Transcript day 7 how the heart works

How the Heart Works.
Electrical activity in the heart.
Blood flow through
the heart
http://www.youtube.com/watch?v=Ww2OAsAUIT0
Heat Beats
Step 1: Enter Atrium
• Right Side
- Deoxygenated blood
enters the right atrium
through 2 large veins
- Superior vena cava: upper
half of the body
- Inferior vena cava: below
the diaphragm
Left Side
- Oxygenated blood
(from the lungs)
enters the left
atrium through the
pulmonary vein
Heat Beats
Step 2: Contract Atrium
• Blood flows from the atrium into the
ventricle
• The atrioventricular (AV) valve
allows for a one-directional flow
• The AV valve closes once the
ventricle is full
Heat Beats
Step 3: Contract Ventricle
Right Side
•Right ventricle contracts
•Blood flows through the
pulmonary valve into the
pulmonary arteries
•Blood flows towards the lungs
Left Side
•Left ventricle contracts
•Blood flows through the
aortic valve into the aorta
(largest artery)
•Blood flows out towards the
body
2 parts of the heart beat
• Two parts of Heart Beat
– LUB: closure of the AV valves (beginning of
ventricular contraction - systole)
– DUB: closure of the pulmonary & cardiac valves
(end of ventricular systole – diastole)
Electrical structures of the heart
Electrical activity through the heart
Starts from SA node in the Right
Atrium (top R)
Causes Atria to contract (ventricles fill
with blood)
Impulse sent to the AV node (bottom
R of RA)
Impulse travels down bundle branches
& Purkinje fibres
Ventricles contract!
Electrocardiogram - ECG
• P wave: SA node fires and the
•
•
atria contract
QRS complex: AV node
stimulates the ventricles to
contract (AV valves close)
T wave: ventricles relax (the
pulmonary valve and aortic valve
close)
Normal sinus rhythm
ECG is used to measure:
- heart rate & regularity of heartbeats
- the size and position of the chambers
- any damage to the heart
- the effects of drugs or devices used to regulate the heart
Atrial Fibrillation
• Visible: lack of P wave
• Cause: hypertension
• Result: chest pain, heart palpitations,
fainting, heart failure, higher risk of stroke
• Treatment: blood thinners, medication to
slow heart rate
Ventricular Fibrillation
• Visible: no clear rhythm
• Cause: heart attack
• Result: chest pain, NO heart beat
• Treatment: defibrillation (Shock)
AV Block
• Visible: delay between S wave & P wave
• Cause: many... decrease O2 in blood
• Result: depends on severity
• Treatment: pacemaker
Asystole
• Visible: no waves
• Cause: lack of electrical activity
• Result: no blood flow, no contractions
• Treatment: none