Explain how acetylcholine (ACh) initiates skeletal muscle contraction.

Analyse how capillary and mitochondrial densities affect slow twitch (type I) muscle fibres.

Explain the role of insulin and muscle contraction on glucose uptake during exercise.

changes the electrical/neural impulse into a chemical stimulus at the motor end plate
OR
ACh is released when an action potential arrives at the motor end plate ✔

ACh binds to post synaptic receptors✔

increases membrane permeability to sodium ions/Na⁺ ✔

which causes Ca⁺⁺ to be released <into the muscle cell> ✔

ACh is broken down < by cholinesterase> to prevent continual muscle stimulation✔

Type I has a high density of capillaries and mitochondria✔

high capillary density allows for increased oxygenation ✔

high mitochondrial density allows for increased use of oxygen
OR
high mitochondrial density allows for use of aerobic respiration «producing high amounts of ATP» ✔

both contribute to activities that require prolonged energy supply 
OR
increases fatigue resistance ✔

insulin production is a response to high blood sugar/glucose levels ✔

insulin stimulates glucose uptake from the blood into skeletal muscle
OR
insulin improves cell membrane permeability to glucose ✔

muscle contraction stimulates glucose uptake from the blood into skeletal muscle
OR
exercise improves cell membrane permeability to glucose ✔

increased sensitivity leads to decreased insulin/glycogen production ✔

Award [2 max] for either insulin or muscle contraction

Getting full marks for (a) was not always easy for candidates.

Was generally well done with the vast majority of students knowing that capillary and mitochondrial density was high in type I muscle and the implications of this in terms of function.

Candidates generally showed good understanding of insulin and its effect on glucose uptake but struggled with the muscle contraction component.