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PHSL 101 > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

(76 cards)

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1
Q

Functions of the CVS?

A

Delivers oxygen and nutrients around the body, removes waste products and maintains blood flow - determined by pressure and resistance.

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2
Q

Anatomy of the Heart? (4)

A

Left side = oxygenated blood
Right side = deoxygenated blood
The walls of the atria and ventricles are made of cardiac muscle tissue (myocardium)
The left ventricle is 3x thicker than the right because it generates more force.

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3
Q

Describe the blood flow through the heart.

A

Deoxygenated blood from the body returns to the heart through the vena cava. It enters the right atrium and into right ventricle. Blood is then pumped out of the right ventricle through the pulmonary trunk to the lungs.

Blood becomes oxygenated in the lungs

Oxygenated blood from the lungs travels back to the heart through the pulmonary veins into the left atrium. It then flows into the left ventricle and pumped into the aorta to flow around the body.

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4
Q

What are atrioventricular valves (AV Valves)?

A

Between the atria and ventricles (left - bicuspid, right - tricuspid).
They prevent the backflow of blood from the ventricles into the atria.
They are connected to papillary muscles by the chordae tendinea.

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5
Q

What are semilunar valves (SL Valves)?

A

Between the ventricles and arteries (right - pulmonary valve, left - aortic valve).
They prevent the backflow of blood from the major arteries into the ventricles.
They are thick cusps of connective tissue - fill with blood from the arteries to close without needing muscle.

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6
Q

What is the Sinoatrial (SA) Node?

A

The ‘pacemaker’ region of the heart. Produces action potentials to generate the heartbeat - the action potentials depolarise cells.

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7
Q

Whats the electrical signal pathway?

A

Sinoatrial node –> internodal pathway –> atrioventricular node –> moderator band –> purkinje fibres

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8
Q

What is an ECG?

A

Electro cardio gram - measures the electrical activity in the heart

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9
Q

What is diastole?

A

The relaxation phase (2/3 of cardiac cycle)
Ventricles relax and fill with blood

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10
Q

What is systole?

A

The contraction phase (1/3 of cardiac cycle)
Ventricles contract and pump blood out of the heart

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11
Q

Describe the start of the cardiac cycle.

A

All four chambers are relaxed, SA node spontaneously releases action potential.
Pressure in the atria is higher than in the ventricle - AV vales are open
Pressure in the artery is higher than in the ventricle - SL Valves are closed

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12
Q

What happens in step 1 of the cardiac cycle?

A

Ventricular filling 2 - diastole
Atria depolarise and contract = ECG P-wave
AV valves are open
SL valves are closed

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13
Q

What happens in step 2 of the cardiac cycle?

A

Isovolumetric contraction - systole
Ventricles depolarise and start to contract = QRS Complex
AV valves are closed
SL valves are closed
Pressure builds in ventricles but no volume change = isovolumetric

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14
Q

What happens in step 3 of the cardiac cycle?

A

Ventricular ejection - systole
Ventricles are still depolarised and continue to contract = no new electrical activity
AV valves are closed
SL valves are open

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15
Q

What happens in step 4 of the cardiac cycle?

A

Isovolumetric relaxation - diastole
Ventricles repolarise and relax = T-wave
AV valves are closed
SL valves are closed

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16
Q

What happens in step 5 of the cardiac cycle?

A

Ventricular filling 1 - diastole
All chambers are repolarised and relaxed
AV valves open
SL valves closed

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17
Q

What is heart sound 1?

A

“lub” happens with closing of the AV valves as the ventricles contract. Happens after the QRS complex, ventricles depolarise and contract

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18
Q

What is heart sound 2?

A

“dub” happens with closing of the SL valves as the ventricles relax. Happens after the T-wave, ventricles repolarise and relax

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19
Q

What is Heart rate?

A

How often the heart goes through one complete cardiac cycle. In a healthy adult, HR ~60-100bpm at rest
Slower = bradycardia
Faster = tachycardia

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20
Q

What is stroke volume?

A

How much blood the left ventricle pumps out in one heart beat. In a healthy adult, SV is ~70ml at rest

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21
Q

What is cardiac output?

A

CO = HR x SV
Volume of blood pumped per min. In a healthy adult, CO ~5L/min at rest

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22
Q

What is flow determined by?

A

F = P/R
Pressure gradient
Resistance

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23
Q

What is pressure gradient determined by?

