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Human A&P
Membrane Potentials & Nerve Impulses
Answer all of the following questions. You will find all of the
answers contained within Chapter 8 (pgs. 203 to 205) and in your
lecture notes.
1. What is the difference in charge between the interior and
exterior of most cells? What do we call this differential?
2. What two factors contribute to this polarity?
3. Which ions are involved? What are their relative
concentration inside/outside of the cell?
4. What is the function of the sodium-potassium ion pump? How
does this relate to the relative permeability of the membrane
regarding these two ions?
5. Please study figures 8.7 and 8.8 thoroughly.
6. Check () all descriptions that apply to a resting neuron:
_____
Its inside is negative relative to its outside.
_____
Its outside is negative relative to its inside.
_____
The cytoplasm contains more sodium and less potassium
than does the extracellular fluid.
_____
The cytoplasm contains more potassium and less sodium
than does the extracellular fluid.
_____
A charge separation exists at the membrane.
_____
The electrochemical gradient for the movement of sodium
across the membrane is greater than that for potassium.
_____
The electrochemical gradient for the movement of
potassium across the membrane is greater than that for
sodium.
_____
The membrane is more permeable to sodium than
potassium.
_____
The membrane is more permeable to potassium than
sodium.
7.
Using the choices below, select the terms defined in the
following statements. Write the LETTER of the correct
answer in the blank provided.
A.
Absolute refractory
G.
Polarized
period
H.
Relative refractory
B.
Action potential
period.
C.
Depolarization
I.
Repolarization
D.
Frequency of impulses.
J.
Sodium-potassium pump
E.
Graded potential
K.
Subthreshold
F.
Hyperpolarization
L.
Threshold
_____
Corresponds to the period of repolarization of the
neuron.
_____
Process by which the resting potential is decreased as
sodium ions move into the axon.
_____
State of an unstimulated neuron’s membrane.
_____
Period (event) during which potassium ions move out of
the axon.
_____
Also called the nerve impulse.
_____
Period when a neuron cannot be restimulated because
its sodium gates are open.
_____
Mechanism by which ATP is used to move sodium ions out
of the cell and potassium ions into the cell;
completely restores and maintains the resting
conditions of the neuron.
_____
Point at which an axon “fires.”
_____
Term for a weak stimulus.
_____
Self-propagated depolarization.
_____
Codes for intensity of the stimulus.
_____
Membrane potential at which the outward current
carried by K+ is exactly equal to the inward current
carried by Na+.
_____
A voltage change that reduces the ability of a neuron
to conduct an impulse; the membrane potential becomes
more negative.
_____
A local change in membrane potential in which current
flow is quickly dissipated, that is decremental.
_____
An all-or-none event.
_____
A voltage change that brings a neuron closer to its
threshold for firing; the membrane potential becomes
less negative and moves toward zero.
_____
Results from the opening of voltage-regulated ionic
gates.
_____
Results from the opening of chemically regulated gates
or energetic stimuli.
_____
Characterized by a rapid polarity reversal.
8.
Circle the term that does not belong in each of the
following groupings:
(Note: Cl- = chloride ion; K+ = potassium ion; Na+ = sodium ion)
a.
Inside resting cell High Na+
b.
High Clresting cell
c.
out
Protein anions
Na+/K+ Pump
ATP required
Low Na+
High K+
Low Cl-
Cytoplasm
3 Na+ out / 2 K+ in
d. Nerve impulse
Graded potential
Short-lived signal
e.
Depolarization Inside
Hyperpolarization
-70 mV to -50 mV
f.
Can generate AP
processes Cell bodies
of
3 Na+ in / 2 K+
Short-distance
membrane
Axons
less
signal
negative
Peripheral
9.
Graph the following set of data.
Then, label the
following: absolute refractory period, action potential (AP),
depolarization, graded potential, hyperpolarization, relative
refractory period, repolarization, resting membrane potential (RMP).
**If you have the capability, you may plot these data points on your
TI Graphing Calculator or Computer (excel) and then print the graph.
Voltage
(mV)
Time
(ms)
-70
-70
-65
-70
-70
-60
-70
-70
-50
+30
-65
-75
-78
-71
-70
-70
2.0
0.5
0.7
1.0
1.5
1.7
2.0
2.5
3.0
3.5
4.0
4.2
4.5
5.0
5.5
6.0
** Remember to label axes and give your graph a title!! Your graph
should be approximately one page in size to accommodate all data
points and labels.