Poll Questions

Question 1

Which best describes a “myofibril”?

Answer 1

It is a cylindrical cellular organelle
composed of myofilaments

Question 2

What is the role of calcium in muscle contractions?

Answer 2

to bind with troponin, changing its shape so
the actin filament is exposed.

Question 3

You have designed a drug that is supposed to bind to the myosin binding sites on actin. You inject it into a relaxed muscle, but find that none of the drug is bound. Why?

Answer 3

The myosin binding sites on actin are covered by
tropomyosin.

Question 4

How is the length of a skeletal muscle cell related to the
force it can generate?

Answer 4

Skeletal muscle cells generate the most force when the
contraction occurs at an intermediate length

Question 5

What would be the result if the administration of a
drug sequesters (inactivates) all the ATP in a
cell?

Answer 5

All cross-bridges will remain tightly bound to
actin

Question 6

The major physiological difference between single-unit
smooth muscle and multi-unit smooth muscle is

Answer 6

Action potentials can spread from cell to cell in single-
unit, but not in a multi-unit muscle.

Question 7

Which group of chemicals does
NOT contain hormones?

Answer 7

Carbohydrates

Question 8

The specific action of hormones is due to:

Answer 8

hormone-specific receptors in target cells

Question 9

When a certain gland extract gland is applied to
some cells, these cells respond by starting cell
division. However, when a c-AMP inhibitor is first
applied to the cell and then the gland extract is
applied, the cells do not divide.
Therefore, the gland extract most likely contains

Answer 9

a peptide hormone

Question 10

The anterior pituitary gland releases all of
the following hormones

Answer 10

follicle-stimulating hormone (FSH).
thyroid stimulating hormone (TSH).
prolactin.
growth hormone (GH)

Question 11

What controls the release of corticoids
from the adrenal cortex?

Answer 11

Higher brain centers
CRH from the hypothalamus
ACTH from the anterior pituitary

Question 12

Which of these pituitary hormones is not
released in response to a releasing hormone
from the hypothalamus?

Answer 12

ADH
Insulin

Question 13

Which of these is true of the adrenal medulla?

Answer 13

It functions as part of the sympathetic nervous
system

Question 14

The mode of action of insulin is by

Answer 14

adding GLUT-4 transporters to muscle and fat
cells
stimulating phosphorylation of intracellular
glucose in liver cells.

Question 15

Blood samples from an individual who has fasted
(not eaten) for 24 hours would have:

Answer 15

high levels of glucagon and low levels of insulin.

Question 16

he hormone ____ is a modified amino
acid, whereas ____ is a steroidal hormone.

Answer 16

epinephrine, testosterone

Question 17

George’s symptoms
1. Frequent urination: polyuria.
2. Increased thirst: polydipsia.
3. Increased appetite: polyphagia.
Are George’s symptoms consistent with
type 1 DM, type 2 DM, both, or neither?type 1 DM, type 2 DM, both, or neither?

Answer 17

Both

Question 18

Where is the Atrial repolarization?

Answer 18

Hidden in QRS complex.

Question 19

In vertebrate heart, many pacemaker cells
(myogenic cells) in SA node, each with their
own spontaneous AP firing rate.
If they all start firing at the same time, which
pacemaker cell determines the basic heart
beat frequency?

Answer 19

Cell with fastest AP frequency

Question 20

In vertebrate heart, many pacemaker cells
(myogenic cells) in SA node, each with their own
spontaneous AP firing rate.
What happens to the heart beat frequency if
this pacemaker cell dies? Which cell
determines basic heart rate frequency?

Answer 20

Cell with next fastest AP frequency

Question 21

If the stroke volume is 80 ml and the
heart rate is 70 beats per minute, the
cardiac output is

Answer 21

5600 ml/min
CO = HR X SV

Question 22

Through which vessel is the velocity
of blood flow the slowest?

Answer 22

capillaries

Question 23

Which of the following statements concerning the
capillaries is FALSE?

Answer 23

Increasing capillary hydrostatic pressure decreases
the likelihood that filtration will occur.

Question 24

The affinity of hemoglobin for oxygen is
____ if PO2 is low and is ____ if PO2 is high.

Answer 24

low, high

Question 25

The Bohr effect describes the ________

Answer 25

effect of pH on the affinity of hemoglobin
for oxygen

Question 26

For maximum efficiency in loading oxygen
at the lungs

Answer 26

the temperature should be slightly lower
than normal body temperature

Question 27

The ventilation/perfusion ratio ______

Answer 27

increases when blood flow is decreased

Question 28

In muscle physiology, the correct technical meaning of “contraction” is:

Answer 28

b. the active state of a muscle, producing some combination of force or movement

Question 29

The thick filament of a myofibril of a skeletal muscle contains a protein called

Answer 29

myosin

Question 30

arrange this list of events in excitation-contraction coupling in the correct order

Answer 30

motor endplate depolarizes
action potential travels over muscle cell membrane
action potential travels down t-tubules
Ca++ released through channels from SR
Ca++ pumped into SR

Question 31

The major functional difference between single-unit (visceral) smooth muscle and multi-unit smooth
muscle is:

Answer 31

a. action potentials can spread from cell to cell in single-unit, but not in multi-unit

Question 32

What will happen to the muscle contraction if ATP is unavailable?

Answer 32

d. The muscle becomes rigid due to failure of cross-bridges to detach from actin filaments.

Question 33

A motor unit in muscles

Answer 33

d. includes all muscle fibers connected to one motor axon.

Question 34

8. The energy used for muscle contractions after 30 minutes mostly comes from

Answer 34

Fatty acids

Question 35

9. The difference between a muscle twitch and tetanus is due to

Answer 35

a. the duration of the active state of the muscle.

Question 36

The primary role of calcium in the activation of smooth muscle is to

Answer 36

c. activate myosin molecules so they can interact with actin filaments

Question 37

11. During an isometric muscle contraction the

Answer 37

c. series elastic components stretch

Question 38

12. In regards to the relationship between resting muscle fiber length and tension generated, ________.

Answer 38

a. maximal tension is generated when the thick and thin filaments slightly overlap

Question 39

Which muscle fiber type produces a high level of force-generation, a fast speed of contraction, and has a
low level of oxgygen capacity?

Answer 39

c. Fast glycolytic

Question 40

14. Myosin contains binding sites for ________ and ________.

Answer 40

c. ATP; actin

Question 41

15. The T-tubules __________

Answer 41

provide a means of rapidly transmitting the AP from the surface into the central portions of the muscle
fiber.
d. contain the DHP-receptor.