SSN SBPM Workshop~ Exam 2
Multiple Choice Questions
**Last year’s histology handouts are available at
http://cpmcnet.columbia.edu/student/ssn/histology/block2.htm
1-3. From the list below, choose the appropriate configuration for the majority of channels
on a motor nerve axon at the given membrane potential (Na+ channel = voltage gated
Na+ channel and K+ channel = voltage gated K+ channel):
a.
b.
c.
d.
K+ channels closed, Na+ channels open, K+ leak channels open.
Na+ channels closed (active), K+ channels closed, K+ leak channels open.
Na+ channels closed (inactive), K+ leak channels open, K+ channels open.
Na+ channels open, K+ channels open, K+ leak channels closed.
1. At -70 mV prior to an action potential.
2. At -82 mV during the hyperpolarizing afterpotential.
3. At 0 mV during the upstroke.
4-6. Match each of the following structures with the best statement from the list below:
a. Integrates all the inputs into a neuron and determines whether the cell fires an
action potential.
b. Characterized by a narrow synaptic cleft, and fewer dense projections.
c. Characterized by a wider synaptic cleft, and round synaptic vesicles.
d. Found on the dendritic spine, and/or dendritic shaft.
e. Characterized by both C & D.
4. Axon Hillock (trigger zone)
5. Type I Synapse
6. Type II Synapse
7. Myelination of a peripheral nerve is done by ______ cells. Nerves in the CNS are
myelinated by _____ cells and supported by _____ cells.
a.
b.
c.
d.
e.
Oligodendrocytes, schwann, astroglial
Schwann, oligodendrocytes, astroglial
Oligodendrocytes, schwann, microglial
Schwann, oligodendrocytes, microglial
None of the above
8. Ion channels
a. Often have a selectivity filter of AA side chains that provide ion specificity
b. Always open and close in perfect synchrony with each other.
c. Can exist in states other than open or closed
d. Will never saturate; higher ion concentrations always leads to faster ion flow
e. None of the above
9. Increasing the afterload on a skeletal muscle fiber
a. Increases the velocity of shortening
b. Decreases the force produced by the muscle after shortening
c. Decreases the interval between excitation and shortening
d. Increases the amount of shortening
e. None of the above
10. In smooth muscle, Ca2+ is released from the sarcoplasmic reticulum by which of the
following?
a. Diacylglycerol (DAG)
b. The GTP binding protein (G protein)
c. Phospholipase C
d. Inositol triphosphate (IP3)
e. Adenylate Cyclase
11. Depolarization of the T tubule is directly linked to the opening of Ca2+ channels on the
sarcoplasmic reticulum of
a. Skeletal muscle
b. Cardiac muscle
c. Both A and B
d. Neither A nor B
12. Alteration in preload alters the force of contractions in which of the following muscle
type or types?
a. Cardiac muscle
b. Skeletal muscle
c. Smooth and cardiac muscle
d. Smooth and skeletal muscle
e. Smooth, cardiac, and skeletal muscle
13-18. Which type of Connective Tissue is found in each structure:
(you can use each answer once, more than once, not at all...)
a. Loose CT proper
b. Dense CT proper
c. Elastic Fibers
13. Ligament
14. Lamina propria of alimentary canal
15. Vertebral ligament
16. Tendon
17. Aponeurosis
18. Aorta
19. The word "Reticular" means:
a. vesicular
b. net-like
c. repeating subunits
d. orthagonal layers
20. In a haversian system, the oldest osteocytes are located peripherally/centrally (circle
one); in cartilage, the oldest chondrocytes are located peripherally/centrally (circle
one).
21.
Significant features of the ground substance include:
a. High density of glycosaminoglycans (GAGs), whose positive charge leads to water
hydration due to osmotic activity
b. High density of glycosaminoglycans (GAGs), whose negative charge leads to water
hydration due to osmotic activity
c. Abundant collagen of types II, IX, and XI in cartilage, and types I and V in bone
d. A highly organized, minimally permeable substance consisting largely of
connective tissue
SSN SBPM Workshop~ Exam 2
Answers to Multiple Choice Questions
1.
2.
3.
4.
5.
6.
7.
8.
B
C
A
A
E
B
B
C
9. E
The afterload is the weight that a muscle lifts during an isotonic contraction. When the afterload
on a skeletal muscle is increased, the velocity of shortening slows, the amount of force produced
by the muscle increases (force = load for the muscle to shorten), the intervals between excitation
and shortening increases (it takes longer for muscle to build up enough force to lift the load), and
the amount of shortening decreases.
