Cardiovascular System Flashcards
Why is the heart important?
The heart is the pumping muscle that keeps the blood in motion
Ultimately all of the functions of the body depend on the heart keeping the blood moving
Rapid transport
oxygen, glucose, amino acids, fatty acids, vitamins, drugs and water to the tissues
Carbon dioxide, urea and creatinine away from the tissues
Control system
Distributing hormones to the tissues and secreting a hormone (atrial natriuretic peptide)
how does body temperature regulation work?
Transporting heat from deep organs to the skin surface for dissipation
Functions of the CVS
Rapid transport
Control system
Body temperature regulation
Important points
Both circuits begin and end at the heart
Blood must travel through them in sequence
Blood is constantly moving in both circuits
Both ventricles eject equal amounts of blood at the same time
One way valves ensure that the blood follows this pattern
The pulmonary circulation is unique in that the arteries carry oxygen poor blood and the veins carry oxygen rich blood
Normal values
Stroke volume in a normal adult is typically 70-80ml
Cardiac Output
Cardiac output (CO) is the volume of blood ejected by one ventricle in one minute
heart rate
The number of times the heart contracts in a minute
stroke volume
Each time a ventricle contracts the amount of blood ejected
Blood flow
the volume of blood flowing through a vessel in a given period (ml/min)
Blood pressure
the force per unit area exerted on a vessel wall by the contained blood, expressed as mmHg. The pressure gradient provides the driving force to keep blood moving
Resistance
the opposition to flow and is the amount of resistance blood encounters as it passes through the vessels
Darcy’s law of flow
Flow, Q (written with a dot over it) is the volume transferred per unit time (ml/min)
Flow is proportional to the pressure difference between the inlet pressure and outlet pressure in a steady state, along a rigid tube – P1-P2 (mmHg)
Resistance (mmHg/ml/min), R is inversely proportional to conductance the ease of flow
Hence: Q = (P1-P2)/R
Resistances in series
Resistances in wide vessels is low, in narrow vessels is high
When vessels are connected in series their resistances are added
the resistance of the large aorta is low as it is connected in series to narrow arterioles and capillaries the overall resistance of the systemic circulation is high
Systemic circulation resistance is 0.02mmHg per ml/min
Pulmonary circulation resistance is much lower at 0.003mmHg per ml/min