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A-levle Biology > 3.1.2 - Transport In Animals (set B - Mammalian Heart) > Flashcards

3.1.2 - Transport In Animals (set B - Mammalian Heart) Flashcards

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1
Q

What is an electrocardiogram (ECG)?

A

Recording of the electrical activity of the heart - it measures tiny electrical differences in your skin and result of electrical activity of the heart

  • ECG converts electrical excitations into a trace, used to help diagnose certain heart conditions (eg abnormal heart rhythms and coronary heart disease)
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2
Q

Explain how electrocardiograms are recorded?

A

Electrodes are stuck to clean skin (to get good contact for reliable results) - signal from electrodes are fed into the machine which produces an ECG

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3
Q

Explain an important use of electrocardiograms?

A

If someone is having a heart attack, recognisable changes take place in the electrical activity of their heart, which can be used to diagnose the problem and treat it correctly

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4
Q

Give 4 heart rhythm abnormalities that commonly show up on ECGs?

A
  • tachycardia
  • bradycardia
  • ectopic heartbeat
  • atria fibrillation
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5
Q

What is an tachycardia rhythm what does it show on an ECG, describe what it’s like ?

A

When the heartbeat is very rapid (greater then 100 bpm) however its normal especially when exercising or due to a fever

  • if it’s abnormal it may be a problem in the electrical control of the heart and made need treatment
  • on an ECG there is fast heart rate and evenly spaced beats
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6
Q

What is an bradycardia rhythm what does it show on an ECG, describe what it’s like ?

A

When the heart rate slows down to below 60 bpm, common in fit people

  • severe bradycardia may need an artificial pacemaker to keep the heart being steadily
  • slow heart rate, beats evenly spaced
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7
Q

What is an ectopic heartbeat rhythm what does it show on an ECG, describe what its like ?

A

Extra heartbeats that are out of normal rhythm (most people have at least one a day) - usually normal but can be serious when frequent

  • altered rhythm, extra beat (extrasystole) followed by longer than normal gap before next beat
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8
Q

What is atrial fibrillation rhythm what does it show on an ECG, describe what its like ?

A

Example of an arrhythmia (meaning abnormal rhythm of the heart) - rapid electrical impulses are generated in the atria, they contract (filtrate) up to 400 times a minute however they don’t contract properly and some are passed on to the ventricle (which contracts less often) - heart does not pump effectively

  • abnormal irregular rhythm from atria, ventricles loose regular rhythm
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9
Q

What is the heart, give a brief description?

A

The heart is a complex organ made up of cardiac muscle (supplied oxygen by coronary arteries) which contracts and relaxes in a regular rhythm, pumping blood throughout the body within a double circulatory system

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10
Q

Explain the brief overall structure of of the heart?

A

Made of cardiac muscle, which contracts and relaxes (without getting fatigued) the muscle is supplied oxygenated blood by coronary arteries - the heart contains 4 chambers with 4 valves which prevents back flow

  • the heart is surrounded by inelastic pericardial membranes
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11
Q

Explain the function of the coronary arteries?

A

Coronary arteries supply cardiac muscles of heart with oxygenated blood so it can continue to contract and relax

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12
Q

Explain very briefly the overall flow and function of the heart?

A

Heart consists of two pumps joined together, with deoxygenated blood flowing in the right side of the heart which pumps to the lungs, and oxygenated on the left which is pumped to the body

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13
Q

Explain the purpose of the inelastic pericardial membranes around the heart?

A

Heart is surrounded with inelastic pericardial membranes - prevent the heart over-distending with blood

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14
Q

Explain the flow of blood through the heart starting with the vena cava (1) - explain where its comes from and any extra information?

A

Deoxygenated blood from the upper body and head enters right atrium through superior vena cava and the lower body through the inferior vena cava

  • at relatively low pressure
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15
Q

Explain the flow of blood through the heart after it enters through the vena cava (2) - explain what happens to the valve with reference to pressure?

A

Blood flows into the atria (which have thin muscular walls) causing a slight pressure increase until the atria-ventricular valve (tricuspid valve) opens - letting blood into the right ventricle

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16
Q

Explain the flow of blood through the heart after it enters the right ventricle (3) - reference the stretching of ventricle and valve closing?

A

When both the atrium and ventricle are filled with blood, the atrium contracts - forcing all the blood into the right ventricle, causing the ventricle walls to stretch - as the ventricle starts to contract the atrio-ventricular valve closes (preventing back flow into the atrium)

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17
Q

Explain the flow of blood from the right ventricle to the lungs (4) - reference the contraction of the ventricle,artery involved and valves involved?

A

The right ventricle contracts fully and pumps deoxygenated blood through the semi-lunar valve into the pulmonary artery (transporting it to the capillary beds of the lungs) - semi-lunar valves prevent any back flow of blood into the heart

18
Q

Explain the function of tendinous cords on the valves?

A

Tendinous cords make sure the valves are not turned inside out by the pressure exerted when the ventricle contracts

19
Q

Explain the subsequent flow of blood from the lungs to the heart (5) - reference the vein involved and the valve involved?

A

At the same time oxygenated blood enters the left atrium from the pulmonary vein - pressure in the atrium builds causing the atrio-ventricualr valve (bicuspid valve) to open - oxygenated blood flows into the left ventricle

20
Q

Explain the flow of blood from the left ventricle to the rest of the body (6) reference the valves involved and the artery?

