VPHY 3100 Exam 2 Practice Questions
with correct answers 100% passed
Skeletal muscles are different from neurons in that only skeletal muscle cells:
experience depolarizations
fire actions potentials
contract
have leaky K+ channels
have a resting membrane potential around -70 mV - correct answer ✔✔contract
Lower (alpha) motor neurons always cause skeletal muscle cells to contract
because:
the motor nerve terminal releases glutamate into the NMJ
the motor nerve terminal releases GABA into the NMJ
muscarinic receptors are expressed on the motor end plate
nicotinic receptors are expressed on the motor end plate - correct answer
✔✔nicotinic receptors are expressed on the motor end plate
The sarcolemma is:
the cytosol of a skeletal muscle cell
part of the sarcoplasmic reticulum
the skeletal muscle cell's plasma membrane
,the smallest contractile unit of a skeletal muscle cell - correct answer ✔✔the
skeletal muscle cell's plasma membrane
The two proteins that are (1) physically coupled together at triads and (2)
essential for proper excitation/contraction (E/C) coupling are:
DHPRs (dihydropyridine receptors) and RyRs (ryanodine receptors)
nicotinic receptors and voltage-gated sodium channels
troponin and tropomyosin
actin and myosin - correct answer ✔✔DHPRs (dihydropyridine receptors) and
RyRs (ryanodine receptors)
True/False: skeletal muscles relax when calcium ions are moved out of the
sarcoplasm by Ca pumps. - correct answer ✔✔True
During sarcomere contraction:
Thin filaments shorten
Z-discs move further apart
A-bands narrow
I-bands narrow - correct answer ✔✔I-bands narrow
True/False: Rigor mortis (muscle stiffening after death) occurs when cellular ATP is
depleted and myosin head groups cannot detach from thin filaments. - correct
answer ✔✔True
, Myasthenia gravis (MG) is an autoimmune disease that causes muscle weakness,
especially of the facial muscles. Patients generate antibodies against their own
nicotinic receptors of the NMJ, and these antibodies act as antagonists of the
receptor. Which of the following might be a potential treatment for MG?
neostigmine, an inhibitor of acetylcholinesterase
muscarine, an agonist of muscarinic receptors
Botox, a toxin that inhibits the release of acetylcholine from motor nerve
terminals
atropine, an antagonist of muscarinic receptors - correct answer ✔✔neostigmine,
an inhibitor of acetylcholinesterase
Which of the following events occurs immediately downstream of Ca2+ binding to
troponin?
Ca2+ ions are released from the SR (sarcoplasmic reticulum)
Myosin & actin engage in active cross-bridge cycling
Dihydropyridine receptors (DHPRs) sense an action potential in the T-tubules
Sarcomeres shorten
Tropomyosin shifts its position relative to thin filaments - correct answer
✔✔Tropomyosin shifts its position relative to thin filaments
True/False: The knee-jerk reflex causes an increased action potential firing rate of
the alpha-motor neurons innervating the quadriceps. - correct answer ✔✔True
Which of the following is TRUE about testosterone (T)?
T is synthesized from the CYP19A1 gene
T is stored until LH/FSH stimulates its release from the gonads
with correct answers 100% passed
Skeletal muscles are different from neurons in that only skeletal muscle cells:
experience depolarizations
fire actions potentials
contract
have leaky K+ channels
have a resting membrane potential around -70 mV - correct answer ✔✔contract
Lower (alpha) motor neurons always cause skeletal muscle cells to contract
because:
the motor nerve terminal releases glutamate into the NMJ
the motor nerve terminal releases GABA into the NMJ
muscarinic receptors are expressed on the motor end plate
nicotinic receptors are expressed on the motor end plate - correct answer
✔✔nicotinic receptors are expressed on the motor end plate
The sarcolemma is:
the cytosol of a skeletal muscle cell
part of the sarcoplasmic reticulum
the skeletal muscle cell's plasma membrane
,the smallest contractile unit of a skeletal muscle cell - correct answer ✔✔the
skeletal muscle cell's plasma membrane
The two proteins that are (1) physically coupled together at triads and (2)
essential for proper excitation/contraction (E/C) coupling are:
DHPRs (dihydropyridine receptors) and RyRs (ryanodine receptors)
nicotinic receptors and voltage-gated sodium channels
troponin and tropomyosin
actin and myosin - correct answer ✔✔DHPRs (dihydropyridine receptors) and
RyRs (ryanodine receptors)
True/False: skeletal muscles relax when calcium ions are moved out of the
sarcoplasm by Ca pumps. - correct answer ✔✔True
During sarcomere contraction:
Thin filaments shorten
Z-discs move further apart
A-bands narrow
I-bands narrow - correct answer ✔✔I-bands narrow
True/False: Rigor mortis (muscle stiffening after death) occurs when cellular ATP is
depleted and myosin head groups cannot detach from thin filaments. - correct
answer ✔✔True
, Myasthenia gravis (MG) is an autoimmune disease that causes muscle weakness,
especially of the facial muscles. Patients generate antibodies against their own
nicotinic receptors of the NMJ, and these antibodies act as antagonists of the
receptor. Which of the following might be a potential treatment for MG?
neostigmine, an inhibitor of acetylcholinesterase
muscarine, an agonist of muscarinic receptors
Botox, a toxin that inhibits the release of acetylcholine from motor nerve
terminals
atropine, an antagonist of muscarinic receptors - correct answer ✔✔neostigmine,
an inhibitor of acetylcholinesterase
Which of the following events occurs immediately downstream of Ca2+ binding to
troponin?
Ca2+ ions are released from the SR (sarcoplasmic reticulum)
Myosin & actin engage in active cross-bridge cycling
Dihydropyridine receptors (DHPRs) sense an action potential in the T-tubules
Sarcomeres shorten
Tropomyosin shifts its position relative to thin filaments - correct answer
✔✔Tropomyosin shifts its position relative to thin filaments
True/False: The knee-jerk reflex causes an increased action potential firing rate of
the alpha-motor neurons innervating the quadriceps. - correct answer ✔✔True
Which of the following is TRUE about testosterone (T)?
T is synthesized from the CYP19A1 gene
T is stored until LH/FSH stimulates its release from the gonads
