4.1 Explain the mechanisms for regulating ventilation and pulse rates.

Your heart rate and breathing is controlled by the sympathetic and parasympathetic nervous system. The effect of exercise is to speed up the heart rate and increase the breathing which happens when the sympathetic nerves transmit signals to the SA node and this stimulates the release of adrenalin from the adrenal medulla situated at the top of the kidneys and released by the sympathetic neurons. This happens when the body becomes under pressure, the body realises that oxygen is needed in certain parts of the body and energy is needed to be released. The heart rate increases and breathing becomes deeper in an attempt to get oxygen pumping round the body quicker. A similar thing occurs when you react to a situation, it maybe a stressful situation or a frightening experience as this is the body’s way of survival. When your body becomes under pressure the breathing and the heart rate increases but so does your blood pressure. These messages are located in the aorta and carotid artery and then received by the cardiac centre, this responds by sending out impulses via the parasympathetic nerves to the SA node and the heart rate slows down.When the body no longer feels under threat the parasympathetic nervous system kicks in striving for homeostasis and regulating heart rate and breathing.