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ANAT 1111 > CVS- The Heart (8) > Flashcards

CVS- The Heart (8) Flashcards

1
Q

What is the cardiovascular system?

A

> It provides the transport system that ensures blood continuously circulates to fulfil homeostatic need
Heart is transport system pump and blood vessels are the delivery route
Blood is transport medium and heart constantly propels oxygen, nutrients, wastes and other substances through blood vessels

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2
Q

What is the heart anatomy?

A

> Roughly size of fist
250-350g
Enclosed within mediastinum (medial cavity of thorax)- slightly left of midline, superior of diaphragm and anterior to vertebral column

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3
Q

What are the coverings of the heart (layers of the pericardium)?

A

1) Fibrous pericardium
2) Parietal pericardium
3) Serous pericardium
4) Visceral pericardium

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4
Q

What is the pericardium?

A

A double-walled sac that encloses the heart

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5
Q

What is the fibrous pericardium?

A

A superficial loose layer that protects the heart, anchors it to surrounding structures and prevent overfilling of heart with blood

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6
Q

What is the parietal pericardium?

A

> Lines the internal surface of the fibrous pericardium
At superior margin of heart, it attaches to the large arteries exiting the heart, then turns inferiorly and continues over the external heart surface as the visceral layer.

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7
Q

What is the serous pericardium?

A

> Thin, slippery, 2-layer serous membrane that forms a closed sac around the heart

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8
Q

What is the visceral layer?

A

> Also called epicardium

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9
Q

What is the pericardial cavity?

A

> Contains film of serous fluid
The serous membranes that are lubricated by the fluid glide smoothly past each other which allows the heart to work in a relatively-free friction environment

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10
Q

What is pericarditis?

A

Inflammation of the pericardium which roughens the serous membranes so when the heart beats it rubs against the sac, causing pain.

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11
Q

What are the 3 layers of the heart wall?

A

Epicardium
Myocardium
Endocardium

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12
Q

What is the myocardium?

A

> Composed of specialised cardiac muscles found only in the heart
Not under voluntary control
Forms the bulk of the heart and is the layer that contracts
Branching cardiac muscle cells are connected to one another by crisscrossing connective tissue fibres, arranged in spiral/circular bundles
These bundles link the whole heart together
The connective tissue forms the ‘fibrous skeleton of the heart’ which reinforces the myocardium and anchors the cardiac muscle fibres
The network of collagen and elastic fibres is thicker in some areas e.g. where vessels leave the heart and around the heart valves- without this, vessels and valves may become stretched due to continuous pressure of blood pumping through them
Connective tissue isn’t electrically excitable so the fibrous skeleton limits the spread of action potentials across the heart

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13
Q

What is the endocardium?

A

> Glistening white sheet of squamous endothelium resting on a thin connective tissue layer
On the inner myocardial surface, it lines the heart chambers and covers the fibrous skeleton of the valves
It is continuous with the endothelial linings of the blood vessels entering and leaving the heart.

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14
Q

What is the epicardium?

A

> The visceral layer of the heart

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15
Q

What is the pulmonary circulation loop?- part 1

A

> Happens on the right side of the heart
Right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into pulmonary trunk (this splits off to form the left and right pulmonary arteries)
Blood goes through pulmonary artery into lungs where it can be oxygenated and loses co2.
blood moves back into the heart by pulmonary veins into the left atria (area of lowest pressure).

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16
Q

What is the systemic loop?- part 2

A

> Happens on the left side of the heart
Left atrium contracts, increasing pressure so the blood moves through the mitral valve, into the left ventricle
Left ventricle contracts, increasing pressure so blood moves through the aortic semilunar valve into the aorta, sending blood to the rest of the body (transported by smaller systemic arteries).

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17
Q

Part 3

A

> Deoxygenated blood enters heart by superior vena cava and inferior vena cava into right atrium
Right atrium contracts, forcing blood through the tricuspid valve into the right ventricle

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18
Q

What is lub-dub?

A

Lub- Mitral and tricuspid valves closing- do this because ventricles contract to increase pressure to pump blood out of heart
> Dub- aortic and pulmonary semilunar valves closing

19
Q

What is systole?

A

Contraction of the heart muscle

20
Q

What is diastole?

A

Relaxation of the heart muscle

21
Q

What are the different pressures in the heart?

A

> Atria have low pressure and thin walls as only have to pump blood to the ventricles
Ventricles have high pressure and thick walls as have to pump blood around the body
Blood will flow from areas of high pressure to low pressure

22
Q

How is the heart divided into two?

A

The septum

23
Q

What is the main role of the valves?

A

To ensure that the flow of blood is unidirectional

24
Q

What are the AV heart valves?

A

> Atrioventricular valves lie between the atria and the ventricles
They prevent the back flow into the atria when the ventricles contract
Chordae tendineae anchor AV valves to papillary muscles
Tricuspid and mitral

25
Q

What is the aortic semilunar valve?

A

> Lies between the left ventricle and the aorta

> Prevents the back flow of blood into the ventricles

26
Q

What is the pulmonary semilunar valve?

A

> Lies between right ventricle and pulmonary trunk

> Prevents backflow of blood into the ventricles

27
Q

What supplies the heart with blood for its own nourishment?

A

> Coronary arteries
Supply blood flow to the myocardium
Deliver blood when heart is relaxed as it is ineffective to do so when the ventricles are contracting because they are compressed by the myocardium.

28
Q

How does the left coronary artery supply the heart?

