the control of the heart rate

Question 1

the control of the heart rate is…. ?

Answer 1

myogenic

Question 2

what does myogenic mean ?

Answer 2

• this means that the cardiac cycle is controlled by the hearts natural pacemakers

Question 3

what are the hearts natural pacemakers ?

Answer 3

• SAN ( sinoatrial node )
• AVN ( atrioventricular node)

Question 4

what are the natural pacemakers made up of ?

Answer 4

• clusters of muscle cells

Question 5

by what is the heart rate modified by ?

Answer 5

• part of the brain called medula oblongata

Question 6

step 1 of how the cardiac cycle is controlled ?

Answer 6

• The SAN produces waves of depolarisation
• causes the muscles of the atria to contract

Question 7

step 2 of how the cardiac cycle is controlled ?

Answer 7

• the waves of depolarisation are insulated from the rest of the heart by insulating tissue
• SAN pauses for about 0.5ms
• this allows time for blood to flow from the atria to the ventricles

Question 8

step 3 of how the cardiac cycle is controlled ?

Answer 8

• after a delay, the AVN relays the electrical depolarisation down the bundle of his
• this means that contraction of the ventricles starts from the base of the ventricles
• this forces blood up the aorta and pulmonary artery

Question 9

what is the bundle of his made of ?

Answer 9

• purkyne fibres

Question 10

what is the function of the bundle of his ?

Answer 10

• it conducts impulses

Question 11

when the ventricles or the atria contract, what happens to the pressure and volume ?

Answer 11

• volume decreases
• pressure increases

Question 12

what is the site of the cardiovascular centre ?

Answer 12

• in the medula oblongata

Question 13

what are the 2 types of receptors found at the top of the heart ?

Answer 13

• carotic body
• aortic body

Question 14

what kind of stimuli are the receptors in the caroted artery and aorta sensitive to ?

Answer 14

• pH (chemoreceptors)
• pressure (baroreceptors)

Question 15

what kind of neurones connect the SAN and AVN with the medula oblongata ?

Answer 15

• parasympathetic motor neurones
• sympathetic motor neurones

Question 16

what kind of neurone connects the carotic body and the aortic body with the medula oblongata ?

Answer 16

• sensory neurones

Question 17

what kind of neurotransmitter is released from the parasympathetic sensory neurone ?

Answer 17

• acetyl choline

Question 18

what kind of neurotransmitter is released from the sympathetic motor neurone ?

Answer 18

• noradrenaline

Question 19

how does Ach and noradrenaline act ?

Answer 19

• they are antagonistic
• they have equal and opposite effects
• so can cancel eachother out