Lesson 3- circulatory system Flashcards
definition of diffusion?
net movement of molecules moving from a region of high concentration to a region of low concentration
where does the movement of molecules in diffusion come from?
achieved by the random collision of molecules up against each other. Rate at which they collide with each other depends on the temperature of the fluid. higher temp = better diffusion
what is bulk flow?
The movement of a fluid from a region of high pressure to a region of flow pressure
in bulk flow, the pressure gradient is established by what?
an external motive force (the muscular heart)
does blood flow bidirectionally or unidirectionally down a network of interconnected blood vessels?
unidirectionally
what escapes when blood courses through blood capillaries?
plasma carrying dissolved nutrients and other molecules
which phyla have open circulatory systems?
arthropods and most mollusks
what fluid circulates through open circulatory systems?
hemolymph, moving by the heart’s pressure gradient
what happens when the heart relaxes in an open circulatory system?
the pressure in the vessels drops and the hemolymph is pulled back through pores equipped with one-way valves.
the contracting heart…?
keeps fluid in motion, constantly washing over internal organs.
what is the fluid that circulates through closed circulatory systems?
blood confined within vessels
which phyla have closed circulatory systems?
cephalopods within the mollusk phylum
-annelids
-all vertebrates within the chordate phylum
list the vessels in order from the heart. (7)
- Aorta
- arteries
- arterioles
4.capillaries
5.venules - veins
- vena cava (returns blood back to the heart)
what is systolic pressure?
the spike in blood pressure caused by the powerful contractions of the ventricles stretch in the arteries
for healthy adults, what is a healthy amount of systolic pressure?
120 mmHg
when the heart is relaxed, pressure within the arteries drops to…?
80 mmHg
what is diastolic pressure?
a drop in pressure caused by the elastic recoiling of the arteries
what is reduced as the blood flows through narrower tubes?
maximum flow is greatly reduced