how the heart works. electrical activity in the heart
TRANSCRIPT
How the Heart Works.Electrical activity in the heart.
Blood flow through the heart
http://www.youtube.com/watch?v=Ww2OAsAUIT0
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 BeatsStep 1: Enter Atrium
Heat BeatsStep 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 BeatsStep 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 fibresVentricles 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