Muscles (General, Skeletal, Smooth) Flashcards
Generated from Lectures 13-17
Skeletal muscle fibers can be up to __________ cm long.
30
A muscle cell from a biceps contains approximately __________ sarcomeres.
100,000
The protein __________ connects F-actin to the dystroglycan complex.
Dystrophin
__________ is a protein greater than 1 µm in length found in skeletal muscle.
Titin
The thick filaments of skeletal muscle are __________ nm in diameter.
16
The __________ complex is a heterotrimer consisting of three different proteins.
Troponin
The troponin subunit TnT binds to __________.
Tropomyosin
The troponin subunit TnC has two pairs of __________ binding sites.
Ca2+
When intracellular ATP is depleted, skeletal muscles enter a state of __________.
Rigor (death!!!!)
__________ muscle is not under voluntary control.
Smooth
Skeletal muscle receives excitatory neuronal input via __________ motor neurons.
Somatic
The __________ is a specialized region of the skeletal muscle fiber membrane where a motor neuron terminates.
Motor end plate
Curare is a plant alkaloid that inhibits the __________ receptor
Nicotinic acetylcholine
__________ is an autoimmune disease in which antibodies block acetylcholine receptors at the neuromuscular junction.
Myasthenia gravis
The __________ receptor in the T-tubule triggers Ca2+ release from the sarcoplasmic reticulum.
Dihydropyridine
The dihydropyridine receptor physically interacts with the __________ receptor to release Ca2+ from the sarcoplasmic reticulum.
Ryanodine
RyR1 is the primary ryanodine receptor isoform expressed in __________ muscle.
skeletal
Diltiazem and amlodipine are examples of dihydropyridine receptor __________.
antagonists
Ryanodine is a _______ alkaloid that can act as a ryanodine receptor agonist or antagonist depending on the concentration.
plant
Caffeine activates ryanodine receptors by potentiating their sensitivity to __________.
Ca2+
Malignant hyperthermia is a rare, life-threatening condition often caused by mutations in the __________ receptor gene.
Ryanodine
.
__________ is a muscle relaxant that prevents Ca2+ release from the sarcoplasmic reticulum and is used to treat malignant hyperthermia.
Dantroline
Tacrolimus is an __________ drug that binds to FKBP12, a protein that regulates ryanodine receptor activity.
immunosuppressant
SERCA stands for sarco/endoplasmic reticulum Ca2+ -__________.
ATPase
__________ is a regulatory protein that inhibits SERCA activity.
Phospholamban
Increased β-adrenergic stimulation __________ the association between SERCA and phospholamban.
reduces
The protein __________ connects actin filaments to the Z-line
α-actinin
In an __________ contraction, muscle length remains constant while force increases
isometric
In an __________ contraction, muscle shortens while force remains constant.
isotonic
__________ contraction is analogous to isovolumetric contraction in the heart.
Isometric
__________ contraction is analogous to ventricular ejection in the heart.
Isotonic
A muscle __________ is a single contraction-relaxation cycle in response to a single action potential.
twitch
The __________ of shortening is the speed at which a muscle changes length during contraction
velocity
The maximum velocity of shortening occurs at the __________ load.
smallest
The maximum force a muscle can generate occurs at the __________ load.
greatest
__________ occurs when a muscle fiber is stimulated at a high frequency and does not relax completely between stimuli.
Tetanus
__________ muscles oppose the action of agonist muscles
Antagonist
Bones act as __________ in the lever systems of the body
levers
Joints act as __________ in the lever systems of the body.
fulcrums
A __________ lever system amplifies velocity.
third-class
The force developed by a single muscle cell increases with increasing __________ of stimulation.
frequency
The force developed by a whole muscle can be increased by recruiting more __________.
motor units
__________ muscle fibers have the fastest contractile speeds.
Fast/Type II
__________ muscle fibers utilize oxidative phosphorylation to produce ATP.
Slow/Type I
__________ muscle fibers have the largest diameter
Type IIb
The __________ isoform determines a muscle fiber’s type.
Myosin heavy chain (MHC)
Skeletal muscle can produce ATP through three main pathways: direct phosphorylation, __________ glycolysis, and __________ cellular respiration.
anaerobic, aerobic
__________ is a molecule stored in muscle that can rapidly regenerate ATP from ADP.
Creatine phosphate
Creatine supplementation can modestly improve performance in __________ , __________ exercise lasting less than 30 seconds.
intensive, repetitive
Caffeine can __________ the ergogenic benefit of creatine.
counteract
__________ is the primary energy source for muscle contraction.
ATP
During short-duration exercise, ATP stored in muscles is used __________.
first
After about 10 seconds of exercise, ATP is formed from __________ and ADP.
creatine phosphate
Anaerobic glycolysis becomes the primary source of ATP production after about __________ seconds of exercise.
