mechanism for controlling the cardiac cycle and the pulse rate

Question 1

function of a SA node

Answer 1

acts as a pacemaker causing the heart to beat at a slower or faster rate depending on the needs of the body

Question 2

what is the average pulse rate for people in their rest position

Answer 2

72heart beats per minute

Question 3

the average pulse rate of a resting adult male

Answer 3

70-72 beats per minute

Question 4

the average pulse rate of a resting adult female

Answer 4

78-82 beats per minute

Question 5

pulse rate of well trained athletes

Answer 5

heart beats as low as 40 to 50 heart beats per minute when they rest

Question 6

why does the heart beat faster when a person takes part in vigorous physical activity

Answer 6

so that the blood containing oxygen and glucose may be pumped to the muscle more quickly

Question 7

what is the average pulse rate during vigorous physical activity

Answer 7

200 beats per minute

Question 8

why does the heart beat slower when you are sleeping

Answer 8

because less energy is required by the muscles

Question 9

how does the body know whether the heart needs to beat faster or slower

Answer 9

by the amount of carbon dioxide in the blood

Question 10

how are the changes of the rate of heart beats brought about

Answer 10

1. special receptor cells in the carotid ateries near the heart can pick up whether the coarbon dioxide level is higher or lower than normal
2. this message is sent by nerves to the mandulla oblongata of the brain
3. when the carbon dioxide level is high,sympathetic nerves from the mandulla oblangata carry a message to the pace maker of the heart causing it to beat faster
4. when the carbon dioxide level is low ,parasympathetic nerves from the mandulla oblangata carry a message to the pacemaker of the heart causing it to beat slower