Physiology And Pathophysiology Of Skeletal Muscle Contraction Flashcards
What is contraction?
Interaction of actin and myosin
What is contraction fuelled and driven by?
Fuelled by ATP and driven by a rise in [Ca2+]
Where do t tubules come out of?
An invagination in the sarcolemma
What are four diseases that happen when contraction goes wrong?
Multiple sclerosis, myeasthesia gravis, non-dystrophic myotonia and muscular dystrophy
What is the myelin sheath formed of?
Schwann cells wrapping around the axon many times
What is the node of ranvier?
A section of unmyelinated axon membrane between two Schwann cells
What causes multiple sclerosis?
Immune attack of myelin
What does multiple sclerosis cause?
Leaky blood brain barrier -> sclerotic lesions
What are the symptoms of multiple sclerosis?
Numbness, tingling, speech problems, visual problems and debilitating muscle weakness
Are multiple sclerosis symptoms constant?
They can be or they can be remitting
What is myaesthesia gravis?
Autoimmune condition causing the Progressive loss of nicotinic acetylcholine receptor
What are the different types of myaesthesia gravis?
Destruction of the morphology of the membrane, modulation of the receptors and antibodies binding to the receptor binding site
What does myaesthesia gravis target?
Alpha 1 subunit
What are non-dystrophic myotonias?
Delayed relaxation of the muscle after voluntary contraction or mechanical stimulation
How are non-dystrophic myotonias electrophysiologically characterised?
Highly organised repetitive electrical activity of the muscle fibres
What are the 5 different skeletal muscle disorders caused by mutation to the SCN4A gene?
Potassium-aggravated myotonia, paramytonia congenita, hyperkalaemia periodic paralysis, hypokalaemia periodic paralysis and congenital myasthenic syndrome
What do mutations cause in most non-dystrophic myotonia cases?
Decreased rate of channel inactivation or increased rate of recovery from inactivation or slower channel deactivation
Which is the largest gene identified in humans?
The dystrophin gene
Where is the dystrophin gene located?
On the short arm of the X chromosome
What does dystrophin allow?
The cell membrane to be stabilised during muscle contraction
What is duchennes?
Total loss of dystrophin?
What is Becker?
Reduced or dysfunctional dystrophin
Why does dystrophic myopathy more often affect boys?
X linked disease
What does dystrophic myopathy lead to?
Fibrosis and damage of skeletal muscle
