Mastering Muscles Flashcards
What is the role of calcium in the cross bridge cycle?
Calcium binds to troponin, altering its shape
What role does tropomyosin play in the cross bridge cycle?
The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form.
How does troponin facilitate cross bridge formation?
Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin.
What, specifically, is a cross bridge?
myosin binding to actin
Which event causes cross bridge detachment?
ATP binding to the myosin head
Where in the cross bridge cycle does ATP hydrolysis occur?
during the cocking of the myosin head
How/when does the myosin head cock back to store energy for the next cycle?
After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.
BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?
Myosin heads would remain detached, unable to cock.
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.
What is the type of chemical reaction used to rebuild ADP into ATP?
dehydration synthesis
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
glycolysis
Which of the following processes produces 36 ATP?
Krebs cycle and oxidative phosphorylation
The “rest and recovery” period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
Pyruvic acid is converted back to lactic acid.
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
white fast twitch fibers
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.
How is acetylcholine (ACh) removed from the synaptic cleft?
simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisterns (cisternae) of the sarcoplasmic reticulum
Which of the following statements best describes the pathology associated with periodic paralysis?
Skeletal muscles are plagued by being flaccid for short periods.
What are the ions directly associated with all forms of periodic paralysis due to the fact that the channels for these ions are defective?
sodium and calcium
How does the permanent depolarization of the skeletal muscle result in a flaccid (non-contracted) paralysis?
The muscle cell would not be able to depolarize a second time because the voltage-gated sodium channel never inactivates.
There are several hypotheses about the causes of muscular fatigue. These include depleted muscle glycogen stores, ion imbalances (especially K+), and which other mechanism?
Elevated Pi interfering with Ca2+ release
