Flashcards in Heart Deck (65):
What is the name of the groove between the sinus venarum and pectinate muscles in the right atrium?
The sulcus terminalis on the outside, and crista terminalis on the inside.
What is the formula for blood pressure?
Blood pressure = cardiac output * peripheral resistance
Does the septum secundum develop of the left or right side of the septum primum?
Right side, it develops from the top and grows down and also from the endocardial cushions and grows up.
What causes the pacemaker potential in nodal cells?
Funny channels opening and allowing a slow influx of sodium ions (a funny current). Also, transient Ca2+ ions briefly open.
L-type calcium channels open as phase 0 is initiated.
What are SERCA channels in the myocardium?
Sarco-Endoplasmic Reticulum Ca2+-ATPase, which pump Ca2+ back into the sarcoplasmic reticulum to relax the cardiac muscle.
What happens in phase 0 of a ventricular action potential?
There is rapid depolarisation as voltage-gated fast Na+ channels open.
What happens in phase 1 of a ventricular action potential?
K+ channels open so there is a transient outward current of K+, and the Na+ channels are inactivated.
What happens in phase 2 of a ventricular action potential?
L-type Ca2+ channels open so that Ca2+ diffuses into the cell and the depolarisation is maintained. (Calcium induced - calcium release occurs in the cell.)
What happens in phase 3 of a ventricular action potential?
The Ca2+ conductance is decreased, the K+ delayed rectifier channels open, and the SERCA channels open so Ca2+ is removed from the cytosol.
At a normal heart rate of 70bpm, what is the duration of systole?
At a normal heart rate of 70bpm, what is the duration of diastole?
What is the Frank-Starling law of the heart?
The strength of the heart's systolic contraction is directly proportional to its diastolic expansion (preload) with the result that under normal physiological conditions the heart pumps out of the right atrium all the blood returned to it without letting any back up in the veins.
What factors affect cardiac output?
1) Preload. (The degree of stretch experienced by the ventricular muscles during diastole - directly proportional to end diastolic volume.)
2) Afterload. (Tension required by ventricular muscles to force open the semilunar valves and eject blood.)
3) Contractility. (Force produced by contraction of the ventricles at a given preload.)
What is the equation that links pressure gradient to blood flow?
Flow = Change in pressure/Resistance.
What is the action of vasodilators and local vasodilators?
To promote the relaxation of pre-capillary sphincters.
What is the name of the sounds you hear when measuring blood pressure?
What is pulse pressure?
The difference between systolic and diastolic pressure.
What is mean arterial pressure (MAP)?
MAP = diastolic pressure + (pulse pressure)/3.
What factors affect blood pressure?
Blood volume, blood viscosity, peripheral resistance, total length of blood vessels, cardiac output, age, gender.
What is the mechanism of action of digoxin and other cardiac glycosides?
Digoxin inhibits the K+/Na+ ATPase in the myocardium. This causes a build up of Na+ inside the cells so that the Na+/Ca2+ exchanger can no longer work, so Ca2+ accumulates inside the cells so the force of contraction is increased (positive inotropy), but the rate of contraction is decreased because the ionic balance is not restored (negative chronotropy and negative lusitropy).
What is the mechanism of action of acetylcholine released by parasympathetic stimulation of the vagus nerve in the myocardium?
The acetylcholine binds to muscarinic receptors (GPCR) which activate GIRK receptors (G protein inwardly rectifying channel) which pumps K+ out of the cell to depolarise it and decrease contractility.
ACh also inhibits the T-type calcium channel to stop Ca2+ entry from extracellular fluid.
What is the Haldane effect?
The lower the amount of oxyhaemoglobin in the blood, the higher the carbon dioxide carrying capacity of the blood.
What is the mechanism of action of adrenaline and noradrenaline released by sympathetic nerves in the myocardium?
Adrenaline and noradrenaline bind to B1 adrenergic receptors (GPCR) in the myocardium. This activates adenylate cyclase to produce cAMP from ATP, which then activates protein kinase A. Protein kinase A phosphorylates the L-type Ca2+ channels (dihydropyridine channels) so they stay open longer. This means there is a bigger Ca2+ influx into the myocardium so more troponin-C is bound and tropomyosin moved to expose myosin binding site, and the contractility is increased.
Also, lusitropy requires two channels to remove Ca2+ from the cytosol (Na+/Ca2+ exchanger in the sarcolemma, and SERCA in the sarcoplasmic reticulum). Protein kinase A phosphorylates phospholamban to stop it inhibiting SERCA, so faster relaxation, and more Ca2+ stored in sarcoplasmic reticulum, and more released for the next contraction.
What does the R wave on the ECG represent?
The depolarisation of the inter ventricular septum down to the apex.
What is the P-R interval on an ECG?
The time taken for the signal to pass from the AV node to the ventricle.
Why does atropine increase heart rate?
Atropine generally decreases the activity of the parasympathetic system, so the firing of the SA node is increased.
Does the autorrhythmic firing of the nerve fibres in the myocardium increase or decrease in rate as you proceed from the SA node to the Purkinje fibres and the cardiac myocytes?
