Coronary Circulation & Conduction System Flashcards
what are the 5 key physiological features of the heart
chronotropy dromotropy (conduction) bathmotropy (excitability) ionotropy (contractility) Lusitropy (relaxation)
blood supply to the heart tissue
supplied by coronary arteries and their branches
Right coronary artery (RCA)
Left coronary artery (LCA)
where does the endocardium receive oxygen and nutrients from
the chambers of the heart
what and where are the coronary arteries
the only branches of the ascending aorta and they emerge in the aortic sinuses
what happens to the aortic sinus during systole
they fill up which means that coronary arteries also fill up
during systole they are blocked off as the valves are pushed open
RCA
arises from the right aortic sinus
- has a SA nodal branch, supplies the node of the conduction system
- its atrial branches supply the right atrium
- the right (acute) marginal branch
- usually gives off posterior inter ventricular branch (aka posterior descending artery)
- anastomoses with branches of left coronary artery in the artery sulcus at the apex
LCA
arises from the left aortic sinus between the left auricle and the pulmonary trunk
- shorter but thicker than the RCA
- enters the coronary sulcus and divides into the circumflex and the anterior interventricular branches (LAD)
LAD - left anterior inter ventricular descending artery (2nd branch of the LCA)
- supplies the sternocostal surface
- anasomoses with posterior inter ventricular branch of the RCA at the apex
- artery of sudden death, as when it gets blocked it causes instant death
circumflex branch of the LCA
branches to the left (obtuse) marginal branch which anastomoses with the branches of the RCA
RCA and its branches supply
- the walls of the RA and RV
- SA and AV nodes
- Posterior part of the inter ventricular septum (the proximal portion of the bundle of His)
- Small areas of the walls of LA and LV
LCA and its branches supply
- Walls of LA and LV
- most of the atrioventricular septum including part of the AV bundle
CORONARY DOMINANCE
✓ The artery that gives off the posterior interventricular/posterior descending artery determines the coronary dominance
✓ In ~80% of the people RCA is dominant
If both are involves it is called coronary co-dominance
Where and what is the likelihood of a myocardial infarction happening in what artier
LAD - 40-50%
RCA - 30-40%
Circumflex 15-20%
what damage could of myocardial infarction do to the conducting system
if its in the LAD = it supplies the AV bundles
RCA supplies both the SA and AV nodes
Heart block can cause bradycardia
Coronary Artery Bypass Grafting (CABG)
this bypasses the occluded portion of the vessel using the internal thoracic artery
CORONARY ANGIOPLASTY
Percutaneous Transluminal Coronary Angioplasty
✓ With or without stent (drug-eluting v bare-metal stents)
✓ Anticoagulation medication
where is the catheter of the coronary angioplasty
femoral artery
cardiac veins
✓ Most of the venous blood drains into RA via coronary sinus
great cardiac vein
anterior inter ventricular vein joins the coronary sinus
small cardiac vein
accompanies the right marginal branch
middle cardiac vein
posterior ventricular vein drains into the coronary sinus
anterior cardiac veins
drain independently into the RA
what is the coronary sinus
✓ Lies between the LA and LV ✓ Surrounded by muscle fibers
from LA
✓ Drains 60% of the venous blood of the heart into the RA
✓ 40% is drained by smallest cardiac veins (thebesian veins) and anterior cardiac veins
the cardiac conduction system
form 2 networks separated by fibrous skeleton: Atrial and ventricular networks
electrical impulses through the heart
There is a group of specialized, modified cardiac muscle cells that
− lie immediately beneath the endocardium
− can generate electrical impulses without external stimuli
✓ Cardiac muscle cells distribute electrical impulses through the myocardium,
– causing the heart to contract in the proper sequence
what is the role of the autonomic nervous system in conduction
✓ Autonomic nervous system shortens or prolongs the duration of a cardiac cycle
what are the components of the cardiac conduction system
− Sinu-atrial node (SA node) − Atrioventricular node (AV node) − Atrioventricular bundle (bundle of His) • Left bundle branch • Right bundle branch − Purkinje fibers. ✓ None of them are macroscopic
SINU-ATRIAL (SA) NODE
✓ Keith-Flack node
✓ Pace-maker
✓ The basic depolarization rate of the SA node is 70 to 80 beats per minute
✓ Located anterior to the opening of the SVC, upper end of crista terminalis
✓ Usually supplied by branches of the right coronary artery
ATRIOVENTRICULAR (AV) NODE
✓ Aschoff-Tawara node
✓ Located at the postero- inferior part of IA septum, close to the opening of the coronary sinus
✓ Usually supplied by AV nodal branch of the right coronary artery
ATRIOVENTRICULAR (AV) BUNDLE
✓ Bundle of His
− Continuation of the AV node
− Runs along the membranous part of the IV septum.
− Splits into right and left bundle branches
✓ Right Bundle branch
− Descends on the right side of the
membranous part of the IV septum.
− Enters the septomarginal trabecula to reach the base of the anterior papillary muscle
− Splits into Purkinje fibres which spread out into the ventricular walls
✓ Left Bundle branch
− Descends on the left side of the
membranous part of the IV septum.
− Splits into Purkinje fibres
The AV bundle of His role
✓ The AV bundle of His is (and should be) the only conductive route through the fibrous skeleton
✓ This system ensures synchronous contraction, in the correct sequence, toward the outflow of each chamber
NERVE SUPPLY OF THE HEART - workbook
✓ Cardioacceleratory and Cardioinhibitory centers in the Medullary reticular formation
✓ Superficial and deep cardiac plexus
− Lie inferior to the aortic arch, adjacent to the bifurcation of both the
pulmonary trunk and the trachea
− Supply conduction system, coronary blood vessels, and myocardium
1. Presynaptic sympathetic fibres travel in T1-5(6) spinal nerves
− Increase the heart beat and force of contraction
− Dilate coronary arteries
2. Parasympathetic fibres reach in vagus
− Decrease the heart beat (and force of contraction)
− Constrict coronary arteries
3. General visceral afferents
Cardiac referred pain
pain caused by ischaeia and damage to the cardiac muscle
- the visceral sensory nerve ending are activated
- the GVA sympathies fibres carrying sense travel with the sympathecis in the T1-5 spinal nerves
- pain fibres from organ and skin travel in the spina cord together
- pain is not felt in heart but is referred to somatic areas supplied by the T1-5 (which is the anterior chest wall and possilby the medical aspect of the left arm
