Physiology And Pathophysiology Of Skeletal Muscle Contraction

Question 1

What is contraction?

Answer 1

Interaction of actin and myosin

Question 2

What is contraction fuelled and driven by?

Answer 2

Fuelled by ATP and driven by a rise in [Ca2+]

Question 3

Where do t tubules come out of?

Answer 3

An invagination in the sarcolemma

Question 4

What are four diseases that happen when contraction goes wrong?

Answer 4

Multiple sclerosis, myeasthesia gravis, non-dystrophic myotonia and muscular dystrophy

Question 5

What is the myelin sheath formed of?

Answer 5

Schwann cells wrapping around the axon many times

Question 6

What is the node of ranvier?

Answer 6

A section of unmyelinated axon membrane between two Schwann cells

Question 7

What causes multiple sclerosis?

Answer 7

Immune attack of myelin

Question 8

What does multiple sclerosis cause?

Answer 8

Leaky blood brain barrier -> sclerotic lesions

Question 9

What are the symptoms of multiple sclerosis?

Answer 9

Numbness, tingling, speech problems, visual problems and debilitating muscle weakness

Question 10

Are multiple sclerosis symptoms constant?

Answer 10

They can be or they can be remitting

Question 11

What is myaesthesia gravis?

Answer 11

Autoimmune condition causing the Progressive loss of nicotinic acetylcholine receptor

Question 12

What are the different types of myaesthesia gravis?

Answer 12

Destruction of the morphology of the membrane, modulation of the receptors and antibodies binding to the receptor binding site

Question 13

What does myaesthesia gravis target?

Answer 13

Alpha 1 subunit

Question 14

What are non-dystrophic myotonias?

Answer 14

Delayed relaxation of the muscle after voluntary contraction or mechanical stimulation

Question 15

How are non-dystrophic myotonias electrophysiologically characterised?

Answer 15

Highly organised repetitive electrical activity of the muscle fibres

Question 16

What are the 5 different skeletal muscle disorders caused by mutation to the SCN4A gene?

Answer 16

Potassium-aggravated myotonia, paramytonia congenita, hyperkalaemia periodic paralysis, hypokalaemia periodic paralysis and congenital myasthenic syndrome

Question 17

What do mutations cause in most non-dystrophic myotonia cases?

Answer 17

Decreased rate of channel inactivation or increased rate of recovery from inactivation or slower channel deactivation

Question 18

Which is the largest gene identified in humans?

Answer 18

The dystrophin gene

Question 19

Where is the dystrophin gene located?

Answer 19

On the short arm of the X chromosome

Question 20

What does dystrophin allow?

Answer 20

The cell membrane to be stabilised during muscle contraction

Question 21

What is duchennes?

Answer 21

Total loss of dystrophin?

Question 22

What is Becker?

Answer 22

Reduced or dysfunctional dystrophin

Question 23

Why does dystrophic myopathy more often affect boys?

Answer 23

X linked disease

Question 24

What does dystrophic myopathy lead to?

Answer 24

Fibrosis and damage of skeletal muscle

Question 25

What do dystrophic myopathies cause?

Answer 25

Increased permeability to macromolecules causing: muscle fibre necrosis, fibrosis and fat infiltration