Review Worksheet for Chapters 4

Here is a worksheet covering chapters 4 for you to prepare yourself for the exam. This will give you an idea of what is important and where to focus your studying. If you can’t find the answer, use ALL your resources before coming to me. (Not that I don’t want to help-I do-it’s just that you learn more if you discover the answer for yourself.)

Chapter 4 Neural Communication

Define Membrane Potential.- the seperation of positive and negative charges across a membrane

Define the following terms:

Resting potential- when the mp of cells is at rest and around -70 mV

Depolarization- when the membrane potential moves closer to 0mV.

Repolarization- when mp moves back toward rp

Hyperpolarization- when mp is below rp

Now draw a graph to illustrate the above:

Be sure that for the above graph, you are labeling the axis (both vertical and horizontal) and make sure you numbers are logical.

Is hyperpolarization an upward or downward deflection from RMP?

What 2 types of cells are excitable (or irritable)-muscle and neuron

Draw a simple cell and show where the Na+ and K+ are highest.

Now if diffusion is going to take place, which way will these ions move?

This is the whole basis of this chapter and the next and the next and the next and the next, so if you don’t understand it, don’t proceed until you do.

We have mainly talked about 2 kinds of channels:Voltage gated and chemically gated. Write your notes about these below:

Voltage gated: -gated channels that open and close in response to changes in mp.

Chemically gated: -gated channels that open and close in response to binding of a chemical messenger to a surface membrane receptor

There are 2 types of electrical signals that we have talked about. Graded Potentials and Action Potentials. Write your complete notes about these below: Be sure to use the comparison chart in the book.

Graded Potentials:-occurs in small, specialized region of excitable cell membranes-magnitude of GP varies directly with magnitude of the triggering event-decremental spread, therefore the signal gradually decreases

Action Potentials:-brief rapid large (100mV) changes in membrane potential during which inside becomes more + then outside-non decremental conduction, signal arrives at full strength-threshold potential-mp to which membrane must be around -50 mV to initate impulse

How is decremental conduction like throwing a pebble in the water?-waves dissipate over time

How is non decremental conduction like shooting a gun?-rapid, virtually no change in signal

Which of the above is true of AP conduction and which for GP conduction?2 1

Do APs generate GPs or do GPs generate APs?

Are EPSPs and IPSPs APs or GPs?

Can APs be summated?-no

What does the all or none law mean?- if threshold (-50 or -55 mV) is not met than there will be no AP

Do APs or GPs use chemically gated channels?

Do APs or GPs use voltage gated channels?

Define threshold potential:- potential that must be reached in order to conduct and impulse (-50 or -55 mV)

Now let’s look at ion movement during action potential conduction…One more time, draw the cell/neuron with the Na+ and K+ where they belong and also show where they would like to diffuse to if gates should open.Draw the sodium gate with the activation and inactivation gates.

At what voltage do the sodium activation gates open?- threshhold so -50 to -55 mV

At what voltage do the inactivation gates close? 30 mV

Now draw the much simpler K+ gates.

At what voltage do the potassium gates open? 30 mV

At what voltage do the gates close?

--80mV

Draw the action potential graph and label all parts.

Now describe what is happening with the ion movement in each area of the graph. Be complete.

- Na gates open- Na gates close- K gates open- Resting potential restored

Where in the graph is the sodium potassium pump working? Can you see anything on the graph?

Now draw a neuron and label all the parts. Add where the GPs occur and where the APs begin. What direction does the AP travel?

Is the neuron you drew myelinated or unmyelinated?

What is the difference?

How will the above affect impulse speed and conduction/propagation type?Myelinated=slowUnmyelinated=fast

What are Schwann cells and Oligodendrocytes? Be complete.- Schwann cells- Oligodendrocytes

What ensures that impulse conduction is a one way event?

Define absolute and relative refractory period. Don’t forget to add what the channels are doing to cause these events?Abs- unresponsive to further stimulationRel-a second ap can be produced by a triggering event considerably stronger then usual