Download Ch12 - Seattle Central College

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Study Guide Chapter 12
1. Draw a concept map that shows the structural and functional divisions of the nervous system and
shows their relationships to each other.
2. Many variables are maintained at set points (e.g. body temperature) by negative feedback to
maintain homeostasis. Please describe regulation of one variable where the control center is the
nervous system. Include discussion of set point, receptors, the afferent pathway, control
centers, the efferent pathway, and effectors and draw a graph to illustrate.
3. Draw a picture and identify parts of a neuron and their functions: dendrites, cell body (soma),
organelles (ER, Golgi, vesicles, nucleus, cytoskeleton), axon (and branches), nodes of Ranvier,
myelination (Schwann cells or oligodendrocytes), pre-synaptic terminal.
4. Draw the general structure of the three neuron types (unipolar, bipolar, multipolar) and describe
in words the features of the 3 functional classes of neurons (12-3 and text).
5. Identify and describe the main functions of the 4 main types of glial cells in the CNS 2 main types
in the peripheral nervous system.
6. Describe the anatomy and function of the myelin sheath (central tracts and peripheral nerves).
What are the anatomical and functional differences of myelinated and unmyelinated axons.
7. Define membrane permeability. List two molecules that permeate the lipid bilayer. How do ion
channels embedded in the membrane effect permeability of the bilayer?
8. Describe the relative concentrations of “physiological important” ions inside and outside the cell
(K+, Na+, Ca++, Cl-).
9. With respect to ion channels: differentiate between leak and gated channels. Gated channels are
opened and closed by various stimuli. What are these stimuli that define categories of gated ion
channels?
10. Define the terms: voltage, potential difference, current, electrochemical gradient, Nernst
Potential, depolarization, repolarization, graded potential, local current. What is the function of
current flow across cell membranes?
11. Explain the resting membrane potential and how it is generated (balance between electrical and
chemical forces)
12. I will teach you how to do this in class. Fill in table below for Equilibrium potentials using Nernst
equation (Resource: http://www.st-andrews.ac.uk/~wjh/neurotut/mempot.html) and calculating
the voltage (electrical potential energy) that exactly balances the concentration gradient for the
important physiological ions in the table below (Note: These concentrations are artificial to make
calculations easier but are about the right magnitude).
The Nernst equation expresses the energy of the concentration gradient in terms of the
electrical gradient: “For any monovalent ion (like K+), a 10 fold concentration gradient
contains exactly the same energy as a 60mV voltage difference (at 37C).” This means that
if K concentrations are 10 mM outside and 100 mM inside, the resting membrane potential
of the cell is -60 mV (with only leaky K channels in the cell membrane).
Ion
[IN] in [OUT] in mM
Nernst or Equilibrium Potential
mM
Na
1
100
+
K
100
1
Cl
1
100
++
Ca
.0001
1
Where z = valence (charge) of the permeant ion (Ca++ = 2, Na+ = 1, Cl- = -1)
+
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LOG HELP
Log 10 1 = 0
rest
Log 10 10 = 1
Log10 100 = 2
Log 10 1000 = 3
Log 10 10000 = 4
Log10 .1 = -1
Log10 .01 = -2
and so on (therefore, and Log 10 .001 = -3)
E
60
[ion]out
log 10
z
[ion]in
Again, the equation above is a simplified Nernst equation that gives the membrane potential
(energy) that exactly balances a concentration gradient (energy). The equation is derived from
thermodynamic principles. Normally cells have permeability to K at rest because they have leaky
K ion channels open in their membranes. When stimulated, different ion channels open and shift
the resting potential towards the equilibrium potential for that ion. For example, acetylcholine
released at the neuromuscular junction opens a ligand-gated Na channel (cation channel) that
depolarizes the cell to threshold and triggers a muscle action potential that leads to muscle
contraction. When many voltage-gated Na channels open, the permeability of the membrane to
Na is very high and the membrane potential of the cell will shift towards the equilibrium potential
(aka Nernst potential) for Na. You calculated this value is in the table above. In our bodies,
concentrations of ions outside and inside our cells change very little so most shift in membrane
potential are due to the opening and closing of ion channels.
13. Determine the resting potential for all the cells listed below.
a. Cell 1: has only Na leak channels in its membrane
b. Cell 2: only K leak channels in its membrane
c. Cell 3: only Ca leak channels in membrane
d. Cell 4: only Cl leak channels in its membrane.
e. Cell 1 has 100 Na leak channels that set its resting potential. A drug is added to Cell 1
that opens 100 K leak channels so there are now an equal number of Na and K leak channels
open in the cell membrane. What is the membrane potential of this cell?
f. Make the cell in A have a resting potential = to 0 mV by changing the permeability of the
membrane to ions (you can have more than one channel type open at the same time).
g. Make the cell in A have a resting potential = 0 mV by changing ion concentrations.
