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Heart > Physiology > Flashcards

Physiology Flashcards

1
Q

What is the electrical conduction system?

A

Specialised cardiac cells generate their own action potential/electical currents that stimulate the heart to contract and relax
They are electrically unstable - discharge impulses rapidly and regularly

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2
Q

What is the pathway for the electrical conduction system?

A

SA node
AV node
Bundle of his
Two bundle branches
Purkinje fibres

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3
Q

What happens when the SA node transmit a signal?

A

Atria contract
Transmitted to AV node

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4
Q

Why does the AV node delay electrical transmission?

A

To ensure atria have completely contracted

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5
Q

What is stroke volume?

A

The amount of blood the heart pumps out each ventricle each heartbeat

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6
Q

What is cardiac output?

A

The amount of blood the heart pumps out in one minute

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7
Q

What is the equation for cardiac output?

A

Stroke volume x heart rate

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8
Q

What are the three factors that regulate stroke volume?

A
  1. Preload
  2. Force of contraction
  3. Afterload
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9
Q

What is preload?

A

The amount of stretch in the cardiac muscle relates to the force they contract during systole
The stretch relates to how much blood is in the ventricle before the next contraction and this is dependent on venous return
The more the ventricles fill, the more the muscle will stretch resulting in stronger force of contraction which increases stroke volume and cardiac output

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10
Q

What is force of contraction?

A

Strong contractions increase stroke volume
Can be affected by hormones
Sympathetic nervous system increases force

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11
Q

What is afterload?

A

Refers to the pressure in the arteries that the ventricles must overcome in order to eject blood
An increase in arterial pressure increases afterload, making it more difficult for ventricles to pump blood

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12
Q

What sets the heart rate?

A

SA node

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13
Q

What can change heart rate?

A

NS activated -
Sympathetic nerves release noradrenaline which leads to excitation of SA
Parasympathetic releases acetylcholine and reduces impulses in the SA

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14
Q

What is BP?

A

Force or pressure which blood exerts of the wall of the blood vessels when the ventricles contract

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15
Q

What is a healthy BP?

A

120/80

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16
Q

What is the equation for BP?

A

Cardiac output x peripheral resistance

17
Q

What is a baroreceptor?

A

Specalised receptors in carotid sinus and aortic arch
Sensitive to changes in BP
Sense impulses to the medulla oblongata
Provides a quick response
Short term BP regulation

18
Q

What are chemoreceptors?

A

Nerve endings in the aortic arch and carotid arteries
Sensitive to change in oxygen, Co2 and pH
Receptors send impulses to medulla oblongata
Increases sympathetic activity
Increases cardiac output and BP

19
Q

What are the 5 phases of the cardiac cycle? What happens at each?

A
  1. Artial diastol
    - Artia and ventricles are relaxed
    - Blood fills the atria
    - Mitral and tricuspid valves are open due to low pressure in atria and ventricles
    - Blood flows through to ventricle
  2. Artrial systole
    - SA node sends impulse
    - Atria contract forcing blood into ventricles
  3. Isovolumetric ventricular contraction
    - Mitral and tricuspid valves close due to higher pressure in the ventricles
    - Ventricles begin to stretch and contract
    - Lub sound
  4. Ventricular systole
    - AV node sends impulse down bundle of his
    - Ventricles contract
    - Rise of pressure in ventricles
    - Pulmonary and aortic valves open
    - Ejection of blood
  5. Ventricular disastole
    - Ventricles relax and pressure falls
    - Pressure is higher in arteries so aortic and pulmonary valves close
    - Dub sound
  6. Complete cardiac diastole
20
Q

What is the normal heart rate?

A

60-100 bpm

21
Q

What is the P wave?

A

SA node impulses travel to the atria
Atria contracts

22
Q

What is the QRS wave?

A

Electrical impulses reach the ventricles
Both ventricles contract

23
Q

What is the T wave?

A

Relaxation of ventricles

24
Q

What is sytole?

A

Contraction

25
Q

What is diastole?

A

Relaxation

26
Q

What does the top and bottom number mean in BP?

A

Systole
_______
Diastole

27
Q

What is depolarisation?

A

Contraction

28
Q

What is repolarisation?

A

Relaxation

Heart (2 decks)

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