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Cardiovascular System
Systemic and pulmonary systems
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Pulmonary – blood to the lungs (right ventricle to left atrium), deoxygenated
blood (blue) to alveoli
Systemic – blood to the rest of the body (left ventricle to right atrium),
oxygenated blood (red)

Cardiac physiology
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Left ventricle – increased muscular mass and thicker walls – pump blood
around the body, whereas right ventricle only pumps blood to lungs (higher
blood pressure required for LV)
Baroreceptors in carotid arteries in close proximity to the brain;
deoxygenation in the brain leading to loss of consciousness
Vasoconstriction – constriction of arteries to increase blood pressure
(opposite = vasodilation)

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Increase in size

decrease in pressure

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Decrease in size increase in pressure

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Unidirectional movement of blood through valves – pressure gradient
Aorta – largest artery, Vena cava – largest vein
Interventricular septum – wall between ventricles prevents blood mixing

Pericardium (“around the heart”)
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Triple layered
Keeps heart in place but allows movement
Two portions – fibrous (tough and elastic dense, connective tissue) and serous
(thinner, delicate, membrane bound, double layered – parietal and visceral)
Pericardial cavity – in between parietal and visceral serous layers, reduces
friction between layers of serous pericardium, filled with fluid
...
Pressure build-up
in aorta causes closure, preventing backflow
Heart murmur – occurs in blood moves backwards through a defective valve

SA and AV nodes
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Sinoatrial (SA) node – group of autorhythmic cells located in the wall of the
right atrium, sets the rate and timing of cardiac muscle cell contraction
Atrioventricular (AV) node – impulses are delayed for approximately 0
...
Valves prevent bidirectional flow of blood
Vasodilation (relaxation of smooth muscle in arteriole) – causes fall in blood
pressure
Vasoconstriction (contraction of smooth muscle in arteriole) – increase blood
pressure

Generation of Action Potential in the Heart
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Three main ions important in heart function – Na+, Ca2+ and K+
Sodium-potassium pump (Na+/K+/ATPase) – movement of 3 sodium ions into
cells, 2 potassium ions out, slow influx of calcium ions
Calcium ions bring cell voltage down (82 to 20 mv)

Coronary System
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Encased around the heart
Small blood vessels internally and externally to heart
Thinner than aorta and vena cava
Fatty streaks – deposits of fat, dislodged fat from aorta which can block
coronary arteries

Blood Pressure
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Systolic blood pressure – Pressure in the arteries when the heart contracts
...
Readings above
140 mmHg considered to be hypertension
Diastolic blood pressure – indicates pressure in the arteries when the heart
rests between beats, minimal arterial pressure during relaxation and dilation
of ventricles
Pulse pressure – difference between systolic and diastolic readings
...
Manually
recorded (fingers on wrist)
Mean arterial pressure – average blood pressure in an individual in one
cardiac cycle

Blood Pressure Regulation
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Determinants – blood volume, elasticity, cardiac output, peripheral resistance

Neural Pathways (Medulla Oblongata)
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Baroreceptors and chemoreceptors in carotid arteries and aortic arch detect
changes in pressure and pH respectively
Sympathetic pathway – SAN increases heart rate, increase in diastolic
depolarisation, increased number of contractions, release of adrenaline and
noradrenaline increase breathing rate
Parasympathetic pathway – release of acetylcholine to decrease heart rate,
decreased number of contractions, reduced breathing rate
Down-regulation of sympathetic pathway – decrease in heart rate and stroke
volume – decreased blood pressure
Vasodilation – decrease in peripheral resistance
Decreased blood pressure – down-regulation of parasympathetic pathway
Vasoconstriction – increase peripheral resistance – increased blood pressure

Humoral Pathway (Renin-Angiotensin-Aldosterone System)
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In response to falling blood pressure, juxtaglomerular cells in the kidney
secrete Renin into the blood, which converts he plasma protein Angiotensin to
Angiotensin I
Angiotensin I is converted to Angiotensin II by the Angiotensin converting
enzyme in the lungs
...
Blood surges through the tear,
causing the inner and middle layers to dissect
Aneurysm – localised swelling of blood vessels, usually occurring in the brain
(brain aneurysm) or aorta (abdominal aortic aneurysm)
Myocarditis – inflammation of the heart muscle, usually caused by viral
infection
Pericarditis – swelling of the pericardium, usually as a result of infection
...
Can result in stroke or heart attack
Treatment – anticoagulant medication, such as Heparin

Systolic Hypertension
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Elevated systolic blood pressure of over 140 mmHg
Isolated systolic hypertension – elevated systolic blood pressure but normal
diastolic blood pressure (less than 90 mmHg)
Causes include artery stiffness, overactive thyroid (hyperthyroidism) or
diabetes
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Lead to health problems such as stroke, heart disease and chronic kidney
disease
Reduced compliance of aorta with increased age
...
Can also occur in pregnancy
Symptoms – medication not reacting, sudden onset of high blood pressure
before 30 or after 55
Diagnosis – ECG, urinalysis, blood tests, kidney ultrasound
Treatment – β-blockers, thiazide diuretics



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