Muscles - A2 Flashcards

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1
Q

Describe the structure of a skeletal muscle.

A

Compound of many muscle fibres bound together by connective tissue. Each muscle fibre is surrounded by a thin membrane called sarcolemma, containing nuclei. Cell contains many microfibrils, surrounded by sarcoplasmic reticulum. Microfibrils made up of myofilaments (actin). These are arranged into contractile units called sarcomeres.

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2
Q

Describe the sliding filament theory of muscle action.

A
  • calcium ions are released from sarcoplasmic reticulum
  • calcium ions bind to troponin and cause tropomyosin to move, exposing the myosin head binding sites on the actin filament
  • myosin heads bind to actin binding sites forming cross bridges
  • each myosin head contains a molecule of ATP which hydrolyses into ADP + Pi by ATPase. This energy released causes nod action of myosin head, pulling the actin filament a short distance.
  • a new ATP attaches to myosin head, breaking cross bridge and separating it from actin
  • The process repeats moving the actin along a bit more each time
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3
Q

Describe and explain the role of ATP and phosphocreatine in providing energy during contraction.

A
  • phosphocreatine is store in muscle fibres for when ATP in muscle fibres runs out (4 seconds roughly)
  • it generates ATP from ADP rapidly in aerobic conditions
  • provides energy for muscle contraction
  • phosphate is given to ADP hence phosphocreatine becomes creatine
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4
Q

Describe and explain slow twitch muscle fibres.

A
  • have lots of mitochondria
  • respire aerobically to regenerate ATP
  • high concentration of myoglobin for a very high affinity to oxygen which is stationary and stays in muscle
  • closely associated with large number of capillaries to provide good oxygen supply
  • less extensive sarcoplasmic reticulum as less calcium ions required at one time
  • less glycogen as glucose broke fully down via aerobic respiration
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5
Q

Describe and explain fast twitch muscle fibres.

A
  • produce rapid, strong contractions but only sustained over short period of time
  • thicker myosin, stronger heads
  • have store of oxygen and glucose (x19 more ATP)
  • anaerobic respiration - not much oxygen supply
  • use phosphocreatine to regenerate ATP
  • have fewer mitochondria
  • lower concentration of myoglobin
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