Anatomy of Skeletal and Smooth Muscles

Questions and Answers

Number of nuclei per cell

Type of protein filaments present

Presence or absence of striations (correct)

Shape of the muscle cells

~250 ms

~2 ms

~5 ms (correct)

~200-300 ms

To release Ca2+ for muscle contraction (correct)

To release ATP for muscle contraction

To break down ATP and reduce muscle contraction

To sequester Ca2+ and prevent muscle contraction

Stroke volume Signup and view all the answers

Excitation, calcium release, cross-bridge formation, power stroke Signup and view all the answers

Sarcomere Signup and view all the answers

~200-300 ms Signup and view all the answers

QRS complex Signup and view all the answers

Study Notes

Skeletal muscle: Multinucleated fibers, striated, and organized into sarcomeres and myofibrils, with components including epimysium, perimysium, endomysium, and fascicles
Smooth muscle: Single nucleus per cell, non-striated, with dense bodies instead of sarcomeres, and organized into sheets or bundles found in walls of hollow organs

Skeletal muscle action potential: Short duration (~2 ms), short refractory period (~5 ms), and all-or-nothing propagation
Cardiac muscle action potential: Long duration (~200-300 ms), long refractory period (~250 ms), and graded propagation influenced by autonomic nervous system

Sarcomere: Basic contractile unit of muscle fiber
Contraction: Actin and myosin filaments slide past each other, shortening the sarcomere
Relaxation: Calcium ions are pumped back into the sarcoplasmic reticulum, actin and myosin filaments return to resting position

Stroke Volume (SV): Amount of blood ejected by a ventricle per beat, regulated by preload, contractility, and afterload
Cardiac Output (CO): Total volume of blood pumped by the ventricle per minute, calculated by CO = SV x Heart Rate (HR)
End-Diastolic Volume (EDV): Volume of blood in the ventricle at the end of diastole, affected by venous return and filling time
End-Systolic Volume (ESV): Volume of blood remaining in the ventricle after systole, affected by contractility and afterload
Preload: Degree of stretch of cardiac muscle fibers at the end of diastole, influenced by venous return