6996109
Descripción
Fichas por McKenzie Sanders, actualizado hace más de 1 año
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Creado por McKenzie Sanders
hace alrededor de 8 años
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| Pregunta | Respuesta |
| What does the action potential do? | Depolarizes membrane abruptly, allowing neuron to communicate over long distances |
| What is the concentration of sodium ions in a neuron at rest? | More sodium ions outside the cell than inside |
| What is the concentration of potassium ions in a neuron at rest? | More potassium ions inside the cell than outside |
| Are there more sodium or potassium ions in a neuron at rest? | Sodium |
| Is the outside of the neuron more positively or negatively charged than the inside of a neuron at rest? | Positive |
| Why is the inside of a neuron at rest more negative than the outside? | Fewer potassium ions inside than sodium ions outside |
| What does membrane potential measure? | Difference in electrical potential inside and outside of the cell Measured with respect to the outside of the cell |
| What is the approximate potential of a neuron at rest? | -70 mV |
| What is resting potential? | Membrane potential of a neuron at rest or when it is not being excited or inhibited by other inputs |
| In comparison to hyperpolarization, how negative is depolarization? | Less negative Towards zero |
| What is a depolarization? | Reduction of the membrane potential from its normal resting potential |
| In comparison to depolarization, how negative is hyperpolarization? | More negative |
| What is a hyperpolarization? | Increase in the membrane potential relative to the normal resting potential |
| What is the name of the voltage level that triggers an action potential? | Threshold of excitation |
| What is the approximate level of the threshold of excitation? | -60 mV |
| What 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 |
| What are the 2 forces that move ions? | Diffusion Electrostatic pressure |
| What 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 |
| What is electrostatic pressure? | Force of attraction or repulsion between ions Opposites attract Likes repel |
| What produces membrane potential? | A balance between the forces of diffusion and electrostatic pressure |
| Which ions are in the extracellular fluid? | Cl- Na+ |
| Which ions are in the intracellular fluid? | K+ Organic anions (A-) |
| How 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 |
| How 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 |
| How 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 |
| What type of ion channels play a role in action potentials? | Voltage-dependent or voltage-gated |
| What do voltage-gated ion channels open in response to? | Changes in membrane potential Specific ion |
| How sensitive are voltage-gated Na+ channels? Do they require a large amount of depolarization? | Very sensitive Require minimal depolarization to open |
| How sensitive are voltage-gated K+ channels? Do they require a large amount of depolarization? | Less sensitive Require more depolarization to open |
| What is the change in membrane potential at the peak of an action potential? | 100 mV |
| What change in membrane potential causes voltage-gated K+ channels to open? | Membrane potential becomes less negative/more positive |
| At what measurement do Na+ channels become refractory? | +40 mV |
| What happens to Na+ channels when they enter the absolute refractory period? | Na+ channels are unable to open No more Na+ enters |
| What returns the membrane back to rest during an action potential? What is this period called? | Outflow of K+ Overshoot/afterhyperpolarization |
| What mechanism returns the neuron to resting potential? | Na+/K+ transporter |
| At 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 |
| What 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 |
| What 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 |
| What does the firing frequency of an action potential reflect? | Magnitude of the depolarization |
| What would the firing rate from a strong stimulus elicit in comparison to a weaker stimulus? | Higher firing rate from neuron |
| What is firing rate limited by? | Refractory period |
| What is the firing rate of a neuron during an absolute refractory period? | No AP |
| What is the firing rate during a relative refractory period? | AP can be triggered given enough stimulation |
| What is saltatory conduction? | Conduction of APs in myelinated axons AP jumps from one node of Ranvier to the next |
| Do 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 |
| What 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 |
| What effect will increasing the size of the axon have on conduction? | Increases conduction speed |
| What is synaptic transmission? | Primary means of communication between neurons |
| What does synaptic transmission produce? | Postsynaptic potentials (PSPs) |
| What is the presynaptic membrane? | Membrane of a terminal button that lies adjacent to the postsynaptic membrane |
| What is the postsynaptic membrane? | Membrane on the cell that receives the message that is opposite the terminal button |
| Which area of the postsynaptic membrane has receptors on it? | Thickened areas of the postsynaptic membrane have receptors on them |
| What are receptors? | Protein molecules embedded in the membrane |
| What do synaptic vesicles contain? | Molecules of chemical messenger |
| What happens at the synapse? | Release of a neurotransmitter |
| What 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 |
| Where are neurotransmitters synthesized? | Axon terminal or cell body |
| Where is the NT packaged while waiting to be released? | Vesicles |
| What type of transport is involved in the NT moving from the cell body to the terminal buttons? | Anterograde axoplasmic transport |
| What can trigger a single vesicle to release its contents into the synaptic cleft? | A single AP |
| What are packets of NT called? | Quanta |
| What causes quantal release? | Vesicle storage/release system |
| What does an AP arriving at the terminal button trigger? | Opening of voltage-gated Ca2+ channels |
| What is the flow of Ca2+ during release of a NT? | Inward Down electrostatic gradient and concentration gradient |
| What 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 |
| What process allows for the vesicle to be recycled and reused? | Endocytosis |
| What protein is activated by Ca2+ entering the terminal? | Calmodulin |
| What is the function of calmodulin? | Activates synapse proteins that allow vesicles to fuse to the membrane |
| What is the synaptic cleft? | Space between presynaptic and postsynaptic neurons |
| What is a ligand? | A chemical (molecule of NT or a drug) that binds to a binding site of a receptor |
| What does ligand binding form? | Ligand-receptor complex |
| How 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 |
| What does ligand binding result in? | The opening or closing of ion channels Changes in membrane potential in postsynaptic neuron |
| What 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 |
| What is an excitatory postsynaptic potential (EPSP)? | A brief depolarization of the postsynaptic membrane caused by the neurotransmitter release and subsequent receptor activation |
| What is a graded response? | Amplitude of response is proportional to intensity of the signal |
| What is an inhibitory postsynaptic potential (IPSP)? | A brief hyperpolarization of the postsynaptic membrane caused by the neurotransmitter release and subsequent receptor activation |
| What is neural integration? | The interaction of all of the IPSPs and EPSPs a neuron receives |
| Where does neural integration take place? | Initial segment of neuron |
| In what 2 ways can PSPs be summed? | Spatially and temporally |
| What is spatial summation? | Summing of PSPs generated simultaneously at different synapses on a neuron |
| What is temporal summation? | Summing of PSPs that occur at the same synapse in rapid succession |
| What are the two types of receptors? | Ionotropic (ligand-gated) Metabotropic (G-protein coupled-GPCR) |
| What is an ionotropic receptor? | Receptor that is an ion channel and contains a binding site for a neurotransmitter |
| What is a metabotropic receptor? | A receptor that contains a binding site for a neurotransmitter and that is coupled to a G-protein |
| What are the characteristics of ionotropic receptors? | Ligand binding opens ion channel allowing ions to pass through Relatively fast Usually selective for a particular ion |
| What 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 |
| What 2 mechanisms keep PSPs brief? | Enzymatic deactivation & reuptake |
| What is enzymatic deactivation? | Enzyme that destroys the neurotransmitter at the synapse |
| What are the components that a NT is broken down into during enzymatic deactivation? | Metabolites |
| What is enzymatic deactivation especially important for? | ACh and neuropeptides |
| What 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 |
| What 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 |
| What effects reuptake? | Drugs |
| What can neurotransmitters be taken up by? | Neurons that release it Other neurons in the vicinity Nearby astrocytes |
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