control of the heart rate

Question 1

cardiac muscle is myogenic, what does this mean

Answer 1

it can contract and relax without receiving signals from nerves

Question 2

where does the process start

Answer 2

in the sinoatrial nerve (SAN) which is located in the wall of the right atrium

Question 3

what does the SAN do, what is it similar to

Answer 3

like a pacemaker which sets the rhythm of the heartbeat by sending out regular waves of electrical activity along the atrial walls

Question 4

what does the wave of electrical activity from the SAN cause in the heart

Answer 4

it causes the atria to contract at the same time

Question 5

what prevents the electrical activity from being passed directly from atria to the ventricles

Answer 5

non-conducting collagen tissue

Question 6

where are the electrical waves transferred to

Answer 6

into the atrioventricular node (AVN)

Question 7

what is the atrioventricular node responsible for

Answer 7

passing the waves of electrical activity on to the bundle of His

Question 8

why Is there a slight delay before the AVN reacts

Answer 8

to make sure the atria have emptied before the ventricles contract

Question 9

what is the bundle of His

Answer 9

a group of muscle fibres responsible for conducting the waves of electrical activity between the ventricles to the apex of the heart

Question 10

what is the apex of the heart

Answer 10

the bottom of it

Question 11

what is the purkyne tissue

Answer 11

where the bundle of His splits into finer muscles fibres at the apex in the right and left ventricle walls

Question 12

what does the purkyne tissue do

Answer 12

carries the electrical activity into the muscular walls of the right and left ventricles which causes them to contract simultaneously from the bottom up

Question 13

what is the rate at which the SAN fires electrical impulses controlled by

Answer 13

unconsciously controlled by part of the brain called medulla oblongata

Question 14

what are baroreceptors, where are they located and what stimulates them

Answer 14

pressure receptors in the aorta and the carotid arteries which are stimulated by high and low blood pressure

Question 15

what are chemoreceptors, where are they located and what is their function

Answer 15

chemical receptors in the aorta, the carotid arteries and in the medulla, they monitor the oxygen level in the blood and also carbon dioxide and pH.

Question 16

if the body detects high BP, high blood O2, low CO2 or high pH levels what happens

Answer 16

the baroreceptors or chemoreceptors detect this and an impulse is sent to the medulla which sends an impulse along the parasympathetic neurone, acetylcholine is secreted which binds to the receptors on the SAN to fix the problem

Question 17

if the body detects low BP, low blood O2, high CO2 or low pH levels what happens

Answer 17

the baroreceptors or chemoreceptors detect this and an impulse is sent to the medulla which sends an impulse along the sympathetic neurone, noradrenaline is secreted which binds to the receptors on the SAN to fix the problem