Cardiovascular P1 Flashcards
1
Q
What is Cardiovascular system made up of?
A
The heart, Blood and Blood vessels
2
Q
In which direction do arteries pump the blood?
A
Away from the heart (typically with oxygenated blood)
3
Q
In which direction do veins carry the blood?
A
Back to the heart (typically deoxygenated blood except for the pulmonary veins)
4
Q
What do capillaries do?
A
Permit nutrient, waste and gas exchange.
5
Q
Where does the heart sit?
A
Near the anterior (front of the chest wall, behind the sternum.
Sits in the mediastinum (middle section of the chest) and slightly to the left.
Surrounded on both sides by the lungs.
6
Q
What makes up the heart wall?
A
Three layers.
Epicardium (outer)
Myocardium (middle)
Endocardium (inner)
7
Q
Outer layer of the heart - also known as the visceral pericardium
A
Epicardium
8
Q
Muscular wall of the heart - contains cardiac muscle tissue, vasculature and nerves.
A
Myocardium
9
Q
Inner layer of the heart - lining of epithelial cells
A
Endocardium
10
Q
Visceral
A
Internal organs
11
Q
How many times does the heart beat each day?
A
Approx 100,000 times a day
12
Q
How many times does the heart beat each year?
A
35 million times per year
13
Q
How much blood does the heart pump each day?
A
14,000 litres of blood per day
14
Q
How much blood does the heart pump each year?
A
5 million litres per year.
15
Q
Is the heart reliant on the nervous system for activation?
A
No, ANS and endocrine system can modulate function.
16
Q
Which side of the heart connects to the body?
A
The left
17
Q
Which side of the heart pumps blood to the lungs?
A
The right, it enables gas exchange.
18
Q
What does the pulmonary circuit do?
A
oxygenate blood and remove CO2.
19
Q
What does the systemic circuit do?
A
Supplies cells with O2 and nutrients and removes CO2 and waste.
20
Q
What is the total blood volume of a female?
A
4-5 litres
21
Q
What is the total blood volume of a male?
A
5-6 Litres
22
Q
Where is the bulk of the blood found?
A
Systemic veins and venules (blood reservoirs) 64%
23
Q
How much blood lies in the Pulmonary vessels?
A
9%
24
Q
How much blood lies in the heart?
A
7%
25
How much blood lies in the systemic arteries and arterioles?
13%
26
How much blood lies in the systemic capillaries?
7%
27
What does the right atrium do?
Receives blood from the systemic circuit through the two great veins: the superior vena cava and the inferior vena cava.
It also receives blood from the coronary sinu.
28
What does the superior vena cava do?
Delivers blood to the heart from the head, neck, upper limbs, and chest.
29
What does the inferior vena cava do?
Delivers blood to the heart from the rest of the trunk, the viscera and the lower limbs.
30
What does the coronary sinus do?
Receives blood from the coronary veins.
31
32
What separates the left and right atria?
The interatrial septum.
33
What does the left atrium do?
Receives blood from the pulmonary circuit via four pulmonary veins - two left pulmonary veins and two right pulmonary veins.
34
What does the right ventricle do?
Pumps blood low in oxygen to the lungs via the pulmonary valve.
- Thicker myocardium compared to both atria.
35
What are trabeculae carneae?
Protruding ridges of myocardium found on the inner ventricular surface.
36
How many chambers does the heart have?
4
37
What is the role of the left ventricle?
To pump the oxygenated blood around the systemic circuit.
- Thickest heart chamber.
- Myocardium required to generate high pressure to force blood throughout body.
-Contains trabeculae carneae and papillary muscles.
38
What is the difference between the right and left ventricles?
- Pressure required to pump through pulmonary and systemic circulation.
- Left ventricle is thicker.
39
Where do the pectinate muscles lie?
Right Atrium - in the anterior atrial wall and inner surface of the auricle.
40
What are the heart valves?
- Two atrioventricular valves
- Two semilunar valves
41
What is the job of the heart valves?
- To guide the blood flow through the heart.
- Prevents backflow of blood through the heart.
42
Where are the atrioventricular valves located?
Between atria and ventricles.
43
What are the main components of the AV valves?
- Cusps that open and close.
- Chordae tendineae that prevent the cusps from eversion (turning inside out).
- When open, permits filling of ventricle, but when ventricular contraction occurs, pressure forces them shut.
- Directs blood through semillunar valves.
