Muscle MCQ Flashcards
The major difference between ion channels and ion pumps is
A their dependence on adenosine trisphosphate (ATP)
B the species of ions that they move
C their locations on the cell membrane
D their specificity for moving particular ions
E their molecular weights
A
Which of the following BEST describes the period of time between the peak of an action potential and the peak of the cytoplasmic Ca2+ transient during excitation-contraction coupling in mammalian skeletal muscle (at normal body temperature)?
A 2 s
B 0.2 ms
C 20 ms
D 2 ms
E 0.02 ms
C (?)
A potential five-fold increase in cardiac output in a person going from a resting state to one of intense exercise suggests that
A resistance in the arteries has increased
B both the stroke volume and pacing rate of the heart must have increased
C the diastolic phase of the cardiac cycle has increased
D the rate of Na+ (sodium) channel inactivation per heart beat in the ventricular myocytes has changed
E the systolic phase of the cardiac cycle has increased
B
At high heart rates (e.g. 150 bpm), the ventricles still fill with blood, because
A of the long relative refractory period
B blood bypasses the atria
C reflexes control ventricular filling
D filling is accomplished in early diastole
E the atria contract with greater force
D
Which of the following is NOT an effect of the parasympathetic nervous system on the heart?
A increased inward Ca2+ current
B slowed pacemaker activity
C slowed closure of K+ channels
D weakened atrial contraction
E decreased inward Ca2+ current
A
What is the major difference between skeletal and cardiac type excitation-contraction coupling?
A Ca2+ and Na+ action potentials
B different loads of Ca2+ inside the sarcoplasmic reticulum
C a physical coupling of the voltage sensor and Ca2+ release channel in skeletal muscle, and a chemical coupling in cardiac muscle
D the volume of mitochondria in skeletal muscle is much higher than in cardiac muscle, to cope with the relatively higher energy demand
E the rate of action potential propagation between the respective cells, to allow for faster contraction in skeletal muscle compared with cardiac muscle
C
During tetani in skeletal muscle
A there is a fusion of the cytoplasmic Ca2+ transient and force responses that may be complete or incomplete
B there is a fusion of action potentials only
C there is a fusion of the cytoplasmic Ca2+ transient but not force responses
D action potentials regenerate through the T-system via the sarcolemma (surface membrane) to allow fusion of force responses
E there is a fusion of action potentials causing the fusion of force responses
A
Water from a common domestic household source provide a more appropriate medium for the continued beating of an isolated toad heart than double-distilled water from a laboratory, because
A there are more ions in the double-distilled water than the common household water
B the double-distilled water may not have been prepared from the pond where the toad was previously living
C common tap water contains ions such as Ca2+ that are necessary components of the bathing solution of the heart for its normal function
D the heart will more likely generate arrhythmias in the double distilled water than in the common household water
E double-distilled water contains more Ca2+ than common household water
C
The inactivation of the voltage-gated sodium channel in the ventricular cardiomyocyte is
A an event that causes the membrane potential to immediately return to polarised potentials
B an event that takes about 200 milliseconds to occur
C dependent on the opening of potassium channels
D a timed event, occurring very rapidly after activation of the channel
E an event that causes the membrane potential to remain depolarised for about 200 milliseconds
D
The main role of the sarcoplasmic reticulum in striated muscle is to
A generate the force response inside the cell
B hold all of the intracellular potassium ions
C provide magnesium binding sites in the cytoplasm
D to regulate the action potential frequency
E release and resequester calcium ions
E
Cardiac muscle has special structures to ensure electrical and mechanical coupling. These are the
A myobrils and sarcoplasmic reticulum
B desmosomes and gap junctions
C plasma membrane and mitochondria
D gap junctions and Na+ channels
E Na+ channels and desmosomes
B
The transverse (t-) tubule system of skeletal muscle is an important structure that
A allows action potentials to be brief in skeletal muscle
B allows action potentials to propagate rapidly into all areas of the fibre
C allows the fibre to be highly elongated
D is an important source of Ca2+ ions
E allows a high frequency of action potentials to excite the muscle
B
If the voltage sensor of the skeletal muscle tubular (t-) system failed to move from its activated state to its inactivated state,
A the muscle would remain refractory to action potentials
B it would activate a damaging contracture
C the muscle would depolarise
D calcium ion release through the ryanodine receptor would be prolonged
E it would cause an arrhythmia
D
What does a voltage-gated Na+ channel require to move from its inactivated state to a reprimed state?
A Ca2+ channels to open
B repolarisation of the membrane
C another action potential to excite the cell
D the Na+ gradient across the membrane to change
E phosphorylation of the channel
B
The electrical events of the atria and ventricles are isolated from each other
A so that the ventricles do not excite the atria
B to prevent the back-flow of blood between the chambers
C so that the left and right side of the heart have the same cardiac output
D so that atrial contraction can finish before ventricular contraction begins
E so that the ventricular contraction terminates during the refractory period of the Na+ channel
D
