BM 1041:03 Lecture Notes - Lecture 10: Resting Potential, Voltmeter, Membrane Potential

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ambercattle379

23 May 2018

School

James Cook University

Department

Course

BM 1041:03

Professor

alex trollope

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From one end of neuron to the other (electrical signals)

From neuron to neuron/effector (chemical signals)

Neurophysiology - communication of the nervous system

Explain the basis for resting membrane potentials and passive

changes of membrane potential

Occurs in all cells

Potential = electrical change due to movement of ions across a membrane

Allows Na+ to flow INTO cell with its conc gradient

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Then pumped out by Na+/K+ pump

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Na+

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Flow K+ OUT of cell

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Then pumped back in by Na+/K+ pump

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K+

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Constant flow of ions across membrane at rest

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Na+ and K+ ion channels

Phosphate ions and proteins inside the cell make it negative at rest

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More K+ leak channels than Na+ so more K+ leaves than Na+ comes in

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Therefore more negative inside (charge separation)

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Screen clipping taken: 21/03/2018 11:47 PM

Leak channels

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Polarised at rest (negative inside, positive outside)

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Negative at rest inside cell

Ionic gradient underlies membrane potential

AT REST = -70mV

Resting membrane potential

L1 and 2- Neurophysiology

Wednesday, 21 March 2018

11:30 PM

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Screen clipping taken: 21/03/2018 11:45 PM

Measures size of charge separation

Voltmeter

+30 mV

Inside is now more positive, Na+ moves inside cell

Activated

Depolarisation (charge reversal)

Screen clipping taken: 21/03/2018 11:46 PM

-90mV

Outside is more positive, K+ leaves cell

Inhibitory

Hyperpolarisation (reinforcement, hyper=more)

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Screen clipping taken: 21/03/2018 11:46 PM

Local, short-lived

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Spreads in all directions

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Not very useful

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Occurs in response to opening of mechanically gated or ligand gated ion channels

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Can be found in cell body (anywhere in cell)

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Graded potential

Type of signals

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Document Summary

From one end of neuron to the other (electrical signals) Explain the basis for resting membrane potentials and passive changes of membrane potential. Potential = electrical change due to movement of ions across a membrane. Allows na+ to flow into cell with its conc gradient. Constant flow of ions across membrane at rest. Phosphate ions and proteins inside the cell make it negative at rest. More k+ leak channels than na+ so more k+ leaves than na+ comes in. At rest = -70mv wk 5 page 1. Inside is now more positive, na+ moves inside cell. Occurs in response to opening of mechanically gated or ligand gated ion channels. Can be found in cell body (anywhere in cell) Screen clipping taken: 21/03/2018 11:47 pm wk 5 page 3. Only occurs in axon, as this is where voltage gated ion channels are found. All or none - once threshold reached, whole sequence must occur.

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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

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(1) What would be thelikely outcome if an increase in both intracellular sodium ionlevels and extracellular potassium ion levels were tooccur?

A: The Na+-K+ pump would accelerate because it needs to restorethe membrane's resting concentration gradient.

B: The Na+-K+ pump would slow down because it needs to restorethe membrane's concentration gradient.

C: Sodium and Potassium ions would be pumped out of thecell.

D: Sodium and Potassium ions would increase their movement inboth directions across the cell membrane.

(2) Due to the unequal transport of sodium and potassiumions by the Na-K pump, a membrane potential isgenerated.

True or False

(3) If a pump moves 3 positive ions out and 2 positiveions in against their concentration gradients, the membranepotential in the cell will become more positive.

True or False

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Santiago Ramon y Cajalâs theory of dynamic polarization refers to the:

(a)membrane potential of a neuron at rest.

(b)membrane potential of a neuron firing action potentials.

(c)opening and closing of gated channels in the membrane.

(d)one way flow of information in neurons from dendrites to axon terminals.

(e)one way flow of information in neurons from axon terminals to dendrites.

Over the course of scientific history, there are many examples of scientists reaching the right conclusion for the wrong reasons. When Schwann first proposed that the nervous system was made of individual cells, he based it on observations of:

(a)synapses.

(b)dendrites

(c)axon terminals.

(d)astrocytes.

(e)Nodes of Ranvier.

The synaptic cleft was finally seen in the 1950s. What prevented scientists from seeing it earlier?

(a)The resolution of the light microscope.

(b)They were looking in the wrong place.

(c)Their tissue was not appropriately stained.

(d)Myelination of the axons.

(e)all of the above

The resting membrane potential of a neuron is approximately:

(a) +65 V

(b) +65 mV

(d) -65 mV

What is largely responsible for the resting membrane potential in a neuron?

(a)Axonal insulation by myelin

(b)Voltage-Gated Sodium Channels

(c)The Action Potential

(d)Potassium Leak Channels

Which of the following would DECREASE the propagation velocity of an action potential down an axon?

(a)Increase in axon diameter

(b)Increase myelination between nodes of Ranvier

(c)Remove myelination between nodes of Ranvier

(d)Decrease density of voltage-gated Na+ channels except at the Nodes of Ranvier

The resting membrane potential of a neuron can be estimated using the:

(a)Nernst equation

(b)Goldman equation

(c)Hodgkin and Huxley equation

(d)Ohmâs law

18. What would happen to the resting membrane potential of a neuron if you added K+ to the extracellular fluid?

(a)Resting membrane potential would increase (become more positive)

(b)Resting membrane potential would decrease (become more negative)

(c)Resting membrane potential would not change

(d)Resting membrane potential would be abolished

. Which of the following statements is FALSE for Graded Potentials

(a)Magnitude changes with magnitude of triggering stimulus

(b)Magnitude decreases with distance from initial site

(c)Cannot be summed

(d)No refractory period

In the nervous system, the strength of the stimulus is coded into:

(a)The frequency of action potentials generated

(b)The amplitude of action potentials generated

(c)Both the frequency and amplitude of action potentials generated

(d)The duration of individual action potentials generated

Ion movement during both the depolarization and repolarization phases of an action potential are the result of:

(a)active transport pumps along the neuron membrane.

(b)diffusion of ions down their electrochemical concentration gradients.

(c)negative feedback loops.

(d)All of the above

At the peak of the action potential, the membrane potential is:

(a)Exactly at the Na+ equilibrium potential

(b)Greater (more positive) than the Na+ equilibrium potential

(c)Above 0 mV but less positive than the Na+ equilibrium potential

(d)0 mV

BM 1041:03 Lecture Notes - Lecture 10: Resting Potential, Voltmeter, Membrane Potential

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