Muscle Diseases Flashcards
What changes occur in muscle atrophy?
Loss of protein
Muscle fibre diameter decreases
Reduced power
What can cause disuse atrophy?
Limb immobilisation
Bed rest
Sedentary behaviour
What other factors can cause muscle atrophy?
Age
Denervation
What is myasthenia gravis caused by?
Autoimmune destruction of the end plate acetylcholine receptors
There is a loss of junctional folds in the end plate and a widening of the synaptic cleft.
What are some symptoms of myasthenia gravis?
Fatiguability
Sudden falling
Drooping eyelids
Double vision
How is myasthenia gravis treated?
Given acetylcholinesterase inhibitors to keep up the concentration of acetyl choline
However the condition is progressive
What is botulism caused by
Acetyl choline release is blocked by toxins
What happens in organophosphate poisoning?
Acetylcholinesterase is irreversible inhibited.
What are muscular dystrophies caused by?
A genetic fault causes there to be an absence or reduced synthesis of proteins which anchor the actin filaments to the sarcolemma. The muscle fibres tear themselves apart on contraction.
What happens in Duchenne muscular dystrophy?
Complete absence of dystrophin causing:
- muscle fibres tear themselves apart
- creatine phosphokinase is released into the serum
- calcium enters the cell causing cell death (necrosis)
- pseudohypertrophy (swelling) before fat and connective tissue replace muscle fibres
What are signs and symptoms of Duchenne muscular dystrophy?
Early onset
Gower’s sign
An imbalance between agonist and antagonist muscles (contractures)
How is Duchenne treated?
Steroid therapy
Currently genetic research
How is malignant hyperthermia inherited?
Autosomal dominant
What happens in malignant hyperthermia
When given anaesthesia and succinylcholine. This inhibits Ach, by acting non-competitively with nicotinic receptors. It is degraded by butyrylcholinesterase much more slowly than Ach by acetylcholinesterase.
What are signs/symptoms of malignant hyperthermia
Drugs can induce a drastic increase in oxidative metabolism, overwhelming the body’s ability to take in oxygen and remove carbon dioxide. This can lead to circulatory collapse and death.
