CVS Flashcards
What are some characteristics of coronary arteries?
They supply the myocardium with oxygenated blood.
They are functional end arteries.
They are prone to atheroma.
What are the 3 types of arteries and what does the size of the artery depend on?
Large arteries are elastic arteries, such as the aorta.
Medium sized arteries are distributing arteries, such as the renal arteries.
Small arteries are resistance vessels, the arterioles - help control blood pressure.
The size of the arteries mainly depends on the thickness of the muscle.
By what factor can the cardiac output increase by during exercise?
Between 4 and 7 times - the CO increases from 5L/min to 20-35L/min.
What is serum?
It is plasma without the clotting factors.
Why does turbulent flow occur, and where is it seen?
It occurs when the flow of blood is disorganised, when the pressure is greater than the flow can match.
It occurs when there is a change in direction of a vessel, and in stenoses.
What is a stenosis?
An abnormal narrowing of an artery or a heart valve.
Why is the velocity at the capillary level so slow?
Due to the large cross-sectional area, there is a much larger volume for the blood to fill.
Below what pressure does organ perfusion become impaired?
70mmHg.
What will the effect on pulse pressure be with exercise, and why?
Increase in pulse pressure because stroke volume increases, and vasodilation occurs, decreasing the afterload.
What are the names referred to for blood flow that can be felt and heard?
Thrill can be felt.
Bruit can be heard.
What are the two layers of the serous membrane around the heart adhered to?
The parietal layer is adhered to the fibrous pericardium.
The visceral layer is adhered to the epicardium.
What is central venous pressure and arterial pressure?
CVP = the pressure in the large veins draining into the heart.
Arterial pressure = the pressure in the large arteries.
How does smooth muscle work to meet the demands of tissues, close to their targets?
The arterioles and pre-capillary sphincters will dilate.
What does the ventricular compliance curve state?
The higher the venous pressure, the more the ventricles fill.
The more the heart fills, the higher the left ventricular pressure.
What does the ventricular filling depend on?
The greater the venous pressure, the greater the filling.
The greater the compliance of the ventricles, the greater the filling.
What is calcium sensitivity of the heart influenced by?
The stretch of the muscle fibres - the greater the stretch of the muscle fibres, the greater the calcium sensitivity.
What is contractility?
The force of contraction, for a given fibre length.
What happens to the total peripheral resistance when metabolism increases, and what is the effect on arterial and venous pressure?
It decreases to supply more blood to meet the demand.
This means that arterial will decrease and venous pressure will increase.
What is the response of the heart to a decrease in arterial blood pressure?
It will increase contractility and heart rate to increase cardiac output, and so the arterial blood pressure will also increase.
What is jugular venous pressure measured in?
Cm of H2O.
What is the length of a cardiac action potential?
Relatively long at 280ms.
How long is the action potential held at the AV node for, and why does this occur?
120ms.
This is because the ventricles need time to fill before contracting.
What percentage of ventricular filling is accounted by atrial contraction?
10%.
What is the average EDV and ESV?
EDV = 120ml.
ESV = 50ml.
When is the S3 sound normal and abnormal?
It is normal in ventricular filling in children, but abnormal in adults.
What is heard in:
- Aortic valve stenosis.
- Aortic valve regurgitation.
- Mitral valve regurgitation.
- Mitral valve stenosis.
Aortic stenosis = systolic murmur: crescendo-decrescendo.
Aortic regurgitation = diastolic murmur: early decrescendo diastolic murmur.
Mitral regurgitation = systolic murmur: holosystolic.
Mitral valve stenosis = diastolic murmur: snap as the valve open - diastolic rumble.
What are the cardiogenic fields derived from?
The mesoderm.
What do the 6 parts of the primitive heart tube go on to form?
Aortic roots - forms the arteries of the aortic arch.
Truncus arteroisus - forms the pulmonary trunk and aorta.
Bulbous cordis - forms the pulmonary trunk and aorta.
Primitive ventricle - forms the ventricles.
Primitive atrium - forms the atria.
Sinus venosus - forms part of the right atrium and vena cava.
What is the sinus venosus split into?
The left and right sinus horns.
What does the left sinus horn become?
The coronary sinus - drains blood from the coronary vessels into the right atrium.
Where does the trabeculated and smooth muscle of the heart come from?
Trabeculated is from the primitive atrium and ventricle.
Smooth is from the pulmonary veins.
What are the 5 different aortic arches?
I, II, III, IV, VI.
V does not form.
What do the left and right aortic arches of the 6th, 4th, and 3rd arches form?
The 6th left and right aortic arches form the pulmonary arteries.
The 4th left aortic arch form the arch of the aorta.
The 4th right aortic arch forms the right subclavian.
The 3rd left and right aortic arches form the common carotids and the first part of the internal carotids.
Why does the laryngeal nerve only loop behind the 4th aortic arch on the right and not left?
Because some of the 6th aortic arch on the right is remodelled.
What is central cyanosis?
Where the partial pressure of oxygen in the systemic tissues is low, leading to a blue discolouration of the face, mouth and tongue.
Why does patent ductus arteriosus result in right-sided heart failure?
Blood flows from the aorta to the pulmonary artery, increasing after load of the right side of the heart, which increases the workload and oxygen demand of the right side of the heart, leading to right-sided heart failure.
Why does pulmonary hypertension and oedema occur with atrial septal defects? What else can it lead to?
Blood flows from the left atrium into the right atrium, increasing the blood volume and pressure being pumped to the lungs. This increases the hydrostatic pressure in the lungs, which can cause a small amount of pulmonary oedema, but it can also cause fibrosis of the arteries of the lungs, increasing the hydrostatic pressure further.
Due to the increase in pulmonary pressure, there can be right-sided heart failure.
Eventually, what happens in an atrial septal defect, and what is it referred to as?
The increased after load increases the pressure in the right side of the heart sufficiently to lead to blood being pumped into the left side of the heart, referred to as Eisenmenger’s syndrome.
Why is patent foramen ovale not classed as an atrial septal defect?
It is a unidirectional shunt from the right to left atria (but the blood doesn’t actually tend to move in any direction due to the increased pressure in the left atrium). There is no defect in the septum of the atria.
What is the hole called that is formed during embryology and persists, most commonly, in a ventricular septal defect? If left untreated, what will form?
Primary interventricular foramen.
Pulmonary hypertension and right-sided heart failure.
What causes hypoplastic left heart?
Mitral or aortic valve stenosis, causing less blood to flow into the left ventricle, leading to its underdevelopment.
When do right to left shunts occur?
When there is a defect in the atrial or ventricular septa, with an obstruction, increasing the pressure in the right side of the heart.
What is Ek?
The equilibrium position at which the movement of potassium ions inside and outside the cell are equal, around -95mV.
What is the main factor that affects the resting membrane potential of ventricular myocytes?
The leaky potassium channels.
What type of channels are used in the funny current? What do they allow the movement of, and in what direction?
HCN channels - hyperpolarisation-activated cyclic nucleotide-gated channels.
They allow the influx of sodium ions.
What is the plasma potassium concentration range?
3.5 - 5.5mM.
Give some examples of where M2 and M3 receptors are found.
M2 are seen in the heart.
M3 are seen in the pupil of the eye, the airways of the lungs and sweat glands.
What nerve gives parasympathetic input to the heart, and what receptor is acted upon for what result?
The vagus nerve releases ACh onto M2 receptors.
These are located on the SA and AV nodes to decrease the rate of contraction.
Why does the parasympathetic nervous system not decrease the force of contraction of the heart?
There are no M2 receptors on the myocardium.