lecture 5 - cardiovascular system: introduction to CVS Flashcards
why do we need a cardiovascular system?
exchange and transport of nutrients to maintain life
single cell organisms don’t need a specialised exchange system
functions of the CVS
controlled and continuous flow of blood
homeostasis
transport of hormones
organisation of the CVS
2 circulations in series served by 2 pumps in series
what are the 2 circulations in the CVS?
systemic
• high pressure, left, oxygenated
• supplies whole body
pulmonary
• low pressure, right, deoxygenated
• only supplies the lungs
each circulation receives the same volume of blood
what are the 2 chambers of the heart
atrium and ventricle
what are the 2 types of valves in the heart?
atrioventricular valves
semilunar valves
what are the 2 atrioventricular valves?
right = tricuspid left = mitral/bicuspid
what are the 2 semilunar valves?
right = pulmonary left = aortic
what causes the valves to open and close
pressure differences
what is stroke volume (SV)?
volume of blood pumped by 1 ventricle
what is cardiac output (CO)?
total volume of blood pumped per ventricle per minute
CO = HR x SV
what is venous return (VR)?
amount of blood returning to the heart
under steady state conditions VR = CO
what is the vascular system made of?
arteries
arterioles
capillaries
veins
arteries
- high pressure
- elastic
- distribution
arterioles
- high resistance
- site for control of blood flow to tissues
- surround by lots of vascular smooth muscle
capillaries
- thin walled
- exchange of materials
- arranged in parallel
veins
- low pressure
- capacitance
- collection
- 70% of blood is in the venous system at any time
what is capacitance?
the ability of a system to store an electrical charge
in the veins
what is blood flow driven by?
pressure gradient setup by the heart acting as a pump
energy is required to maintain the pressure gradient
pressures in the vascular system
decreases from arteries to veins
greatest fall in pressure in the arterioles
pressure is pulsate in large arteries
systemic system > pulmonary system
what is systolic pressure?
- maximum pressure
* when contracting
what is diastolic pressure?
- minimum pressure
* relaxed and filling with blood
what parameters determine the resistance?
- length of the blood vessel
- radius of the vessel
- viscosity of blood
equation for blood velocity
V = flow / XSA
XSA = cross sectional area
how does blood velocity differ?
the higher the XSA the lower the velocity
velocity is lowest in the capillaries for efficient exchange