14. Draw AP figure (voltage vs. time) like that shown Figure 12-14 and table 12-3.
1. Label the following using the values you calculated above: Equilibrium potential for K (Ek),
resting potential, Equilibrium potential for Na (Ena), threshold, depolarization,
repolarization, hyperpolarization, absolute and relative refractory period.
2. Refer to your figure and explain what you expect the gates on the voltage-gated Na and K
channels to be doing at rest, during depolarization, repolarization, absolute refractory
period, and relative refractory period.
3. Describe a threshold stimulus.
i. How do graded potentials generated on dendrites lead to the all-or-none behavior
of the action potential?
ii. Define what is meant by all or none.
iii. What is the role of the axon hillock in generating an AP?
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4. What is the role of the Na/K pump in the AP?
5. How is the resting potential in our simple cell (only K leak channels open to set rest)
different from the more complex situation found in many real cells?
1. Why is there a “hyperpolarization” after the AP in the figure from your book
(below)?
2. Why is the peak of the action potential less that the Nernst potential for Na in
figures shown in your book?
15. Identify the effects of axon diameter and myelination on conduction velocity of axons.
16. Define EPSP and IPSP and interpret graphs showing the voltage vs. time relationship for each.
17. Draw and label the general anatomical features of a chemical synapse. Use your drawing to explain
the steps of synaptic transmission – start with an EPSP in the pre-synaptic cell at a dendrite.
Include discussion of summation, threshold, action potential propagation, events at the presynaptic terminal leading to post-synaptic response and discuss how synaptic potentials differ
from action potentials.
18. List the chemical and functional classes of neurotransmitters, name a member of each class, and
an example of transmitter receptor for each.
1. What is the major excitatory transmitter in the human brain?
2. What is the main inhibitory transmitter in the human brain? spinal cord?
3. What is the difference between a direct acting transmitter and an indirect acting
transmitter?
4. Understand how disease and drugs effect specific transmitter actions (We’ll go over these
in class/lab): Parkinson’s disease, amphetamines, Prozac, valium, heroin, viagra, cocaine,
alcohol, nicotine, ether, curare, lidocaine.
19. Define temporal and spatial summation. Use a plot of voltage vs. time like Figure 12.19 and 12.20
to explain.
20. Twenty neurons synapse with a single receptor neuron. Fifteen of these neurons release
neurotransmitters that produce EPSP's at the postsynaptic membrane, and the other five release
neurotransmitters that produce IPSP's. Each time one of the Inhibitory or Excitatory neurons is
stimulated, it releases enough neurotransmitter to produce a 2mV change in potential at the
postsynaptic membrane (+2 mV or – 2 mV).
1. If the postsynaptic neuron threshold is 10mV, how many excitatory neurons must be
stimulated to produce an action potential in the receptor neuron if all five inhibitory
neurons are stimulated? (Assume that spatial summation occurs.)
21. A drug that blocks Na,K ATPase is introduced into an experimental neuron preparation. The
neuron is then repeatedly stimulated and recordings are made of the response. What effect
would you expect to observe?
22. Mr. Miller is hospitalized for cardiac problems. Somehow the medical orders are mixed up and
Mr. Miller is infused with a 10 mM K+ intravenous solution meant for another patient who is taking
potassium wasting diuretics (that is, drugs that cause excessive loss of potassium from the body
in the urine). Mr. Miller's potassium levels are normal before the IV is administered
(physiological: 3 - 5 mM). What do you think will happen to Mr. Miller's neuronal resting
potentials? To his neurons' ability to generate action potentials?
23. General and local anesthetics block action potential generation, thereby rendering the nervous
system quiescent while surgery is performed. What specific process do anesthetics impair, and
how does this interfere with nerve transmission? We discussed lidocaine and halothane.
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24. Rochelle developed multiple sclerosis when she was 27. After eight years she had lost a good
portion of her ability to control her skeletal muscles. Why did this happen?
25. Describe:
1. Multiple Sclerosis
2. Myasthenia gravis
3. Shingles caused by the varicella zoster virus
4. Tay-Sach’s disease
5. Lou Gerhigs disease (ALS)
6. Parkinson’s
7. Heavy metal poisoning (e.g. Mercury, Lead, Cadmium)
8. Botulism
9. Glioblastoma