A

> Supplies the left atrium and the left ventricle
It runs towards the left side of the heart and divides into 2 branches…
1) Anterior interventricular artery
2) Circumflex artery

29
Q

How does the right coronary artery supply the heart?

A

> Supplies the right atrium, right ventricle, sinoatrial node and AV nodes.
Has 2 branches…
1) Right marginal artery
2) Posterior interventricular artery

30
Q

What is the role of the coronary veins?

A

> To bring all the deoxygenated blood back to the right atrium, through the coronary sinus (seen by looking at a posterior view of the heart)
Coronary sinus has 3 main veins joining to it- small cardiac vein, middle cardiac vein and the great cardiac vein- these help to move the deoxygenated blood back to the right atrium
There is also the anterior cardiac veins which empty the deoxygenated blood directly into the right atrium, without going through the coronary sinus

31
Q

What is the sinoatrial node?

A

> Right atrium
Small mass of cells, just below the entrance of the superior vena cava
Called the pacemaker because it generates impulses 75X/min (without nervous and hormonal influences, would be 100X/min
Sets the pace for the whole heart (faster depolarisation rate than any other region in conduction system)
Its characteristic rhythm is called synus rhythm

32
Q

What is the atrioventricular (AV) node?

A

> The depolarisation wave spreads via junctions across the atria from the SA node to the AV node
Located in inferior (lower) part of interatrial septum, directly above the tricuspid valve
At the AV node, the impulse is delayed for approximately 0.1 secs, allowing the atria to respond and complete their contraction before the ventricles contract
Once through the AV node, the impulse can then pass through the rest of the system
If there is a problem with the SA node, the AV node will take over its functions however it is slower (40-60bpm)

33
Q

What is the atrioventricular bundle?

A

> Also called the bundle of His
The only electrical connection between the atria and the ventricles
Its a mass of specialised fibres that originates from the AV node and then passes through the fibrous ring which seperates the atria from the ventricles
When it meets the upper end of the interventricular septum, it divides into the left and right bundle branches which move towards the apex of the heart
Within the ventricular myocardium, they become purkinje fibres

34
Q

What are the purkinje fibres?

A

> The left and right bundle branches break up into fine fibres called purkinje fibres
The AV bundle (bundle of His), left and right bundle branches and the purkinje fibres all transmit electrical impulses to the apex of the myocardium
More elaborate on the left side of the heart

35
Q

What is the conduction pathway of the heart?

A

> SA node generates an impulse which rapidly spreads to the muscle fibres of the atria, making them contract
Impulse then picked up by AV node which then conducts it through the AV bundle (bundle of His) and the left and right bundle branches which causes the ventricles to contract
Time between initiation and depolarsation of ventricles is 0.22 secs in healthy heart

36
Q

What are the different rates for the autorhythmic cardiac cells?

A

> SA node= 75bpm
AV node= 40-60bpm
AV bundle and purkinje fibres= 30bpm
They occur in this order if the previous one fails- the slower ones cannot dominate the heart unless the faster ones stop functioning

37
Q

What is special about cardiac muscle fibres?

A

> They have special features which reflect its unique blood pumping role
Adjacent cardiac cells interlock with desmosomes which anchors the ends of cardiac muscle fibres together which allow ions to pass from cell to cell, transmitting a current across the entire heart
Due to this, myocardium acts as a single coordinated unit
Large mitochondria account for 25-35% of the volume of cardiac cells which means that cardiac cells are highly resistant to fatigue

38
Q

How does the heart contract?

A

> The heart possesses the property of autorhythmicity which means it generates its own electrical impulses and beats independently of nervous and hormonal control (it is not dependent on external mechanisms)
It is supplied with sympathetic and parasympathetic nerve fibres which increase and decrease the heart rate
It also responds to hormones e.g. adrenaline
The heart either contracts as a unit or not at all
Depolarisation wave travels across the heart via ion passage
There is a long refractory period in cardiac cells (after an impulse is initiated it is unable to initiate a new impulse for a certain amount of time)- Na channels are open.
- Prevents tetanic contractions which would stop the hearts pumping action

39
Q

What is the cardiac cycle?

A

> During each heartbeat, a cardiac cycle takes place

> Does not start at a particular point, it is a cycle

40
Q

What are the 3 stages of the cardiac cycle?

A

1) Atrial systole
2) Ventricular systole
3) Complete cardiac diastole

41
Q

What is the nerve supply to the heart?

A

> The heart is influenced by autonomic nerves from the cardiovascular centre in the medulla oblongata
Vegus nerve supplies SA and AV nodes and atrial muscle
Autonomic nervous system- parasympathetic slows HR, sympathetic nervous system increases HR.

42
Q

What is cardiac output?

A

> The amount of blood pumped out by each ventricle in 1 min
Measured in Litres/min
Stroke volume (SV) is the volume of blood pumped out by 1 ventricle with each beat (correlates with the force of ventricular contraction)

CO= HR X SV 
Normal= 75(bpm) X 70(ml) = 525 L/min

> Cardiac output varies depending on HR and SV

43
Q

What factors can affect heart rate?

A 
> Gender (female is quicker)
> Autonomic nervous system
> Age (faster when younger)
> Hormones e.g. adrenaline, thyroxine
> Activity/exercise 
> Temperature (faster when hotter)
> Emotional states
> Rest and relaxation
44
Q

What factors affect stroke volume?

A

> EDV
Position of the body
Strength of myocardial contraction
Blood volume

ANAT 1111 (14 decks)

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