Lecture 19 Flashcards
(44 cards)
What is the absolute refractory period?
Period during which no action potential is possible due to the inactivation gate of voltage-gated Na+ channels being closed
Occurs after depolarization to +30mV
What is the relative refractory period?
Period during which a large stimulus can generate an action potential, but the membrane potential is more negative due to K+ efflux
Inactivation gates are in the process of opening
Describe the movement of an action potential down the axon of a neuron.
An action potential activates adjacent segments of the axon by opening voltage-gated Na+ channels, propagating the signal along the axon
This process is known as active propagation
What is synaptic transmission?
The process where neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, causing local potentials
This process occurs at the axon terminal
Fill in the blank: Na+ = _______
Sodium
Fill in the blank: K+ = _______
Potassium
Fill in the blank: Cl- = _______
Chloride
Fill in the blank: Ca2+ = _______
Calcium
What types of channels are found on dendrites of some sensory neurons?
Mechanically-gated ion channels
More detail is provided in Lecture 23
What are chemically gated channels?
Channels that open when a chemical molecule, such as a neurotransmitter, binds to a receptor, allowing ions to flow down their electrochemical gradient
Define excitatory post-synaptic potential (EPSP).
A local potential that results in depolarization, making the membrane potential more positive, often due to Na+ influx
Define inhibitory post-synaptic potential (IPSP).
A local potential that results in hyperpolarization, making the membrane potential more negative, often due to K+ efflux or Cl- influx
What is temporal summation?
The process where local potentials arrive close together in time, allowing their effects to add together
What is spatial summation?
The process where local potentials occur close together spatially, allowing their effects to combine
At resting membrane potential (RMP), what is the state of the activation and inactivation gates of voltage-gated Na+ channels?
Activation gate closed, inactivation gate open
What occurs during depolarization to threshold?
Activation gates of voltage-gated Na+ channels open, allowing Na+ to flow into the cell
Describe the rapid depolarization phase of an action potential.
Na+ flows into the cell, causing a rapid increase in membrane potential to +30mV
What happens during the inactivation phase of voltage-gated Na+ channels?
The inactivation gate closes, preventing further Na+ flow into the cell
What initiates the repolarization phase of an action potential?
Opening of voltage-gated K+ channels, allowing K+ to leave the cell
What causes hyperpolarization during an action potential?
Efflux of K+ as voltage-gated K+ channels close slowly
What is the role of myelination in action potential propagation?
Myelin acts as insulation, preventing ion movement across the membrane except at Nodes of Ranvier, speeding up signal propagation
What is the function of Nodes of Ranvier?
Gaps in the myelin sheath that contain concentrated numbers of voltage-gated Na+ and K+ channels, facilitating rapid regeneration of action potentials
What is the unidirectional flow of information in synaptic transmission?
The flow of information is from the presynaptic neuron to the postsynaptic neuron
What is the role of calcium ions (Ca2+) in synaptic transmission?
Ca2+ influx triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft