Skeletal Muscle Flashcards
(50 cards)
What is the largest tissue in the body that is responsive to insulin?
Skeletal muscle
When seen in the blood, what enzyme is indicative of some form of damage to the structural integrity of a muscle?
Creatine kinase
What sign of lower extremity weakness is seen as children push themselves up?
Gower sign
How does a mutation in the dystrophin gene contribute to increased creatine kinase blood levels?
Dystrophin complexes links actin of the muscle fibril to the extracellular matrix to provide strength and support to the cell membrane, and when thisis mutated the cell membrane will lose integrity and creatine kinase will leak out
In which condition does an individual developm antibodies to cholinergic receptors?
Myasthenia Gravis
To which cholinergic receptor will ACh bind on the motor plate?
Nictonic (N1) receptor
Binding of acetylcholine to its receptor on the motor plate triggers what immediate event?
The opening of ligand-gated Na+ channel
The influx of what ion into the axon terminal is required for synaptic release of acetylcholine?
Ca2+
What structure of the skeletal muscle cell is especially helpful in propagating an action potential?
T-tubules
The influx of what ion into the muscle cell is responsible for depolarization? What channels are subsequently opening by the wave of depolarization?
Sodium; Opens votalge-gated Na and K channels
Where are dihydropyridine (DHP) receptors located within the cell? What type of channel are they?
The sarcolemma; L-type voltage-gated Ca channel
What is the biochemical function of dihydropyridine receptors?
Activation of ryanodine (RyR2) receptors
Where are ryanodine (RyR2) receptors located within the cell? What type of receptor is it?
The sarcoplasmic reticulum; Calcium channels?
What is the chemical result of the opening of ryanodine receptors?
A 100-fold increase in cytosolic [Ca++]
What causes the depolarization to end?
Degradation of ACh by acetylcholinesterase
What is the advantage of having action potentials that are as narrow as those in muscle depolarization?
It allows the membrane to be stimulated again and elicit another action potential that wil lincrease the strength of contraction
What displaces tropomyosin I from the myosin-binding site on actin filaments?
Cytosolic calcium binds to troponin C, which undergoes a conformational change and causes a drop in tropinin I concentration attached to actin and displaces tropomyosin
The binding of ATP to the myosin head causes what conformational change?
The release of myosin from actin
What causes the rapid formation of the cross bridge and the subseqeunt power stroke?
The release of Pi from the myosin head
When is ADP released from the mysoin head? What is the subsequent action?
It is released at the end of the power stroke and then the myosin goes back to a rigor state
What biochemical event results in muscle relaxation?
Decrease in cytosolic calcium
What is the mechaism of cytosolic calcium decrease?
Sodium/ calcium exchanger on the plasma membrane, and reuptake into the sarcoplasmic reticulum
True or false: Energy is required for muscle relaxation?
True
What chaperone proteins bind Ca2+ in the sarcoplasmic reticulum?
Calsequestrin and calreticulin
