When the same presynaptic fiber fires action potentials in quick succession, their EPSPs add together.
