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Physiology, neurobiology and cell signalling > Lecture 13: The heart as a pump > Flashcards

Lecture 13: The heart as a pump Flashcards

Tuesday 11th February 2025

1
Q

How many deaths in the UK are cardiovascular related?

A

1/3 of deaths in the UK are cardiovascular related.

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2
Q

How many people in the UK die from cardiovascular disease yearly?

A

> 180,000, which is 1 in 3 of all deaths.

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3
Q

How many people in the UK die of coronary heart disease yearly?

A
  • 82, 000
  • ## 20% are male and 12% are female
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4
Q

How many people in the Uk die of stroke yearly?

A

> 49,000

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5
Q

How often do people die of heart attacks in the UK?

A

Every 6 minutes

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6
Q

What is the function of the cardiovascular system?

A
  • To deliver oxygen and sugar to respiring tissues and to remove CO2 and the products of metabolism.
  • This allows for homeostasis to occur and for hormones to be delivered to their site of action.
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7
Q

What is the weight of the human heart?

A

between 200 to 425g.

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8
Q

How many times a day does the heart beat?

A

It beats ~100,000/day

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9
Q

How many litres of blood does the heart pump a day?

A

~7,000 litres of blood/day.

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10
Q

Mice have a high SA:vol ration, so…

A
  • They lose surface heat all the time.
  • This means that their heart pumps several times per min (450/min).
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11
Q

Is it true that humans have the highest number of lifetime heartbeats?

A
  • Yes
  • 2.21 billion beats over an average of 70 years, despite a moderate heart rate (75 bpm).
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12
Q

Despite having a slower heart rate than many small animals, humans live long enough to accumulate the highest total number of heartbeats.

It reflects how different species balance heart rate and lifespan, potentially linked to metabolic rates and evolutionary adaptations.

A

Despite having a slower heart rate than many small animals, humans live long enough to accumulate the highest total number of heartbeats.

It reflects how different species balance heart rate and lifespan, potentially linked to metabolic rates and evolutionary adaptations.

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13
Q

What is the position of he heart?

A

The heart sits centrally with the
apex situated on the left side

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14
Q

What controls blood flow in the heart?

A

The heart valves

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15
Q

What does the superior vena cava do?

A

Carries deoxygenated blood from the head and other major body organs back to the right atrium of the heart.

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16
Q

What does the inferior vena cava do?

A

Brings deoxygenated blood from other parts of the body to the right atrium of the heart.

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17
Q

Tricuspid valve …

A

Controls blood flow from the right atrium to the right ventricle, preventing backflow.

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18
Q

Pulmonary valve…

A

Regulates blood leaving the right ventricle into the pulmonary artery toward the lungs.

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19
Q

Mitral (bicuspid) valve…

A

Allows blood to flow from the left atrium to the left ventricle, blocking backward flow.

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20
Q

Aortic valve…

A

Opens to let blood leave the left ventricle into the aorta, then closes to stop it from returning.

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21
Q

Describe blood flow in the heart

A

Deoxygenated blood from the body enters the right atrium via the superior and inferior vena cava.

Blood flows through the tricuspid valve into the right ventricle.

The right ventricle pumps it through the pulmonary valve into the pulmonary artery, sending it to the lungs to pick up oxygen.

Oxygenated blood returns from the lungs into the left atrium via the pulmonary veins.

It then flows through the mitral (bicuspid) valve into the left ventricle.

The left ventricle pumps the oxygen-rich blood through the aortic valve into the aorta, which distributes it to the rest of the body.

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22
Q

Why does the left side of the heart have thicker walls than the right side?

A

Because the left side of the heart operates under significantly higher pressure than the right side.

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23
Q

Systemic: higher pressure blood

Pulmonary: lower pressure blood

A

Systemic: higher pressure blood

Pulmonary: lower pressure blood

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24
Q

Is it true that the heart spends twice as much time in diastole (relaxing) than it does in systole?

