I achieved a high A* Grade in my final A-Level exams using these notes!!!
I believe you can achieve an A* if you can memorise these notes! Simply use blurting, a method of active recall, to write everything you remember from the notes, then identify the parts you couldn’t remember, then repeat ...
Unicellular Multicellular
- high SA:V ratio = short distance for material to - low SA:V ratio = long distance for material to
travel travel
- low metabolic needs – slow transport sufficient - high metabolic needs – needs faster rate of
exchange
b. Open vs Closed
Insects: open circulatory system
blood has direct contact with tissues & organs
no respiratory gases/pigments in blood – via tracheal system
haemolymph (blood) pumped by dorsal tube-shaped heart (runs length of body) into haemocoel (cavity)
haemolymph then re-absorbed by dorsal vessel
Earthworm: closed circulatory system
blood vessels: higher pressure (conc grad) / circulate faster / transport longer distances
respiratory gases in blood – aided by pigment = concentration gradient
5 pseudoheart pairs pump blood
blood vessels – run length of body
- Ventral: distributes blood to body segments
- Dorsal: collects blood from body
c. Single vs Double
Fish: closed single circulatory system
through heart once
2 heart chambers
- heart ventricle pumps deoxygenated blood to gill capillaries – high pressure
- gill capillaries reduce pressure & oxygenate blood – slows blood flow to body tissues
o slower rate of delivery/removal – but efficient for metabolic activity (don’t maintain body temperature)
- deoxygenated blood flows back to heart atrium – then heart ventricle
Mammal: closed double circulatory system – 1 circulation = through heart twice
through heart twice: pulmonary circulation (heart & lungs) & systemic circulation (heart & body tissue)
4 heart chambers (more complex)
- high pressure sustained after oxygenation
o maintain concentration gradient
o fast flow rate – meet high metabolic needs (need to maintain body temperature)
- oxygenated/deoxygenated kept separated – improves oxygen distribution
, d. mammalian circulatory system
Heart (cardiac muscle): 4-chambered pump – for double circulation & separation of de/oxygenated blood
atria: receive blood – thin walls
atria-ventricular valves: prevent backflow from ventricles to atria
ventricles:
- thick walls: contraction generates high pressure – blood pumped great distance
- L>R – thicker muscular wall: generates higher pressure – blood must travel greater distance
semi-lunar valves: prevent backflow from arteries to ventricles
Vena cava (superior/inferior): deoxygenated blood from body (upper/lower regions)
Right atrium
Tricuspid – atrio-ventricular valve
Right ventricle
Pulmonary – semi-lunar valve
R/L pulmonary artery: deoxygenated blood to lungs
R/L pulmonary veins: oxygenated blood to left atrium
Left atrium
Bicuspid / mitral – atrio-ventricular valve
Left ventricle
Aortic – semi-lunar valve
Aorta: oxygenated blood to systemic circulation
Blood vessels: distribute blood
further from heart – decrease pressure & rate
- more branched = bigger total cross-sectional area
- smaller diameter = more friction
- tissue fluid formed
Arteries – away: pressure corresponds with ventricular systole
- Protective outer layer: tough collagen fibres – resists over-stretching (could cause loss in recoil)
- Thick muscular layer & many elastic fibres: withstand high pressure
smooth muscle contract/relax – adjust diameter of lumen = control blood flow
elastic recoil: allow stretching to accommodate changing blood flow
- Smooth endothelium – reduce friction
- Smaller lumen
Arterioles: connect arteries to capillaries
Capillaries: form networks within tissues – for exchange
Thin endothelium – single-cell: short diffusion pathway
Dense network: large cross-sectional area – reduces to low pressure
Narrow: red blood cells can lie flat against wall – reduces diffusion distance to Hb
Narrow lumen (small diameter) – friction: slow blood flow – more time for diffusion/exchange
Permeable to gas
Pores/fenestrations: tissue fluid formation & solute/water exchange
Venules: connect capillaries to veins
Veins – back
- Protective outer layer: tough collagen fibres
- Thin muscular layer & few elastic fibres – low pressure
- Smooth endothelium – reduce friction
- Bigger lumen: largest diameter – maximise flow
Skeletal muscle (surrounds vein) contracts: compresses vein – reduces volume & increases pressure inside
forces blood through semi-lunar valve & causes valve behind to close – ensures 1 direction flow
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller tnotes. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