A

Once both the left atrium and ventricle are full the atrium contracts forcing all the oxygenated blood into the left ventricle, which then contracts and pumps oxygenated blood though the semilunar valves into the aorta and around the body - as the ventricle contracts, tricuspid valve closes preventing back flow

21
Q

Explain why the muscular walls of the heart are thicker on the left side than the right?

A

The lungs are relatively close to the heart and much smaller than the rest of the body - so the right side of the heart has to pump the blood a relatively short distance and only has to overcome the resistance of pulmonary circulation

  • left has to overcome the resistance of aorta and the arterial systems of the whole body and move the blood under pressure
22
Q

Explain what the septum in the heart is - give its function?

A

The inner diving wall of the heart, prevents mixing of deoxygenated and oxygenated blood

23
Q

Explain why their is sometimes a hole in the septum, what is the impact?

A

Development of septum is not complete until after birth - in the fetus the blood is oxygenated in the placenta, not lungs (all the blood in the heart is similar and mixes freely) - closes in the days after birth so blood is no longer mixed

  • many may still have a small hole, but if its too large it can lead to severe health problems
24
Q

Explain what the cardiac cycle is - what is the length of time?

A

The cardiac cycle describes the events in a single heartbeat, which lasts about 0.8 seconds in a human adult

25
Q

Explain why atrial pressure is always relatively low?

A

Atrial pressure is relatively low becauase the thin walls of the atrium cannot create much force - it is highest when they are contracting

  • drops when the antrioventricular valve closes and its walls relax
26
Q

Give the 3 stages of the cardiac cycle - briefly explain each stage?

A
  • diastole - (chambers are relaxed and filling with blood)
  • atria systole/ventricular diastole - (atria contract and remaining blood is pushed into ventricles)
  • ventricular systole/atrial diastole - (ventricles contract and push blood out through aorta and pulmonary artery)
27
Q

Explain what happens during diastole?

A
  • ventricles and atria are both relaxed
  • pressure in ventricles drops below that in aorta and pulmonary artery - forces semilunar valve shut
  • atria continue to fill with blood - as blood returns via vena cava and pulmonary artery
  • pressure in atria rises above ventricles forcing AV valve open - passive flow of blood into ventricles - cycle begins with atria systole
28
Q

Explain what happens during atrial systole?

A
  • walls of atria contract (volume decreases, pressure increases)
  • pressure in atria greater than in ventricles - AV valve opens - blood forced into ventricles, results in slight increase in ventricular pressure
  • ventricles are relaxed at this point (ventricular diastole)
29
Q

Explain what happens during ventricular systole?

A
  • walls of ventricles contract (volume decreases, pressure increases)
  • pressure rises above that in atria - AV valve closes
  • pressure in ventricle greater than aorta and pulmonary artery (forces semilunar valve open) - blood forced out of heart
  • atria diastole coincides with ventricular systole
30
Q

Explain the position of the valves during atrial systole?

A

Atrioventricular - open
Semilunar - closed

31
Q

Explain the position of the valves during ventricular systole?

A

Atrioventricular - closed
Semilunar - open

32
Q

Explain the position of the valves during diastole?

A

Atrioventricular - open
Semilunar - closed

33
Q

Explain what causes the sound of a heartbeat which can be heard?

A

Two sounds of a heartbeat are described as ‘lub-dub’

  • ‘lub’ sound comes as the blood is forced against the AV valves as the ventricles contract
  • ‘dub’ - due to back flow of blood which closes the semilunar valves in the aorta and pulmonary artery as ventricles relax
34
Q

Explain the significance of cardiac muscle?

A

Myogenic (meaning it has its an intrinsic rhythm)

  • prevents the body wasting resources maintaining the basic heart rate
35
Q

Outline how the basic rhythm of the heart is maintained - reference any nodes or fibres involved?

A

1) Wave of electrical excitations begins in SAN - initiates heartbeat

2) AVN picks up electrical activity - imposes a slight delay before stimulating the bundle of His

3) bundle of His conducts wave of excitation to the apex of the heart

4) purkyne fibres spread through walls of ventricles causing a contraction from the apex

36
Q

Outline and explain the role of the Sino-atrial node (SAN)?

A
  • initiates the heartbeat by sending out a wave of electric excitation from the pacemaker area
  • causes the atria to contract
  • non-conducting tissue prevents excitation passing to ventricles
37
Q

Outline and explain the role of the atrio-ventricular node (AVN)?

A
  • Picks up electrical activity from SAN
  • AVN imposes a slight delay before stimulating the bundle of His
  • delay ensures the atria have stopped contracting before ventricles contract
38
Q

Outline and explain the role of the bundle of His?

A
  • bundle of conducting tissue made up of purkyne fibres
  • split into 2 branches and conduct the wave of excitation to the apex of the heart
39
Q

Outline and explain the role of the purkyne fibres?

A
  • purkyne fibres penetrates through the septum between the ventricles
  • at the apex the fibres spread out through the walls of the ventricles - triggers the contraction of the ventricles, starting at the apex
  • ensures efficient emptying of ventricles
40
Q

Explain how pressure changes during the cardiac cycle?

A

Contraction of the heart muscle increases pressure as the volume is decreased (ventricular systole and atrial systole)

  • valves open when the pressure of blood behind them is greater than the pressure in front of them - close when greater pressure behind

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