Flashcards
Lecture 3: The Action Potential
Flashcards do conjunto (95)
- 1What does the action potential do?Depolarizes membrane abruptly, allowing neuron to communicate over long distances
- 2What is the concentration of sodium ions in a neuron at rest?More sodium ions outside the cell than inside
- 3What is the concentration of potassium ions in a neuron at rest?More potassium ions inside the cell than outside
- 4Are there more sodium or potassium ions in a neuron at rest?Sodium
- 5Is the outside of the neuron more positively or negatively charged than the inside of a neuron at rest?Positive
- 6Why is the inside of a neuron at rest more negative than the outside?Fewer potassium ions inside than sodium ions outside
- 7What does membrane potential measure?Difference in electrical potential inside and outside of the cell
Measured with respect to the outside of the cell - 8What is the approximate potential of a neuron at rest?-70 mV
- 9What is resting potential?Membrane potential of a neuron at rest or when it is not being excited or inhibited by other inputs
- 10In comparison to hyperpolarization, how negative is depolarization?Less negative
Towards zero - 11What is a depolarization?Reduction of the membrane potential from its normal resting potential
- 12In comparison to depolarization, how negative is hyperpolarization?More negative
- 13What is a hyperpolarization?Increase in the membrane potential relative to the normal resting potential
- 14What is the name of the voltage level that triggers an action potential?Threshold of excitation
- 15What is the approximate level of the threshold of excitation?-60 mV
- 16What happens during an AP? (step by step)Neuron at rest: -70 mV
Threshold of excitation reached: -60 mV
Voltage-gated Na+ channels open; Na+ enters
Voltage-gated K+ channels open; K+ exits
Depolarizes to +40 mV
Na+ channels close; K+ continues to exit
Repolarizes to -75mV; after-hyperpolarization
Na+/K+ transporters re-establish resting potential; -70 mV - 17What are the 2 forces that move ions?Diffusion
Electrostatic pressure - 18What is diffusion?Movement of molecules from regions of high concentrations to regions of low concentrations
Tend to be distributed evenly throughout the medium over time - 19What is electrostatic pressure?Force of attraction or repulsion between ions
Opposites attract
Likes repel - 20What produces membrane potential?A balance between the forces of diffusion and electrostatic pressure
- 21Which ions are in the extracellular fluid?Cl-
Na+ - 22Which ions are in the intracellular fluid?K+
Organic anions (A-) - 23How do diffusion and electrostatic pressure act on K+ ions? Net movement at rest?Diffusion pushes it out of the cell
Electrostatic pressure pushes it into the cell
Net movement: none - 24How do diffusion and electrostatic pressure act on Cl- ions? Net movement at rest?Diffusion pushes it into the cell
Electrostatic pressure pushes it out of the cell
Net movement: none - 25How do diffusion and electrostatic pressure act on Na+ ions? Net movement at rest?Diffusion pushes it into the cell
Electrostatic pressure pushes it into the cell
Net movement: ready for action - 26What type of ion channels play a role in action potentials?Voltage-dependent or voltage-gated
- 27What do voltage-gated ion channels open in response to?Changes in membrane potential
Specific ion - 28How sensitive are voltage-gated Na+ channels? Do they require a large amount of depolarization?Very sensitive
Require minimal depolarization to open - 29How sensitive are voltage-gated K+ channels? Do they require a large amount of depolarization?Less sensitive
Require more depolarization to open - 30What is the change in membrane potential at the peak of an action potential?100 mV
- 31What change in membrane potential causes voltage-gated K+ channels to open?Membrane potential becomes less negative/more positive
- 32At what measurement do Na+ channels become refractory?+40 mV
- 33What happens to Na+ channels when they enter the absolute refractory period?Na+ channels are unable to open
No more Na+ enters - 34What returns the membrane back to rest during an action potential? What is this period called?Outflow of K+
Overshoot/afterhyperpolarization - 35What mechanism returns the neuron to resting potential?Na+/K+ transporter
- 36At what rate do Na+ and K+ move in comparison to the other in an action potential?Na+ enters much faster than K+
K+ enters later than Na+ and over a longer period of time - 37What does the all-or-none law state?Once an action potential is triggered, it is transmitted without decreasing in size to the end of the neuron
AP is always the same size - 38What does the rate law state about an AP?Variations in the intensity of a stimulus or other information transmitted in an axon are represented by variations in the firing rate
- 39What does the firing frequency of an action potential reflect?Magnitude of the depolarization
- 40What would the firing rate from a strong stimulus elicit in comparison to a weaker stimulus?Higher firing rate from neuron
- 41What is firing rate limited by?Refractory period
- 42What is the firing rate of a neuron during an absolute refractory period?No AP
- 43What is the firing rate during a relative refractory period?AP can be triggered given enough stimulation
- 44What is saltatory conduction?Conduction of APs in myelinated axons
AP jumps from one node of Ranvier to the next - 45Do myelin and the nodes of Ranvier make contact with the extracellular fluid during an AP?Nodes of Ranvier do
Myelinated portion of axon does not - 46What are the advantages of saltatory conduction?Economical; less Na+/K+ transporters that require energy
Speedy; transmission between nodes is very fast
Allows for faster reaction times/faster thinking - 47What effect will increasing the size of the axon have on conduction?Increases conduction speed
