B.B. Exam II Study Guide.docx - Neurophysiology Action Potential and Resting Potential Ions involved in a.p are Na and K(Na in K out At rest K and

B.B. Exam II Study Guide.docx - Neurophysiology Action...

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Neurophysiology Action Potential and Resting Potential Ions involved in a.p. are Na+ and K+ (Na+ in, K+ out) At rest, K+ and A- (organic compound) are highly concentrated inside cell At rest, Na+ and Cl- are highly concentrated outside of cell Gradients Concentration gradient o Force of diffusion o From high low concentration (moves ions to where there are larger amounts) K+ move out along this gradient Na+ moves in along this gradient Electrical gradient o Force of electrostatic pressure o Ions flow from areas of opposite charges “opposites attract” K+ moves in along this gradient Na+ moves in along this gradient Voltage-gated Channel channel in which ions pass thru v.g. Na+ channel o allows Na+ into cell v.g. K+ channel o transports K+ out of cell Process of Action Potential NT’s bind to receptors on neuron if axon hillock depolarizes to -40mV (threshold) then Na+ v.g. channels open Na+ rushes into cell (force of diffusion) cell becomes depolarized K+ v.g. channel opens & Na+ channel closes K+ rushes out of cell cell becomes hyperpolarized (-65mV) Neurophysiology Terms polarized : difference in membrane
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depolarization: inside of cell is less negative than -60mV hyperpolarization : inside of cell is more negative than -60mV repolarization: return of membrane to a negative value after depolarization resting potential : -60mV b/c of the unequal distribution of ions across the membrane threshold : (-40mV) trigger for a.p. in an axon o threshold must be reached at the axon hillock for a.p. to occur Sodium-Potassium Pump energetically expensive mechanism that pumps Na+ out of the cell and pulls K+ in causes a buildup of K+ inside cell Myelin and AP myelin on the axon speeds conduction of messages at each node, the opening and closing of Na+ and K+ channels occurs; ap jumps from node to node salutatory conduction : process of ap jumping from node to node Speed of AP conduction velocity depends on: o diameter of axon (wider axon=faster) o degree of myelination (more myelin=faster) All or Nothing vs Graded response think toilet analogy o a toilet cannot semi-flush. It either flushes, or it doesn’t ap either fires its full amplitude, or does not fire at all graded potentials are postsynaptic potentials (EPSPs and IPSPs ) meaning it is depolarized or hyperpolarized Ca2+ role in neuron a.p. opens voltage-gated Ca2+ channel in the membrane of the terminal Ca2+ triggers release NT release into synaptic cleft (Ca2+ channels are in presynaptic terminals) Spatial and Temporal Summation summation of postsynaptic potentials determines if threshold is reached spatial summation: o summation of postsynaptic potentials originating from different locations on the neuron temporal summation:
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o summation of postsynaptic potentials that reach the neuron/axon hillock at different times Agonists and Antagonists agonist: a drug that mimics or increases the effects of a NT o
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