Action Potentials

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What is an action potential?
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What is the confirmation of voltage gated Na and K channels at resting membrane potential?Both are closedThe permeability of what ion dominates the membrane during an action potential?SodiumWhat happens as the membrane potential continues to depolarize before hitting threshold?More and more sodium voltage channels open, continuing to depolarize the membraneWhat is the peak depolarization of the action potential? Why?+30, because at this point inactivation gates begin to closeWhat initiates the inactivation gate of voltage Na channels to close?The activation gate opening, however inactivation gates close slowlyWhat causes the voltage gated potassium channels to open? How does this help repolarize the membrane?The peak depolarization of the action potential. It allows potassium to exit the cell quickly and return it to restingWhat are the three events that happen when an action potential hits threshold?Rapid opening of voltage gated Na channels activation gates causing potential to shoot up to its peak Slow closing of Na inactivation gates to keep potential from going past the peak Slow opening of K gates which cause the potential to plummet from peak back to resting (or slightly past)The rising phase of action potential is due to ______ influx and the falling phase is due to _______ effluxNa, KWhat happens to both K and Na voltage gated channels once the membrane returns to resting after an action potential?Na inactivation gates open again while activation gates remain closed (closed but capable of opening), K gates close (a little slow causing a brief hyperpolarization)What works to gradually restore concentration gradients disrupted by action potentials? Why is this important?Sodium potassium pump, because eventually after repeated action potentials the concentration gradients would be run down enough to where they could not continueDoes the membrane have to wait for concentration gradients to be restored (which takes a bit) after an action potential for another one to happen?No, resting potential just needs to be restoredThe ________ of a neuron houses the nucleus and organelles and may be a sit of signal reception from other neurons if the PM contains protein receptors to bind chemical messengersCell body/somaThe ______ of a neuron receive signals from other neurons (PM contains protein receptors that bind chemical messengers), and project off the cell body to increase surface areaDendritesWhat projects off of dendrites to even further increase surface area?Dendritic spinesGraded potentials are produced where in a neuron?Cell body and dendritesThe _____ of a neuron is a single, elongated tubular extension that conductions action potentials away from the body to terminate at other cellsAxon/nerve fiberAxon potentials are propagated from where to where?Axton hillock to axon terminalThe axon terminal releases _____ onto another cellChemical messengersOnce an action potential is initiated, the impulse is automatically conducted throughout the axon by one of what two methods?Contiguous conduction, saltatory conductionIn ____ conduction, the action potential spreads along every patch of membrane down an axon like a wave in a stadiumContiguousWhat ensures the one way propagation of an action potential away from the site of activation?Inactivation gates creating the refractory periodWhat what refractory period are the Na voltage channels of a recently activated patch of membrane in a closed and not capable of opening position?AbsoluteThe ____ refractory period follows the absolute and is when the cell is hyperpolarizedRelativeAnother action potential can be initiated during the relative refractory period under what condition?The triggering stimulus is considerably stronger than normal (has to bring cell from hyperpolarized state to threshold)How do you tell the strength of a stimulus if no matter the strength, an action potential is the same magnitude?Strength of stimulus is coded in part by the frequency of action potentials. A stronger stimulus will also cause more neurons to reach threshold sending more info to the CNSWhat does the velocity of an action potential traveling down the axon depend on?If the fiber is myelinated, the diameter of the fiberWhat is myelin?A primarily lipid cell that covers the axon at regular intervalsThe myelin cells of the peripheral nervous system are calledSchwann cellsThe myelin cells of the central nervous system are calledOligodendrocytesHow does the myelin coating act as an insulator to ions?It is impermeable to water soluble ionsWhat is the exposed axon between myelin cells called? What are concentrated here?Nodes of Ranvier, Na and K channelsWhat kind of conduction occurs in myelinated neurons?Saltatory conductionWhat are pros to myelinated cells during action potential?50x faster, conserves energy (ATPase pumps dont have to do as much work to restore membrane potential)The ______ the fiber diameter, the faster the action potentialLargerWhat kind of myelinated fibers on axons have the ability to regenerate themselves?Those in the peripheral nervous systemHow do schwann cells promote regeneration?They phagocytize debris from damaged cells and form a regeneration tube that guides the regenerating nerve fiber to its proper