Cardiovascular system Flashcards
What is the function of cardiovascular system?
To maintain an adaptable supply of blood to the tissue.
What is hemodynamics?
The study of the blood flow. It is determined by resistance and pressure difference
What is Darcy’s Law?
F (flow)= Pressure difference / resistance difference
What determines resistance?
Length of vessel, radius of vessels, fluid viscosity.
What is the equation of resistance?
R = rLn / pi x r^4
What is systole?
Contraction
Why could blood pressure increase with age?
The systole blood pressure can increases because of artery stiffness or blocked artery.
How would you calculate the Mean Arterial pressure?
Diastolic Pressure + 1/3 pulse pressure.
What is pulse pressure?
The difference between systole and diastole pressure.
Describe the conduction pathway of the heart
SA node down the right atria to the AV node. A delay to allow atrial contraction and blood to go into ventricle. Down the bundle of His and then at the apex branches into the Purkinje fibres. This causes ventricular contraction.
Describe the cardiac cycle
1) Atrial systole
2) Atrial diastole
3) Ventricular systole
4) Ventricular diastole
5) Blood fills ventricles from atrias passively
What isometric ventricular contraction?
Change in pressure without change in volume. Occurs in early ventricular systole.
What is ECG?
Electrocardiogram. Detects electrical responses of the heart. Shown as the graph seen in hospital.
What order does the ECG waves go?
P-wave, QRS complex, T wave.
What is the P wave?
Atrial contraction
What is the QRS complex
Shows the contraction of ventricles. The atrial relaxation is masked and causes a sharp peek instead of wave.
What is the T-wave?
Ventricular relaxation and masks atria contraction
What is QT- interval?
The time from initiation of ventricular contraction to the end of ventricular relaxation.
What is the equation of cardiac output?
Cardiac Output = Heart rate x stoke volume.
What is stroke volume ?
Volume of blood ejection by each ventricle per beat.
What is repolarisation?
When relaxing occurs
What is depolarisation?
When contraction occurs
What does innervate mean?
To supply nerves to.
Give the three ways the heart can be innervated
1) As a result of blood volume
2) Autonomic Innervation (Parasympathetic and Sympathetic nerves)
3) Sympathetic via adrenal gland (secreting hormones such as adrenaline and noradrenaline)
Does noradrenaline increase heart rate?
Yes
Does acetlycholine increase heart rate?
No, slows down
Does adrenaline increase heart rate?
Yes
What is the vagus nerve?
A parasympathetic nerve which innervates the heart and decreases heart rate.
What is a chronotropic effect?
Those that change the heart rate. Positive chronotropes increase heart rate and negative decrease heart rate.
What is used more in resting heart rate, Parasympathetic or sympathetic?
Parasympathetic, sympathetic only a little
What is the average heart range for an adult?
60-100 Bpm
Give the equation for stroke volume?
End diastolic Volume - End systolic Volume
What factors affect stroke volume?
Preload, contractility and afterload.
What is Preload?
Venous return and Filling time.
What is venous return determines by?
Posture (standing decreased venous return), muscle pump and respiratory pump moves blood into the atria.
What is Starlings Law?
The energy of contraction is proportional to the initial length of the cardiac muscle fibre
What is Tachycardia?
Fast heart rate (>100)
What is Bradycardia
Slow heart rate (<60)
What is contractility?
The contractile ability of cardiac muscle at a given preload
What is inotropic agent?
Increasing or decreasing the strength of muscular contraction. Negatively weakens contractions, positively is increasing strength.
What is Blood pressure?
The force placed on the wall of blood vessels by blood as it flows.
What is the equation for Blood pressure?
Blood pressure = Cardiac Output x Total Peripheral Resistance
What determines the total peripheral resistance (TPR)?
The difference in arteriole diameter.
What do baroreceptors detect?
Blood pressure
What do chemoreceptors detect?
CO2 level
What happens to increase Blood pressure?
Cardioacceleatory and vasomotor centre increase which increases vasoconstriction and increase CO and HR.
What happens to decrease Blood Pressure?
Cardioinhibitory centre is increased and the vasomotor centre decreases. This decreases CO, HR and decreases vasodilation.
Describe a long term mechanism for increasing blood volume and pressure
Kidney release Erythropoietin which increases red blood cell to increases blood volume and pressure. Renin is also released which leads to angiotensin 2. This stimulates thirst and secrete aldosterone which also increases blood volume
Describe a short term mechanism for decreasing blood volume and pressure?
Natriuretic peptides is released by the heart which increases Na+ and water loss in urine. Reduced thirst. Blockage of positive inotropic. vasodilation. To reduce blood volume and pressure
What is Net filtration pressure?
Net filtration pressure = Net hydrostatic pressure - Net colloid osmotic pressure.
