Unit 6: Heart rate

Question 1

The heart is myogenic. What does this mean?

Answer 1

Muscular contractions of the heart originate from within the heart muscle itself

Question 2

What is the function of the heart rate increasing during exercise?

Answer 2

Increases blood to muscles bringing more oxygen/glucose and getting rid of carbon dioxide

Question 3

what is the sinoatrial note?

Answer 3

act as a pacemaker and initiates the heartbeat

Patch of modified muscle cells in the wall of the right atrium which produces regular waves of electrical impulses

Question 4

How does the atria contract?

Answer 4

impulses spread rapidly through the walls of the right/left atrium causing the atria to contract together

Question 4

What happens before atrioventricular node reacts?

Answer 4

there is a 0.15 second delay before the AV node reacts to ensure the atria is empty and ventricles are full of blood and contract after the atria

Question 5

what happens after the AV node reacts?

Answer 5

impulsive from the AV note travel rapidly through the purkyne tissue in the bundle of his to all parts of the ventricle

Question 6

What happens when impulses reach the ventricles?

Answer 6

venteicles are stimulated to contract together starting at the bottom of the heart to push to blood up and out into the arteries

Question 7

What neurotransmitter causes an increase in heart rate

Answer 7

noradrenaline by the sympathetic neurones

Question 8

what neurotransmitter causes the slowing down of the heart rate

Answer 8

the release of acetylcholine by the parasympathetic neurones

Question 9

What regulates heartrate

Answer 9

the cardiac centre in the medulla

Question 10

how is heart rate sped up

Answer 10

medulla sends more impulses along the sympathetic neurone to the SAN

noradrenaline is released from sympathetic neurones stimulating SAN

Question 11

how is heart rate slowed down

Answer 11

medulla sends more impulses along the parasympathetic neurones to the SAN

acetylcholine is released; inhibiting SAN

Question 12

What effect does the increase in respiration during exercise have?

Answer 12

increases production of CO2

Question 13

What is the effect of the increase in CO2 during exercise

Answer 13

CO2 dissolves in blood producing carbonic acid lowering the pH by increasing the conc oh H+ ions

chemoreceptors in the aortic and carotid bodies are stimulated

Question 14

What are the function of chemoreceptors

Answer 14

transmit more impulses to the cardiac centre in the medulla
this increases heart rate by transmitting more impulses from the medulla via sympathetic neurones to the SAN

Question 15

What happens when heart rate is returned to resting rate

Answer 15

conc of CO2 in blood had been reduced

fewer impulses are transmitted from chemoreceptors to medulla

Question 16

What is the respiratory centre?

Answer 16

in the medulla
receives impulses from the chemoreceptors and increases rate of ventilation

Question 17

What effect does increased blood flow to the heart have on the cardiac muscle?

Answer 17

causes cardiac muscle to contract more strongly pumping out an increased volume of blood

Question 18

What are baroreceptors

Answer 18

located in wall of aorta and carotid artery
detect increase in blood pressure

Question 19

What happenes if blood pressure is above normal

Answer 19

baroreceptors send more impulses to medulla stimulating the cardioinhibitory centre and inhibiting the cardioacceleratory centre

Question 20

How is the heart rate decreased

Answer 20

more impulses are sent from the cardiac centre along parasympathetic neurones to the SAN preventing heart from overworking