Exam 10 - Long Term Control Of BP

Question 1

If MAP increases….what happens to local flow?

Answer 1

• adjust to bring back down to normal flow

- due to short and long term responses

Question 2

Long term control of BP

Answer 2

• keeps MAP constant over course of life
• tied into control of ECF volume and CBV
• movement of body fluid driven by solute concentration
• osmotically active salutes = anything impermeable
  - proteins / electrolytes / etc.

Question 3

Increase CBV increases pressure via 3 ways:

Answer 3

• Increased volume in arteries/veins -> up pressure
  - if no change in compliance
• Up VR -> up preload -> up SV -> up CO -> up pressure
  - if no change in SVR
• Up CO -> up flow -> up auto reg -> up constriction -> up SVR
  
  • > up pressure
    - response to mechanism two
• Decrease in CBV is just the reverse

Question 4

Small change in CO can cause:

Answer 4

• large change in BP

- 5-10% increase in CO can raise MAP 50 mmHg

Question 5

Increase in CBV will do what to MAP

Answer 5

• Increase
• Kidneys increase urine output
• decrease reabsorption of H2O/Na
• reverse is true

Question 6

Control of fluid and salt output

Answer 6

• done by kidneys
• water follows salt
• kidneys can bring MAP back to baseline

Question 7

Normal fluid intake

Answer 7

2300 ml/day

• 200 via metabolism
• 2100 via ingestion

Question 8

Normal fluid output

Answer 8

2300 ml/day

• 100 via sweat
• 100 via feces
• 700 via respiratory tract/skin
• 1400 via urine

Question 9

Renal output

Answer 9

Renal filtration - renal reabsorption

Question 10

Factors affecting filtration

Answer 10

• MAP
• Renal blood flow
• Pressure in glomerular caps
  
  • constrict afferent = down filtration
  • constrict efferent = up filtration
• oncotic pressure in glomerular caps
  
  • increase causes decrease in filtration
  • hemodilution increases filtration

Question 11

Factors affecting reabsorption

Answer 11

• [ angiotensin II ]
• Aldosterone
• ADH
• all will increase reabsorption

Question 12

Renal-Body fluid system response to increase in MAP

Answer 12

• increase filtration and/or decrease reabsorption
• water/salt output > intake
• decreased CBV
• MAP decreases until back to original level
• Reverse is true

Question 13

Pressure Diuresis (acute changes)

Answer 13

• Kidneys have highest critical closing pressure
  
  • will close before all other organs
• If MAP changes…CBV will move up or down to match water/salt intake
• difficult to change long term MAP w/o changing renal output curve or intake curve

Question 14

What will cause a chronic increase in MAP

Answer 14

• decreased renal function

- increased salt intake

Question 15

What if long term change in SVR

Answer 15

• Kidneys will bring MAP back to normal via CBV
• Problem if change in renal resistance…
  - this decreases renal function and MAP will go up

Question 16

Renin-Angiotensin System

Answer 16

• in play when pressure goes down
• Prorenin (produced/stored in juxtaglomerular cells)
• splits into renin -> released into afferent arterioles and circulates
• renin in blood 30-60 minutes…acts on angiotensinogen
• releases angiotensin I (mild vasoconstrictor)
• carried to lungs where ACE turns into angiotensin II
  
  • ACE also in epi cells of renal tubules and periph vessels
• Ang II lasts for 1-2 min then deactivated by angiotensinase

Question 17

Angiotensin II

Answer 17

• potent vasoconstrictor on arterioles/minor on veins (minutes)
  - changes SVR
• increased water/salt reabsorption (days)
• causes adrenal glands to release aldosterone
  - increases water/salt reabsorption
• WILL shift renal function curve to right…increase MAP

Question 18

Salt tolerance in normal renal function

Answer 18

• if Kidneys normal / renin secretion normal…
• person salt insensitive
• Renin-angiotensin system allows us to change salt intake and keep same MAP

Question 19

Normal salt intake

Answer 19

1500 mg or 25 mEq per day

Question 20

Walter vs Salt Intake

Answer 20

• easier to excrete water
• increase salt -> stimulate thirst center/hypoth and post pit
• thirst center -> increase water intake -> increase ECF volume
• hypoth and post pit -> up ADH -> up reabsorption -> up ECF
• increase in salt intake creates more change in CBV than water

Question 21

Hypertension

Answer 21

• MAP > 110….trending down (d>90….s>135)
• shortens lifespan
• causes: volume loading / renin-angiotensin imbalance / constriction
• can be primary (known) and essential (unknown)

Question 22

Diuretic curve shit

Answer 22

• shift renal curve left

Question 23

Coarctation of aorta

Answer 23

• clamp-like obstruction distal to arch
• kidneys perceive lower pressure than normal
  
  • increase angio II…distal becomes normal…proximal high MAP
• flow remains normal due to local control

Question 24

Preeclampsia

Answer 24

• increase MAP in pregnancy
• decreases filtration rate
• decreases release of vasodilators

Question 25

Neurogenic hypertension

Answer 25

• caused by strong stimulation of sympathetic

- anxiety, excited, etc.

Question 26

Neurogenic hypertension via baroreceptors

Answer 26

• baroreceptors cut off
• over activation of vasomotor center
• cannot inhibit vasomotor center

Question 27

Essential hypertension

Answer 27

• 90-95% of cases
• obesity account for large risk (65-75%)
• weight loss and exercise is treatment
• increase in CO / sympathetic / angiotensin II and aldosterone /
• impairment of renal function….need to give drugs too
  Treatment: lifestyle / vasodilator drugs / reabsorption block drugs
  
  • drugs target renal arterioles….make Kidneys think up in BP