10. D
In smooth muscle, Ca2+ is released from the SR by an IP3-activated channel. In skeletal muscle,
Ca2+ is released from the SR through a ryanodine receptor that is activated by depolarization in
skeletal muscle and by Ca2+ in cardiac muscle.
11. A
Release of the Ca2+ from the SR in both skeletal and cardiac muscle is activated by T tubule
depolarization. However, in skeletal muscle, the Ca2+ release channel in the SR is opened
directly by the depolarization of the T tubule membrane. In cardiac muscle, Ca2+ is
released from the SR by a Ca2+-induced Ca2+ release process. The Ca2+ used in this process
enters the cell through a voltage-gated Ca2+ channel associated with the T tubule membrane.
12. E
13. B
14. A
15. C
16. B
17. B
18. C
19. B
20. Peripherally, Centrally
21. B
SSN SBPM Workshop~ Exam 2
Short Answer Questions
Note: These questions may not be similar to the on-line short answer
questions for your exam. The purpose of these questions is to explain
topics in more detail than is allowed by the Multiple-choice format. Also,
these questions offer an opportunity to go over some topics that the SSN
teachers do not have time to teach during the SSN session.
1. Explain how myelination allows a neuron to increase the rate of action potential
propagation. What other mechanism do neurons take advantage of for increasing the
speed of propagation? What is meant by saltatory conduction?
Myelination insulates the nerve fiber, greatly increasing the resistance across the membrane.
Thus, when there is a depolarizing current within the cell, less of the current travels across
the now high resistance membrane, and a greater amount flows along the inner membrane
where resistance is lower. By increasing membrane resistance, myelination increases the
length constant for a given neuron.
Neurons may also increase the speed of conduction by increasing their axon diameter,
and thereby decreasing the resistance to charge within the axon. Anatomic constraints limit
the practicality of this approach and myelination is a further adaptation to increase speed of
conduction.
Saltatory conduction refers to the apparent “jumping” of action potentials along a
myelinated axon from one node of Ranvier to another.
2. We owe a lot of our knowledge regarding ion channels to the patch-clamp technique.
What is this technique? In your answer be sure to include the meaning of “patch” and
“clamp.”
The patch clamp technique uses a fine glass tube as a microelectrode to make electrical
contact with the cell. This setup is used to detect current flowing through an ion channel.
The “patch” is the segment of the membrane that is held to the glass tube by suction. The
“clamp” refers to maintaining a constant voltage to determine how that voltage affects the
opening and closing of ion channels.
3. Name 3 different types of Collagen, and where they're found:
Type I Collagen -loose and dense CT
Type II Collagen -hyaline and elastic cartilage -fine fibrils
Type IV Collagen -nonfibrillar network
- provides structural cohesion to the basal lamina
4. Distinguish between appositional and interstitial growth of cartilage.
Appositional growth: New cartilage develops on inner layer of perichondrium,
Result = ↑diameter
Interstitial growth:
Chondrocytes DIVIDE within their lacunae, forming new cartilage
Result = ↑length
5. Explain why bone tissue can only grow by appositional growth. And what’s the deal with
endochondral ossification?
Only cartilage tissue can do interstitial growth, because chondrocytes can still divide while
osteocytes are post-mitotic. BUT cartilage doing interstitial growth can produce a cartilage
model, which then gets transformed into bone…this is called Endochondral Ossification. The
bone grows by “interstitial growth”, but the bone tissue itself is not doing interstitial growth
since it can’t divide.
6. Which layers of bone contain osteoprogenitor cells?
Both the inner layer of the periosteum & the endosteum. With appropriate stimuli, these will
differentiate into osteoblasts.
7. Acetylcholine can bind to receptors in the gut that activate the Gq signaling protein.
Explain a plausible mechanism as to how doing this leads to muscle contraction without
actually depolarizing the muscle.
The reason that acetylcholine binding to muscarinic receptors can initiate smooth muscle
contraction is that it activates the Gq protein, which in turn, activates phospholipase C. PLC
cleaves PIP2 to IP3 and DAG. IP3 in turn induces calcium influx into the myocyte, which is
all that is necessary for activation of calmodulin and subsequent steps. ONLY smooth
muscle can do this; both skeletal muscle and cardiac muscle need to be depolarized before
calcium can influx.
8. Does the biceps muscle generate the most tension when it is contracting at:
1) 0 degrees flexed, 2) 45 degrees flexed, or 3) 90 degrees flexed? Why?
The tension generated will be greatest at about 45 degrees flexion. This is because at this
muscle length, there is maximal overlap between the myosin-actin filaments. At 0 degrees,
the muscle is too stretched and there is little overlap between the filaments; at 90 degrees,
overlap is near maximal as it is, and there is little room left to contract further (the thick
filaments would literally "bump into" the Z disks).