Renal 8 Flashcards
All things that stimulate AVP release also stimulate thirst, what is the exception
Dry mouth stimulates thirst
What are 2 physiological changes that influence sodium appetite
Increase aldosterone
Increase ANG II
What other behaviours can prevent dehydration
Avoidance behaviours
Ex) midday nap to avoid hottest part of day
What does the CV system respond to
Changes in blood volume and pressure
What does the renal system respond to
Changes in blood volume and/or osmolarity
What do behavioural mechanisms respond to
Osmolarity and blood volume
May occur with eating salty food and drinking liquids at the same (=ingestion of hypertonic saline)
Increase volume and increase osmolarity
Need to excrete the solid and liquid to match what was taken in
If salt and water is ingested in equivalent to isotonic solution (water=salt)
Increase volume, no change in osmolarity
Drinking pure water without ingesting solute
Increase volume and decrease osmolarity
- kidneys cannot excrete pure water so some solute lost
- need behavioural mechanisms to bring salt in
Eating salt without drinking water
No volume change, increase in osmolarity
- increases ECF osmolarity shifting water from cells to ECF
- thirst and kidneys produce concentrated urine
Water and solutes lost in sweat but only water replace
No change volume, decrease in osmolarity
- can lead to hypokalemia
- sports drinks can replace both
Dehydration due to heavy exercise or diarrhea
Decrease volume and increase osmolarity
- can lead to cell dysfunction
- increase water intake
Decrease volume and no change in osmolarity
Hemorrhage, need blood transfusion or isotonic solution
Decrease volume and osmolarity
Incomplete compensation for dehydration
What does severe dehydration result in
Loss of ECF volume, decrease BP, increase osmolarity
What 3 compensatory mechanisms restore dehydration factors
- Conserving fluid
- Trigger CV reflexes to increase BP
- Stimulate thirst
During severe dehydration decrease ECF volume would signal what
Increase aldosterone release but also increased osmolarity inhibits this
Osmolarity reigns and aldosterone not secreted
What signals CVCC during dehydration
Carotid and aortic baroreceptors
What does CVCC cause during dehydration
SA node control shifts from parasympathetic to sympathetic
What does sympathetic shift cause during dehydration
A. Force of ventricular contraction increases
B. increase peripheral resistance
C. vasoconstriction of afferent arterioles on kidney decreases GFR, conserves fluid
D. Activity at granular cells increases renin secretion
What are the renal mechanism during dehydration
Decreased BP decreases GFR
Renin-angiotensin mechanisms in response to dehydration
Paracrine feedback at macula dense cells cause granular cells to release renin
Granular cells respond to decreased BP and release renin
What is hypothalamic mechanisms to dehydration
Decreased BP, volume, increased osmolarity, and increased AG II stimulate vasopressin and thirst center
ANGII reinforces CV response
What do all the mechanisms to repair dehydration result in
- Rapid attempt by CVCC to maintain BP
- Restoration of water by conservation and fluid intake
- Restoration of osmolarity by decrease Na reabsorption and increase water reabsorption + intake
What is the pH of a solution
Measurement of H+ concentration
What is normal H+ concentration of arterial plasma
~0.00004 mEq/L very small
What is pH expressed as
Logarithmic pH scale of 0-14
What is pH 7
Neutral
Below 7.0 and H+ concentration greater than 1x10^-7
Acidic
Above pH of 7.0 and H+ below 1x10^-7 M
Alkaline (basic)
What is normal plasma pH of body
7.38-7.42, slightly alkaline
What sections of body can be very acidic
Gastric region 1.0-3.5
Urine 4.5-8.0
What are sensitive to pH changes
Intracellular proteins such as enzymes and membrane channels
what does the function of proteins depend on
Normal three dimensional structure
What do changes in H+ concentration result in
Disruptions in hydrogen bond altering structure and denaturing proteins
Very low pH (excess H+) can result in
Acidosis
- CNS depression, confusion, coma
High pH, low H+ can cause
Alkalosis
- hyperexcitability in sensory neurons and muscles
- sustained respiratory muscle contraction
In day to day function what is the body challenged with pH balance
Intake and production of acids more than bases
What is acid input due to
Diet and acid production during metabolism
What is the largest source of acid
CO2 from aerobic metabolism
What three mechanisms does pH homeostasis depend on
- Buffers (first line of Defense)
- Ventilation (75% of disturbances)
- Renal regulation of H+ and HCO3(slowest)
Buffer
Molecule that moderates, but does not prevent changes in pH by combining with or releasing H+
What does presence of buffers do
H+ is bound not contributing to pH
Where are buffers found
Within cells and in plasma
Intracellular buffers
Cellular proteins (hemoglobin), phosphate ions
What is the most important extracellular buffer
HCO3 (buffers h+ from non respiratory sources, no co2)