What is the arteriole hydrostatic pressure?
35 mmHg
What is the venous hydrostatic pressure?
18 mmHg
What is the hydrostatic pressure of the interstitial fluid?
0 mmHg
What is the Net hydrostatic pressure?
Capillary HP- Interstitial fluid HP
What is the equation for the Net colloid osmotic pressure?
Blood colloid osmotic pressure (BCOP) - interstitial Fluid colloid osmotic pressure (ICOP)
What is the approx value for BCOP ?
25 mmHg
What is the approx value for ICOP?
0 mmHg
When does fluid move out of the capillary?
When the capillary hydrostatic pressure is grater than the colloid osmotic pressure
Where is the transition site found between filtration and reabsorption?
Closer to the venous end not in the centre because maximum filtration pressure is greater than maximum absorption pressure.
What happens to absorption when there is high blood pressure?
Less absorption because hydrostatic pressure increases throughout the capillary. This means there is a smaller difference between osmotic and HP.
What disease can occur if the COH is very high or the Osmotic pressure is really low
oedema due to extreme fluid collection
Why does pulmonary artery have a lower BP than systemic?
Because vascular resistance is very low. The arterioles are thinner wider and shorter.
What is the BP of pulmonary arteries?
10 mmHg
What does distensibility mean?
The vessels can swell as a result of pressure. This means can accommodate increased CO. Occurs in pulmonary circulation.
What is bigger in pulmonary circulation BCOP (osmotic pressure) or HP?
BCOP > CHP. This means there can be absorption throughout the capillary.
What can be a consequence in hypertension in pulmonary circulation?
Less absorption of fluids can lead to a build up in alveoli. So less respiration.
What blood pressure is for Hypertension?
140/90
What is primary hypertension?
The most common type of hypertension. It is due to unknown medical conditions
What is secondary hypertension?
Occurs due to medical causes such as kidney disease.
How does Ca2+ channel antagonists decrease blood pressure?
cause vasodilation and decrease CO
How does Angiotensin 2 Receptor Antagonists decrease blood pressure?
Blocks the actions of the angiotensin 2, which causes vasoconstriction and normally increases the heart blood pressure.
How does Angiotensin converting Enzyme inhibitors decrease blood pressure?
Inhibits angiotensin 2 and stops absorption of Na+/ H20 and vasoconstriction.
How does Thiazide Diuretics decrease blood pressure?
Increases Na+ and water loss
How does a-blockers decrease blood pressure
Inhibits noradrenaline and reduces the Total Peripheral Resistance (TPR) which decreases blood pressure
How does B blockers decrease blood pressure?
Decreases rein secretion.
What are risks of high blood pressure?
Atherosclerosis, stroke, heart failure, renal failure and aneurysms
What is Arteriosclerosis?
The hardening and thickening of artery walls due to loss of tissue elasticity. Happens with aging
What is Atherosclerosis?
Fatty plaque in the wall of blood vessel. It narrows the lumen of the vessel and so restricts blood flow. Can cause damage of endothelium.
What is Ischaemic Heart Disease?
Heart attack due to atherosclerosis in the coronary artery. When blood flow is insufficient.
What is regurgitation?
Back flow of blood
What is stenosis?
Inadequate opening of the valve.
What is Arrhythmias?
Deviation from the heart’s normal SAN rhythm. E.g irregular heartbeat
What are causes of Bradycardia?
Slowed SAN signal, pause at the SAN, conducting damage.
What is the cause of Inappropriate Sinus Tachycardia?
Caffine, amphetamines, overactive thyroid gland
What causes non-sinus Tachycardia?
Abnormal impulses caused by automaticity, triggered beats and re-entry/ circus activity. Detected by ECG
What is thrombosis?
Blood clot forms in veins (occurs mainly in legs)
What is Ventricular fibrillation (Automaticity)?
Uncontrolled twitching or quivering of muscle fibres. Blood doesn’t move out of the heart and can result in death.
What is triggered beats?
A cause of Tachycardia (non-sinus). Defect in ion channels so irregular depolarisation.
What is LQT syndrome?
Result of triggered beats. Affects repolarisation of the heart after a heart beat. Have irregular heartbeat.
What is Re-entry or circus movement?
When the transmission of electrical impulses is abnormal. Occurs due to heart damage of conduction block
What is Chronic Heart failure?
When Cardiac output is inadequate despite venous return being adequate.
What is cause of chronic heart failure?
Damage to cardiac muscles so cannot contract strong enough. Stiff and thick chambers or stretched and thin chambers.
What symptoms of chronic heart failure?
Breathlessness, fatigue.
What happens if it is right ventricular failure?
Then the legs get swollen and purple
What happens if it is left ventricular failure?
Fluid builds up in the lungs due to congestion of the veins in the lungs,
