CSB332H1 Lecture Notes - Lecture 6: Gas Constant, Cytosol, Reversal Potential

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coraleel39

25 Feb 2014

School

UTSG

Department

Cell and Systems Biology

Course

CSB332H1

Professor

Francis Bambico

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Document Summary

You can use a tool to measure the membrane potential in neurons. The reference electrode is in the extracellular environment, and the other electrode is sticking into the neuron, and you connect them to a voltmeter that measures the membrane potential. Membrane potential is a potential energy, which is stored energy. Membrane potential is the work that can be invested because of the presence of the potential energy. If there is work done, then there is a force that displaces the object. An electrical potential may refer the work done, or the force (electromotive force), or the potential energy: you can measure the energy that is stored in nervous tissue using a voltmeter. Voltage is equivalent to one coulomb of positive charge (e. g. , one coulomb per change in voltage). Neurons are able to store energy indefinitely in the form of chemical energy. The movement of ions can only be possible based on the chemical composition of the neurons.

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

An electrophysiologist is studying the electrical properties of an isolated squid neuron placed in normal extracellular fluid. She places a recording electrode inside the cell to record the potential difference across the membrane. She records a resting membrane potential of -70 mV.

A. Name three factors that contribute to this resting membrane potential and explain âhowâ they contribute to this negative value

She then applies an electric current across the membrane and records a slight change in the membrane potential. When she increases the current and stimulates the cell again, she notices a rapid reverse in the membrane potential to +30 mV followed by a drop in membrane potential to -75 mV before it returns to -70 mV. When she increases the current some more and stimulates the cell again, she records the same electrical pattern that is the same as what was obtained with the previous current that was applied.

B. What name can be given to the small change in membrane potential seen with the first electrical current applied?

C. Given the type of stimulus, what triggered this change in membrane potential?

D. What is the name given to the electrical pattern obtained with the next current used?

E. What allowed this stimulus to work but not the previous one?

F. Explain the type of feedback mechanism that occurs when this pattern was initiated.

G. Describe the cellular mechanisms that account for the rise and then fall in this electrical pattern

H. Why did the pattern remain the same when the highest stimulus was applied?

The research then changes the extracellular solution (making sure to keep the osmolarity the same) so the it contains double the concentration of Ca²⁺.

I. Would resting membrane potential change? Why /why not?

J. When she stimulated the cell with the highest current, would the shape of the electrical pattern change? Why / why not?

K. Would synaptic transmission change? Explain

Nerve cells that conduct messages are called (1) ____. (2) _____ cells, which support and nurture the activities of neurons, make up less than half the volume of the nervous system. (3) _______ neurons respond to specific kinds of environmental stimuli, (4) ______ connect different neurons in the spinal cord and brain, and (5) ______ neurons are linked with muscles or glands. All neurons have a (6) _______ ________ that contains the nucleus and the metabolic means to carry out protein synthesis. (7) _______ are short, slender extensions of the (6), and together these two neuronal parts are the neuronsâ âinput zoneâ for receiving (8) _____. The (9) _____ is a single long, cylindrical extension away form the (10) ______; in motor neurons, the (11) ______ has finely branched (12) ________ that terminate on muscle or gland cells and are âoutput zones,â where messages are sent on to other cells. A neuron at rest establishes unequal electric charges across its plasma membrane, and a(n) (13) ____ ____ is maintained. Another name for (13) is the (14) _____ _____ _____; it represents an ability for the membrane to be disturbed. Weak disturbances of the neuronal membrane might set off only slight changes across a small patch, but strong disturbances can cause a(n) (15) _______ ______, which is an abrupt, short-lived reversal in the polarity of charge across the plasma membrane of the neuron. For a fraction of a second, the cytoplasmic side of a bit of membrane becomes positive with respect to the outside. The (16) ______ that travels along the neural membrane is nothing more than short-lived changes in the membrane potential. A. Neurons H. Sensory B. Motor I. Endings C. Interneurons J. Disturbance D. Cell body K. Signals (stimuli) E. Axon L. Voltage differential F. Dendrites M. Resting membrane potential G. Neuroglial N. Action potential

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CSB332H1 Lecture Notes - Lecture 6: Gas Constant, Cytosol, Reversal Potential

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