A

By the pressure generated by the left ventricle during contraction.
Pressure in the arteries is higher than in the venous system

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24
Q

What is resistance proportional and inversely proportional to?

A

Resistance = 8nl/πr^4 (poiseuille’s law)
Proportional to: Fluid viscosity (n) and Blood vessel length (l)
Inversely to: Blood vessel radius (r)
Increased resistance = reduced flow

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25
What is flow proportional and inversely proportional to?
Proportional to: pressure gradient (P) and blood vessel radius (r) Inversely to: resistance (r), blood vessel length (l) and fluid viscosity (n)
26
What is laminar flow?
Smooth flow through vessels
27
What is turbulent flow?
Increases resistance and reduces flow eg. plaque deposit in vessels
28
What are arteries? (5)
Arteries carry blood away from the heart Have thick walls and large diameters Combination of elastic tissue and smooth muscle layers Low resistance vessels Provide a pressure reservoir
29
What are elastic arteries? (4)
The aorta is an elastic artery. Elastic arteries reduce fluctuations in flow and pressure from ventricle ejection. Reduces pulsatile flow to provide steady blood flow into smaller arteries High compliance vessels
30
What are muscular arteries? (3)
Medium-sized arteries Contain more smooth muscle than elastic arteries Distribute blood to skeletal muscle and internal organs through arterioles
31
What are arterioles? (4)
Arterioles are the smallest type of arteries Contain smooth muscle and endothelium Responsible for determining relative blood flow to individual organs Main factor for determining mean arterial blood pressure
32
What is pulse pressure?
Pulse pressure is SP-DP Systolic pressure (SP) - peak pressure in arteries, ~120mmHg Diastolic pressure (DP) - ~80-90mmHg
33
What is mean arterial blood pressure (MABP)?
MABP = (1/3 x PP) + DP MABP is tightly regulated as it drives blood flow to the tissue throughout the cardiac cycle MABP = CO x TPR
34
What is Total Peripheral Resistance (TPR)?
The combined resistance to blood flow of all the systemic blood vessels. It's determined by: - Vascular resistance - Fluid viscosity - Turbulence
35
What is the most common mechanism to alter blood flow?
To change the radius of the vessel (flow is proportional to radius)
36
What is vasodilation?
When blood vessels become wider. Radius increases, resistance decreases, flow increases
37
What are physiological vasodilators? (4)
Adrenaline acting on Beta receptors in vessels Increased nitric oxide released by endothelium Atrial natriuretic peptide Local increases in CO2 levels
38
What is vasoconstriction?
When blood vessels become narrower. Radius decreases, resistance increases, flow decreases
39
What are physiological vasoconstrictors? (4)
Adrenaline acting on Alpha receptors in vessels Endothelin - 1 release by endothelium Vasopressin and angiotensin II Local increases in O2 levels
40
What are sympathetic nerves? (4)
Innervate arterioles Controlled by the brainstem Release noradrenaline onto the smooth muscle cells of the blood vessel Activates a-adrenergic receptors
41
What is hypermia?
Increased blood in vessels It's a physiological response to a regional increase in metabolic activity, eg. the skeletal muscle Key response to maintaining blood flow to muscle during exercise Increased activity in tissue/organ --> increased CO2, decreased O2 --> triggers regional vasodilation --> increased blood flow to tissue/organ
42
What is flow autoregulation?
The CVS tries to maintain blood flow. If arterial pressure is changed, the blood vessels themselves can respond to keep flow constant = myogenic autoregulation
43
What are capillaries?
Thin walled vessels made of endothelial cells, no smooth muscle layer. Network of blood vessels between arterioles and venules and where exchange occurs
44
What are the 3 main types of capillaries?
1. Continuous - least 'leaky' 2. Fenestrated - 'In between types' 3. Sinusoidal - most 'leaky'
45
Of all the blood vessels, capillaries have:
Smallest diameter Largest cross-sectional area Lowest velocity of blood flow
46
What does capillary exchange involved a combination of?
Filtration Diffusion Osmosis
47
Where can capillary exchange occur?
Across the endothelial cell membrane (directly or through channels) Through pores of fenestrated capillaries By vesicle transport
48
What is filtration determined by?
Capillary hydrostatic pressure (CHP) Blood colloid osmotic pressure (BCOP)
49
What is CHP?
Capillary Hydrostatic Pressure Blood pressure within the capillaries The driving force to PUSH fluid out of the blood stream Highest at start of capillary bed
50
What is BCOP?
Blood colloid osmotic pressure Osmotic pressure within the blood Force which PULLS fluid into the blood stream Increases when water leaves the blood but solutes left behind
51
