BIOSC-116 Lecture Notes - Lecture 22: Axon Hillock, Threshold Potential, Cell Membrane

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coppermule660

16 Jun 2020

School

Diablo Valley College

Department

Biological Science

Course

BIOSC-116

Professor

Khan

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Document Summary

The threshold level of depolarization has been reached at the axon hillock. Na+ voltage gated channels to open causing a rapid depolarization of the axon. These channels open when the membrane potential hits -55 mv (threshold potential). Gates of sodium channels open and sodium will flow in very quickly, as it flows in, the inside of the membrane starts to become positive (+30) At -55 voltage gated channels open which allow sodium to flow into the axon from both sides and it will depolarize the axon to the point where the axon potential reverses it becomes positive (+30) As na+ ions flow into the axon, their positive charges start to reduce the negative charge within. Na+ ions diffuse along the inside of the membrane, once the threshold level of depolarization is reached it will trigger the next voltage gated na+ channels to open etc. Once the threshold level of depolarization has been reached the action potential starts and is self-propagating.

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

Please help

29. The action potentialâ¨

a. begins with the membraneâs increased permeability to potassium.

b. returns to resting when the sodium channels open.â¨

c. can be triggered by opening of ligand gated Na and K channels.â¨

d. involves voltage-gated Chloride channels in the membrane.â¨

e. can be triggered by opening of voltage gated Na+ and K+ channels.

30. Which of the following is not a step in the propagation of action potentials?

â¨a. Sufficient local inward current causes the axon to reach threshold.

â¨b. Local depolarization/inward current spreads to adjacent axonal regions.â¨

c. Adjacent regions eventually reach threshold and exhibit an action potential waveform.

â¨d. Current/depolarization continue to spread directionally along the axon, repeating steps aâc

e. All of the above are steps contributing to the propagation of action potentials.

31. Which of the following is important for the unidirectional propagation of action potentials?

a. The voltage dependence of the sodium channels

â¨b. The voltage dependence of the potassium channels

â¨c. The presence of a refractory period at a location where an action potential has just fired

d. Sufficient âleakinessâ of the axons, such that backward propagation of action potentials is prevented

â¨e. The capacity of axons to function as perfect insulators and prevent current leakage and backpropagation

3. Which of the following is TRUE about a motor neuron?

		It passes information to another motor neuron.
		It passes information to another neuron.
		It stimulates cells associated with muscles or glands.
		It cannot generate an action potential.

2. Choose the immediate event that needs to occur for a nerve to fire an action potential.

		Voltage-gated potassium ion channels need to open.
		A threshold potential will need to be reached.
		Depolarization will need to be happen.
		Voltage-gated sodium ion channels need to close.

1. Choose the TRUE statement with respect to axons and/or dendrites.

		Dendrite is the location that a neurotransmitter moves into the synamptic cleft.
		Action potentials travel along the axon of a neuron.
		A neuron will typically have more axons than dendrites.
		More than one is correct

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BIOSC-116 Lecture Notes - Lecture 22: Axon Hillock, Threshold Potential, Cell Membrane

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