- 48What is synaptic transmission?Primary means of communication between neurons
- 49What does synaptic transmission produce?Postsynaptic potentials (PSPs)
- 50What is the presynaptic membrane?Membrane of a terminal button that lies adjacent to the postsynaptic membrane
- 51What is the postsynaptic membrane?Membrane on the cell that receives the message that is opposite the terminal button
- 52Which area of the postsynaptic membrane has receptors on it?Thickened areas of the postsynaptic membrane have receptors on them
- 53What are receptors?Protein molecules embedded in the membrane
- 54What do synaptic vesicles contain?Molecules of chemical messenger
- 55What happens at the synapse?Release of a neurotransmitter
- 56What happens during the release of a neurotransmitter?An AP is conducted down an axon to the terminal buttons
AP triggers synaptic vesicles to fuse with the presynaptic membrane
Fusion of synaptic vesicles and presynaptic membrane causes release of chemical messenger (neurotransmitter) from inside the vesicles into the synaptic cleft
NT diffuses across synapse to postsynaptic membrane
Interacts with receptors located in postsynaptic membrane - 57Where are neurotransmitters synthesized?Axon terminal or cell body
- 58Where is the NT packaged while waiting to be released?Vesicles
- 59What type of transport is involved in the NT moving from the cell body to the terminal buttons?Anterograde axoplasmic transport
- 60What can trigger a single vesicle to release its contents into the synaptic cleft?A single AP
- 61What are packets of NT called?Quanta
- 62What causes quantal release?Vesicle storage/release system
- 63What does an AP arriving at the terminal button trigger?Opening of voltage-gated Ca2+ channels
- 64What is the flow of Ca2+ during release of a NT?Inward
Down electrostatic gradient and concentration gradient - 65What does an elevation in Ca2+ levels trigger? What is this process called?A sequence of events that causes vesicles to fuse to presynaptic membrane and release contents
Exocytosis - 66What process allows for the vesicle to be recycled and reused?Endocytosis
- 67What protein is activated by Ca2+ entering the terminal?Calmodulin
- 68What is the function of calmodulin?Activates synapse proteins that allow vesicles to fuse to the membrane
- 69What is the synaptic cleft?Space between presynaptic and postsynaptic neurons
- 70What is a ligand?A chemical (molecule of NT or a drug) that binds to a binding site of a receptor
- 71What does ligand binding form?Ligand-receptor complex
- 72How does formation of the ligand-receptor complex happen?Induces conformation change (physical change in shape) in receptor
Conformation change induces a chain of physiological events - 73What does ligand binding result in?The opening or closing of ion channels
Changes in membrane potential in postsynaptic neuron - 74What does receptor activation do?Can open ion channels, changing membrane potential (PSP)
Can have intracellular effects
Can affect ion channels by making them more or less likely to open or close
Affect gene transcription - 75What is an excitatory postsynaptic potential (EPSP)?A brief depolarization of the postsynaptic membrane caused by the neurotransmitter release and subsequent receptor activation
- 76What is a graded response?Amplitude of response is proportional to intensity of the signal
- 77What is an inhibitory postsynaptic potential (IPSP)?A brief hyperpolarization of the postsynaptic membrane caused by the neurotransmitter release and subsequent receptor activation
- 78What is neural integration?The interaction of all of the IPSPs and EPSPs a neuron receives
- 79Where does neural integration take place?Initial segment of neuron
- 80In what 2 ways can PSPs be summed?Spatially and temporally
- 81What is spatial summation?Summing of PSPs generated simultaneously at different synapses on a neuron
- 82What is temporal summation?Summing of PSPs that occur at the same synapse in rapid succession
- 83What are the two types of receptors?Ionotropic (ligand-gated)
Metabotropic (G-protein coupled-GPCR) - 84What is an ionotropic receptor?Receptor that is an ion channel and contains a binding site for a neurotransmitter
- 85What is a metabotropic receptor?A receptor that contains a binding site for a neurotransmitter and that is coupled to a G-protein
- 86What are the characteristics of ionotropic receptors?Ligand binding opens ion channel allowing ions to pass through
Relatively fast
Usually selective for a particular ion - 87What are the characteristics of metabotropic receptors?Ligand binding results in G-protein which while affect an ion channel or affect an enzyme which controls production of 2nd messenger
Relatively slow
Suited for slow sustained signaling or for modulating fast transmission - 88What 2 mechanisms keep PSPs brief?Enzymatic deactivation & reuptake
- 89What is enzymatic deactivation?Enzyme that destroys the neurotransmitter at the synapse
- 90What are the components that a NT is broken down into during enzymatic deactivation?Metabolites
- 91What is enzymatic deactivation especially important for?ACh and neuropeptides
- 92What happens to metabolites during enzymatic deactivation?Recycled presynaptic neuron takes up the precursor and reuses it for NT synthesis
Neuroglia take it up for excretion via the bloodstream - 93What is reuptake?Rapid removal of the neurotransmitter from the synaptic cleft by the terminal button
Special transporters actively take NT back into presynaptic cell's terminal button
Against concentration gradient; requires ATP
Enzymes inside cell can then deactivate NT - 94What effects reuptake?Drugs
- 95What can neurotransmitters be taken up by?Neurons that release it
Other neurons in the vicinity
Nearby astrocytes
Informações
- Descrição
- Taken from lecture 3 of PSY 314
- Criado por
- McKenzie Sanders · nov 2016
- Atualizado
- 16 nov 2016
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