Decrease in rate, so that sinus rhythm (caused by spontaneous depolarisation of the SA node) has the fastest rate, and each subsequent nerve fibre has a slower rate if it is stimulating itself and not being stilted from outside nervous impulses.
What might cause a murmur?
1) Blood flow through a leaking valve.
2) Blood flow through a narrowed (stenotic) valve.
3) Blood flow through an abnormal shunt.
4) Excessive blood flow through a normal valve.
What happens when the atria release atrial natriuretic peptide?
When the stretch receptors in the atria detect high blood pressure, atrial natriuretic peptide is secreted which is a vasodilator and stimulated the excretion of sodium and therefore water.
What do the stretch receptors in the atria do?
When blood pressure is increased, the stretch receptors in the atria cause the atria to release atrial natriuretic peptide which decreases the reabsorption of sodium and therefore water, so blood pressure decreases.
In which component of the heart is electrical conduction the slowest?
The atrio-ventricular node.
Where is the vertical height measured from when looking at the JVP?
The sternal angle.
When does blood flow into the coronary arteries?
What is the smooth part of the right atrium (not the pectinate muscles) called, and what does it develop from?
Sinus venarum, from the sinus venosus.
Where is the pulmonary valve best heard from?
2nd left intercostal space.
What is the immediately posterior relation of the pulmonary artery?
The transverse pericardial sinus.
What is the tetralogy of Fallot?
Right ventricular hypertrophy
Interventricular septal defect
(All caused by abnormality in development of aorticopulmonary septum)
What are the three layers of pericardium?
What is formed by the J shaped reflection between the parietal and visceral pericardium that surrounds the pulmonary veins?
Oblique pericardial sinus.
What is formed by the passage between the two sites of reflected serous pericardium, that is posterior to the ascending aorta and pulmonary trunk?
Transverse pericardial sinus
Where does the heart lie on the left and right side of the sternum?
Right side - parasternal region, between 3rd and 6th costal cartilages
Left side - between 2nd costal cartilage and 5th intercostal space midclavicular line
Heart is from level T5 to T8
Match the heart surfaces to the chambers.
Base = left atrium
Right pulmonary surface = right atrium
Left pulmonary surface and diaphragmatic surface = left ventricle
Anterior (sternocostal) surface = right ventricle.
What four things make up right margin of the heart?
Right brachiocephalic vein, superior vena cava, right atrium, inferior vena cava.
What three things make up the left margin of the heart?
Arch of aorta, pulmonary trunk, left ventricle.
What makes up the inferior margin of the heart?
Mostly right ventricle.
What is contained in the coronary sulcus?
Coronary sinus, right coronary artery, circumflex branch of left coronary artery.
What is contained in the anterior interventricular sulcus?
Left anterior descending artery, great cardiac vein.
What is contained in the posterior interventricular sulcus?
Posterior interventricular artery, middle cardiac vein.
Name the two parts of the right atrium and their embryological origin. What are they separated by?
Sinus venarum - smooth part derived from sinus venosus
Pectinate muscles - rough part from the primitive atrium
Separated by the crisis terminal is on the inside and sulcus terminals on the outside
Name three features of the right ventricle.
Papillary muscles connected by chordate tendinae to tricuspid valve
Infundibulum (conus arteriosus)
What is the embryological origin of the fossa ovalis?
What is directly posterior to the left atrium?
Oblique pericardial sinus.
What is the usual pace set by the sino-atrial node (in the upper border of the crista terminalis)? What is the usual pace set by the ventricles?
Sinus = ~60bpm
Ventricles = ~40bpm
Though what orifice does blood enter the right atrium?
What is the embryological origin of the infundibulum (smooth part) of the right ventricle?
What is the purpose of papillary muscles and chordate tendinae?
To keep the tricuspid valve shut so there isn't a backflow of blood when the ventricles contract.
What is the moderator band?
It is the septomarginal trabecula (trabeculum septomarginalis) which bridges between the lower portion of the interventricular septum and the anterior papillary muscle, carrying the right bundle of the atrioventricular bundle (Bundle of His) so functions in cardiac conduction.
How does blood enter the left ventricle?
Through the left atrioventricular orifice.
Which of the aortic sinuses does the right coronary artery originate from, and which does the left coronary artery originate from?
Right coronary artery from anterior aortic sinus
Left coronary artery from left posterior aortic sinus
What is unusual about the coronary arteries?
They are the only arteries that fill up during diastole, so they are at lower pressure than all other arteries.
During diastole the blood pressure is maintained by elastic recoil of the aorta.
Name the branches of the right coronary artery.
Sinu-atrial nodal branch.
Right marginal artery.
Posterior interventricular branch.
Name the branches of the left coronary artery.
Anterior interventricular artery (left anterior descending).
Left circumflex branch.
Left marginal artery.
Which arteries do the great coronary vein, middle coronary vein, small coronary vein run along with?
Great coronary vein - runs in anterior interventricular sulcus, along with left anterior interventricular artery
Middle coronary vein - runs in posterior interventricular sulcus, along with posterior interventricular artery
Small coronary vein - runs with marginal arteries
What are the vessels called that supply the walls of larger vessels?