6 Physiology of Muscle Flashcards
What is myotonia?
A failure to relax at the end of a voluntary contraction
Problems with either the Na or Cl channels making the cell hyperexcitable
What is malignant hyperthermia?
A rare but possibly fatal disease
Anaesthesia triggered simultaneous release of calcium from the SR in ALL muscle cells
- increase in temperature
- death by respiratory failure
Dantrolene blocks the SR calciu release
What is a sarcomere and what 2 filament types is it comprised of?
A single contraction unit falling between 2 Z lines
Thick filaments - myosin
Thin filaments - actin troponin and tropomyosin
Describe the cross bridge cycle
Causes shortening of sarcomere length
Myosin heads = oars, actin filaments = water
- myosin head attaches to trponin on actin filament
- Troponin displaces tropomyosin
- Mysoin head can now bind to that revelaed site
- Myosin strokes and consumes 1 ATP
- Detachment
Describe the 4 sources of ATP
What can go wrong?
McArdles disease - describe
Lacks myophosphorylase - an enzyme which is needed to break down glycogen
Normal strength, but rapid, painful fatigue beyond gentle exercise
What can go wrong?
Mitochondrial myopathies - describe
Very poor exercise tolerance
Can get very severe metabolic acidosis (caused by anerobic glycolysis resulting in lactic acid production)
Histologically - damaged mitochondria
What can go wrong?
Ischaemia - describe
Skeletal muscle, unlike cardiac is quite resistant
This is because it is unactive at rest and has a reasonable supply of anaerobic pathways
Really long ischaemia will not replace the ATP used in contraction - you also need ATP to detach the myosin head:
no blood
no more ATP
Rigor mortis
