Week 10 Flashcards
Short term adjustment for low arterial blood pressure
- Low blood pressure detected by baroreceptors
- increased sympathetic activity which leads to increased cardiac output and increased vasoconstriction
- Increased vasoconstriction leads to increased total peripheral resistance
- Cardiac output and peripheral resistance leads to increased arterial blood pressure
Long term adjustment for low arterial blood pressure
- Low blood pressure detected by baroreceptors
- Leads to increased sympathetic activity which increases arteriolar vasoconstriction which leads to decreased glomerular capillary blood pressure which leads to decreased GFR which leads to decreased urine volume and conservation of salt and fluid
- this leads to increased arterial blood pressure
What happens when there is low NaCl, ECF volume and arterial blood pressure
- Detected by the juxtaglomerular apparatus
- Triggers kidney to release renin
- Liver continually releases angiotensinogen
- Renin converts angiotensinogen to angiotensin I
- The lungs release ACE which converts angiotensin I to angiotensin II
- Angiotensin II triggers thirst (increases ECF volume), an increase in vasopressin (conserves H2O), arteriolar vasoconstriction (helps bp), and the adrenal medulla to release aldosterone
- Aldosterone acts on the kidney and promotes Na+ reabsorption (Na+ and Cl- conserved which osmotically holds more H2O in ECF which increases H2O conserved)
ACE2
- vasodilator
- key enzyme in angiotensin pathway
- receptor for sars
Aldosterone
-Stimulates Na+ absorption
- Increases K+ secretion when K+ is high
- Acts in distal tubule and early collecting duct
Proximal tubule function
Mostly reabsorption
Loop of Henle function
Establishment of osmotic gradient
Distal tubule function
K+ and H+ secretion
Collecting duct function
Determination of urine osmolarity
Weak osmoconcentrators
cortical nephrons
Strong osmoconcentrator
- Desert dwelling mammals
- Juxtamedullary nephrons
-elongated medulla leads to exaggerated vertical osmotic gradient
Regulation mechanism of ECF volume
-Maintenance of salt balance
- Aldosterone and Na+ secretion
Regulation mechanism of ECF osmolarity
- ADH (excretion of H2O in urine) and free H2O balance
What occurs when there is a loss of H2O and Na+ during severe diarrhea
- Decreased Plasma volume which leads to decreased venous pressure
- The decrease in venous pressure will lead to two things
- A decrease in venous return which decreases end diastolic volume, which leads to decreased stroke volume and cardiac output which decreases arterial pressure which decreases glomerular filtration pressure
- An increase in sympathetic activity which leads to vasoconstriction of afferent arterioles which causes decreased glomerular filtration pressure
- Decreased glomerular filtration pressure leads to decreased GFR which leads to less Na+ and H2O secreted
Physiologic role of Aldosterone in restoration of plasma volume
- Decrease plasma volume leads to decrease in venous, atrial and arterial pressures
- Leads to a decrease in GFR and increase of activity of renal sympathetic nerves (which also leads to decrease in GFR) which leads to an increase in renin secretion due to a decrease in flow to macula densa which leads to an increase in angiotensin II which leads an increase in aldosterone from adrenal cortex which leads to an increase in Na and H2O reabsorption which leads to less Na and H2O excreted
What triggers release of ADH
Osmoreceptors detect increase in blood osmolarity in hypothalamus trigger release of ADH from pituitary gland
Where is the ADH receptor located
basolateral membrane in epithelial cell in collecting duct
Where are AQP 3 and 4 located
basolateral membrane
Where do AQP 2 get inserted
Luminal membrane
Effect of alcohol on hypothalamus
inhibits ADH secretion
Physiologic reflexes to severe sweating
Severe sweating leads to loss of hypoosmotic salt solution which leads to two things: a decrease in plasma volume which leads to a decrease in GFR and an increase in Aldosterone which leads to a decrease in Na+ excretion. Also an increase in plasma osmolarity which leads to thirst and an increase of ADH secretion which leads to less H2O secreted
pH
=log(1/[H+])
pH of pure H2O at 25 and 37 degrees C
7 and 6.81 respectively
pH of arterial blood
7.45
pH of venous blood
7.35
pH range compatible with life
6.8 to 8
Weak acid vs strong acid
strong acids have H+ fully dissociated and weak acids have a small amount of H+ dissociated
Sources of H+ Gain
-Generation of H+ from CO2
- Production of nonvolatile acids from metabolism of proteins or other organic molecules
- Loss of bicarbonate in diarrhea
- Loss of bicarbonate in urine
Sources of H+ Loss
- Utilization of H+ in metabolism
- Loss of H+ during vomiting
- Loss of H+ in urine
- Hyperventilation (respiratory alkalosis)
Characteristics of H+ generation
-Unceasing
- Highly variable
- Essentially unregulated
Defense against [H+] changes
- Chemical buffer system
- Respiratory mechanisms (short term regulation)
- Excretory mechanisms (long term regulation)