Comparison Of Muscle Types

Question 1

Fiber dimensions

Answer 1

Sk = 100um X up to 30cm 
C= 10-20um x 50-100um 
Sm = 5-10um x 30-200 um

Question 2

Nuclei

Answer 2

Sk = multiple, near sarcolemma
C = generally single, centrally located 
Sm = single, centrally located

Question 3

Filament organisation

Answer 3

Sk = in sarcomeres along myofibrils 
C = in sarcomeres along myofibrils 
Sm = scattered through sarcoplasm

Question 4

Sarcoplasmic reticulum

Answer 4

Sk = terminal cisternae in trains at zones of overlap 
C = sr tubules at Z lines 
Sm = disordered throughout sarcoplasm, no T tubules

Question 5

Control mechanism

Answer 5

Sk = neural, at single neuromuscular junction 
C = automaticity (pacemaker cells) 
Sm = automaticity (pace setter cells), neural or hormonal

Question 6

Ca2+ source

Answer 6

Sk = released from SR 
C = extracellular fluid and released from SR 
Sm = extracellular fluid and release from SR

Question 7

Contraction

Answer 7

Sk = rapid onset, may be tetanized, rapid fatigue 
C = slower onset, cannot be tetanized, resistant to fatigue 
Sm = slow onset, maybe tetanized, resistant to fatigue

Question 8

Energy source

Answer 8

Sk = aerobic metabolism at moderate levels of activity: glycolysis 
C = aerobic metabolism, usually lipid or carbohydrate substrates 
Sm = primarily aerobic metabolism (anaerobic during peak activity)