CSB332H1 Chapter 4: Chapter 4

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coppercattle724

14 Jan 2012

School

UTSG

Department

Cell and Systems Biology

Course

CSB332H1

Professor

Melanie Woodin

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Document Summary

Permeability & concentration determine channel conductance: 2 types of electrical signals in nerve cells: Action pots (propagated along entire neuronal: resting pot = steady electrical pot across membrane. (-) = inside of membrane (-) relative to outside membrane pot. Propagate along axons: signalling in ns mediated by changes in, act pots = large brief pulses off depolarization, changes in membrane pot always produced by ion movement. K out or cl in inside more (-), hyperpolarization: rapid ion movement thru ion channels. Ion currents regulated by rate of opening & closing. Perception & analysis of signals, generation of complex motor outputs all depend on ion channel activity. The nerve cell membrane: bilayer 6nm thick, sparingly impermeable to water. Transport molecs (pumps & carriers) move substances against their electrochem grads. Maintain ionic composition of cytoplasm by pumping leaked ions & metabolic substances. What does an ion channel look like: spans membrane, central water-filled pore widens to form vestibule on either membrane side.

Related Questions

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

sapphirepanda54

In order for Neurons to communicate, Resting Membrane Potential must CHANGE. Examples of changes in Membrane Potential included Graded Potentials and Action Potentials. In order for there to be a change in membrane potential, ions must move across the plasma membrane. There are THREE Primary types of Ion Channels: Passive (Leak) Channels, Voltage-gated Channels and Chemically-gated Channels.

DIRECTIONS

Select ONE type of Ion Channel and indicate whether that Ion Channel is MOST important for producing Resting Membrane Potential, Graded Potentials or Action Potentials. Provide detailed support for your choice.

purpleweasel693

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

CSB332H1 Chapter 4: Chapter 4

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