Muscle Tissue 2 Flashcards
What are the initiation steps leading to contraction of skeletal muscle?
Initiation: nerve impulse along motor neurone axon arrives at neuromuscular junction. Impulse prompts release of acetylcholine into synaptic cleft causing local depolarisation of sarcolemma. This causes the voltage-gated NA+ channels to open and Na+ ions enter cell.
Other events leading to contraction of skeletal muscle.
Depolarisation spread into T tubules, causing its membrane to change their conformation. Gated Ca2+ ion-release channels are activated and Ca2+ ions are rapidly released into the sarcoplasm.
Role of ionic calcium in contraction.
As Ca2+ binds to TnC of troponin, a conformational change moves tropomyosin away from actin’s binding sites. This allows myosin heads to bind actin, and contraction begins.
What is ptosis?
The drooping of an upper eyelid which can occur in one or both eyes.
Describe atrophy and hypertrophy in terms of muscle remodelling.
Destruction>replacement = atrophy. Replacement>destruction = hypertrophy.
Describe Duchene muscular dystrophy.
Inherited through X-linked recessive pattern, with a mutation of the dystrophin gene. An absence of dystrophin allows excess Ca to enter muscle cell -> Ca taken up by mitochondria -> water taken with it and mitochondria burst -> muscle cells burst and creatine kinase/myoglobin levels in the blood are extremely high.
What is creatine kinase?
An important enzyme in metabolically active tissues, it used to be measured to diagnose heart attacks. It is also released into the blood by damaged skeletal muscle and brain.
