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Biology > The Heart > Flashcards

The Heart Flashcards

1
Q

What is the heart?

A
  • A muscular organ that pumps blood through the circulatory system by increasing blood pressure relative to the lowest blood pressure in the blood vessels
  • The difference in pressure causes the blood to flow
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2
Q

What is the wall of the heart made up of?

A
  1. EPICARDIUM- outer layer of heart wall and inner layer of pericardial membrane
  2. MYOCARDIUM- cardiac muscle
  3. ENDOCARDIUM- lines chambers and covers heart valves
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3
Q

What is the pericardium?

A
  • A double walled sac that encloses the heart for protection of the heart
  • Fluid between the inner and outer pericardial membranes lubricates the movement of the heart
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4
Q

What is cardiac muscle joined by?

A

Intercalated discs

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5
Q

What is cardiac muscle made up of?

A

Cardiomyocytes

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6
Q

Why do cardiomyocytes need to be able to contract in coordination?

A

To efficiently pump blood

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7
Q

What is an intercalated disc?

A

A type of cell junction that joins all cardiomyocytes to allow them to contract in a coordinated manner

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8
Q

Why do cardiomyocytes have so many mitochondria?

A

So they can undergo a lot of aerobic respiration and so do not fatigue under repeated contraction

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9
Q

What is the function of the papillary muscles?

A

Prevent the heart valves from folding too far back during heart contractions

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10
Q

What is the function of the chordate tendineae?

A

Connect the papillary muscles to the cusps of the atrioventricular valves

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11
Q

What is the function of the trabecular carneae?

A

Line the ventricles to help to help the papillary muscles in preventing the infolding of the atrio-vetricular valves

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12
Q

What are the two layers of the pericardium?

A
  1. FIBROUS PERICARDIUM- outer layer made of strong connective tissue, largely of a fixed shape
  2. SEROUS PERICARDIUM- inner layer made of serous membrane, which is smooth to allow a sliding motion
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13
Q

What does the pericardial fluid protect?

A

Protects the heart against infection and blunt trauma, and lubricates the heart’s movements

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14
Q

What are the three stages of the cardiac cycle?

A
  1. Atrial systole
  2. Ventricular systole
  3. Diastole
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15
Q

What happens in atrial sytstole?

A
  • The muscles of the atria contract
  • The pressure inside the atria increases
  • The semilunar valves in the vena cava and the pulmonary vein close
  • The triscupid and biscupid valves opens, allowing blood into the ventricles
  • Pressure decreases
  • Last about 0.1 seconds
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16
Q

What happens in ventricular systole?

A
  • Muscle of ventricles contract
  • Pressure inside ventricles increases
  • The triscupid and biscupid valves close
  • The semilunar valves in the aorta and pulmonary arteries open
  • Pressure decreases
  • Lasts about 0.3 seconds
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17
Q

What happens in diastole?

A
  • Pressure in the ventricles decreases
  • Semilunar valves in the aorta and the pulmonary arteries close
  • All the heart muscles relax
  • Blood flows into the atria and ventricles again from the vena cava and pulmonary vein
  • Blood pressure remains low inside the atria and ventricles
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18
Q

How are valves controlled?

A

High pressure behind the valve forces it to open and high pressure in front of the valve closes it

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19
Q

What causes the LUB DUB sound?

A
  • Closure of AV valves heard as LUB

- Closer of semilunar valves heard as DUB

20
Q

What is cardiac output?

A

The volume of blood being pumped by the heart, by the left and right ventricle, per unit time

21
Q

What is stroke volume?

A

Volume of blood pumped from the ventricles per beat

22
Q

What is the equation from cardiac output?

A

Cardiac output = Stroke Volume x Heart Rate

23
Q

What is the special feature of cardiac muscle?

A

It is myogenic

24
Q

What does myogenic mean?

A

It has its own heart rate, known as the Synus Rhythym

25
Q

What is a Synus Rhythm?

A

Any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sino-atrial node

26
Q

What are the two nodes that control the cardiac cycle?

A
  1. Sino-Atrial Node

2. Atrio-Ventricular Node

27
Q

Where is the SAN located?

A

Right atrium

28
Q

What are the features of the electrical conduction system of the heart?

A
  • SAN
  • AVN
  • Bundle of His
  • Purkinje Fibres
29
Q

What happens when a contraction occurs?

A

A wave of depolarisation spreads from the SAN

30
Q

Describe how the heart beat is initiated and controlled?

A
  1. SAN in the wall of the right atrium sends a wave of depolarisation across the two atria causing them to contract
  2. The wave of depolarisation is stopped by the septum between atria and ventricles
  3. This delay allows the atriole systole to be completed
  4. AVN receives wave of depolarisation and then spends it own wave down the Bundle of His and Purkinje Fibres
  5. Ventricles contract from the base, upwards.
31
Q

Where does the inferior and superior vena cava bring blood from?

A

Superior- Upper body (arms and brain)

Inferior- Lower body (legs)

32
Q

Where does the left and ventricles force blood to?

A

Left- Body via aorta

Right- Lungs via pulmonary artery

33
Q

Why is the left ventricle much thicker than the right ventricle?

A

Left ventricle needs to be thicker to be able to generate enough force to push the blood all around the body. It has to pump against greater resistance. Compared to the right atrium which only has to force blood to the lungs, so less force is requires so the wall can be thinner (pump against smaller resistance)

34
Q

What can cause coronary arteries to become blocked?

A

Eating food with high cholesterol content can cause plaque to build up on the artery wall

35
Q

What can be done to treat coronary heart disease?

A

Angioplasty, where a balloon is inserted into the artery and inflated to allow better blood flow

36
Q

What causes the heart chambers to contract together?

A

Cardiac muscle is myogenic

37
Q

What factors maximise the efficiency of heart contractions?

A
  1. Substantial atrial to ventricular delay to allow the atria to completely empty their contents into the ventricles before the ventricles contract
  2. Coordinated contraction of ventricular myocytes to maximise systolic pressure to force blood through circulation
  3. Contract from bottom upwards of ventricles squeezes blood towards the exit, which is more efficient
  4. Wave of depolarisation spreads through cardiac muscle very quickly which allows cells of ventricles to contract almost simultaneously
38
Q

What are the Purkinje Fibres?

A

Specialised conducting fibres located in the inner ventricular walls. They conduct cardiac action quicker and more efficiently than any other cells in the heart

39
Q

What is an ECG?

A

Graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin

40
Q

What are the three main components of an ECG?

A
  1. P WAVE - represents depolarisation of atria
  2. QRS COMPLEX - represents depolarisation of ventricles
  3. T WAVE - represents repolarisation of ventricles
41
Q

What is Bradychardia?

A

SAN dysfunction with a rate that is generally lower than normal
> 60bpm

42
Q

What is Tachychardia?

A

Elevated sinus rhythm, an increase in the rate of electrical impulses arising from the SAN
>100bpm

43
Q

What is an ectopic beat?

A

An extra contraction that is not in the normal rhythm

Often a premature ventricular contraction that is initiated by the Purkinje fibres opposed to the SAN

44
Q

What is atrial fibrillation?

A

Rapid and irregular contractions of the atria

Causes the heart to pump blood inefficiently as the atria are not able to fill up completely before contracting

45
Q

What is an artifical pacemaker?

A

A medical device that generates electrical impulses delivered by electrodes to cause the heart chambers to contract
Primary purpose is to to maintain an adequate heart rate

46
Q

Why may someone need a pacemaker?

A
  1. SAN is not fast enough

2. There is a block in the heart’s electrical conduction system

Biology (33 decks)

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