Coronary Circulation & Conduction System

Question 1

what are the 5 key physiological features of the heart

Answer 1

chronotropy 
dromotropy (conduction)
bathmotropy (excitability)
ionotropy (contractility) 
Lusitropy (relaxation)

Question 2

blood supply to the heart tissue

Answer 2

supplied by coronary arteries and their branches

Right coronary artery (RCA)

Left coronary artery (LCA)

Question 3

where does the endocardium receive oxygen and nutrients from

Answer 3

the chambers of the heart

Question 4

what and where are the coronary arteries

Answer 4

the only branches of the ascending aorta and they emerge in the aortic sinuses

Question 5

what happens to the aortic sinus during systole

Answer 5

they fill up which means that coronary arteries also fill up

during systole they are blocked off as the valves are pushed open

Question 6

RCA

Answer 6

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

Question 7

LCA

Answer 7

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)

Question 8

LAD - left anterior inter ventricular descending artery (2nd branch of the LCA)

Answer 8

• 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

Question 9

circumflex branch of the LCA

Answer 9

branches to the left (obtuse) marginal branch which anastomoses with the branches of the RCA

Question 10

RCA and its branches supply

Answer 10

• 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

Question 11

LCA and its branches supply

Answer 11

• Walls of LA and LV

- most of the atrioventricular septum including part of the AV bundle

Question 12

CORONARY DOMINANCE

Answer 12

✓ 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

Question 13

Where and what is the likelihood of a myocardial infarction happening in what artier

Answer 13

LAD - 40-50%
RCA - 30-40%
Circumflex 15-20%

Question 14

what damage could of myocardial infarction do to the conducting system

Answer 14

if its in the LAD = it supplies the AV bundles
RCA supplies both the SA and AV nodes

Heart block can cause bradycardia

Question 15

Coronary Artery Bypass Grafting (CABG)

Answer 15

this bypasses the occluded portion of the vessel using the internal thoracic artery

Question 16

CORONARY ANGIOPLASTY

Answer 16

Percutaneous Transluminal Coronary Angioplasty
✓ With or without stent (drug-eluting v bare-metal stents)
✓ Anticoagulation medication

Question 17

where is the catheter of the coronary angioplasty

Answer 17

femoral artery

Question 18

cardiac veins

Answer 18

✓ Most of the venous blood drains into RA via coronary sinus

Question 19

great cardiac vein

Answer 19

anterior inter ventricular vein joins the coronary sinus

Question 20

small cardiac vein

Answer 20

accompanies the right marginal branch

Question 21

middle cardiac vein

Answer 21

posterior ventricular vein drains into the coronary sinus

Question 22

anterior cardiac veins

Answer 22

drain independently into the RA

Question 23

what is the coronary sinus

Answer 23

✓ 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

Question 24

the cardiac conduction system

Answer 24

form 2 networks separated by fibrous skeleton: Atrial and ventricular networks

Question 25

electrical impulses through the heart

Answer 25

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

Question 26

what is the role of the autonomic nervous system in conduction

Answer 26

✓ Autonomic nervous system shortens or prolongs the duration of a cardiac cycle

Question 27

what are the components of the cardiac conduction system

Answer 27

``` − 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 ```

Question 28

SINU-ATRIAL (SA) NODE

Answer 28

✓ 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

Question 29

ATRIOVENTRICULAR (AV) NODE

Answer 29

✓ 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

Question 30

ATRIOVENTRICULAR (AV) BUNDLE

Answer 30

✓ Bundle of His − Continuation of the AV node − Runs along the membranous part of the IV septum. − Splits into right and left bundle branches

Question 31

✓ Right Bundle branch

Answer 31

− 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

Question 32

✓ Left Bundle branch

Answer 32

− Descends on the left side of the membranous part of the IV septum. − Splits into Purkinje fibres

Question 33

The AV bundle of His role

Answer 33

✓ 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

Question 34

NERVE SUPPLY OF THE HEART - workbook

Answer 34

✓ 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

Question 35

Cardiac referred pain

Answer 35

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