Heart Cardiac Cycle And ECG Flashcards
Function of the heart
-Part of the Cardiovascular system
-A physiological pump
• Contributes to overall pressure maintenance (total peripheral resistance, blood flow, heart rate, cardiac output
-Perfusion of orgrans (delivers and removes)
• What is the approximate cardiac output of a healthy 20 year old person?
~ 5 - 6 litres/min
Layers
Starting from the inside
-endocardium
-myocardium
-visceral layer
-pericardial cavity(space in between) filled with pericardial fluid ,ultra lean plasma which acts as a lubricant
-Parietal layer
Fibrous layer(attached to blood vessels and diaphragm sometimes )
Inside view of the heart
4 cardiac chambers
4 valves(made of fibrous tissue)
Tricuspid atrioventricular valve
Mitral atrioventricular valve
Pulmonarv semistinar valve(leads to Pulmonarv artery)
Aortic semi-lunar valve (leads to Aorta)
What does left ventricle generate
Highest pressure of all cardiac chambers
Sinoatrial node
-Spontaneously depolarising pacemaker
-Located in the Right Atrium at the junction of superior vena-cava)
-Responsible for atrial contraction
-Atrioventricular (AV) node
-In the right posterior portion of inter-atrial septum
-Oversees ventricular contraction
Right coronary artery
Supplies blood to
-righy ventricle
-right atrium
-Septum
-sa and av nodes
What does right coronary artery branch to
-right posterior descending artery
-marginal artery
Left main coronary
Supplies blood to
-left ventricle
-left atrium
What does left main coronary branch into
-circumflex artery(encircles the heart muscle,supplies the back and outer side of the heart )
-left anterior descending artery(supplies the front of the left side of the heart)
Myocardial cells
-branched
-striated
>lines visible through cells
>indicate the sarcomere edges
-mononucleated
>rich in mitochondria
Myofibril
Contains parallel myofilaments
Sarcomere
Contractile functional unit
Contains parallel myofilaments
Sarcolemma
Muscle cell membrane
Sarcoplasmic reticulum
Cells main calcium store
Myocardial filaments
-Z disc
Edge of the sarcomere
-M line
Centre of the sarcomere
-1 band
Contains ONLY light myofilaments - Actinband
light
- h zone
-Contains ONLY heavy myofilaments - Myosin
-A band
Contains heavy myofilaments
and overlapping region with actin
Myocardial contraction
Synchronised contraction of muscle cells
•FIRST in the atria and THEN the ventricles
• Activation of contractile machinery requires calcium
• Calcium cycle used to regulate contraction
Calcium stores:
• Outside the cell - extracellular
• Intracellular calcium store - the (sarco)endoplasmic reticulum
Calcium cycle
Low calcium in cytoplasm=relaxation
High calcium in cytoplasm=contraction
Cardiac circulatory cycle
Atrial systole
Early ventricular systole
Ventricular systole
Early ventricular diastole
Ventricular diastole
Cardiac output
Heart rate x stroke volume
Frank starling mechanism
-pressure volume loop in the left ventricle during the cardiac cycle
-relationship between blood volume and force required to eject it
Positive deflection
Current is moving towards electrode
Negative deflection
Current is moving away from electrode
Basic pattern of electrical activity In the heart
P wave
Atria depolarisation (Contraction)
QRS interval
Ventricular depolarisation (Contraction)
& Atrial repolarisation (Relaxation)
Q wave - Septal depolarisation
R wave - Depolarisation of the majority of ventricular mass
S wave - Depolarisation of the Purkinje fibres
T wave
Ventricular repolarisation (Relaxation)
U wave
Rare! Late repolarisation
(of Purkinie fibres and some ventricular myocytes)
