ZOOL344 Lecture Notes - Lecture 4: Axon Hillock, Semipermeable Membrane, Afterhyperpolarization

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raspberryminnow639

15 Nov 2017

School

University of Alberta

Department

Zoology (Biological Sciences)

Course

ZOOL344

Professor

John Chang

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Document Summary

If you inject currents that cause it to be more negative, this is. Hyperpolarization (current and voltage change: why at rest is the cell membrane inside more negative, 1. The cell membrane being not (relatively) permeable to many anions (eg. na+, Atp-dependent transporters pumping ions (na+ and k+) across the membrane to redistribute and maintain charge separation: kick sodium out and take potassium in (3 sodium out, 2 potassium in, 1 charge difference, 4. Large anionic proteins in the intracellular domain: voltage changes when you penetrate the cell membrane, cell membranes are largely made from phosphilipids, which are good. Insulators: ca(cid:374)"t really for(cid:272)e a (cid:272)urre(cid:374)t through, can also separate charges from each other. It is a function of the axial resistor (equation) If the length constant is of a high value, then it means it can exert an influence further down the tube: stimuli at the dendritic area can carry towards the axon hillock.

Related Questions

1.	Action Potentials
2.	Graded Potentials

Match the characteristic/descriptor in the left-hand column withthe correct type of change in membrane potential listed in theright-hand column.

Question 16 options:

12	propagate along the length of the axon with no decrease inmagnitude as they move away from their site of origin
12	are decremental changes in membrane potential - meaning they arethe type that decrease in magnitude as they spread further fromtheir sites of origin
12	cause an actual reversal of membrane potential during which theinside of the cell membrane temporarily becomes positive withrespect to the outside of the cell membrane
12	are non decremental changes in membrane potential - meaning theypropagate along the plasma membrane with no observable decrease inintensity as they move further and further from their sites oforigin
12	occur in the 'receptive' regions of the neuron - including thecell body and dendrites - in response to opening of ligand-gatedion channels
12	begin at the axon hillock and propagate to the axon terminal
12	occur along the length of the axon in response to opening ofvoltage-gated sodium and potassium ion channels
12	weaken as they spread further and further along the plasmamembrane and away from their site of origin
12	required no 'threshold' change in membrane voltage to occur.
12	occur in 'all or none' fashion

blushjellyfish481

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

1. The plasma membrane of liver cells contains a glucose uniportthat transports glucose by facilitated diffusion. When the[glucose] is higher inside the liver cell than the [glucose]outside the liver cell, the glucose uniport will

A. couple the transport of glucose out of the cell to thehydrolysis of ATP

B. couple the transport of glucose into the cell to thehydrolysis of ATP

C. switch to a closed conformation, allowing no transport ofglucose

D. transport glucose out of the cell by passive transport

E. transport glucose in of the cell by passive transport

2. Unlike the positive charged ion shown in the middle diagramof figure 11-4B, K+ is higher in concentration inside the cell. Howwill the membrane potential of a cell at rest (shown in both themiddle and right-hand diagrams of Figure 11-4B) affect theelectrochemical gradient for K+?

A. The membrane potential will increase the electrochemicalgradient

B. The membrane potential will decrease the electrochemicalgradient

C. The membrane potential will have no effect on theelectrochemical gradient

3. Which of the following proteins carries out activetransport?

A. gluclose symport

B. Bacteriorhodopsin

C. ABC transporter

D. NA K pump

E. All of the above

4. Aquaporin will not transport Na+ ions because

A. Two asparagine residues in the channel prevent the passage ofNa+ ions by binding the oxygen of each water molecule as it passesby

B. Na+ ions are repelled by the positive charges at the entranceto the channel

C. Na+ ions cannot make contact with the carbonyl (C=O) groupson all four sides of the channel

D. The passage of Na+ ions is energetically unfavorable becauseone side of the channel is hydrophobic in nature

5. The acetylcholine receptor is different from other channelproteins we have discussed, such as the K+ leak channel,because

A. The acetylcholine channel is composed of a single polypeptiderather than multiple subunits

B. The acetylcholine channel transports Na+ ions against theconcentration gradient for sodium

C. The acetylcholine channel has a much smaller diameter thanother channel proteins

D. The acetylcholine channel transports ions with theirassociated shell of water molecules

E. The acetylcholine channel is always open, and never switchesto a closed conformation

6. After opening briefly along the axon of a neuron,voltage-gated ion channels switch to an inactivated conformationthat slowly returns to the original closed conformation of theprotein. This slow change in conformation, requiring about amillisecond, is important because

A. all of the ions that were transported across the membranewhen the ion channels were open must be actively transported backto the other side of the membrane, restoring the originalconcentration gradient, before the ion channels can open again

B. ATP hydrolysis is necessary to drive this energeticallyunfavorable change in conformation

C. it prevents the action potential from reversing direction andtraveling back toward the cell body of the neuron

D. the channel protein must be dephosphorylated in order tocomplete the transport process and return to the originalnonphosphorylated conformation

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ZOOL344 Lecture Notes - Lecture 4: Axon Hillock, Semipermeable Membrane, Afterhyperpolarization

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