q&a smooth muscles Flashcards

1
Q

The action potential of skeletal muscle

A

spreads inward to all parts of the muscle via the T tubules.

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2
Q

The functions of tropomyosin in skeletal muscle include

A

acting as a “relaxing protein” at rest by covering up the sites where myosin
binds to actin.

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3
Q

The cross-bridges of the sarcomere in skeletal muscle are made up of

A

myosin

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4
Q

The contractile response in skeletal muscle

A

produces more tension when the muscle contracts isometrically than when
the muscle contracts isotonically

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5
Q

Gap junctions

A

are present and provide the pathway for rapid spread of excitation from one cardiac muscle fiber to another

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6
Q

Which of the following characteristics is
shared by simple and facilitated diffusion of
glucose?

A

Occurs down an electrochemical gradient

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7
Q

During the upstroke of the nerve action
potential

A

there is net inward current and the cell
interior becomes less negative

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8
Q

Solutions A and B are separated by a
semipermeable membrane that is perme
able to K+, but not to Cl–. Solution A is
100 mM KCl, and solution B is 1 mM KCl.
Which of the following statements about
solution A and solution B is true?

A

K+ will diffuse from solution A to solu
tion B until a membrane potential
develops with solution A negative with
respect to solution B

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9
Q

The correct temporal sequence for events
at the neuromuscular junction is

A

uptake of Ca2+ into the presynaptic terminal; release of acetylcholine (ACh);
depolarization of the muscle end plate

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10
Q

Which characteristic or component is
shared by skeletal muscle and smooth muscle?

A

Elevation of intracellular [Ca2+] for
excitation–contraction coupling

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11
Q

Repeated stimulation of a skeletal muscle
fiber causes a sustained contraction (tetanus).
Accumulation of which solute in intracellular
fluid is responsible for the tetanus?

A

Ca2+

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12
Q

Solutions A and B are separated by a mem
brane that is permeable to Ca2+ and imper
meable to Cl–. Solution A contains 10 mM
CaCl2, and solution B contains 1 mM CaCl2.
Assuming that 2.3 RT/F = 60 mV, Ca2+ will be
at electrochemical equilibrium when

A

solution A is –30 mV

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13
Q

A 42-year-old man with myasthenia gravis
notes increased muscle strength when he is
treated with an acetylcholinesterase (AChE)
inhibitor. The basis for his improvement is
increased

A

levels of ACh at the muscle end plates

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14
Q

In a hospital error, a 60-year-old woman
is infused with large volumes of a solution
that causes lysis of her red blood cells
(RBCs). The solution was most likely

A

300 mM urea

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15
Q

During a nerve action potential, a stimulus is delivered as indicated by the arrow
shown in the following figure. In response
to the stimulus, a second action potential

A

will not occur

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16
Q

Solutions A and B are separated by a
membrane that is permeable to urea.
Solution A is 10 mM urea, and solution B is
5mM urea. If the concentration of urea in
solution A is doubled, the flux of urea across
the membrane will

A

triple

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17
Q

A muscle cell has an intracellular [Na+] of
14 mM and an extracellular [Na+ ] of 140 mM.
Assuming that 2.3 RT/F = 60 mV, what would
the membrane potential be if the muscle cell
membrane were permeable only to Na+?

A

+60 mV

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18
Q

At which labeled point on the action
potential is the K+ closest to electrochemical
equilibrium?

19
Q

What process is responsible for the
change in membrane potential that occurs
between point 1 and point 3?

A

Movement of Na+ into the cell

20
Q

What process is responsible for the
change in membrane potential that occurs
between point 3 and point 4?

A

Movement of K+ out of the cell

21
Q

The velocity of conduction of action
potentials along a nerve will be increased by

A

myelinating the nerve

22
Q

Solutions A and B are separated by a semi
permeable membrane. Solution A contains
1mMsucrose and 1 mM urea. Solution B con
tains 1 mM sucrose. The reflection coefficient
for sucrose is one and the reflection coefficient
for urea is zero. Which of the following statements about these solutions is correct?

A

Solution A is hyperosmotic with
respect to solution B, and the solutions
are isotonic

23
Q

Transport of D- and L-glucose proceeds at
the same rate down an electrochemical gradient by which of the following processes?

A

Simple diffusion

24
Q

Which of the following will double
the permeability of a solute in a lipid bilayer?

A

Doubling the oil/water partition coefficient of the solute

25
A newly developed local anesthetic blocks Na+ channels in nerves. Which of the following effects on the action potential would it be expected to produce?
Decrease the rate of rise of the upstroke of the action potential
26
At the muscle end plate, acetylcholine (ACh) causes the opening of
Na+ and K+ channels and depolarization to a value halfway between the Na+ and K+ equilibrium potentials
27
An inhibitory postsynaptic potential
hyperpolarizes the postsynaptic membrane by opening Ca2+ channels
28
Which of the following would occur as a result of the inhibition of Na+,K+-ATPase?
Increased intracellular K+ concentration
29
Which of the following temporal sequences is correct for excitation contraction coupling in skeletal muscle?
Action potential in the muscle mem brane; depolarization of the T tubules; release of Ca2+ from the sarcoplasmic reticulum (SR)
30
Which of the following transport process es is involved if transport of glucose from the intestinal lumen into a small intestinal cell is inhibited by abolishing the usual Na+ gradient across the cell membrane?
Cotransport
31
In skeletal muscle, which of the following events occurs before depolarization of the T tubules in the mechanism of excitation contraction coupling?
Depolarization of the sarcolemmal membrane
32
Which of the following is an inhibitory neurotransmitter in the central nervous system (CNS)?
γ-Aminobutyric acid (GABA)
33
Adenosine triphosphate (ATP) is used indirectly for which of the following processes?
Absorption of glucose by intestinal epithelial cells
34
Which of the following causes rigor in skeletal muscle?
An increase in adenosine triphosphate (ATP) level
35
Degeneration of dopaminergic neurons has been implicated in
Parkinson’s disease
36
Assuming complete dissociation of all solutes, which of the following solutions would be hyperosmotic to 1 mM NaCl?
1 mM CaCl2
37
A new drug is developed that blocks the transporter for H+ secretion in gastric parie tal cells. Which of the following transport processes is being inhibited?
Primary active transport
38
A 56-year-old woman with severe mus cle weakness is hospitalized. The only abnormality in her laboratory values is an elevated serum K+ concentration. The elevated serum K+ causes muscle weakness because
Na+ channels are closed by depolarization
39
Which of the following hormones causes contraction of vascular smooth muscle?
Antidiuretic hormone (ADH)
40
Which of the following hormones causes constriction of vascular smooth muscle through an inositol 1,4,5-triphosphate (IP3) second messenger system?
Antidiuretic hormone (ADH)
41
Which of the following substances acts on its target cells via an inositol 1,4,5 triphosphate (IP3)–Ca2+ mechanism?
Oxytocin acting on myoepithelial cells of the breast
42
A key difference in the mechanism of excitation–contraction coupling between the muscle of the pharynx and the muscle of the wall of the small intestine is that
Ca2+ binds to troponin C in the pharynx, but not in the small intestine, to initiate contraction
43
norepinephrine inhibits contraction of smooth muscle in the __________
intestine
44
norepinephrine stimulates contraction of smooth muscle in ___________
blood vessels