Muscle

Question 1

List features of the ultrastructure of skeletal muscle cells

Answer 1

Multinucleated
striated due to sarcomeres - functional unit
many cells fused together
myofibre bundles
made of myofibrils which have dark and light bands
Actin - thin, nebullin, capZ, tropomodulin, tropomyosin and troponin

Question 2

List functional characteristics of skeletal muscle cells

Answer 2

connect to bones 
antagonistic pairs 
flexor/extensor 
movement 
voluntary

Question 3

Explain excitation-contraction coupling in skeletal muscle

Answer 3

AP myofibril membrane and T tubules
Dihydropyridine (DHP) receptors conformational change
contact with RyR (ryanodine receptors) on sarcoplasmic reticulum - calcium influx from sarcoplasm
muscle contraction

Question 4

Explain the mechanism in contraction of skeletal muscle

Answer 4

sarcomere
Ca ions bind to troponin - discharge of ADP
move tropomyosin from actin, myosin head bind
ADP bound, power stroke
Actin pulled to centre of sarcomere
ATP hydrolysis - myosin return to charged state, can rebind

Question 5

Explain the structure, function and physiology of cardiac muscin, including EC coupling

Answer 5

Uninuclear - cells joined with tight junction - INTERCALATED DISKS - MANY GAP JUNCTIONS
in heart
heart contraction constanty
AP - VGCC open - Ca influx - CICR - contraction

Question 6

Explain EC coupling in smooth muscle

Answer 6

depolarisation - VGCC 
Ca influx
bind to calmodulin 
Ca-CAM complex
activate myosin light chain kinase (MLCK) 
contraction

Question 7

describe the structure and physiology of smooth muscle

Answer 7

round 
not striated 
uninuclear, spindle shaped 
no control - involuntary 
irregular arrangement of actin and myosin