lecture 10: guyton ch 19 Flashcards
the rapidly acting arterial pressure control mechansms come from para or sympathetic nervous symtpoc
sympatethic
what does the sympathetic nervous system have an effect on for arterial pressure control
effect on total peripheral vascular resistance and capacitance as well as cardiac pump
what are some examples of rapidly acting arterial pressure control mechanisms
metabolic controls
myogenic controls
shift of fluid thorugh cap walls
things like metabolic controls, myogenic controls etc are acute or long term control
acute
metabolic controls depend on
the tissues metabolic needs
myogenic cotnrols depeond on
pressure stretching
what is the cocnept taht explaisn how the body maintainns flow despite increase in BP
autoregulation
when you think of long term control mechanisms for arterial BP what organ is important
kidneys
what organ is important for long term BP regulationn
kidney
long term mechanisms for BP regulation are related to what
maintaining homeostatis of body fluid volume
long term mechanisms for BP regulation is based on what
on maintaining a balance between intake and output of body fluid
(overall regulation of kidney excretion of h20 and na+)
what is the simple concept behind long term regulation
Increase in extracellular fluid results in increased blood volume and arterial pressure
Normal body response: kidneys excrete excess extracellular fluid and returns the pressure to normal
Mechanism reverses if reduced blood volume
the simple concept of long term conctrol is based on what mechanism
starling
an increase in extracellular fluid reslts in an inxreased or decreased blood volume and pressure
increase
what is the bodyies normal response if there is an increased bp and fluid
kidneys excrete excess extracellular fluid and returns the pressure to normal
explain why exrta fluid inn extracellular space will cause increse BP and stim the kidneys
increase fluid from extracellular space will go into plasma, travel trhough circulation innto the kidneys
=kidneys will excrete extra fluid to return the bp to normal
what are some reasons that extracellular fluid would inxrease
dysfunctional lymph, increae water intake
what are renal corpuscles\glomular bodies
they enclose bundles of capillariies, make them pressure together and have a high pressure
is the hydrostatic capilary pressure in the kidneys high? and why
yes very high because of corpuscles
what is the mainn pressure that drives fluid from cap to inerstricum
hydrostatic cap pressure
In kidneys blood flows from capillary to regular intersticium
false from capillaries to glomular bodies
what are the determinants of net fluid movement across the kidney capilaries
the high pressures
what is the Amount of filtrate produced in the kidneys each minute.
125mL/min = 180L/day (because of high BP)
what are the factors that alter filtration pressure change GFR
Increased renal blood flow
Increased GFR
Decreased plasma protein
Increased GFR. Causes edema.
Hemorrhage
Decreased capillary BP
Decreased GFRwhat is GFR
glomerular filtration rate
explain how incnreased renal blood flow leads to an increased GFR
there will be more blood to glomerular bodies, increase hydrostatic pressure, increase filtration, increase GFR
explain how decreased plasma leads to an icnreased GFR
if there is not a lot of plasma protein in blood, there will be an icnreased filtration (removing fluid from blood) to maintain plasma concentration
increase GFR filtration (edema)
explain how hemmorage will lead to a decreased GFR
you are losing blood volume (which decreases stroke and cardiac output therefore decreaes BP)
=decrease GFR to maintain fluid within our plasma to maitnain plasma volume
GFR is important for controllinng/reduces changes in bp how
by adjusting blood flow
Glomerular filtration rate is regulated using three mechanisms which are
- Renal autoregulation
- Neural regulation
- Hormonal regulation
all three mechanisms of GFR adjust what
adjust renal blood pressure and resulting blood flow
the renal body fluid system plays a dominant role in what
in long term pressure control
as extracellular fluid volume increases, what happens to arterial pressure and why
it increases because CO will increase, increase stroke volume etc)
an increase in arterial pressure causes the kidneys to do what
to lose NA and water to retrun exrtacellular fluid volume to normal (icnrease urinary)
over long term, water and salt inntake must equal water
the output
explain how over long term, water and salt intake must equal output
ex: eating something salty means you need to drink a lot of water )
what are the two determinantns of long term arternal pressure
Location of renal output curve (shift?)
Level of intake line
where is the equilibrium point on the renal body fluid mechansm
where intake=output
renal body fluid feeback ssystem has infinite or finite gain
infine
long term mechanisms control BP (renal regulation) by doing what
alterinng blood volume
increased BP stimulates the kidneys to do what to water
eliminate watera nd reduce bp_
decreased BP stimulates the kidneys to do what to blood volume
increase blood volume and BP
true or false: long term kidneys will be able to return the BP back to normal due to increased filtration
true
true or false: kidneys act directly or inndirectly to maintain long term pressure
both
what mechanism alters blood volume directly
direct renal mechanism
=thru starling
indirect renal mechanisms involves what
renin angiotensin mecahnisms (hormones)
what happens if we end up witih an increased TPR
Get acute rise in arterial pressure
However, normal kidney function will respond by returning arterial pressure to the pressure level of the equilibrium point – How?
