renal and endocrine systems Flashcards
what is normal blood pH?
7.35-7.45
at what ranges would the blood acidic/alkalinity be fatal?
< 6.8 or > 7.8
what is maintaining pH essential?
for structures of proteins
what’s a buffer?
a substance that can reversibly bind H+
what happens in H+ increases or decreases when a buffer is present?
increase - reaction is forced to the right
decrease - reaction is forced to the left
what is the major extracellular buffer system?
the carbon dioxide/ bicarbonate system
what are the major intracellular buffers?
phosphate and proteins
what happens if bicarbonate is lost in the body?
it is the same as if the body has lost a H+. this causes the reaction to be driven to the right generating H+
what are sources of H+ gain?
- generation of H+ from CO2
- production of non- volatile acids from metabolism of proteins and other organic molecules
- gain of hydrogen due to loss of bicarbonate in diarrhoea
- loss of bicarbonate in urine
what are sources of H+ loss?
- use of H+ in the metabolism of various organic anions
- loss of H+ in vomit
- lose of H+ in urine
- hyperventilation
what is respiratory acidosis and alkalosis?
acidosis - due to retention on CO2
alkalosis - due to excessive elimination of CO2 eg. hyperventilation
what is metabolic acidosis and alkalosis?
acidosis - due to gain of H+
alkalosis - due to loss of H+
what organs work together to control balance H+ concentration?
respiratory system (rapid) and kidneys (hours to days)
what mechanism happens during acidosis?
the kidneys do not excrete bicarbonate in the urine, the kidney tubular cells produce new bicarbonate and add it to the plasma
what mechanism occurs when alkalosis occurs?
the kidneys response is to excrete large quantities of bicarbonate
how does renal metabolism of glutamine and new bicarbonate occur?
During acidosis
- glutamine is metabolised to bicarbonate and ammonium ion
- the ammonium ion is excreted
- there is a net get of bicarbonate in the plasma (alkalinisation)
what are juxtaglomerular cells?
modified smooth muscle cells in the afferent arteriole that detect changes in the bp
when bp is low, these cells are stretched less and produce more renin
what is the macula densa?
- located at the end of the ascending limb of the loop of henle
- senses Na+ in the tubular fluid
- a decreased salt concentration, increases renin secretion
- it is though that the macula densa cells release paracrine signals (eg. adenosine or prostaglandins), which affect juxtaglomerular cells
what is aldosterone?
- steroid hormone secreted by adrenal cortex
- stimulates sodium reabsorption
- when plasma aldosterone is high, all Na+ reaching collecting ducts is reabsorbed
- aldosterone also stimulates K+ excretion
what is antidiuretic hormone?
- secreted by posterior pituitary gland in response to several physiological stimuli
- angiotensin II stimulates ADH production
- ADH is secreted when the body becomes dehydrated and is detected by osmoreceptors in the hypothalamus
- ADH is secreted when blood osmolality increases
- ADH is secreted when blood volume is low or blood pressure is low
what are the two tubular sections where water permeability is under physiological control?
cortical and medullary collecting ducts
what does ADH stimulate the insertion of?
aquaporin channels in apical membrane of the collecting ducts
what is atrial natriuretic peptide?
- 28-amino acid peptide that is synthesised, stored and released by atrial myocytes
- secretion is increased by an increase in blood volume
- ANP also acts on renal blood vessels to increase GRF
- ANP acts on the tubules to inhibit Na+ reabsorption. Promotes Na+ excretion
- ANP produces a decrease in blood volume and a decrease in bp
