Circulatory/cardiovascular system - SB8 Flashcards
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which way does blood in arteries flow?
away from the heart
which way does blood in the veins flow?
to the heart
what do arteries divide into?
narrow capilaries
what are qualities of arteries?
- blood away from heart
- narrow tube (lumen)
- thick layer of elastic and muscle fibres
what are qualities of veins?
- veins carry blood to heart
- wide tube
- thin, flexible wall
how is a pulse created?
heart squirts blood into arteries at high pressures - arteries stretch and pass along artery walls
how is blood enabled to flow smoothly?
muscle and elastic fibres in the artery walls cause arteries to contract again. Stretching / contracting of arteries makes blood flow smoothly
what prevents backwards bloodflow?
valves
why are only thin walls needed in viens?
blood flows under low pressure
how many red blood cells is in a cubic milimeter of blood?
5 mil
how many white blood cells are in a cubic milimeter of blood?
7,000
how many platelets are in 1 cubic milimeter of blood?
0.25 mil
what substance are cells suspended in?
plasma
what substances does plasma carry?
glucose, CO2 and urea
what is in red blood cells that binds with oxygen, what does it do with oxygen?
haemoglobin - releases O2 in tissues
What are the physical features of red blood cells? why are they designed this way?
- No nucleus - more space for haemoglobin
- Shaped like discs with dips in ‘biconcave’ shape allows large surface area : volume ratio for oxygen to diffuse in and out
What are the 2 types of white blood cell?
phagocytes and lymphocytes
what is the general role of white blood cells?
to remove foreign cells inside you
what do lymphocytes do to remove foreign cells?
produce proteins called antibodies that stick to foreign cells and help destroy
what do phagocytes do to get rid of foreign cells?
surround foreign cells and digest them
what are platelets?
tiny fragments of cell with no nucleus
why do platlets produce substances?
needed to clot blood prevent further blood loss
What are the 2 main features of the heart ?
- 4 chambers
- valves stop backwards blood flow
what is the first step of blood pathway?
de-oxygenated blood enters through the vena carva (vein)
what is the second step of blood pathway?
blood pumped into right atrium and passes valve into right ventricle
what is the third step of blood pathway?
passes valve into pulmonary artery to bring de-oxygenated blood to lungs
what is the fourth step of blood pathway?
gaseous exchange takes place in the lungs to turn de-oxygenated blood into oxygenated blood
what is the fifth step of blood pathway?
blood returns through the pulmonary vein and enters left atrium of heart
what is the sixth step of blood pathway?
blood goes to left ventricle through valve - blood is pumped at high pressures into aorta to carry to rest of the body
What valve is between the right atrium and ventricle? what does it do?
tricuspid valve - seperates right atrium and ventricle - opens due to high pressure in atrium and prevents backwards blood flow
what valve seperates the right ventricle and left atrium? what does it do?
semilunar valve - prevents backflow of blood to heart
what valve is between the left atrium and left ventricle? what does it do?
bicuspid valve - seperates left atrium and ventricle and prevents backwards blood flow. opens due to pressure in left atrium
what valve seperates the left ventricle and the aorta? what does it do?
semi lunar valve - stops back blood flow to heart
How often do heart attacks occur in the UK?
one every 3 minutes
when does a heart attack occur?
when the blood stops flowing to muscles in part of the heart - damaging them and stopping heart pumping properly.
what can be done if the heart stops completely?
can be re-started usinga defribrilator
what is controlled by impulses from the nervous system?
contraction and relaxation of muscles during a heartbeat
what is heart rate?
the number of times the heart beats per minute
what is stoke volume?
the amount of blood pulsed into the aorta in each beat
what is stroke volume measured in?
litres
what is cardiac output?
volume of blood pushed into the aorta each minute
what is the equation for cardiac output?
stroke volume (liters /beat) x heart rate (beats per min)
why do fit people have bigger stroke volumes and slower heart beats? - why is this important?
regular excercise increases the strength of the heart muscle ad ventricle sixe - so fitter people have bigger stroke volumes and slower heart beats and can achieve the same cardiac output as a less fit person - this puts less strain on the heart
