CSB332H1 Lecture Notes - Lecture 6: Axon Hillock, Tetrodotoxin

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coppercattle724

30 Jan 2012

School

UTSG

Department

Cell and Systems Biology

Course

CSB332H1

Professor

Melanie Woodin

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Document Summary

If reversal pot is depolarizing relative to threshold epsp. If reversal pot is hyperpolarizing relative to threshold ipsp: hold membrane at dif pots w voltage clamp see where reverses. Inhibitory synapse since reversal pot below -50mv threshold. Threshold = voltage where see act pots: method 2: slower, ~20ms. Cl grad, get back if put in back neurotransmitter (na changes but doesn"t affect response, always excitatory) cl can switch from depolarizing to hyperpolarizing since eqm pot near resting; sits near. Inhibition on own no info passed to next neuron, no signal. Ipsps important to stop epsps from reaching threshold powerful inhibition. Excitatory & inhibitory synapses often close together, inhibitory synapse often in good position to shunt. Tho don"t reach threshold, epsps still excitatory since would go towards threshold when summate. E1 stimulated on own know i1 is ipsp presynaptic axons. Record almost no ipsp even tho cl channels open since at reversal pot for this transmitter;

Related Questions

1. True or False: A postsynaptic potential isexcitatory (EPSP) if the ion involved has a reversal potential(Eion) that is more depolarized than the resting membrane potential(Vm or Vrest), even if that Eion is hyperpolarized to the thresholdfor firing an action potential.

2. An EPSP causes adepolarization of 15 mV on a proximal dendrite. At the same time,an IPSP causes a hyperpolarization of 10 mV in a different proximaldendrite.

Vm is -65 mV, and threshold for firing an action potential is-55 mV.

In this case, will an action potential be generated?

		A. No, because the net effect on the membrane is -60 mV, whichis below threshold.
		B. Yes, because the EPSPs travel faster than IPSPs, so thehillock (trigger zone) will be stimulated to -50 mV, which exceedsthreshold.
		C. Maybe. We don't have enough information to answer this.
		D. It depends on factors like "how much will the gradedpotentials decay before they arrive at the hillock". In short, ifthe axon hillock (trigger zone) is depolarized beyond -55 mV, theanswer is "yes". If not, then "no".

harlequinpug814

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

i choose aba for those 3 neuroscience question. but could any one help me if i got right?

5. Patch clamp studies have demonstrated that the following is trueâ¦

a. individual channels carry currents that do not predict the macroscopic current carried by the entire population in an axon

b. ion selectivity varies greatly among individual channels of a particular type (e.g. voltage-gated sodium channels)

c. channel behavior includes random fluctuations

d. individual voltage-gated sodium and potassium channels always open when the membrane is depolarized

7. The following is true regarding membrane property known as thresholdâ¦

a. it is primarily determined by the phospholipid composition of the membrane

b. it is strongly dependent upon the voltage-dependence of the voltage-gated sodium channels

c. it usually occurs when the membrane is hyperpolarized beyond the resting potential

d. it occurs when there is less depolarizing current than the leakage currents e. mutations in the sodium channel S4 domain would not be expected to influence threshold

8. Which of the following is a potential advantage of electrical synapses over chemical synapses?

a. their strength can be modulated at many different steps of synapse function

b. neurotransmitters can bind to distinct receptor types present at the same synapse

c. they can allow second messengers to pass between neurons

d. signals can pass more slowly preventing over-stimulation in the brain e. they help ensure that neurons are not synchronously active

CSB332H1 Lecture Notes - Lecture 6: Axon Hillock, Tetrodotoxin

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