Post on 14-Oct-2015
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ANAT1014
Cardiovascular system and cardiac cycle Dr Abigail Rickard
26th September 2011
Reset your response device..
1. Press and release Go or Ch button
2. While light flashes red and green
3. Press 4 then 1 to set channel to 41
4. Then press Go or Ch
5. Press and release 1/A light will flash yellow to confirm
6. If this doesnt happen try again.
Overview
What is the cardiovascular system?
What are the features of the heart?
What does the heart do?
How does the heart function?
Components of the cardiovascular system
Heart Aorta Vena Cavae Capillaries Venules
Systemic circulation
Cardiac cycle - Blood flow through the heart Superior & inferior vena cave
Pulmonary artery/vein
Aorta
Bicuspid and tricuspid valves
Right/Left atrium/ventricle
Diastole/Systole
Valves
Valves in action
The bicuspid valve is between...
1 2 3
57%
0%
43%
1. The left atrium & left ventricle
2. The right atrium & right ventricle
3. The left ventricle & systemic arch
Coronary circulation
Coronary ostia Left coronary artery Right coronary artery Coronary sinus
Myocardial energy metabolism
High dependence on aerobic metabolism (70-80% available O2 at rest) Primary metabolic substrates are fatty acids Glycogen and lactate
Heart muscle types
Purkinje Fibres Atrial Cells Ventricular cells
Shape Long and broad Elliptical Long and narrow
Length (m) 150-200 ~ 20 50-100
Diameter (m) 35-40 ~ 5 10-25
Intercalated disc/ gap-junctions
Very prominent; abundant gap junctions; fast end-to-end transmission
Side-to-side as well as end-to-end transmission
Prominent end-to-end transmission
Ventricular myocyte features
Cross-striations (myofibrils)
Thick myosin filaments
Thin actin filaments
Cross bridge formation (cycling)
Mitochondria
What features allow for the rapid electrical conductance in purkinje
fibres?
1 2 3 4
0% 0%
50%50%
1. Mitochondria
2. Myosin and actin filaments
3. Intercalated discs and gap junctions
4. I dont know, I wasnt listening
Cardiac cycle - Electrical activity across the heart Sinoatrial node (SAN)
Atrioventricular node (AVN)
Purkinje fibres
Wave of depolarisation
Repolarisation/ Hyperpolarisation
Resting membrane
potential
ECG- P, QRS, T waves
Cardiac electrical activity Pacemaker Cell (SA node)
Intrinsic depolarisation known as automaticity
N.B. Membrane potential is never flat
Ca2+ - induced Ca2+ release from intracellular Ca2+
storage organelle called endoplasmic reticulum
- 65 mV
- 40 mV
Cardiac electrical activity Ventricular Cell
Phase 0 - RAPID inward Na+ current (Upstroke, depolarisation)
Phase 1 Transient outward K+ current (Notch)
Phase 2 Outward Ca2+ current (Plateau)
Phase 3 Fast and Slow outward rectifier K+ currents (repolarisation)
Phase 4 Resting membrane potential N.B. Notice upstroke of action potential is FLAT
- 80 mV
The movement of which ions are responsible for the upstroke of the
ventricular action potential (Phase 1)?
1 2 3 4
25%
0%
13%
63%
1. Na+
2. Ca2+
3. K+
4. Mg2+
Cardiac electrical activity Whole heart P wave - Atrial depolarisation
PR interval - AV nodal conduction
QRS complex - Ventricular Depolarisation
T Wave - Ventricular repolarisation
QT interval - Ventricular depolarisation and repolarisation
P
R
Q S
T
PR
interval
QT
interval
Which of the following represents the time for conduction across the AV
node?
1. P-R interval
2. Q-T interval
3. R-R interval
4. T wave
Summary
Features of the cardiovascular system
Location and morphology of the heart
Cardiac cycle
Electrical activity of the heart
Next time.....
Regulation of cardiac cycle
Blood flow and pressure
Malfunctions and their consequences