HUMB1000 Study Guide - Final Guide: Resting Potential, Action Potential, Exocytosis

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tealminnow552

10 Jun 2018

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Nerve Impulse

The resting membrane potential is -70mV and has high K+ concentration inside the cell and

high Na+ concentration outside the cell. When a stimulus is occurred, some sodium channels

will open and Na+ ions will move into the cell through Na+ channels by diffusion which

increases the voltage until it reaches the threshold which is -55mV. At this point, an all or

none response will occur. More sodium channels will open and Na+ ions floods into the cell

down a concentration gradient which causes the membrane voltage to rise. This process is

called depolarization. After the inside of the cell becomes flooded with Na+, the Na+

channels close, K+ channel gates open and K+ ions floods out the cell down a concentration

gradient which is repolarization. When the K+ channel gates closes, too much K+ has flooded

out of the cell and the voltage is below the resting membrane potential (-70mV) which is

hyperpolarized. So, Sodium Potassium pump pumps out 3 Na+ ions to the outside and 2 K+ ions

will be pumped into the cell which restores the voltage to the resting membrane potential.

Synapse

Impulse passes between two neurons at a synapse. Presynaptic neuron has synaptic knob/bulb

which houses vesicles containing neurotransmitters (acetylcholine/noradrenaline). The

synaptic knop fits into depression on post-synaptic neuron. There’s a gap between neurons

called synaptic cleft. When an impulse travel down axon to synaptic knob, it triggers vesicles

to fuse with presynaptic membrane. This releases neurotransmitter into the synaptic cleft

by exocytosis. Neurotransmitter diffuses to the dendrite of postsynaptic membrane.

Neurotransmitters bind to specific protein receptor on dendrite, triggering a nerve impulse

to be generated in this neuron causing depolarization.

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Document Summary

The resting membrane potential is -70mv and has high k+ concentration inside the cell and high na+ concentration outside the cell. When a stimulus is occurred, some sodium channels will open and na+ ions will move into the cell through na+ channels by diffusion which increases the voltage until it reaches the threshold which is -55mv. At this point, an all or none response will occur. More sodium channels will open and na+ ions floods into the cell down a concentration gradient which causes the membrane voltage to rise. After the inside of the cell becomes flooded with na+, the na+ channels close, k+ channel gates open and k+ ions floods out the cell down a concentration gradient which is repolarization. When the k+ channel gates closes, too much k+ has flooded out of the cell and the voltage is below the resting membrane potential (-70mv) which is hyperpolarized.

Related Questions

6. Consider the presence of hemoglobin in the catheter bag. Whatsymptom would this loss of

hemoglobin most strongly and immediately be linked to in thepatient?

A. Loss of blood volume

B. Loss of heartbeat

C. Drop in blood oxygen saturation

D. Liver failure

When a neuron is stimulated, the area of the membrane at thepoint of stimulation becomes

more permeable to Na+. If a cell starts at resting potential(-70mv), and is then stimulated:

A. The membrane voltage will become < -70mV, because Na+will move OUT of the cell.

B. The membrane voltage will become > -70mV, because Na+will move OUT of the cell.

C. The membrane voltage will become < -70mV because Na+will move INTO the cell.

D. The membrane voltage will become > -70mV because Na+will move INTO the cell.

. At the peak of the action potential, the Na+ voltage-gatedchannels close, and K+ voltage-gated

channels open in response to the positive membrane potential.In order to return the cell to its

negative resting potential quickly:

A. K+ will diffuse along its concentration gradient INTO thecell.

B. K+ will diffuse along its concentration gradient OUT of thecell.

C. Na+ will reverse its direction of diffusion OUT of thecell.

D. The sodium-potassium pump will move Na+ OUT of the cell andK+ INTO the cell.

E. None of the above would return the cell to its negativeresting potential quickly.

You experiment with higher concentrations of toxin and findcases when the cell could not

repolarize at all or, if it began to repolarize, itimmediately depolarized again. This tells you that

the toxin:

A. Prevents voltage-gated K+ channels from opening.

B. Increases the speed that the Na+ ion channels open.

C. Prevents the Na+ ion channels from closing.

D. Makes the Na+ ion channels close too soon.

E. Doesn

lavenderclam549

Why do ion channels not function like open pores?

What is membrane potential?

How do K⁺ leak channels work? Why is the membrane potential of a resting cell negative?

What is patch clamp recording? What is one of the major insights gained from patch clamp reporting experiments?

Compare and contrast the three types of gated ion channels.

Be familiar with the different parts of a neuron.

During an action potential, what happens to the membrane potential, voltage-gated Na⁺ channels, Na⁺ ions, voltage gated K⁺ channels, K⁺ ions, and Na⁺-K⁺ ion pumps?

When an action potential reaches a synapse, what happens to the Ca²⁺ channels, Ca²⁺ ions, neurotransmitters, transmitter-gated ion channels, and the post synaptic neuron?

What effect do excitatory or inhibitory neurotransmitters have on postsynaptic cells?

What is an example of a mechanically gated ion channel?

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

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HUMB1000 Study Guide - Final Guide: Resting Potential, Action Potential, Exocytosis

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