Overview Of The CVS Flashcards
What is the definition of the CVS?
Defined as the heart, blood vessels, and approximately 5 litres of blood (this is approx blood volume)
What are the functions of the CVS?
Dual circulation of blood with parts in parallel and series
- Transport system
- O2 and substrates to cells, (glucose, amino acids, fatty acids), CO2 and metabolites from cells for excretion (e.g. to lungs, liver, kidneys)
- Distribution of hormones, e.g. adrenaline, insulin
- Defence mechanisms, e.g., immune system
- Thermoregulation - chemical reactions need to be at correct temperature
Describe passive diffusion
- Random, undirected, thermal movement of molecules, therefore time needed to diffuse a net distance is proportional to the square of the distance
- This means the further the distance, the longer the time the oxygen will take to diffuse
Describe convection transport
- Causing of movement of fluids + solutes down a pressure gradient, provides resting healthy person a circulating blood flow delivering O2 transport to cells of about 5 L per minute
Why does the body fail when the CVS fails?
Heart failure or loss of pressure gradient (e.g. sepsis) prevents convection transport = NO O2 to tissue + organs
Why is O2 transported via convection transport?
- Passive dissuasion is too unpredictable and slow, therefore would not be able to sustain the body’s functions
- Blood vessels therefore use convection transport to transport exchange materials to capillaries, where capillaries transport oxygen to the lungs or target tissue via passive diffusion, due to their large SA
Describe the delivery of blood in series
- Sequential flow from one vessel to next, illustrated by arrangement of blood vessels with in organ
- Major artery → smaller arteries → arterioles → capillaries → venules → veins
- Total resistance = Sum of resistance in each blood vessel
- Blood flow at each part of system identical, but pressure decreases progressively
Describe the delivery of blood in parallel
- Simultaneous flow through each parallel vessel
- Cardiac output → aorta → branching → cerberal, coronary, renal system etc. → capillaries → venules → veins → vena cava → right atrium
- Total resistance less than any resistance
- Blood flow in each system only small portion of total blood flow → no pressure lost in major arteries (remains same as in aorta)
What part of the heart is responsible for ejecting blood to the body at high pressure?
- Left ventricle, pumps blood though semi-lunar valves into aorta, high pressure creates pressure difference with distance blood vessels,
Why is the pressure difference important between blood vessels?
Drives blood flow
What do systole and diastole mean respectively?
- Systole - contraction
- Diastole - relaxation
What happens in diastole at the right and left sides of the heart?
Right side:
- Heart relaxing
- DeO2 Blood enters through superior + inferior vena cava into RA, then this blood travels into RV through tricuspid valve
Left side:
- Once oxygenated, blood travels back into left atrium, and into left ventricle through mitral valve (bicuspid valve)
What happens in atrial systole on the right and left side of the heart?
Right side:
- Atria contract to eject deO2 blood into ventricles
Left side:
- Atria contract to eject O2 blood into ventricles
What happens in ventricular systole on the right and left side of the heart?
Right side:
- Blood exits RV via pulmonary artery (left and right) to left and right lungs
Left side:
- O2 blood exits LV into aorta, via semi-lunar valves, where it is transported to all over body.
What enables the valves to open?
Capillary muscles
