Components of CV system

Heart

• Establishes pressure gradient needed for blood to flow to tissues
  
  

Blood vessels

• Passageway for blood
  
  

Blood

• Materials dissolved or suspended and transported

Major blood vessels

Aorta

• Largest artery in the body
• Leaves heart at left ventricle
• Carries oxygenated blood to the body
  
  

Vena cava

• Major vein, returns deoxygenated blood from the body to the right auricle
  
  

Pulmonary artery

• Carries deoxygenated blood from right ventricle to the lungs for oxygenation
  
  

Pulmonary vein

• Carries oxygenated blood from lungs to left atrium

3 kinds of blood vessels

1. Arteries

• Carries blood away from heart
• Thick strong walls
• Narrow lumen, varies with heartbeat
  
  
  

2. Capillaries

• Gradually join up to form veins
• Thin, one cell thick
• Very narrow lumen
  
  
  

3. Veins

• Carries blood towards the heart
• Thin walls
• Valves to prevent back flow
  

Chamber of the heart

• Atria
• Ventricles
• Auricles - Wrinkled pouch-like structures, slightly increases the capacity of the atrium
• Sulcus - Grooves which hold blood vessels and fat

Blood flow through the heart

1. Blood enters right atrium from superior and inferior vena cava
2. Blood flows from right atrium through tricuspid valve to right ventricle
3. Contraction of right ventricle causes pulmonary valve to open
4. Blood flows though pulmonary valve to pulmonary artery
5. Blood flows to lungs, unloads CO2 and take up O2
6. Blood returns to heart via pulmonary vein and enters left atrium
7. flows from left atrium though bicuspid valve to left ventricle
8. Contraction of left ventricle causes aortic valve to open
9. Flows though aortic valve to aorta and to the body organs and tissues
10. Unloads O2 and takes up CO2
11. Deoxygenated blood returns to heart via superior and inferior vena cava
    

2 Nerves link the cardiovascular centre in the medulla oblongata to the SA nodes of the heart

1. Accelerator nerve (Sympathetic NS)

• When stimulated releases neurotransmitter at the SA node to increase heart rate
  

2. Vagus nerve (parasympathetic NS)

• When stimulated releases neurotransmitter at the SA node to decrease heart rate

Cardiovascular centre receives input from 4 main receptor groups

1. Pressure receptors in heart (baroreceptors)

• Found in carotid arteries and arch of the aorta
  

2. Chemoreceptors in heart (detects CO2 and O2 levels, and changes in pH)

• Found in carotid arteries and arch of the aorta
  

3. Thermo receptors in muscles

   
   

4. Stretch receptors in muscles

Cations controlling heart rate

K+, Ca2+ and Na+ have a big effect of cardiac function

• Elevated blood K+ and Na+ decrease heart rate and contraction
• Excess Na+ blocks Ca2+ inflow during cardiac action potentials, decreasing the force of contraction, excess K+ blocks generation of action potentials
• A moderate increase in intestinal Ca2+ levels speeds heart rate and strengthens the heart beat
  
  

If you have low potassium levels you may have a heart problem e.g irregular heart beat

High potassium levels, heart muscle activity may be reduced

Ions need ions for action potential, imbalance of ions can therefore alter effectiveness of the heart

Elevated K+ and Na+ blood levels decrease heart rate and contractibility

Exercise makes the heart work harder and increases cardiac output

Proprioceptors (sensory receptors)

• In muscles, tendons, joints inform cardiovascular centre that movement has increased
  
  

Chemoreceptors

• Located in aorta and carotid arteries detect decrease in blood pH due to increase of lactic acid and CO2
  
  

Baroreceptors

• Detect low blood pressure because of vasodilation in skeletal muscles