Circulation + Gas Exchange
- Created by: CJohnstone2001
- Created on: 01-12-20 14:47
Gastrovascular cavity= Diff of substances.
Invertebrate circ syst
Liquid solutes are transported= Blood
Tubes blood moves through= Vessels
Pump= Heart
Insects + Arthropods= Open circ (blood and interstit fluid as one)
Vertebrate circ syst
Closed system
Atria= Blood returns
Ventricles= Blood out
Arteries= Carry blood away
Capill= Solute exch
into
Venules= Become veins/return blood.
Fish
1 atrium/1 ventricle
Blood from ventricle to gills --> oxygenated
Gill capillaries form vessels that supply O2 blood to body.
Blood pressure= low (loss after going through gill capill)
Blood returns to atrium through veins.
Amphibia
2 atria/1 vent
Vent= pumps blood in 2 directions (lung + capill/systemic circ)
O2 blood repressurised after drop from gas exch.
Birds + Mammals
2 atria/2 vent
O2 and deoxy blood separated by septum.
Mammals heart
Atria= thin
Pump blood to vent (thicker walls)
Right vent= Lungs
Left= Body
Cardiac cycle
Contraction= Systole (atrial forces blood to vent/ventricular pumps blood to arteries)
Relax= Diastole (blood enters heart)
Cardiac Output
Volume blood pumped out left vent/minute
Depends on heart rate and stroke vol.
Average--> 75bpm and ml/stroke
Cardiac Contraction
Cells of sinoatrial node (SA) contract/act as pacemaker/generate imoulses/pass to Atriovent node (AV)/ensures atria empty before contraction ventricles.
Regulation
Elec activity SA nose contracts at basal level.
Rate influenced by nervous sig and horm too.
Vessels
Art/Veins= composed of 3 layers.
Outer= Connective tissue/Allows atretching.
Middle= Smooth musc/Elastic fibres.
Inner= Smooth endothelium minimises resistance to flow.
Capill have thin endothelial layer (solute exch)
Thick walls arteries allow rapid/high pressure pumping of blood.
Veins thinner walls as pressure returning blood reduced.
Blood through veins result skeletal muscle contraction.
Blood veloc + Pressure
Veloc dec as diameter dec in arterioles/capill
Veloc inc in venules/veins
Pressure highest= arteries (reduces in arterioles)
Resist to flow in constrict capill= venous pressure is negligible.
Blood Flow
Smooth musc rings (pre capill sphincters) regulate blood flow.
Sphincters contracted= blood flow reduced.
Capillary Exchange
Allow exchange solutes between blood/interstitial tissues.
Net flow fluid out capill due to pressure diff.
Large molecules move across capill endothelial (by exo and endo)
Small diffuse down conc grad.
Fluid return to blood
4-8L fluid/day…
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