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Year 12 - Biology > C5 - The Heart > Flashcards

C5 - The Heart Flashcards

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1
Q

Why do mammals need a mass transport system?

A

Large, multicellular organisms can’t survive relying on diffusion as they have a high basal metabolic rate.
They have structures which increase the available exchange surface and a mass flow system is needed to other parts of the organism.

Plants gain necessary nutrients and oxygen via diffusion across the cell surface membrane; not possible in large organisms.

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2
Q

What are the main components of the heart?

12

A 
Aorta
Superior / anterior vena cava
Inferior / posterior vena cava
Right atrium
Left atrium
Pulmonary artery (deoxygenated)
Pulmonary vein (oxygenated)
Right ventricle
Left ventricle
Atrioventricular valve
Septum 
Semi-lunar valves
Heart strings (chordae tendinae)
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3
Q

What are the functions and arrangements of the internal structures of the heart?

A
  • 2 atria at top of hearts
  • Atrioventricular valves are between the atria and ventricles. (Left is bicuspid, right is tricuspid valve)
  • Left ventricle walls are much thicker / have more muscle.
  • P veins open into the left atrium bringing oxygenated blood from the left and right lungs.
  • Vena cava brings deoxygenated blood from the body.
  • Semi-lunar valves are at the opening of each major artery as it leaves the heart.
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4
Q

What is cardiac muscle?

A

Muscle found on the heart wall which is able to contract without the need of any nerve stimulation and will continue to contract at its own beat.

This is known to be myogenic.

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5
Q

What is the cardiac cycle?

A

A complete sequence of events beginning with atrial systole (atrial walls contract), ventricular systole (ventricle walls contract) then diastole (resting heart).

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6
Q

What are the 3 stages of the cardiac cycle?

A

Atrial systole (atrial walls contract)

Ventricular systole (ventricle walls contract)

Diastole (resting heart).

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7
Q

What occurs during atrial systole?

Muscles/blood/valves/pressure

A
  • The atrial walls contract
  • Blood flows passively into the ventricles changes by atrial contractions, forcing blood into ventricles.
  • The atrioventricular valves are pushed fully open by the blood flowing through.
  • Pressure rises in atria as they contract with a slight rise in ventricles as blood enters them.
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8
Q

What occurs during ventricular systole?

Muscles/blood/valves/pressure

A
  • Ventricle walls contract
  • Blood is forced into the main arteries (from the RV into the pulmonary artery and LV into the aorta)
  • The AV valves are pushed shut as pressure in the ventricles rises above the pressure in the atria, preventing backflow.
    Heart tendons hold the valves in place to prevent the valves inverting.
    Semilunar valve’s pushed fully open as blood enters arteries.
  • Pressure in the atria falls. Pressure in the ventricles rises steeply as muscles contract then falls as blood is emptied from the ventricles. Pressure in the arteries rises as blood enters from the ventricles and falls.
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9
Q

What occurs during diastole?

Muscles/blood/valves/pressure

A
  • The muscular walls are relaxed
  • The atria fill with blood, opening the AV valves. Blood slowly and passively enters the ventricles.
  • Semilunar valves close since pressure in the artery is higher than the pressure in the ventricles.
    AV valves open.
  • Pressure in atria rises as they fill then falls as AV valves open. Pressure in ventricles falls but rises slightly again as they become full.
    Pressure in the arteries falls but remained higher than the ventricles.
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10
Q

What is atrial systole?

A

The contraction of myocardium (heart muscle) of the left and right atria.
This causes the blood to move from the atria into the ventricles.

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11
Q

What is ventricular systole?

A

The contraction of the myocardium (heart muscle) of the left and right ventricles.
Ventricular systole induces increased pressure in the left and right ventricles forcing blood into the main arteries - the pulmonary artery and aorta.
Pressure in the ventricles rises above that of the atria, thus closing the tricuspid and bicuspid valves, which are prevented from inverting by chordae tendineae and papillary muscles.

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12
Q

What is diastole?

A

The part of the cardiac cycle when the heart relaxes and refills with blood after atrial and ventricular systole (contractions)

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13
Q

What does myogenic mean?

A

It [the heart] can contract without the need of any nerve stimulation and will continue to contract at its own beat even when isolated.

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14
Q

What is the order of blood flow?

A

Blood enters the two atria from the pulmonary vein and vena cava.

The atria contract and force blood into the two ventricles.

The ventricles then contracts and blood is pumped out into the main arteries (aorta and pulmonary arteries).

The heart then relaxes so the blood flows back into the chambers.

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15
Q

How does electrical activity take place within the heart?

A

Within the muscular wall of the right atrium is the sinoatrial node (SA node) a.k.a the pacemaker.

From here, and electrical impulse spreads rapidly through the walls of both atria. This causes the walls of the two atria to contract - triggering atrial systole.

A second node called the atrioventricular node (AV node) lies in the septum between the two atria, close to where the valves are situated.

Layers of fibrous tissue that form the valves prevents the wave of contraction from passing on immediately. A short delay occurs allowing the atria to empty the blood into the ventricles.

The AV node picks up the electrical signal and, after a short delay, transmits it on to the ventricles.

