Choose the correct option for each part and please explain the physiological rea
ID: 3518918 • Letter: C
Question
Choose the correct option for each part and please explain the physiological reasoning behind it:
Part 1: During the steady-state of force development, the cross bridge action is asynchronous; i.e. all of the cross bridges are not generating tension simultaneously. This is important because it __
a. makes room on the thin filament so crossbridges can share binding sites
b. reduces the average force exerted on the thin filament
c. allows C-protein attachment between the thick and thin filaments
d. sustains force levels while allowing crossbridges to cycle on and off the thin filament
Part 2: Actin polymerization, i.e. G-actin polymerizing to F-actin requires magnesium ions and what other ligand besides actin itself?
a. Myosin
b. Phosphate
c. Calcium ions
d. ATP
e. Tropomyosin
Part 3: Strain sensing by the thick-filament in the heart is hypothesized to be a molecular mechanism underlying:
a. The Frank/Starling mechanism
b. Systole
c. Diastole
d. Inotropy
e. Changes in heart rate
Explanation / Answer
Answer 1. During the steady state of force development, the cross bridge action is asynchronous I.e. all of the cross bridges are not generating tension simultaneously. This is important because it- answer will be option d that is sustains force levels while allowing cross bridge to cycle on and off the thin filament. The question itself explain it. Cross bridge is formed between actin and myosin and is important for tensile strength of the muscle contraction.
Answer 2. Actin polymerisation I.e. G-actin polymerizing to F protein require magnesium ion. The other ligand besides the actin is ATP. So the answer will be option d that is ATP. ATP form ATP- G- actin monomer. Which is important in the polymerisation of actin. ATP G actin monomer is hydrolyses to the ADP G actin monomer. ADP G actin monomer is present in equilibrium with the actin molecules for the polymerisation of actin.
Answer 3. Strain sensing by the thick filament in the heart is hypothesised to be a molecular mechanism underlying :- answer will be option a that is the frank/ starling mechanism. The frank starling law states that the strength of heart systolic contraction is directly proportional to the dilatation of the ventricular muscles.