destination. They release proteins that promote this processDo myelinated fibers have regenerative ability in the CNS?No, axons do but oligodendrocytes synthesize a protein that inhibits axonal growthWhat is multiple sclerosis?An autoimmune disease in which the immune system attacks the myelin sheath on nerve fibersWhat does research suggest is the causative agent of MS?Genetic predisposition plus environmental factors, namely childhood infection with herpes HHV-6, that can later become reactivatedWhat occurs in MS that can interfere with and even block propagation of action potentials?Hardened scars where myelin was damaged called a sclerosisWhat are the chemical messengers released by axon terminals called?NeurotransmittersNeurons terminate on one of what three structures?A muscle, a gland, another neuronA neuron terminating on a muscle causes contraction, on a gland causes secretion, what this process of a nerve supplying a structure with directions called?InnervationA neuron terminating on another neuron creates aSynapse, ie. the junction between two neuronsThe _______ cell gives the message and the ______ cell receives the messagePresynaptic, postsynapticIn an _____ synapse two neurons are connected through gap junctions allowing ions to flow directly between them in either directionElectricalWhat kind of synapse leads to unbroken transmission of a signal that is rapid, unregulated, and an on/off thing?Electric synapseWhere are electrical synapses found?Where synchronization is paramount ie. cardiac and smooth muscle_______ synapses use neurotransmitters to transmit information one way across a space separating two neuronsChemicalMost synapses in the human nervous system are which type?Chemical synapsesThe ______ is the swollen end of the presynaptic neuronSynaptic knobThe ______ are found in the synaptic knob and contain neurotransmittersSynaptic vesiclesThe _______ is the space between the pre and post synaptic neuronsSynaptic cleftThe ________ bind to the neurotransmitter and are found on the post synaptic cellPostsynaptic receptor channelsWhat stimulates the exocytosis of synaptic vesicles?Voltage gated calcium channels on the synaptic knobWhat happens when an action potential reaches the axon terminal of a presynaptic neuron?Voltage gated Ca channels open, Ca flows into the cell, exocytosis of synaptic vesicles is triggered, NTs are released into the synaptic cleft, NTs bind to postsynaptic receptor channels, they open, ion permeability is modified and membrane potential is changed there, graded potential generatedThe action potential is an ____ signal, the signal in the synapse is a ______ signal, the signal of the graded potential on the postsynaptic neuron is a _____ signalElectrical, chemical, electricalEach presynaptic neuron releases only one type of NT typically, what can different NTs cause on binding with their receptor channels?Different ion permeability changes, ie. excitatory or inhibitory synapsesIn excitatory synapses, NT bind to _______ channels which increases permeability to Na and KNonspecific cationWhat happens in excitatory synapses when NT bind to nonspecific cation channels?A little bit of K move out and a lot of Na moves in, resulting ina small depolarization of the post synaptic neuron, bringing the neuron closer to thresholdWhat is the change in postsynaptic potential ocurring at an excitatory synapse called?Excitatory post synaptic potentialIn inhibitory synapses, binding of a NT to its receptor channels increases the permeability of the postsynaptic membrane to eitherK+ or Cl-, both leaving the cell more negativeWhat kind of change in membrane potential occurs in a post synaptic neuron as a result of increased permeability of K and Cl in an inhibitory synapse?A small hyperpolarization, moving potential away from threshold and making it harder to generate an action potentialWhat is the small hyperpolarization called in an inhibitory synapse?Inhibitory post synapse potentialEPSPs and IPSPs are produced by opening of _______ gated channels, unlike action potentials which are produced by opening of _____ channelsChemical gated, voltage gatedWhat NT is a major NT in the PNS and is released from motor nerves that supply skeletal muscle, and parasympathetic nerves that supply smooth muscle, cardiac, exocrine glands, and acts in the CNS?AcetylcholineAs long as the nucleotide is bound to the receptor channel, what will continue?The opening of chemically gated channels and change in membrane permeabilityWhat mechanisms can remove NT from their receptors?Diffusion, enzymes that inactive the NT, them actively being taken back up into the axon terminal by transport mechanismsHow do selective serotonin reuptake inhibitors work?They block reuptake of serotonin into the presynaptic axon terminalsWhat is myasthenia gravis?An autoimmune disease caused by autoantibodies binding against postsynaptic Ach receptors, which leads to damage to the receptors and the postsynaptic membraneWhat are the symptoms of myasthenia gravis?Fluctuating weakness, can worsen throughout the day, sometimes confined to ocular musclesHow does lambert-eaton myasthenic syndrome differ from myasthenia gravis?The antibodies block release of Ach from presynaptic membranes by blocking presynaptic calcium channelsWhat are symptoms of Lambert-Eaton Myasthenic syndrome?Increased muscle response after rapid repetitive stimulation