When John begins to run, his muscles utilize oxygen and produce carbon dioxide. His body has receptors monitoring these conditions. When the levels stimulate a receptor, the heart rate and respiratory rate elevate to accommodate the change. This is an example of a reflex.

Cardiovascular telex.

Explanation: During physical exercises which involves running, there is a reduction in the systemic vascular resistance produced and these constitutes a change in the heart rate and respiratory rate caused by the neural mechanisms which control the cardiovascular system which regulate the circulation of adequate oxygen supply and release carbon dioxide.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.