physiology 3 Flashcards
what are the 3 types of capillaries
continuous
fenestrated
discontinuous
what are continuous capillaries
no clefts or pores - ie brain
what are fenestrated capillaries
capillaries that have clefts and pores - in the intestines
what are discontinuous capillaries
capillaries that have clefts and massive pores - ie liver
what is bulk flow
the process that occurs in capillaries leading to mass diffusion
what forces push fluid into the capillaries
osmotic, oncotic pressure
what force pushed fluid out of the capillaries
hydrostatic pressure
are there valves in lymph vessels - why
yes - passive transport need fluid to not go backwards
what is oedema
accumulation of fluid
what can cause oedema
lymph obstruction
raise CVP
hypoproteinaemia - liver failure, nutrition
increased capillary permeability - infection
what is Darcy’s law
flow = change in pressure/resistance
what is CVP
central venous pressure
what is central venous pressure - what does it show
the blood pressure in the venae cavae, - reflects the amount of blood returning to the heart
the ability of the heart to pump the blood back into the arterial system
how is Darcy’s law applied to the systemic circulation
MAP = CO x TPR
what is resistance juggling
controlling intrinsic, extrinsic mechanisms - to moderate arteriolar radius
why does arteriolar radius need to be monitored
to make sure MAP is sufficient as well as the blood flow to the vascular beds.
(which contradict each other)
what are intrinsic mechanisms concered with
the selfish needs of individual tissues and organs
what are extrinsic mechanisms concerned with
mataining TPR and in tturn MAP -
what happens if MAP drops
then blood pressure will have droped leading to possible singopy
what are the two types of extrinsic control
neural
hormonal
what are the main nerves in extrinsic control
sympathetic - nor adrenaline - beta 1 - fasoconstriction
parasympathetic usually has no effect
what are the extrinsic hormonal controls
adrenaline
angiotensin 2
vasopressin
atrial natriuretic factor
what are the majority of intrinsic controls
local controls
how does adrenaline effect TPR
same effect as nor adrenaline on the beta 1 receptors
what happens in some other tissures when adrenaline is released
activates beta 2 receptos
causing arteriolar dilation - increased flow with lower TPR
what does angiotension 2 do to the extrinsic control
produced in response to low blood volume
arterial constriction
increased Total pheripheral resistance
what does vasopressin do to the extrinsic control - what is it
antidiuretic hormone
released in response to low blood volume
causes arteriolar constriction
increased TPR
what does atrial natriuretic factor do
released in response to high blood volume
causes arteriolar dilation
decrease TPR
what are the 3 local(intrinsic) controls
active (metabolic) hyperaemia
pressure (flow) autoregulation
reactive hyperaemia
the injury response
what are some of the special circulations
coronary circulation
cerebral circulation
pulmonary circulation
renal circulation
what is special about the renal circulation
main function is filtration which depends on pressure
changes in MAP would have big effects on blood volume
shows excellent pressure autoregulation
what is special about the pulmonary circulation
O2 causes arteriolar constriction
the opposite response to most tissues
ensures that blood is directed to the best ventilated parts of the lung
what is special about the cerebral circulation
must be kept stable whatever otherwise syncope
shows excellent pressure autoregulation
what is special about coronary circulation
blood supply is interrupted by systole
shows excellent hyperaemia
express many beta 2 receptors - swamp any sympathetic arteriolar constriction
how does active metabolic hyperaemia work
increased metabolic activity - increased conc. of metabolites
triggers release of paracrines
arteriolar dilation
increases flow to wash out metabolites
what are some example of paracrine
EDRF - endothelium derived relaxing factor
NO - nitric oxide
what is active metabolic hyperaemia an example of
an adaptation to match blood supply to the metabolic needs of that tissue
what is hyperaemia
an excess of blood in the vessels supplying an organ or other part of the body.
how does reactive hyperaemia work
occlusion of blood supply causes a subsequent increase in blood flow
an extrema version of pressure autoregulation
how does pressure flow autoregulation work
much in the same way as active metabolism regulation as it responds to the accumulation of metabolites
what is different from active metabollic regulation to pressure(flow) regulation
pressure flow regulation is in response to a drop in MAP by dilating to keep flow the same as otherwise it would be reduced
how does the injury response work
mast cell releases histamine leading to increases blood flow/permeability
what do elastic arteries act as
pressure resoviour - dampens down pressure variations
what is the pressure wave (in arteries)
stroke volume
velocity of ejection
elastic of arteries
TPR
what is the normal arterial pressure
120/80 mmHg
what is the systemic filling pressure - what is it
20 to 5 mmHg
the pressure going back in to the right atrium from the veins
how does pressure drop through the vascular tree
small drop through arteries
large drop through arterioles
leaves a small pressure for the capillaries
what is the pressure in the pulmonary circulation
1/5th of the systemic
what is the small drop in pressure through the arteries
95 to 90 mmHg
what is the large drop through the arterioles
90 to 40 mmHg
what are the 5 thighs that effect venous pressure and venous return
gravity
skeletal muscle pump
venomotor tone
systemic filling pressure
what effect doe gravity have on pressure and flow
pools in the legs leading to -30mmHg - head - SUBTRACTS 40mmHg 0 mmHg heart ADDS - 80mmHg \+90 mmHG
what does gravity cause to pressure and flow
causes venous distension in legs
reduce EDV, preload, SV, CO, MAP
cause venous collapse in neck
- estimate central venous pressure
does gravity effect driving pressure from arteries to veins
no way
what is skeletal muscle pump
the moment of blood through the veins by the contraction of muscle
rhythmic vs static exercise
what does skeletal muscle pump prevents
deep vein thrombosis
how does the respiratory pump
the thoracic cavity creates a negative pressure when inspiration
leads to a deficit with +ve pressure in the abdomen pulling blood up to the heart
what is vasomotor tone
state of contraction of the smooth muscle surrounding the venules and veins
mobilises capacitance
what is capacitance
the blood stored up in the veins that is forced up after increased MAP
what is systemic filling pressure
pressure created by ventricles and transmitted through vascular tree to the veins
what does clotting involve
formation of a platelet plug
formation of a fibrin clot
what turns fibrinogen to fibrin
thrombin
what becomes fibrin
fibrinogen
what does fibrinogen become
fibrin
how does the endothelium stop the clotting
anti-clotting mechanisms
what are some of the anti-clotting mechanisms
thrombomodulin
heparin
produces tissue factor pathway inhibitor (TFPI)
t-PA
prostacyclin and NO
what does TFPI tissue factor pathway inhibitor
stop thrombin production
what does thrombomodulin do
binds to thrombin and inactivates it
what does heparin do
inactivates thrombin
what is t - PA what does it do
tissue plasminogen activator
plasminogen which makes plasmin that digests clot
what does prostacyclin and NO do
both inhibit platelet aggregation
