CARDIOVASCULAR SYSTEM

CARDIOVASCULAR SYSTEM

1. FUNCTIONS OF THE BLOOD

   • Transport gasses e.g. oxygen & CO2
   • Distributes nutrients e.g. proteins/lipids/carbohydrates
   • Transport metabolic waste
   • Delivers enzymes & hormones e.g Adrenaline
   • Regulate pH & Electrolytes e.g. salts
   • Defends body against toxins & pathogens
   • Regulate body temperature
   • Restricts fluid loss through damaged vessels

2. COMPOSITION OF BLOOD

   • Blood cells = 45%
   • Plasma = 55%

3. TYPES OF BLOOD CELLS

   • Ethrocytes = red cells
   • Thrombocytes = platelets
   • Leukocytes = white cells

4. TYPES OF BLOOD VESSELS

   • Arteries
     • Arterioles (small artery)
     • Carry blood away from heart
     • Oxygenated blood
     • High pressure
     • Thick muscular elastic walls
       • 3 layers thick
     • Expand & accommodate increase blood volume
   • Veins
     • Venules (small veins)
     • Carry blood to heart
     • Deoxygenated blood
     • Valves present
     • Lower pressure
     • Thin elastic walls
       • 2 layers thick
   • Capillaries
     • Smallest vessel
     • Extremely narrow
     • 1 layer thick
     • Carry blood from artery to vein
     • Pressure is low
     • Flow of blood slow
     • Gaseous exchange & nutrients occur
   • Heart

5. HEART WALL

   • Pericardium
     • Outer layer
     • Blood lymph capillaries & nerve fibres
   • Myocardium
     • Thin middle layer
     • Cardiac muscle tissue
   • Endocardium
     • Inner layer
     • Forms part of valves in heart

6. HEART CHAMBERS

   • Left Atrium
   • Left Ventricle
   • Right Atrium
   • Right Ventricle

7. SYSTOLE

   • 1. Contraction of heart muscle
   • 2. Atria relax & expands
   • 3. Semi lunar valve open
   • 4. Tricuspid & Bicuspid valve closed
   • 5. ventricles contract
   • 6. Blood flows to lungs & body

8. DIASTOLE

   • Relaxation of heart muscle
   • 1. Atria contracts
   • 2. Semi lunar valve closed
   • 3. Tricuspid & Bicuspid valves open
   • 4. Ventricles relax & expand
   • 5. Blood flows from atria to ventricles

9. HEART BEAT

   • Myogenic
     • Inilated from within heart muscle
   • Automatic nerve system in control
   • Cardiac control centre influence cerebrum & hypothalamus
   • Be stimulated or inhibited by nerve impulses
   • Release of adrenaline from adrenal medulla is control factor

10. SA NODE

    • Located in wall of right atria near vena cava
    • Determines heartbeat
    • Initiate heartbeat
    • Usually keeps heartbeat regular
    • Automatic excitation pulse every 0.85 sec
    • Cause artria to contract
    • If SA fails, heart still beats but slower
    • (Sinoatrial)

11. AV NODE

    • Located base of right artria near septum
    • Neuromuscular tissue
    • Signals ventricles to contract
    • Sends impulses to bundle of His
      • Then throughout ventricular walls
    • Wave of excitation conducted along purkinje fibres
    • (Atrioventricular)

12. ECG

    • Measures electrical activity
    • Consists of waves
      • P
        • Movement from SA to AV node
      • QRS
        • Movement down centre across ventricle
      • T
        • ventricle repolarisation
    • Detects abnormal heartbeats
    • Arrhythmia = abnormal heart rhythm
    • Fibrillation = Heart beating rapidly & contractions uncoordinated