Intro to The Cardiovascular System Flashcards
What functions does the CVS aid / carry out in the body?
- Pumps blood through lungs
- Carries O₂, removes CO₂ and waste materials
- Transports nutrients to muscles & organs
- Circulates hormones and immune mediators
- Human reproduction
- Temperature regulation (vasodilation and
vasoconstriction)
What is passive diffusion?
The random, undirected thermal movements of molecules
What is the relationship between time and distance of diffusion?
The time taken to diffuse a given distance, is proportional to the square of the distance
t ∝ d²
Why is diffusion not used for whole body transport?
Diffusion is most effective in distances in µm but is very time consuming for distances > 1 mm
- inappropriate for whole body transport
Give examples of times taken for diffusion to occur in different parts of the body
Synapse - 0.1 µm takes 0.005 ms
Capillary –> cell - 10 µm takes 50 ms
Cartilage - 1 mm takes 8 minutes
Left ventricle wall - 1 cm takes 13 hours
What is myocardium?
The muscular tissue of the heart
What causes a pressure difference in the heart?
Output of blood at high pressure creates a pressure difference in distant blood vessels
What is the average pressure maintained in the aorta and large veins respectively?
Aorta > 100 mm Hg
Large veins 5 - 10 mm Hg
What is meant by systole?
Contraction
What does diastole mean?
Relaxation
Outline the equation to calculate Cardiac output
CO = HR x SV
Describe quantitatively how the CO differs at rest and during exercise
at rest: 70 bpm x 70 ml = 5 litres / min
during exercise: 18 bpm x 120 ml = 20 litres / min
What are the average blood pressures of systemic and pulmonary circulation?
Systemic circulation - 120/80 mm Hg
Pulmonary circulation - 25/15 mm Hg
What is cardiac output?
The volume of blood ejected from the heart per minute, typically around 5 litres / min
What is the role of high blood pressure?
High pressure enables blood to be pumped around the whole body
Typically, how is the cardiac output distributed throughout the body at rest?
25% Liver & GI tract 20% Muscle 20% Kidney 18% Other 13% Brain 4% Myocardium
Describe the structure and function of elastic vessels
Arteries
Large arteries accommodate Stroke volume
Convert intermittent ejection to into continuous flow
How is blood flow and blood pressure controlled?
Controlling the resistance of vessels gives some control of blood flow
High resistance = decreased flow
Blood Flow = (Pa - Pv) / resistance
What are exchange vessels?
Capillaries
Provide nutrient delivery to cell tissue, water, lymph formation and removal of metabolites and waste
What is the function of low blood pressure?
Allows time for exchange of gases and nutrients in capillaries
What factors affect Cardiac Output?
Starling’s law (filling pressure)
Sympathetic + Parasympathetic nervous systems
Chemical factors + hormones
What are the 4 main functional groups of blood vessels?
- Elastic vessels
- Exchange vessels
- Resistance vessels
- Capacitance vessels
Describe the structure of the capillary network
Capillaries are made up of millions of small vessels, giving a large cross-sectional area = slower velocity
What is the consequence of under perfused myocardium and brain?
This creates potential clinical problems
- angina
- MI
- strokes
triggered by relatively moderate falls in perfusion
CO needs to be carefully controlled
Why is pressure in the aorta higher than in capillaries?
The aorta is just one vessel so has a very low cross-sectional area
What is the role of arterioles?
Arterioles are resistance vessels, controlling arterial blood pressure by determining total peripheral resistance (TPR)
Describe the percentage oxygen consumption by the body during rest
30% Liver, GI tract 20% Muscle 18% Brain 10% Kidneys 10% Myocardium 12% other
Why is it important to control blood flow?
Blood flow and blood pressure control is significant for correct bodily functioning
What is meant by series blood flow in dual circulation?
Same blood supply between organs
lower perfusion pressures
medically significant if first organ is under perfused
Describe the arterial vessel wall structure
Thick tunica adventitia (external elastic membrane)
Thick tunica media (smooth muscle)
Contains internal elastic membrane
Tunica intima and endothelium
Give the equation used to calculate blood velocity (m/s)
Blood velocity (m/s) = Blood flow (cm³/s) / SA (cm²)
What is parallel circulation?
When the cardiac output is split up, safeguarding the O₂ supply in organs
Most organs are supplied in parallel
Describe the function of resistance vessels
Arterioles
Control arterial blood pressure and regulate local blood flow
Describe the percentage distribution of the body’s blood volume
5% capillaries 10% arteries 10% heart 10% lungs 24% large veins 24% small veins & venules
What is the role of veins & venules?
Systemic veins & venules act as reservoirs for blood, holding up to 65% of the body’s total blood volume
What are capacitance vessels?
Venules & veins
They control filling pressure and provide reservoir of blood