44
What is the right AV valve?
Tricuspid valve (three cusps)
45
What is the left AV valve?
Bicuspid/mitral valve (two cusps)
46
Where are the semilunar valves located?
- Aortic valve at base of aorta.
- Pulmonary valve at the base of the pulmonary trunk.
47
What do Papillary Muscles do?
- Cone shaped muscles extend from ventricle base.
Anchor the chordae tendineae of the right atrioventricular valve (tricuspid valve).
-Anchor the chordae tendineae of the left atrioventricular valve (bicuspid/mitral valve)
48
What are the characteristics of the semilunar valves?
- Simple valves with cusps that have a half-moon shape.
- open when blood pressure in the ventricles is higher than that in the aorta and pulmonary trunk.
- Higher blood pressure forces the cusps apart and blood flows through the arteries.
49
What prevents the heart valves from stretching under load?
Dense connective tissue rings around each of the four valves forming a fibrous skeleton.
- The tissue acts as an insertion point for cardiac muscle cells and electrically insulates the atria from the ventricles.
50
What do the coronary arteries come from?
the base of the ascending aorta.
- provide most of the blood to the heart
51
Coronary Veins
drains the oxygen poor blood from the heart tissue to the coronary sinus.
52
Does the heart muscle require stimulation from the nervous system?
No, relies on two factors - autorhythmic fibres and special cell junctions.
53
What is heart muscle made of?
striations and sarcomeres that allow for contractility, short (50-100 um), larger and more numerous mitochondria.
54
What does heart muscle do?
pump blood into circulation
55
What does desmosomes do for the heart muscle?
Used for attachment of sacrolemmas of neighbouring muscle fibres.
56
What do gap junctions do for the heart muscle?
-Permits the passage of ions.
- Used to facilitate the conduction of action potentials from one muscle fibre to the next.
57
How do autorhythmic fibres work?
- Spontaneously generate action potentials that spread through gap junctions to neighbouring fibres.
- Act as pacemakers.
- Activate heart's contractile muscle fibres.
58
How does blood flow through the heart?
Right atrium (deoxy blood) -> Tricuspid valve -> Right ventricle -> Pulmonary valve -> Pulmonary trunk and pulmonary arteries -> Pulmonary capillaries (blood lose CO2 and gains O2) -> pulmonary veins (oxy blood) -> Left atrium -> Bicuspid valve -> Left ventricle -> Aortic valve -> Aorta and systemic arteries -> systemic capillaries (blood loses O2 and gains CO2) -> superior vena cava & inferior vena cava & coronary sinus ->
59
How does the Intrinsic conduction system work? SA
- Starts in the sinoatrial (SA) node (located near the top of the right atrium.
- Autorhythmic fibres repeatedly depolarise and repolarise (no stable resting potential)
- Each action potential spreads across both right and left atria via muscle fibre gap junctions.
- Which results in the contraction of the myocardium in both atria at the same time.
60
How does the Intrinsic conduction system work? AV
- Atrioventricular Node (AV)
- Located in the interatrial septum near the base of the right atrium.
- Next step of the conduction system.
- Cell structure creates a bottle neck effect for the conduction pathway.
* Results in a delay of around 100 m/sec
- This delay in the heart's conduction system allows the ventricles to fill with blood.
61
How does the Intrinsic conduction system work? AV Bundle HIS
- Atrioventricular (AV) bundle
* Runs from the AV node and down the upper section of the interventricular septum.
- Vital for the conduction of action potentials from the atria to the ventricles.
* Heart's fibrous skeleton electrically insulates the atria from the ventricles.
62
What is the stable resting potential for cardiac contractile fibres?
~ - 90 mV.
63
What is the rate of depolarisation in the SA node, AV node, AV bundle, bundle branches and Purkinje fibres?
SA Node = 100 times per minute
AV Node = 40-60 times per minute.
AV Bundle, bundle branches and purkinje fibres = 20 -35 times per minute
64
What happens when cardiac contractile fibres are depolarised?
(depolarised by neighbouring cells).
- causes opening of voltage gated Na+ channels.
-Na+ influx down electrochemical gradient.
- Results in rapid depolarisation.
65
What follows depolarisation of CCF?
- plateau phase
* Depolarisation is maintained (0.25 s)
* Caused by opening of slow Ca++ channels
* Limited Ca++ entry into matched by slow K+ efflux.
- Repolarisation via rapid efflux of K+ due to opening of voltage Gated K+ channels.