A

Yes

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25
What happens during systole?
The ventricles contract and push blood into the arteries.
26
What happens during diastole?
The heart relaxes and fills with blood from the atria.
27
Why does the heart spend more time in diastole?
The heart spends more time in diastole because it’s a recovery and refill phase that ensures efficient pumping, proper oxygenation, and heart health.
28
What is mean arterial pressure?
- Mean arterial pressure (MAP) is the average pressure in your arteries during a heartbeat, showing how well blood is flowing to your organs. - It weighs diastolic pressure more because the heart spends more time in diastole.
29
What is the equation for mean arterial pressure?
Mean arterial pressure = 1/3 systole + 2/3 diastole
30
do systole and diastole both contain the same volume of blood?
Yes
31
Does the heart spend double the amount of time in diastole than it does in systole?
Yes
32
Tricuspid valve..
- Shut in systole - Open in diastole
33
Pulmonary valve..
- open in systole - shut in diastole
34
Mitral/bicuspid valve...
- shut in systole - open in diastole
35
Aortic valve...
- open in systole - shut in diastole
36
Is it true that the closing of the valves gives rise to the heart sounds?
Yes
37
Why do the heart valves shut in sequence?
To prevent backflow and to make sure that the blood only travels in one direction.
38
What causes the heart sounds?
The closing of the heart valves (mostly the higher pressure parts).
39
In what type of heart can a 3rd heart sound be found?
In an unhealthy heart
40
What is the equation for cardiac output?
Cardiac output = stroke volume × heart rate
41
What is cardiac output dependant on?
The number of beats and their volume.
42
What is the cardiac output?
The amount of blood your heart pumps in one minute.
43
What is the heart rate?
how many times your heart beats per minute.
44
What is the stroke volume?
how much blood is pumped out with each beat.
45
At rest what is your heart beat?
At rest, your heart beats around 70 times per minute.
46
How many ml of blood does each beat pump (stroke volume) ?
Each beat pumps about 70 milliliters (mL) of blood.
47
How many litres of blood per minute does the heart pump at rest? (cardiac output)
- Your heart pumps about 5 liters of blood per minute at rest — which is roughly your entire blood volume! That means your heart circulates all your blood once every minute at rest. -
48
What happens to the cardiac output during exercise and why?
It increases because your body and muscles needs way more oxygen and nutrients. CO2 and lactic acid also need to be removed at a much quicker rate.
49
Describe Starling's law
- “The more the heart muscle is stretched during filling, the stronger it contracts.” - This increases the stroke volume
50
Why does stretching cardiac muscle fibers increase the force of contraction?
- Because stretching cardiac muscle fibers makes them more sensitive to calcium (Ca²⁺). - More sensitivity = more forceful contraction.
51
Increased blood volume = increased stretch of myocardium Increased force to pump blood out
Increased blood volume = increased stretch of myocardium Increased force to pump blood out
52
Is it true that the pressure of the heart chambers and vessels determines valve open and closure?
Yes
53
What is meant by the fact that the heart is myogenic?
The heartbeat is initiated within the heart itself.
54
What is the sinoatrial node (SA)?
The pacemaker of the heart, which is made up of specialised muscle cells.
55
Why does the electrical impulse pause at the AV node?
To prevent premature contraction
56
Conduction pathway of the heart from atria to ventricles
Heartbeat is myogenic – initiated within the heart itself sinoatrial node (SA) – pacemaker of the heart: specialised muscle cells. Travels through the atrial muscle to the atrioventricular (AV) node Travels to ventricles through Purkinje fibres of the bundles of His and their branches It then spreads throughout the myocardium
57
Summarise the conduction pathway
SA node ---> AV node ---> Bundle of His ---> Purkinje fibres
58
What is the ionic pacemaker resting potential determined by?
Resting membrane potential is determined by K+.
59
What is depolarisation usually caused by?
- Depolarisation is generated by a reduced K+ and increased Na+ permeability - Depolarisation may also be produced by increased Ca2+ permeability.
60
In pacemaker cells, what is depolarisation caused by?
- Depolarisation is mostly due to calcium (Ca²⁺) influx, not sodium. - These cells have a different kind of action potential — slower and more rhythmic.
61
What initially causes depolarisation in pacemaker cells?
A membrane leak
62
Pacemaker potential depends on sodium (to get things started) Depolarisation in SA node depends on calcium (to fire the action potential)
Pacemaker potential depends on sodium (to get things started) Depolarisation in SA node depends on calcium (to fire the action potential)
63
What is the refractory period caused by?
- A delay in repolarisation caused by Ca2+. - Long refractory periods prevents tetanus in cardiac muscle.
64
"Ventricular myocyte refractory period depends on calcium"..
The length of the heart cell’s “rest period” (refractory time) is controlled by the flow of calcium during the action potential — especially in the plateau phase. This is not true for pacemaker cells.
65
What are myocytes?
branched muscles cells, with a single nucleus
66
How do muscle cells look under a microscope?
Striated
67
How are myocytes electrically coupled?
Myocytes are electrically coupled through intercalated disks
68
How aer myocytes connected?
By tight junctions
69
What is the contraction of myocytes activated by?
Contraction activated by entry of Ca2+ Principally from intracellular stores
70
So, while both are important for the heart's function, pacemaker cells are involved in generating the electrical signals that control heart rhythm, whereas myocytes are the muscle cells that contract in response to those electrical signals.
So, while both are important for the heart's function, pacemaker cells are involved in generating the electrical signals that control heart rhythm, whereas myocytes are the muscle cells that contract in response to those electrical signals.
71
P wave..
Atrial depolarization (the electrical impulse traveling through the atria).
72
QRS complex...
Ventricular depolarization (the electrical impulse traveling through the ventricles, causing them to contract).
73
T wave...
Ventricular repolarization (the electrical resetting of the ventricles after contraction).
74
Can ECG's be used to diagnose cardiac disease?
Yes
75
To summarise, this lecture has considered:
The systemic and pulmonary circulations in series The chambers and valves of the heart The changes of pressure and volume during the cardiac cycle The relationship between filling pressure and stroke work The initiation and spread of the heart beat Electrical activity and the ECG and the initiation of contraction
76
77
Is it true that atrial repolarisation is masked by the ventricles?
Yes
78

Physiology, neurobiology and cell signalling (20 decks)

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