mass transport in animals 3.3.4 Flashcards
relate structure of atria to function
thin walled and elastic
so they can stretch when filled with blood
relate structure of ventricles to function
thick muscular walls
pump blood under high pressure
left ventricle thicker
pumps blood all way around body
relate structure of arteries to function
thick muscular walls
handle high pressure without tearing
muscular and elastic to control blood flow
relate structure of veins to function
thin walls
due to lower pressure
valves
ensure blood doesn’t flow backwards
less muscular and elastic tissue
as they don’t have to control blood flow
why are two pumps (left and right) needed instead of one
to maintain blood pressure around the whole body
pressure drops when blood passes through narrow capillaries of lungs
therefore returned to the heart to increase pressure
so it is flowing strongly enough to continue through whole body
describe what happens during cardiac diastole
heart is relaxed
blood enters atria
increases pressure
pushes open atrioventricular valves
allows blood to flow into ventricles
pressure in heart lower than in arteries
so semilunar valves remain closed
what happens during atrial systole
atria contract
pushes any remaining blood into ventricles
what happens during ventricular systole
ventricles contract
pressure increases
closes atrioventricular valves
to prevent backflow
opens semilunar valves
blood flows into arteries
what are the two nodes involved in heart contraction
sinoatrial node (SAN)
atrioventricular node (AVN)
where is the sinoatrial node (SAN) located
wall of right atrium
where is the atrioventricular node (AVN) located
in between the two atria
what does myogenic mean
heart’s contraction is initiated from within the muscle itself
not by nerve impulses
explain how the heart contracts
SAN initiates and spreads impulse across atria so they contract
AVN receives, delays and then conveys impulse down the bundle of His
impulse travels into the Purkinje fibres
they branch across the ventricles
ventricles contract from the bottom up
why does the impulse need to be delayed (by the AVN)
if impulse spread straight from atria into ventricles
there would not be enough time for all blood to pass through
and for valves to close
how is structure of capillaries suited to their function (4)
- walls only one cell thick: short diffusion pathway
- very narrow: can permeate tissues
- red blood cells can lie flat against wall: effectively delivers O2 to tissues
- numerous and highly branched: provide a large SA
what is tissue fluid
watery substance
solution containing glucose, amino acids, oxygen and other nutrients
how is tissue fluid formed
blood is pumped through increasingly small vessels
creates hydrostatic pressure
forces fluid out of capillaries
bathes cells
returns to capillaries when hydrostatic pressure is low enough
purpose of tissue fluid (2)
supplies glucose, amino acids, O2 and nutrients to cells
also removes waste materials
order of structures in the circulatory system
vena cava
right atrium
tricuspid valve
right ventricle
semilunar valves
pulmonary artery
lungs
pulmonary vein
left atrium
bicuspid valve
left ventricle
semilunar valves
aorta
body tissues
describe the structure of haemoglobin (4)
globular
water soluble
4 polypeptide chains
each carry a haem group
where does O2 bind on haemoglobin
the haem groups
3 factors affecting O2/haemoglobin binding
partial pressure / conc O2
partial pressure / conc CO2
saturation of haemoglobin with O2
how does partial pressure of O2 affect O2 - hglbn binding
as pp O2 increases
affinity of hglbn for O2 increases
so O2 binds tightly to hglbn
when pp O2 is low
O2 is released from hglbn
how does partial pressure of CO2 affect O2 - hglbn binding (Bohr affect)
as pp CO2 increases
pH decreases
hglbn changes shape
affinity decreases
O2 released from hglbn
how does saturation of haemoglobin with O2 affect hglbn - O2 binding
difficult for first O2 molecule to bind
once bound, causes molecule to change shape
easier for 2nd and 3rd to bind
4th slightly harder: lower chance of finding a binding site
why does O2 bind to hglbn in the lungs (3)
partial pressure of O2 is high
low conc of CO2 so affinity is high
positive cooperitivity (easier after 1st bound)
why is O2 released from hglbn in respiring tissues (2)
partial pressure of O2 is low
high conc of CO2 so affinity decreases
what do oxyhaemoglobin dissociation curves show
saturation of hglbn with O2 (%)
against partial pressure O2 (kPa)
what does a curve further to the left on an oxyhaemoglobin dissociation curve show
shows hglbn has a higher affinity for O2
how does CO2 affect position of an oxyhaemoglobin dissociation curve
curve shifts to the right
hglbns affinity for O2 has decreased
