Muscle (guest lecture)

Question 1

Smooth Muscle

Cardiac Muscle

Skeletal Muscle

Answer 1

Smooth: involuntary movements. Spindle shaped, central nucleus, no striations.

Cardiac: rapid, forceful movements. linear branched, single central nucleus, intercalated discs.

Skeletal muscle: elongated, striated, peripheral nuclei.

Question 2

Epimysium

Perimysium

Endomysium

Answer 2

Epimysium: covers entire skeletal muscle
Perimysium: surrounds fascicles of muscle fibers
Endomysium: Surrounds single muscle fibers

Question 3

T Tubules

Answer 3

T Tubules: invaginations of plasma membranes. Transmit action potential from outside of cell.

Question 4

Muscle contraction mechanisms

Answer 4

action potential release ach, bind to receptor, initiate muscle impulse in sarcolemma

Impulse goes from sarcolemma along t tubules, calcium ions released into sarcoplasm

Calcium ions bind to troponin, causing tropomyosin to expose active sites on actin. Myosin heads attach.

ATP binds myosin heads, broken to ADP and P.

Question 5

T tubules in cardiac muscle

Answer 5

larger and more numerous than skeletal muscle

organized as a diad (triad is skeletal)

Triad: 2 components of sarcoplasmic reticulum in both sides of t tubule

Diad: only one component on side of t tubule.

Question 6

Skeletal / Cardiac / Smooth muscle

Striations

Answer 6

Present / Present / Absent

Question 7

Skeletal / Cardiac / Smooth muscle

T Tubules

Answer 7

Center of triads at A-I junctions / In dyads at Z discs / Absent; caveolae may be functionally similar

Question 8

Skeletal / Cardiac / Smooth muscle

Control of contraction

Answer 8

Troponin C binds Ca2+, moving tropomyosin and exposing actin for myosin binding / Similar to that of skeletal muscle / Actin-myosin binding occurs with myosin phosphorylation by MLCK triggered when calmodulin binds Ca2+

Question 9

Skeletal / Cardiac / Smooth muscle

Capacity for regeneration

Answer 9

Limited, involving satellite cells mainly / Very poor / Good, involving mitotic activity of muscle cells

Question 10

Dystrophin

Answer 10

Links actin in outermost myofilaments to transmembrane proteins and eventually to fibrous endomysium surrounding the entire muscle cell.

Type of accessory protein

Question 11

Triad

Answer 11

Contact between a T-tubule and two terminal cisternae (dilated portions of sarcoplasmic reticulum)

Transmits action potential from outside of cell