Muscle Physiology: Regulatory Proteins; Tropnin and Tropomyosin

The video tutorial explains the structure and function of myofibrils, focusing on actin and its role in muscle contraction. It details the roles of troponin and tropomyosin in regulating myosin binding sites on actin. The tutorial describes the subunits of troponin (T, I, and C) and their specific functions, particularly how calcium binding to troponin C initiates a conformational change that allows myosin to bind to actin. This process leads to the power stroke, a key step in muscle contraction. The video also provides visual aids to help understand these mechanisms.

What is the primary structure that makes up the thin filaments in muscle fibers?

• Myosin

• Tropomyosin

• Actin

• Troponin

Which protein covers the myosin binding sites on actin?

• Troponin

• Tropomyosin

• Actin

• Myosin

What is the role of troponin T in muscle contraction?

• Holds tropomyosin

• Initiates power stroke

• Binds actin

• Binds calcium

Which subunit of troponin binds calcium ions?

• Troponin T

• Troponin I

• Troponin A

• Troponin C

What triggers the movement of tropomyosin away from the myosin binding sites?

• Binding of ATP

• Binding of calcium to troponin C

• Release of ADP

• Binding of actin

What is the term used to describe the rotation of the myosin head that pulls the thin filament?

• Muscle twitch

• Sliding filament

• Cross bridge

• Power stroke

During the power stroke, in which direction does the thin filament move?

• Towards the Z line

• Towards the M line

• Away from the M line

• Away from the Z line

What is the result of the power stroke in terms of muscle fiber length?

• Twisting

• No change

• Shortening

• Lengthening

Which component of the muscle contraction process is responsible for stabilizing tropomyosin on actin?

• Myosin

• Troponin T

• Troponin I

• Troponin C

What is the sequence of events that leads to muscle contraction?

• Calcium binds to troponin C, tropomyosin moves, myosin binds to actin

• Myosin binds to actin, calcium binds to troponin C, tropomyosin moves

• Tropomyosin moves, calcium binds to troponin C, myosin binds to actin

• Calcium binds to actin, tropomyosin moves, myosin binds to troponin