From the AV node there are conductive fibres called the bundle of His. Please carry the electrical impulse across the fibrous ring and onto the Purkinje tissue.

The Purkinje tissue carries the impulse to the apex of the ventricles then through bundle branches up the walls of the ventricles.

This initiates the contraction of the ventricles from the apex upwards. This contraction is cause ventricular systole.

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16
Q

What causes muscle cells to contract?

A

Muscle cells (myocytes) have a slight electrical charge and a polarised. When the charges reversed they are depolarised which causes them to contract.

Depolarisation is initiated in the sinoatrial node

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17
Q

What is stroke volume?

A

The volume of blood pumped out of the left ventricle during each cardiac cycle, which is approx 60-80cm3.

18
Q

What is cardiac output?

A

The volume of blood pumped out of the left ventricle each minute.

19
Q

What is the heart rate?

A

The number of beats per minute (average of 72bpm)

20
Q

How is cardiac output calculated?

A

Cardiac output = stroke volume * heart rate

21
Q

What is a pulse rate and how is it felt?

A

It’s the number of pulses felt in the artery each minute.

It is felt because pulses are the expansion of the artery walls blood is pumped through with each ventricular systole, followed by the elastic recoil of the artery wall as pressure drops when in diastole (rest).

22
Q

What factors affect heart rate?

A

Age (children have higher)

Inheritance

Activity level (athletes have lower due to stronger heart muscle)

Smoking (nicotine increases heart rate)

Diet

23
Q

What’s an electrocardiogram

A

A display of a persons heartbeat by electrocardiography.

24
Q

What are the various parts of a typical ECG trace?

A 
P wave
PR interval
PR segment
QRS complex
ST segment
QT interval
T wave
25
Q

What parts of an ECG trace correspond to the cardiac cycle?

A

The gentle rise of the P wave corresponds to atrial systole.

The QRS wave/complex corresponds to ventricular systole

The final T wave is linked to ventricular diastole

26
Q

What occurs during the P wave of a typical ECG trace?

A

The P wave is the wave of depolarisation that spreads from the sinoatrial node (right atrium) across the atria, causing atrial systole.

27
Q

What is the PR interval of a typical ECG trace?

A

It is the time taken for the wave of depolarisation to be conducted from the sinoatrial node (SAN) to the ventricles via the atrioventricular node (AVN).

(Measured from the start of the P wave to start of QRS complex)

28
Q

What occurs during the QRS complex of a typical ECG trace?

A

It is the wave of depolarisation that spreads across the ventricles and causes ventricular systole.

29
Q

What is the ST segment of a typical ECG trace?

A

It’s the interval between the end of ventricular depolarisation and the start of ventricular re-polarisation.
(Measured from the end of the QRS complex to the start of the T wave).

30
Q

What occurs during the T wave of a typical ECG trace?

A

It is the re-polarisation of the ventricles in ventricular diastole.

31
Q

What is a myocardial infarction?

How is it caused?

A

A heart attack.
It occurs when the blood supply to part of the heart is partially of totally blocked and that region becomes deprived of oxygen and stops contracting.

32
Q

How can myocardial infarction be identified?

A

On an ECG trace, the troughs and peaks are less distinct, the ST segment is higher than normal and the atria are contracting to an abnormal rhythm.

33
Q

What’s tachycardia?

A

A high resting heart rate (above 100bpm) with little gap between the T and P wave of each trace.

34
Q

What’s bradycardia?

A

A very slow resting heart rate between 40-60bpm. The gap between each peak in the trace is quite long.

35
Q

How can a heart attack be recognised?

A

Crushing pains on the chest, neck or jaw

Breathlessness

A rapid, weak pulse

Nausea / vomiting

36
Q

How do you help someone having a heart attack?

A

Call 999

Sit them in W semi-recumbent position

300mg aspirin

Monitor heart rate

37
Q

How do you help someone in cardiac arrest?

A

Check for breathing

Place heel of hands on persons chest, keep elbows straight and press down vertically 5cm. 30x then mouth to mouth.

100 compressions a minute.

38
Q

How and why are defibrillators used?

A

They are placed across the chest and a reading machine shows if the heart is fibrillation.

If it is, an electric shock is applied to momentarily stop it’s chaotic electrical activity and allow the heart to recover it’s own rhythm led by the sinoatrial node.

39
Q

Why is it pauses within the electrical activity of the heart?

A

To ensure that all blood has left the previous chamber.
For example the delay of electrical activity at the atrioventricular node is to ensure that the atria have contracted and released all the blood they contain before the ventricles contract.

40
Q

What is the sequence of components which electrical activity is conducted to during the cardiac conduction system?

A

It’s begins at the sinoatrial node also known as the pacemaker

The electrical signal is then passed to both atria and atrial systole occurs.

It is then passed to the atrioventricular node where there is a slight delay

The signal then travels to the bundle of His. The bundle is then divided into left and right branches.
They conduct the signal to the apex of the heart.

The signal is then passed to Purkinje fibres. This spreads around the ventricle. This causes ventricular systole.

41
Q

Name the stage of the cardiac cycle that is represented by the QRS wave on the ECG:

A

Ventricular systole.

Year 12 - Biology (15 decks)

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