BSCI 207 Lecture 38: BSCI207 - Lecture 38 - Action Potential and Animal Development

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skycaribou761

26 Jan 2016

School

University of Maryland

Department

Biological Sciences Program

Course

BSCI 207

Professor

Leo Shapiro

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Document Summary

Bsci207 - lecture 38 - action potential and animal development. Changes in membrane potential can be either graded or all-or-none depending on whether threshold (-50 mv) is exceeded. Graded change in membrane potential is a local change in membrane potential. The further away you go from na+ channels, the less the graded change is. Doesn"t get smaller as it propagates along cell membrane of neuron"s axon. A neuron can receive multiple signals (can be from the same neuron) and the resulting depolarizations and hyperpolarizations may sum to bring the membrane potential up to. Triggers a far-traveling action potential that can be rapidly passed along to other neurons. Large, brief localized change in local membrane potential. An impulse or action potential is a state in which the polarity across the cell membrane is reversed. Membrane depolarizes from -65 to +40 (more na+ channels open, draws membrane potential toward na+ nernst potential ~ +60) Other factors limit membrane potential to +40.

Related Questions

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.	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

1.4 An interesting feature of the action potential is this: the amplitude is always the same. That is, whether the nerve is communicating something important or boring, complicated or simple, the amplitude of the pulse moving down the axon is exactly the same. The shape and speed of the pulses are also always the same! Given these constraints, how might action potentials be used to convey more than one piece of information?

1.5 The membrane of the axon cell controls the action potential and therefore determines what we sense, how we think, and much more. The membrane potential is an example of a Nernst potential, described by the equation: delta V = (k_B T / q) ln (c₁/c₂). How might the cell membrane actually control the electric potential that exists between the inside and outside of the cell and what quantities could be measured to test your proposed mechanism? Your answer should refer explicitly to the physics of the Nernst potential. The best answers will relate the state of the membrane to one or more of the phases of the action potential, but please do not write a book. No more than one paragraph is called for here.

1.6 Nerve impulses are transmitted from the end of one axon to the beginning of the next by the release ofneurotransmitters. These are chemicals that cause a modest change in the potential across any nearby axon membrane, including that of the signaling nerve. Consider the features of the action potential. The neurotransmitters released by the signaling nerve do not trigger a return action potential that would run back along the same axon from which the signal came. In light of this observation, how much of a change in potential can these neurotransmitters induce, and for how long? Your answer should be based solely on the model and information provided here, and not from the much more complicated scenarios described on the internet, in articles, and in books.

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BSCI 207 Lecture 38: BSCI207 - Lecture 38 - Action Potential and Animal Development

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