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Physio Exam 3 > Topic 10 > Flashcards

Topic 10 Flashcards

1
Q

Sodium most abundant ion in extracellular fluid. What is its range and average

A

Range 140 to 145 mEq/Liter

Average 142 mEq/Liter

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2
Q

Osmolarities range and average is?

A

Range 291 to 309 mOsm/Liter

Average 300 mOsm/Liter

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3
Q

why is precise control of sodium and osmolarity important?

A

they control distribution of water between intracellular and extracellular compartments

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4
Q

Sodium and associated anions (chloride and bicarbonate) account for __% of all extracellular solute

A

94%

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5
Q

Glucose and urea contribute ____% of total osmolarity

A

3 to 5%

–Urea able to permeate cells easily so exerts little effective osmotic force

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6
Q

Sodium not very permeable so it has a big effect on fluid movement between what compartments?

A

extracellular and intracellular compartments

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7
Q

Plasma osmolarity = [formula]

A

(2.1) x (Plasma Na+ concentration)

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8
Q

what 2 systems control / regulate extracellular osmolarity and sodium concentration?

A

Osmoreceptor – ADH system

Thirst mechanism

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9
Q

Osmoreceptor Cells are Located in?

A

anterior hypothalamus

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10
Q

describe Osmoreceptor Cells mechanism (5 steps)

KNOW

A
  1. Cells shrink in response to increased ECF [Na+] (i.e. increased osmolarity)
  2. As cells shrink, impulses are sent to other nerve cells in supraoptic nuclei
  3. Impulses passed to posterior pituitary
  4. Impulses stimulate release of AHD stored in secretory granules within nerve endings
  5. Increased [ADH] of blood stimulates increased water permeability in late distal tubules, cortical collecting tubules, and medullary collecting tubules
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11
Q

Increased osmolarity results in increased water permeability which allows water to be reabsorbed (conserved) while sodium does what?

A

continues to be excreted at normal rate

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12
Q 
What happens after a WATER DEFICIT:
\_\_\_Extracellular osmolarity
\_\_\_ADH Secretion
\_\_\_Plasma ADH
\_\_\_Water permeability in distal tubules/collecting ducts
\_\_\_Water reabsorption
\_\_\_Water excreted
A 
INCREASE Extracellular osmolarity
INCREASE ADH Secretion
INCREASE Plasma ADH
INCREASE Water permeability in distal tubules/collecting ducts
INCREASE Water reabsorption
deCREASE Water excreted
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13
Q

ADH release is tied into what 2 other systems?

A
  1. arterial baroreceptor reflexes (which respond to changes in blood pressure)
  2. cardiopulmonary reflexes (which respond to changes in blood volume)
    - -Reflex pathways tied into hypothalamic nuclei that control ADH production and release
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14
Q

A Decreased blood pressure and/or decreased blood volume results in an increase or decrease in ADH release?

A

increase

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15
Q

A Small increase in osmolarity of only __% will trigger increase [ADH]

A

1%

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16
Q

Circulating volume must decrease approximately __% before appreciable change in [ADH]

A

10%

17
Q

A ___% reduction in circulating volume produces a HUGE increase in [ADH]

A

15 to 20%

18
Q

What 6 things increase ADH release

A 
Increased plasma osmolarity
Decreased blood volume
Decreased blood pressure
Nausea
Hypoxia
Morphine, Nicotine, Cyclophosphamide
19
Q

What 4 things decrease ADH release

A

Decreased plasma osmolarity
Increased blood volume
Increased blood pressure
Alcohol, Clonidine (antihypertensive), Haloperidol (dopamine blocker)

20
Q

Thirst Mechanism controls what?

A

fluid intake

21
Q

Thirst center is located in what 2 spots?

A
  1. Anteroventricular region of third cerebral ventricle (AV3V region) (Also promotes ADH release)
  2. Anterolaterally in preoptic nucleus
22
Q

The portion of the thirst center in the AV3V region: what does the upper and inferior portion contain?

A

Upper portion contains subfornical organ

Inferior portion contains organum vasculosum of the lamina terminalis

23
Q

when the thirst mechanism is stimulated, what happens?

A

causes immediate drive to drink

–Neurons within area respond to changes in osmolarity (function like osmoreceptors)

24
Q

the thirst mechanism is Stimulated by sodium concentration of?

A

2 mEq/Liter higher than normal

–Threshold for drinking

25
Q

what 5 things increase thirst

A 
Increased plasma osmolarity
Decreased blood volume
Decreased blood pressure
Increased angiotensin II
Dryness of mouth
26
Q

what 5 things decrease thirst

A 
Decreased plasma osmolarity
Increased blood volume
Increased blood pressure
Decreased angiotensin II
Gastric distention
27
Q

describe the mechanism for increased thirst inregards to Decreased blood volume and blood pressure

A

driven by neural input from the baroreceptor and cardiopulmonary reflexes since circulating volume and blood pressure can change without changes in osmolarity

28
Q

describe the mechanism for increased thirst inregards to Increased angiotensin II

A

acts on organum vasculosum of lamina terminalis

29
Q

how long does it take to absorb and distribute ingested fluid?

A

30-60min

30
Q

what would happen if the thirst drive wasn’t suppressed

A

we would be driven to continue our fluid ingestion until osmolarity was returned to normal which would result in over hydration

31
Q

With both osmoreceptor-ADH and thirst mechanism intake, we are able to prevent ______ in sodium concentration even if sodium intake increases 6-fold

A

large changes

32
Q

What happens if either the osmoreceptor-ADH or thirst mechanism intake fail?

A

Even if one system is not functional, other system still maintain the sodium concentration

33
Q

What happens if both the osmoreceptor-ADH and thirst mechanism intake fail?

A

If both systems fail, there is no other system that can regulate sodium concentration so sodium concentration will show large swings depending on sodium intake

34
Q

Angiotensin II and aldosterone play an important role controlling what?

A

SODIUM REABSORPTION

35
Q

Angiotensin II and aldosterone DO NOT play a role in controlling what?

A

SODIUM CONCENTRATION

36
Q

Increased levels of angiotensin II and aldosterone will increase what?

A

sodium reabsorption AND water reabsorption

–(Change in total amount of sodium and total amount of water, but no change in concentration)

37
Q

Extremely high levels of aldosterone will only produce an increase in sodium concentration of?

A

3 to 5 mEq/Liter

38
Q

Complete loss of aldosterone secretion can lead to a significant decrease in? Because?

A

sodium concentration
–Sodium depletion leads to volume depletion and decreased blood pressure which activates thirst reflex and the cardiopulmonary reflex which results in further decrease in sodium concentration as volume is ingested and/or reabsorbed

Physio Exam 3 (6 decks)

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