30-40
The anaerobic threshold is the point at which muscle metabolism shifts from __________ to __________ pathways for ATP production.
aerobic, anaerobic
During prolonged-duration exercise, ATP is generated by the breakdown of nutrient energy fuels through the __________ pathway.
aerobic
__________ is a byproduct of anaerobic glycolysis.
Lactic acid
Lactic acid can be used as fuel by the liver, __________, and __________.
kidneys, heart
The liver can convert lactic acid back into __________ or glucose.
pyruvic acid
Amateur runners often experience “hitting the wall” around kilometer 30-35 due to the depletion of __________ stores.
glycogen
__________ is the largest glycogen storage organ in the body.
Muscle
A single bout of exercise can improve whole-body __________ sensitivity for up to 48 hours.
insulin
The aerobic pathway for ATP production utilizes __________, pyruvic acid, free fatty acids, and amino acids as fuel sources.
glucose
Aerobic respiration produces approximately __________ ATP molecules per glucose molecule.
32
Approximately __________% of the energy released during muscle activity is given off as heat.
60
__________ is the body’s response to cold temperatures, involving rapid muscle contractions to generate heat.
Shivering
Malignant hyperthermia occurs due to mutations in the __________ receptor, leading to uncontrolled muscle contraction and heat production.
Ryanodine
Muscle __________ is the physiological inability to contract despite continued stimulation.
fatigue
Muscle fatigue is not primarily caused by the __________ of ATP.
depletion
Factors contributing to muscle fatigue include lactic acid buildup, __________ command fatigue, and failure of excitation-contraction coupling.
central
During recovery from exercise, __________ reserves are replenished, lactic acid is converted to pyruvic acid, glycogen stores are replaced, and ATP and creatine phosphate reserves are replenished.
oxygen
Excess __________ consumption is required after exercise to return the muscle to its resting state.
oxygen
Muscle __________ are sudden, involuntary contractions that can be painful.
cramps
Factors that can contribute to muscle cramps include dehydration, low blood levels of calcium, magnesium, or __________, and certain medications.
potassium
__________ exercise involves muscle shortening while contracting.
Concentric
__________ exercise is the most efficient way to induce muscle hypertrophy.
Isometric
__________ exercise occurs when a muscle attempts to contract while being passively stretched
Eccentric
Delayed onset muscle soreness (DOMS) and muscular injury typically result from __________ exercise.
Eccentric
During prolonged exertion, muscles produce H+ and __________, leading to acidification.
lactate
The sensation of muscle fatigue is actually a function of the __________.
brain
Muscle pain during exercise is primarily due to __________ accumulation.
harmful metabolite (H+, lactate, ATP(?))
__________ is a plant compound that activates TRPV1 receptors, which are involved in sensing lactate and muscle pain.
Capsaicin
The first phase of DOMS is thought to be caused by __________ of the muscle.
microtrauma
The second phase of DOMS involves __________ and __________ infiltration to remove damaged muscle tissue.
macrophages, neutrophils
__________ produced by macrophages contribute to the soreness experienced during DOMS.
Prostaglandin E2
DOMS typically disappears after a few __________ .
days
Muscle hypertrophy is the __________ in the size of muscle fibers.
increase
Muscle __________ is the decrease in the size of muscle fibers.
atrophy
__________ atrophy occurs when a muscle is not used, such as when immobilized in a cast.
Disuse
__________ atrophy occurs due to nerve damage, leading to loss of muscle function.
Denervation
Smooth muscle contraction is __________ (faster/slower) than skeletal muscle contraction.
slower
Smooth muscle cells lack __________ , which is present in skeletal muscle and regulates contraction.
troponin
In smooth muscle, Ca2+ activates __________ that eventually phosphorylate myosin heads, leading to cross-bridge formation.
kinases
__________ smooth muscle exhibits continuous, low-level contraction.
Tonic
__________ smooth muscle is only active for discrete periods of time.
Rhythmic/phasic
__________ smooth muscle cells act independently, while __________ smooth muscle cells function as a single unit.
Multi-unit, single-unit
Dense bodies in smooth muscle contain __________ that anchor intermediate filaments.
α-actinin
__________ is the major inhibitory neurotransmitter causing relaxation of smooth muscle in the gastrointestinal tract.
Nitric oxide
What is the name of the calcium-binding protein that, when bound to calcium, can bind to and activate myosin light chain kinase in smooth muscle?
Calmodulin
Why is calmodulin important in smooth muscle?
This complex is important because once myosin light chain kinase is activated, it can phosphorylate myosin light chains, allowing myosin to interact with actin and initiate contraction
What enzyme is responsible for dephosphorylating myosin light chains in smooth muscle, leading to relaxation?
Myosin light chain phosphatase
Name the most potent constrictor and the most common vasodilator involved in the local humoral control of smooth muscles.
The most potent constrictor is endothelin, and the most common vasodilator is adenosine
After the motor neuron action potential in skeletal muscle contraction, ______ enters voltage-gated channels and acetylcholine is released into the synapse.
Ca2+
VX nerve gas is a/an ________ inhibitor.
acetylcholinesterase
