12 control of cardiac output

Question 1

What is P in an electrocardiogram?

Answer 1

atrial systole

Question 2

What is QRS in an electrocardiogram?

Answer 2

spread of electrical impulses through the ventricles through bundle of his –> purkinje fibres –> ventricular systole and atrial diastole

Question 3

What is T in an electrocardiogram?

Answer 3

ventricular diastole

Question 4

What is QT in an electrocardiogram?

Answer 4

Time between depolarisation if ventricles and relaxation

Question 5

What are the factors effecting cardiac output?

Answer 5

• stroke volume

- heart rate

Question 6

What is cardiac output?

Answer 6

the amount of blood ejected per ventricle per minute

Question 7

What is stroke volume?

Answer 7

volume of blood ejected per ventricle per minute

Question 8

CO of an athlete vs. non athlete

Answer 8

rest: A-5.5 NA - 5
after exercise: A-30 NA-20
L/MIN

Question 9

SV of an athlete vs. non athlete

Answer 9

rest: A-100 NA-65

After exercise: A-165 NA-105

Question 10

HR of an athlete vs. non athlete

Answer 10

Rest: A-55 NA-75

After exercise: A-180 NA-190

Question 11

Heart weight of an athlete vs. non athlete

Answer 11

500 vs 300g

Question 12

What is stroke volume governed by?

Answer 12

-End diastolic volume
-End systolic volume
(mainly diastolic coz what enters the heart must leave the heart)

Question 13

How is the heart rate slowed down?

Answer 13

The vaygus nerve which acts on the SAN and releases acetylcholine

Question 14

How is the heart rate increased?

Answer 14

The accelerator nerve which acts on the SAN and releases norepinephrine/noradrenaline

Question 15

What is a positive chonotropic effect?

Answer 15

Increases the heart rate

Question 16

Name 4 things that have a positive chonotropic effect on the heart

Answer 16

• norepinephrine
• adrenaline
• glucagon
• thyroid hormones

Question 17

What part of the brain is responsible for the heart

Answer 17

pons?

Question 18

where does adrenaline/ noradrenaline come from?

Answer 18

Adrenal gland
sympathetic nerves
kidneys

Question 19

How do positive chonotopic substances work?

Answer 19

they cause a faster inflow of sodium and calcium ions which causes the threshold to be reached much faster. 
reduced repolarisation (below the line) so there can be more depolarisation

Question 20

How does acetylcholine work on the heart?

Answer 20

It causes K to leave the cell faster and so causes slower depolarisation. its all about what happens before threshold potential is reached - after that its all the same
-the membrane becomes more hyper polarised
acts on the muscarininc K channels (more neg)

Question 21

What is the HR if you cut the vaygus nerve?

Answer 21

110

Question 22

What happens to HR if you inhibit ACH

Answer 22

it increases from 70 to 110

Question 23

What is fast heart rate called?

Answer 23

Tachycardia

Question 24

What is a slow heart rate called?

Answer 24

Bradycardia

Question 25

Why do some people have a lower heart rate? (e.g. athletes)

Answer 25

Increased vaygal tone –> more ACH acting on SAN

Question 26

What is the the preload?

Answer 26

The pressure exerted on the ventricles by the filling of blood. can be measured using the EDV. the amount of blood entering the ventricles/atria

Question 27

How do you work out stroke volume?

Answer 27

EDV-ESV

Question 28

What is the afterload?

Answer 28

the end load against which the heart contracts to eject blood from the ventricles

Question 29

What effects the afterload

Answer 29

• preload volume
• aortic pressure (^=^)
• vasoconstriction

Question 30

What is contractility?

Answer 30

The energy of contraction regulated by SNS and adrenaline