- Contraction simular to skeletal muscles.
* Ca++ bind to troponin, moving tropomyosin and permitting binding of actin and myosin.
66
What is the timing of the intrinsic conduction system?
Step 1- SA node activity and atrial activation begin. Time = 0.
Step 2 - Stimulus spreads across the atrial surfaces and reaches AV node. Elapsed time = 50 msec.
Step 3 - There is a 100-msec delay at the AV node. Atrial contraction begins. Elapsed time = 150 msec.
Step 4 - The impulse travels along the interventricular septum within the AV bundle and the bundle branches to the Purkinje fibres and, via the moderator band, to the papillary muscles of the right ventricle. Elapsed time = 175 msec.
Step 5- the impulse is distributed by purkinje fibres and relayed throughout the ventricular myocardium. Atrial contraction is completed and ventricular contraction begins. Elapsed time = 225 msec
67
How does an ECG work?
- Detects the electrical activity of the heart at the surface of the skin.
- ECG is the recording of this.
- Typically achieved by a 12 lead ECG.
- Consists of 10 electrodes.
* One on each limb (limb leads)
* Remaining 6 in an arc around the heart (chest leads)
- Can produce 12 ECG traces (leads) from different combinations of limb and chest electrodes.
68
What does a P wave mean on an ECG?
Atrial depolarisation
69
What does a T wave mean on an ECG?
Ventricular repolarisation
70
What does a QRS Complex mean on an ECG?
Ventricular depolarisation
71
How does the Intrinsic conduction system work? Bundle Branches
- represents a left and right division of the AV bundle.
- Run down the interventricular septum to the apex of the heart.
72
How does the Intrinsic conduction system work? Purkinje Fibres
- Run from the bundle branches and up each ventricle wall.
- Large-diameter fibres that rapidly conduct the action potentials resulting in ventricular contraction.
73
How are autorhythmic cell action potentials generated?
- No stable resting membrane potential
- Constantly generates action potentials.
- Slower depolarisation compared to neurons.
* Due to Ca++ being the primary cause of depolarisation.
* Slower influx across the cell membrane.
- Repolarisation due to efflux of K+
* Ca++ channels close.
- electrochemical gradients are restored via the Na+-Ca++ exchanger (NCX) and NA+/K+ pump.
74
What is the Cardiac output?
Volume of blood pumped per minute
CO = stroke volume x heart rate.
75
What is stroke volume?
- Volume of blood pumped by left ventricle per beat.
76
What is the Cardiac output of a Stroke volume of 70 ml and a heart rate of 75 bpm?
0.070 L x 75 = 5.25 litres.
77
Can cardiac output be modulated depending on physiological requirements?
Yes, achieved primarily by the nervous system.
78
How is the heart controlled via the nervous system? (para)
-Parasympathetic activity via the vagus nerve releases acetylcholine (ACh) which reduces heart rate.
79
How is the heart controlled via the nervous system? (symp)
- Sympathetic activity via the cardiac accelerator nerves releases norepinephrine (noradrenaline)
* Binds to beta-1 receptors on cardiac muscle fibres.
* Increases depolarisation rate in SA and Av nodes
* Increases contractility via heightened CA++ entry into contractile fibres.
80
How is the heart controlled via the nervous system? mo
-Modulation of Cardiac output is initiated in the cardiovascular centre in the medulla oblongata.
81
How is the heart controlled via the nervous system? (cv)
- The cardiovascular centre receives information from:
* The cerebral cortex, limbic system and the hypothalamus.
* Proprioceptors, baroreceptors and chemoreceptors.
- Then sends out signals via the parasympathetic system or sympathetic system.
82
What are the input to the cardiovascular centre via the nervous system?
FROM HIGHER BRAIN CENTRES-
cerebral cortex, limbic system, and hypothalamus.
FROM SENSORY RECEPTORS -
- Proprioceptors - monitor movements
- Chemoreceptors - Monitor blood chemistry.
- Baroreceptors - monitor blood pressure.
83
What are the output to the cardiovascular centre via the nervous system?
FROM CARDIAC ACCELERATOR NERVES (symp)
- increased rate of spontaneous depolarisation in SA node (and AV Node) increases heart rate
- Increased contractility of atria and ventricles which increases stroke volume.
Vagus Nerves (para)
- Decreased rate of spontaneous depolarisation in SA node (and AV node) decreases heart rate.
