Week 27 - The Cardiovascular System

Cards (15)

  • The cardiovascular system consists of:
    • A muscular pump (the heart)
    • A series of tubes (the blood vessels)
    • A liquid (the blood)
  • Functions of the cardiovascular system include:
    • Transport of materials around the body (to and from all parts of the body)
    • Circulation of oxygen, nutrients (glucose, fatty acids) & water
    • Removal of waste products (CO2, metabolic waste, heat)
    • Cell-cell communication (hormones)
    • Immune defence (White blood cells, antibodies)
  • Divisions of circulation:
    • Pulmonary circulation:
    • Right side receives blood from tissues and sends it to lungs for oxygenation
    • Systemic circulation:
    • Left side receives newly oxygenated blood from lungs and pumps it to tissues
  • Blood flows because liquids move from high to low pressure regions
    • Contraction of the heart creates pressure without changing the volume of blood
    • Pressure in ventricles is called driving pressure
    • Hydrostatic Pressure: exerted by a fluid which is not moving and force is exerted equally in all directions
    • Pressure = Force / Area
  • Flow usually means flow rate, the volume of blood that passes a given point in the system per unit of time
    • Velocity of flow (or simply velocity), the distance a fixed volume of blood travels in a given period of time
    • The tendency of the cardiovascular system to oppose blood flow is called Resistance
    • Velocity depends on the flow rate and the cross-sectional area
  • Factors affecting resistance to fluid flow:
    • Resistance increases as the length of the tube increases
    • Resistance increases as the viscosity (thickness) of the fluid increases
    • Resistance decreases as the tube's radius increases
    • A decrease in blood vessel diameter is known as vasoconstriction
    • An increase in blood vessel diameter is called vasodilation
  • The heart is divided by a central wall or septum
    • Each half functions as an independent pump that consists of an atrium and a ventricle
    • The two sides contract in a coordinated fashion
    • Atria receive blood returning to the heart, right from tissues, left from lungs
    • Ventricles pump blood away from the heart
  • Heart valves:
    • Atrioventricular valves control blood flow between atria and ventricles
    • Semilunar valves control blood flow between the ventricles and the arteries
    • During ventricular contraction, the semilunar valves are open but the atrioventricular valves remain closed
    • During ventricular relaxation, the semilunar valves prevent blood from flowing back into the ventricles
  • Cardiac muscle:
    • Contractile fibers are organized into sarcomeres
    • Attached to each other by intercalated discs containing desmosomes and gap junctions
    • Autorhythmic cells signal for contraction and have no organized sarcomeres
    • Action potential in cardiac myocytes is similar to neurons and skeletal muscle but longer
  • Electrical conducting system of the heart:
    • Sinoatrial (SA) Node acts as the main heart pacemaker
    • Depolarization wave spreads rapidly via Internodal pathways to Atrioventricular (AV) node
    • Purkinje fibers conduct electrical signals rapidly down the Atrioventricular bundle/Bundle of His in the ventricular septum
  • Electrocardiogram (ECG):
    • Records electrical activity of the heart
    • Consists of waves, segments, and intervals
    • 3 major waves on a normal ECG are P wave, QRS complex, and T wave
  • Cardiac cycle:
    • Two main phases are diastole (relaxation) and systole (contraction)
    • Atria and ventricles do not contract and relax at the same time
    • Cardiac cycle begins with the atria and ventricles at rest
  • Blood pressure:
    • Measured in mm Hg
    • Blood flow through the heart is governed by pressure
    • Fluid flows from high to low pressure
  • Cardiac cycle & the Pressure-Volume Graph:
    • Represents changes in left ventricular pressure/volume during one cardiac cycle
    • Follows left heart & aortic pressures, left ventricular volume, & the ECG through 1 cardiac cycle
  • Gallops, Clicks, and Murmurs:
    • Gallops are additional sounds recorded with very sensitive electronic stethoscopes or in certain abnormal conditions
    • Clicking sounds are made by abnormal movement of valves
    • Murmurs are "whoosh" sounds from blood leaking through incompletely closed or stenotic valves