What is net filtration pressure (NFP)?
The difference between CHP and BCOP - CHP > BCOP = filtration = positive NFP (start of capillary) - CHP < BCOP = reabsorption = negative NFP (end of capillary) - CHP = BCOP = no net movement (middle of capillary)
52
What is diffusion determined by?
Concentration gradient Solubility Size
53
What are venules?
Smallest of the venous vessels, thin walled They collect blood form the capillary beds Venules unite to form the larger veins to return blood to the heart
54
What are veins? (6)
Veins carry blood back to the heart Have thinner walls and less smooth muscle than arteries Higher compliance vessels than arteries Veins are highly distensible - can change volume easy Provide a volume reservoir The vena cavae are the largest veins in the body
55
What are red blood cells?
Largest component of the formed elements in whole blood (99.9%): erythrocyte Major function is to carry oxygen - bound to haemoglobin
56
What are white blood cells?
Account for <0.1% of all blood cells Critical function in the body's defence against pathogens and toxins. Neutrophils and lymphocytes are the most abundant
57
What are platelets?
<0.1% of the formed elements in blood Flattened discs that are continuously replaced Clump together and stick to damaged blood vessel walls and release chemicals to trigger blood clotting
58
What are the 3 steps of haemostasis?
1. Vascular phase - vessel constricts to reduce blood flow 2. Platelet Phase - platelets adhere to site of injury, them aggregate and clump 3. Coagulation Phase - fibrous blood clot is formed
59
Where does the sympathetic pathway originate?
In the cardioacceleratory centre
60
Where does the parasympathetic pathway originate?
In the cardioinhibitory centre
61
What do nerves innervate?
Sinoatrial Node Ventricular Myocardium (mostly sympathetic) Atrial Myocardium
62
What do sympathetic nerves release?
Release noradrenaline which binds to beta-adrenergic receptors in the heart
63
Sympathetic nerve activity in the SA Node:
B-receptor activation reduces the resting repolarisation of the cells Cells reach threshold faster = more action potentials Heart rate increases
64
Sympathetic nerve activity in the ventricular and atrial myocardium:
B-receptor activation increases the amount of force produced during contraction Atria and ventricles contract harder and faster and therefore can relax faster Stroke volume increases B-receptor activation speeds up calcium cycling inside the muscle cells
65
What do parasympathetic nerves release?
Release acetylcholine which causes potassium channels in the heart to open
66
Parasympathetic nerve activity in the SA node:
K+ channel activation hyperpolarises the nodal cells Cells reach threshold slower = fewer action potentials Heart rate decreases
67
Parasympathetic nerve activity in the atrial myocardium and ventricle muscle:
Atria contract less Less filling of the ventricles Stroke volume decreases No significant effect in ventricle
68
What is postural hypotension when lying down?
When lying down, the gradient of pressure through our body is low because they are all at a similar height. Therefore gravity has minimal effect on blood pressure
69
What is postural hypotension when stand?
If you stand suddenly, blood will pool in the veins of the legs due to gravity. Increased blood in the veins means less blood returns to the heart = lower venous return. Lower SV Reduced CO BP drops (hypotension)
70
How do we meet the increased metabolic demand during exercise?
Increasing Cardiac Output (CO)
71
What happens to our heart rate during exercise?
When we exercise, the brain responds by decreasing parasympathetic and increasing sympathetic activity to the SA node = Increased HR.
72
What happens to our stroke volume during exercise?
When we exercise, the brain responds by increasing sympathetic activity to the ventricle = increased SV
73
What happens to the cardiac cycle during exercise?
The cardiac cycle becomes shorter as heart rate increases. Most due to diastole shortening as the heart relaxes faster.
74
What happens to our venous system when we exercise?
Increased contractions in exercising muscle pushes more blood out of the veins back to the heart = increased venous return
75
Where is blood flow increased and decreased to during exercise?
Increased to: skeletal muscle, heart and the skin - mainly due to local increase in metabolites - stimulates local vasodilation Decreased to: Kidneys, gut and abdominal organs - mainly due to increased sympathetic activity to non-essential organs during exercise - stimulates regional arteriole vasoconstriction
76
What happens to our blood pressure during exercise?
During exercise, - large increase in CO - some blood vessels dilate and some constrict so overall, TPR is slightly decreased - MABP slightly increases (MABP = CO x TPR)

PHSL 101 (10 decks)

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