6 renal and endocrine systems Flashcards
Describe some functions of the kidney
Removal of waste products
What is normal blood pH?
7.4
What is the equation for pH?
-log[H+]
What is a buffer?
Any substance that can reversibly bind to H+
What is the equation for a weak acid?
H+ + buffer- <-> Hbuffer (weak acid)
What is the major extracellular buffer?
The CO2/ HCO2 system
What are the major intracellular buffers?
Phosphates and proteins
What is the reaction of carbon dioxide and water?
CO2 + H2) <-> H2CO3 <-> H+ +HCO3-
What does bicarbonate loss also mean?
Hydrogen ion gain
How is hydrogen ion gained?
From CO2
How is hydrogen ion lost?
Use of ion in metabolism
What is respiratory acidosis caused by?
Retention of CO2
What is respiratory alkalosis caused by?
Excessive elimination of CO2
What is metabolic acidosis caused by?
Gain of H+
What is metabolic alkalosis caused by?
Loss of H+
Describe the respiratory system response to H+ concentration balance
Very rapid (minutes)
Describe the renal system response to H+ concentration balance
Slow responding (hours to days) and can eliminate imbalance
How do kidneys eliminate or replenish H+?
By altering bicarbonate concentration
Describe what occurs within the kidneys during acidosis
Plasma H+ concentration increases and kidneys do not excrete bicarbonate in urine and kidney tubular cells produce new bicarbonate and add it to plasma. All filtered carbonate is reabsorbed and their is a net gain of bicarbonate as H+ is secreted and combines with non bicarbonate buffers
Describe what occurs within the kidneys during alkalosis
Kidneys response is to excrete large quantities of bicarbonate
What does carbonic anhydrase do?
Break down carbonic acid to water and CO2 which can enter the cell while another form allows CO2 to bind to water to form bicarbonate and be absorbed through the base membrane to the bloodstream
Describe renal metabolism of glutamine and new bicarbonate in acidosis?
All filtered HCO3- is reabsorbed
What are juxtaglomerular cells?
Intrarenal baroreceptors
Describe the action of JG cells when BP is low
They are stretched less and secrete more renin
What are JG cells innervated by?
Sympathetic renal nerve
Where is the macula dense?
At the end of the ascending limb of loop of Henle
What does the macula densa do?
Sense sodium in tubular fluid
What is aldosterone?
A steroid hormone secreted by the adrenal cortex that stimulates sodium reabsorption at the DCT and CD
Describe sodium reabsorption when plasma aldosterone is high
All the sodium is reabsorbed
What does aldosterone do?
Stimulate sodium reabsorption and potassium excretion
What secretes ADH?
Posterior pituitary gland in response to severe physiological stimuli
What stimulates ADH release?
Angiotensin II - when the body is dehydrated
When is ADH secreted?
When blood osmolality increases and BV or BP is low
What is water permeability dependent on?
The permeability of the membrane
Where is water permeability under physiological control?
The cortical and medullary collecting ducts
What is water permeability controlled by?
ADH
How does ADH control water permeability?
Stimulates insertion of aquaporin channels in apical membrane of CDs
What is ANP?
A 28 amino acid peptide that is synthesised
What is ANP secretion increased by?
An increase in BV and BP
How does ANP affect GFR?
Acts on renal blood vessels to increase GFR
How does ANP affect sodium absorption/ excretion?
Acts on tubules to inhibit sodium reabsorption and promote natriuresis
What does ANP do to BV and BP?
Decreases them
