CSB332H1 Lecture Notes - Lecture 3: Teleost, Tetrodotoxin, Invertebrate

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coppercattle724

18 Jan 2012

School

UTSG

Department

Cell and Systems Biology

Course

CSB332H1

Professor

Melanie Woodin

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Document Summary

Early (+) inward na current (-) deflection by voltage clamp from flowing in. Late outward k current after na current peaks. Ion subsititution: substitutions in saline sol"n (rmbr can remove squid axoplasm) see whether or not could reconstitute the real ion concs. Trying to generate act pot by depolarizing past threshold. High conc na outside early inward na current, late outward k current. Substitute na for impermeable (+, maintains osmolarity of cell) ion early outward current reduced, small; abolished early inward na current since no na outside (so na responsible for early inward current) Reversed back to na: have early inward current again. Noticed no significant dif in k outward current: pharmacological blockade use antagonist to channel of ion you think is important. Add tea (specific antagonist to voltage-gated k channels) have early inward na current, lost late outward k current. Get act pot, takes a while to go down.

Related Questions

When the na-channels of an axon open, what would happen?

a. Saltatory conduction

b. repolarization

c. hyperpolarization

d. Na+ ions flow into the neuron

e. Na+ ions flow out of the neuron

When the K-channels in the axon open, what would happen?

a. depolarize the neuron

b. block action potential

c. maintain the membrane potential

d. repolarize the neuron

e. release neurotransmitters.

When a neuron is depolarized closer to the threshold, the neuron is

a. more excitable

b. less excitable

c. more inhibitory

d. inactivated

e. blocked from finding action potentials

If the opening of Na⁺ channels is responsible for depolarizing a neuron (making membrane more positive) to produce an action potential, and a depolarized membrane potential is what keeps Na⁺ channels open, how does the neuron ever repolarize its membrane (make membrane more negative again)?

limegnat199

This is the peak depolarization in an action potential. At this point in an action potential two events start to happen.

1. Na+ channels begin to inactivate, which is equivalent to closing.

2. A majority of the K+ channels are beginning to open.

Determine what happens to the membrane potential when voltage-gated K+ channels are open simultaneously with voltage-gated Na+ channels (and the leak K+ channels which are still open). Increase the membrane permeability to K+ by increasing it to 115.

i. What happens to the membrane potential Em? __________________________

j. Why does the membrane potential change in this direction? __________________________ Now inactivate the voltage-gated Na+ channels by reducing the membrane permeability for Na+ back to 1. k. What is the new membrane potential? _____________

l. Is the new membrane potential less negative or more negative than the resting membrane potential listed in line âbâ of this section? _____________

m. Why? (hint: what 2 types of K+ channels are open now?) n. Under the current ionic concentrations given, what is the most negative value that the membrane potential could reach? _____________ (Increase the permeability of the membrane to K+ to confirm your answer.)

o. What equilibrium potential has the same value? _____________

p. At this point in the action potential, when the membrane potential is more negative than the resting potential, the membrane potential is said to be hyperpolarized. What happens to voltage-gated K+ channels (membrane permeability to K+) to bring the membrane potential back to its resting potential near -70mV?_____________

When the membrane potential became more negative than the Threshold potential, the inactivated voltage-gated Na+ channels became reactivated. After the voltage-gated K+ channels closed to enable the membrane potential to return to resting membrane potential they became ready to open again. Both channels are ready to open again in order to fire another action potentia

sapphirepanda54

CSB332H1 Lecture Notes - Lecture 3: Teleost, Tetrodotoxin, Invertebrate

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