epxlain how an icnrease TPR can be regulated by kidneys
1) increased TPR w/o icnrease in vascular resistance
2) increase arterial pressure
3) increase sodium and water extretionn
4) to re maintain the arterial pressure there will be reasborption of extracellular bluid volume from other tissues 0
true or false: Changes in TPR does not affect long-term arterial pressure level
true
how do you get long term changes in artterial pressure
One must alter the renal function curve in order to have long-term changes in arterial pressure.
ex: changing renal vascular resistance does lead to long-term changes in arterial pressure.
what are some ways to change renal vasculat resistance
plaque formation
diabtes (increase glucose)
what does an increase NA intake stimulate
increases dirnking/thirst
changes in Na intake leads to changse in what bolume
interstitial fluid volume
if theres more Na in interstiium, wyou will take fluid from other cells to dilute it making u thirst
what is interstial fluid volume determined by
determined by the balance of Na intake and output
a low effective circulation volume triggers what
triggers 4 parallel effector pathways that act on the kidney
the 4 parallel effector patways act on the kidneys how
Either changes haemodynamics or changes Na+ transport by renal tubule cells.
explain atrial and pulmonary artery reflexes
Low pressure receptors (ANP) in atria and pulmonary arteries minimize arterial pressure changes in response to changes in blood volume.
what does ANP stand for
atrial natriuretic peptide
inrcases in blood volume in the atrial and pulmonary activates what
activates low pressure receptors which in turn lower arterial pressure.
how does activation of low pressure receptors enhances NA and water by what methods
Decreasing rate of antidiuretic hormone
- Increasing glomerular filtration rate
Decreasing Na reabsorption
what does ANP promote
natriuresis (loss of sodium)
what do atrial myocytes do in terms of ANP
Atrial myocytes synthesise, store and release ANP in response to stretch (low pressure / volume sensor).
what is the major effect of ANP release
renal vasodilation, icnrased blood flow and increased GFR
=more Na+ reaches macula densa cells and more na is excreted
what is ADH
antidiuretic hormone
what is AVP
arginine vaspressine
what is the main goal of ADH
concetrate urine
what is the function of ADH
Increases permeability of collecting ducts to H2O by inserting H2O channels (Aquaporins).
Helps make small amounts of concentrated urine.
ADH allows blank of urine concentration
allows rapid graded control of urinne concentration
very sensitve
ADH released is response to waht
ADH released in response to plasma osmolality and interstitial fluid volume – osmoreceptors and baroreceptors.
what is the proble mwith volume loding hypertension
overtime, without fully funcntional kidneys, even as fluid, CO and BV goes down, TPR will icnreae and pressure will nerve actually decrease
where is renin synthesized and stored
is synthesized and stored in modified smooth muscle cells in afferent arterioles of the kidney
renin is released is response to
fall in pressure
what does renin act on
acts on a substance called angiotensinogen to form a peptide called angiotensin I (AI).
what is AI converted to
AII
how is AI converted to AII
by a converting enzyme located in the endothelial cells in the pulmonary circulation.
what does angiotension II do
vasoconstric (decrease vessel diamter and affects resistance and BP)
what is the principal factor controllingn ANG II levels
renin release
what stimulates renin release
decrease circualting volume
Decreased circulating volume stimulates renin release via what
Decreased BP (symp effects on JGA).
Decreased [NaCl] at macula densa (“NaCl sensor”)
Decreased renal perfusion pressure (“renal” baroreceptor)
what does aldosterone stimulate
stimulates Na+ reabsorption and K+ excretion by the renal tubule.
was is RAS
renin angiotension system
aldosterone exerts what type of feedback on RAS
negative
how does Aldosterone exerts indirect negative feedback on RAS by
increasing interstitial volume and by lowering plasma [K+].
what is imporatnt in conserving Na+ and water
aldosterone
aldosteronne is imporatnt for consevring Na+ and water but also good at …
preventing massive swings in K+ levels.
what are the 3 main action of reninn angiotensinn system
Causes vasoconstriction (direct effect)
Causes Na retention by direct and indirect actions on the kidney (increased secretion of aldosterone by the adrenal cortex)
Causes shift in renal function curve to right (acts on brain to increase thirst)
RAS is imporant in mainting what during changes in NA intake
normal arterial pressure
as Na intake is increased, renin levels fall or rise to near what
fall near 0
as Na intake is decreased renin levels BLANK
icnrease signifcantly
RAS causes the Na loading renal funcnntion curve to be steep or not
steep
essential hypertension or seconndary is more common
essential
what is the incidence of essential hypertensionn
90%
what is the cause of essential hypertension
not exactly known but hereditaty component
what is the incidence of secodnary hypertension
less than 10%
what are the common causes of secondaary hypertension
common causes: chronic kidney disease, renovascular disease
Prescription drugs, street drugs, natural products, food, industrial chemicals
severe BP does water to blood flow
doesnt allow good flow by breaking up vessels
