Question Booklet Corrections Flashcards
Describe the role of calcium ions in bringing about the contraction of a myofibril
Calcium ions activate ATPase
And they bind to Troponin, causing tropomyosin to move, exposing myosin binding site
Suggest two functions of the energy released by the mitochondria in the synaptic knob
Synthesis of Acetylcholine
Movement of vesicles
Why are details visible under the electron microscope but not under the optical microscope
Electron microscope has greater resolution
Explain how the action potential arriving at the neuromuscular junctions results in acetylcholine secreted into the synaptic cleft
Depolarisation of presynaptic membrane
Calcium channels open
Influx of calcium
Describe the events which occur in a myofibril which enable it to contract
Myosin heads bind to actin
Creating cross bridges which swivel
Causing actin to move
Energy provided by hydrolysis of ATP
Describe the role of ATP in bringing about the contraction of a myofibril
Hydrolysis of ATP provides energy
The energy is needed to break cross bridges between actin & myosin
What is an advantage of humans maintaining a constant core temperature when exposed to cold external temperatures
Maintain efficient level of enzyme reactions
What is a disadvantage of humans maintaining a constant core temperature when exposed to cold external temperatures
Requires more energy
Explain the part played by negative feedback on the control of core temperature
Core temperature results in reduced sweating
This then results in body temperature returning to normal
This then results in original level of sweating
Explain how the body of a mammal may respond to a rise in the environmental temperature
Heat receptors in skin send nervous impulse to hypothalamus
Arterioles dilate, more blood to surface, heat lost by radiation
Muscles relax, hair flatten on skin surface so less insulation
Sweating increased, evaporation removes heat
Describe the hormonal co-ordination system in mammals
Slow Broadcast Long term Chemical Delivery via blood vessels
How is the nervous system in mammals different to the hormonal co-ordination system
Nervous is: Rapid Direct Short lived Mainly electrical Delivery via nerves
Explain how athletes produce heat when they run
Respiration from muscular activity
Released waste heat
Why do tall thin runners find it easier to keep cool than short tubby runners with the same body mass?
Large surface area to volume ratio
So more heat lost from body surface
Describe how the body responds to a rise in core temperature
Temperature receptors stimulated
Heat loss centre stimulated
Nerve impulses to sweat glands
Increase rate in sweat production
