Phys Exam 1 Quiz

The thin filaments in a sarcomere are

• F-actin

• Myosin

• Tropomyosin

• Myofibril

The thick filaments in a sarcomere are

• Tropomyosin

• F-actin

• Myosin

• Troponin

A 45 year old man presents to the ED with heart palpitations, shortness of breath, chest pain. He is on digoxin and has recently consumed two pedialytes (electrolyte drinks). His resting membrane potential is elevated. What is contributing to this elevation in membrane potential?

• Hyperkalemia (elevated serum potassium)

• Hypokalemia

• Hypernatremia (Elevated serum sodium)

• Hyponatremia

Answer explanation

Digoxin blocks the Na/K ATPase which inhibits K+ intake, leading to decreased potassium flux and thus a shift towards the sodium equilibrium potential.

Calcium binds to ______ in the troponin-tropomyosin complex?

• Troponin

• Tropomyosin

• Myosin

• Actin

Extracellular calcium is important for the contraction of which type of myocyte (muscle cell)?

• Striated myocyte

• Cardiac myocyte

• Smooth myocyte

When calcium binds to calmodulin, it activates which enzyme that enables smooth muscle contraction?

• Myosin Light Chain Kinase

• Myosin Light Chain Phosphatase

• Myosin

• Tropomyosin

How does the troponin-tropomyosin complex regulate striated muscle contraction?

• Calcium binds to tropomyosin which induces a conformational change in troponin that exposes the myosin binding site on the F-actin filament

• Calcium binds to troponin which induces a conformational change in tropomyosin that exposes the myosin binding site on the F-actin filament

• Calcium binds to calmodulin which phosphorylates troponin and exposes the myosin binding site on the F-actin filament

• The myosin light chain kinase is phosphorylates tropomyosin and exposes the myosin binding site on the F-actin filament

L-type calcium channels couple with the _________ receptor to allow for calcium release from the _______ and into the _____.

• DHP ; sarcoplasm ; sarcoplasmic reticulum

• DHP ; sarcoplasmic reticulum ; sarcoplasm

• ryanodine ; sarcoplasm ; sarcoplasmic reticulum

• ryanodine ; sarcoplasmic reticulum ; sarcoplasm

isometric contraction is best defined as:

• A contraction in which the muscle tension developed is greater than the opposing load which causes shortening of the muscle

• A contraction in which the muscle tension developed is less than the opposing load and the muscle remains the same length

Myosin contains a ATPase domain. This intrinsic ATPase allows for myosin to hydrolyze ATP. The hydrolysis of ATP bound to myosin causes _____.

• Dissociate from the myosin binding site on the F-actin filament

• The myosin head to be set into a "cocked" position.

• the powerstroke to occur