38 Questions
What is the primary function of the conducting system of the heart?
To regulate the heartbeat and ensure coordinated contraction
Which of the following is NOT a learning outcome of this lecture?
Describe the structure of the cardiac veins
What is the term for the blockage of a coronary artery?
Coronary artery occlusion
What is the purpose of the coronary sinus?
To drain deoxygenated blood from the heart muscle
Which heart valves can be auscultated?
Mitral and tricuspid valves
How many parts does this lecture on the Dynamics of the Heartbeat consist of?
3
What is the primary function of the coronary arteries?
To supply the heart muscle with blood during diastole
What is the significance of the term 'coronary' in relation to the coronary arteries?
It resembles a crown, hence the two coronary arteries run around the atrioventricular groove
Which of the following is NOT a branch of the right coronary artery?
Interventricular septum
Which cardiac vein is not directly involved in draining the right ventricle?
Coronary sinus
What is the percentage of occlusions that occur in the circumflex artery?
10-20%
What is the main reason why the coronary arteries are considered functionally end-arteries?
Because occlusion of either results in necrosis of the territory supplied by that artery
What is the primary region supplied by the left coronary artery?
The left heart
What is the name of the mixture of cells and cellular debris that contain lipids, calcium, and fibrous connective tissue?
Atheroma
What is the clinical condition that results from the occlusion of a coronary artery?
Angina pectoris
What is the term for the branch of the right coronary artery that supplies the sinu-atrial node?
SA nodal artery
What is the significance of knowing the branches of the coronary arteries?
To understand the territory of supply in the event of coronary artery occlusion
What is the term for the sudden decrease in blood flow to heart muscle?
Myocardial ischaemia
What is the term for the region where the right coronary artery loops around the coronary sulcus?
Crux
Which artery is most commonly occluded?
Anterior interventricular artery
What is the term for the clump that forms from the build-up of material between the endothelium and tunica media of the blood vessels?
Atheromatous plaque
What is the consequence of the rupture of the plaque in the coronary artery?
Formation of a blood clot or thrombus
What is the origin of preganglionic sympathetic nerves to the heart?
T1-T4
Where can the postganglionic sympathetic nerves to the heart be found?
In all three cervical ganglia and T1 to T4 paravertebral ganglia
What is the location of the cardiac plexus?
Both in front and behind the aortic arch
What is the relationship between the sympathetic and parasympathetic nerves in the cardiac plexus?
They mingle together
What is the name of the nerve that emerges from the superior cervical ganglion?
Superior cardiac nerve
What is the color of the sympathetic nerves in the diagram?
Yellow
What is the location of the cervical sympathetic ganglia in the neck?
Close to the main artery ascending up to the brain
What is the relationship between the cervical sympathetic nerves and the vagal branches in the neck?
The cervical sympathetic nerves descend through the neck, close to the vagal branches
What is the origin of the word 'angina'?
Greek word for a strangling
What is the medical term for the death of cardiac muscle due to lack of blood supply?
Myocardial infarction
Which regions of the spinal cord receive the visceral sensation from the heart?
T1-T4 regions
What is the term for the type of pain experienced in angina pectoris?
Referred pain
What is the characteristic of a 'silent' myocardial infarction?
No symptoms at all
What is the duration of symptoms during a heart attack?
30 minutes or longer
What is the common location of referred pain in angina pectoris?
Left upper arm and forearm
What is the description of the pain experienced by patients during a heart attack?
Crushing and severe
Study Notes
The Conducting System of the Heart
- The conducting system of the heart includes the preganglionic sympathetic nerves, which arise from T1-T4, and the postganglionic nerves, which are found in the cervical ganglia (superior, middle, and inferior) and the T1 to T4 paravertebral ganglia.
- The cervical sympathetic nerves descend through the neck, close to the vagal branches, and mingle with parasympathetic nerves in the cardiac plexus before being distributed to the heart.
Arteries and Veins in the Neck
- The internal carotid artery and common carotid artery are located in the neck, accompanied by a bundle of nerves, including the sympathetic and parasympathetic cardiac nerves.
- The superior, middle, and inferior cervical ganglia are located near the internal carotid artery and common carotid artery, giving rise to sympathetic cardiac nerves.
Coronary Arteries
- The coronary arteries fill during diastole, supplying the heart muscle with blood while it is in a relaxed state.
- The right coronary artery supplies the "right heart," and the left coronary artery supplies the "left heart," with minimal anastomosis between them.
- The coronary arteries supply the myocardium and conducting system, with the right coronary artery supplying the SAN and AVN, and the left supplying the interventricular septum.
Right Coronary Artery
- The right coronary artery emerges from the right coronary ostium and gives branches to the conus arteriosus, sinu-atrial node, and right marginal artery.
- The right coronary artery loops around the coronary sulcus posteriorly to reach the crux, where it is joined by the middle cardiac vein and small cardiac veins draining the right ventricle.
Coronary Artery Occlusion
- The most common occlusion occurs in the anterior interventricular artery (40-50%), followed by the right coronary artery (30-40%), and the circumflex artery (10-20%).
- Coronary artery occlusion occurs due to the build-up of an atheroma, a mixture of cells, cellular debris, lipids, calcium, and fibrous connective tissue, which forms an atheromatous plaque that can bulge towards the lumen and occlude the artery.
Angina Pectoris and Myocardial Infarction
- Angina pectoris is the pain felt in the centre of the chest, radiating to the left arm and forearm, caused by myocardial ischaemia due to coronary artery occlusion.
- A heart attack, or myocardial infarction, occurs when the heart muscle dies due to lack of blood supply, leading to symptoms such as sweating, vomiting, dizziness, weakness, shortness of breath, and rapid or irregular heartbeats.
Visceral Sensation and Referred Pain
- Visceral sensation from the heart is carried back to the T1-T4 regions of the spinal cord, and the brain interprets these pain fibres as originating in the skin, creating a perception of pain in the left upper forearm, arm, and armpit.
- This is an example of referred pain.
Learn about the conducting system of the heart, its electrical system and how it works. Understand the dynamics of the heartbeat and its functions.
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