ANAT1014

Cardiovascular system and cardiac cycle Dr Abigail Rickard

26th September 2011

Reset your response device..

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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

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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