12 control of cardiac output Flashcards

1
Q

What is P in an electrocardiogram?

A

atrial systole

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2
Q

What is QRS in an electrocardiogram?

A

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

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3
Q

What is T in an electrocardiogram?

A

ventricular diastole

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4
Q

What is QT in an electrocardiogram?

A

Time between depolarisation if ventricles and relaxation

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5
Q

What are the factors effecting cardiac output?

A
  • stroke volume

- heart rate

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6
Q

What is cardiac output?

A

the amount of blood ejected per ventricle per minute

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7
Q

What is stroke volume?

A

volume of blood ejected per ventricle per minute

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8
Q

CO of an athlete vs. non athlete

A

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

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9
Q

SV of an athlete vs. non athlete

A

rest: A-100 NA-65

After exercise: A-165 NA-105

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10
Q

HR of an athlete vs. non athlete

A

Rest: A-55 NA-75

After exercise: A-180 NA-190

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11
Q

Heart weight of an athlete vs. non athlete

A

500 vs 300g

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12
Q

What is stroke volume governed by?

A

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

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13
Q

How is the heart rate slowed down?

A

The vaygus nerve which acts on the SAN and releases acetylcholine

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14
Q

How is the heart rate increased?

A

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

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15
Q

What is a positive chonotropic effect?

A

Increases the heart rate

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16
Q

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

A
  • norepinephrine
  • adrenaline
  • glucagon
  • thyroid hormones
17
Q

What part of the brain is responsible for the heart

18
Q

where does adrenaline/ noradrenaline come from?

A

Adrenal gland
sympathetic nerves
kidneys

19
Q

How do positive chonotopic substances work?

A
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
20
Q

How does acetylcholine work on the heart?

A

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)

21
Q

What is the HR if you cut the vaygus nerve?

22
Q

What happens to HR if you inhibit ACH

A

it increases from 70 to 110

23
Q

What is fast heart rate called?

A

Tachycardia

24
Q

What is a slow heart rate called?

A

Bradycardia

25
Why do some people have a lower heart rate? (e.g. athletes)
Increased vaygal tone --> more ACH acting on SAN
26
What is the the preload?
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
27
How do you work out stroke volume?
EDV-ESV
28
What is the afterload?
the end load against which the heart contracts to eject blood from the ventricles
29
What effects the afterload
- preload volume - aortic pressure (^=^) - vasoconstriction
30
What is contractility?
The energy of contraction regulated by SNS and adrenaline