FE balance Flashcards
Osmolarity changes through the nephron
- isosmotic fluid leaving the proximal tubule becomes progressively more concentrated at the descending limb. Only water reabsorbed.
- removal of solute in the thick ascending limb creates hyposmotic fluid. ions reabsorbed but no water
- permeability to water and solutes in the distal tubule and collecting duct is regulated by hormones. Variable reabsorption of water and solutes based on body’s needs
- final urine osmolarity depends on reabsorption in the collecting duct
what is vasopressin released by
posterior pituitary gland
explain how vasopressin is released into the blood
- made and packaged in cell body of neuron
- vesicles are transported down the cell
- vesicles containing AVP are stored in posterior pituitary
- AVP is released into blood
what is the stimulus for vasopressin release
when we need more water
- high plasma osmolarity
- low blood volume
- low blood pressure
what does vasopressin do
controls the addition of water pores (aquaporin-2; AQP2) into the apical membrane of collecting duct cells
results in increased water reabsorption and more concentrated urine. Pulling back water if it is needed
- response may be graded (need a bit of h2o, secrete a little vasopressin, more if needed) and depends on the amount of hormone released
what kind of relationship is the effect of plasma osmolarity on vasopressin secretion
linear relationship
what is the the homeostatic response to decreased blood pressure
sensor: carotid and aortic baroreceptors
input signal: sensory neuron to hypothalamus
integrating center: hypothalamic neurons that synthesize vasopressin
output signal: vasopressin released from posterior pituitary
target: collecting duct epithelium
tissue response: insertion of water pores in apical membrane
systemic response: increased water reabsorption to conserve water
what is the homeostatic response to decreased atrial stretch due to low blood volume
sensor: atrial stretch receptor (if there is less blood it will not need to stretch)
input signal: sensory neuron to hypothalamus
integrating center: hypothalamic neurons that synthesize vasopressin
output signal: vasopressin released from posterior pituitary
target: collecting duct epithelium
tissue response: insertion of water pores in apical membrane
systemic response: increased water reabsorption to conserve water
what is the homeostatic response to osmolarity greater than 280 mOsM
sensor: hypothalamic osmoreceptors
input signal: interneurons to the hypothalamus
integrating center: hypothalamic neurons that synthesize vasopressin
output signal: vasopressin released from posterior pituitary
target: collecting duct epithelium
tissue response: insertion of water pores in apical membrane
systemic response: increased water reabsorption to conserve water
what type of hormone is aldosterone
steroid hormone
where is aldosterone made and released
adrenal cortex
what does aldosterone do
acts on principal (P) cells of the distal tubule and collecting duct to increase sodium reabsorption
if we turn this up to increase sodium gradient, water will follow via osmosis
what is the stimulus of aldosterone release
angiotensin 2 (low blood pressure and the Renin-Angiotensin system; RAS)
hyperkalemia (High potassium concentration in plasma)
renin-angiotensin-aldosterone system
stimuli is low BP or BV
granular cells of the afferent arteriole produce the enzyme renin which is released into circulation to act of angiotensinogen (inactive, produced by liver)
renin converts angiotensinogen to ANG 1 and then ACE (angiotensin-converted enzyme located on all vascular endothelial cells) which is active and acts on adrenal cortex
aldosterone is released from adrenal cortex to increase sodium reabsorption
what are the other targets of ANG 2
cardiovascular control center - increase CO, SV, HR
arterioles: powerful vasoconstrictor, increase R and BP
hypothalamus: increases vasopressin release, thirst and salt appetite
what are the buffers in acid base balance
bicarbonate in extracellular fluid
proteins, hemoglobin and phophates in cells
phosphates and ammonia in urine
what are the three mechanisms to maintain normal pH
buffers, regulation of ventilation and kidneys (in this order)
renal compensation in pH homeostasis
H+ secreted and bicarbonate reabsorbed at the proximal tubule
fine regulation of acid-base balance occurs at the collecting duct
interaclated 1 cells (interspersed between P cells) contain high levels of carbonic anhydrase
type A I cells
secrete H+ and reabsorb bicarbonate
response to acidosis
type B I cells
secrete bicarbonate and reabsorb H+
response to alkalosis
function of calcium in extracellular matrix
calcified matrix of bone and teeth
function of calcium in extracellular fluid
neurotransmitter release at synapse
role in myocardial and smooth muscle contraction
cofactor in coagulation cascade
cement for tight junctions
influences excitability of neurons
function of intracellular calcium
muscle contraction and signal in second messenger pathways
hydroxyapatite
calcified extracellular matrix
osteoblasts
synthesize bone
osteoclasts
resorb bone (breakdown)
parathyroid hormone origin
parathyroid glands
parathyroid hormone chemical nature
84-amino acid peptide
parathyroid hormone biosynthesis
continuous production, little stored
parathyroid hormone transport in circulation
dissolved in plasma
parathyroid hormone half-life
less than 20 mins
parathyroid hormone factors affecting release
decrease in plasma calcium
parathyroid hormone target cells or tissues
kidney, bone, intestine
parathyroid hormone target receptor
membrane receptor acts via cAMP
parathyroid hormone whole body tissue reaction
increase plasma calcium
parathyroid hormone action at cellular level
increase vitamin D synthesis; increase renal reabsorption of calcium, increase bone reapsorption
homeostatic loop for calcitirol
stimulus: endogenous precursors converted to your body via sunlight/ diet
vitamin D
liver
calcitrol
increase plasma calcium shuts of PTH secretion
calcitirol chemical nature
steroid
calcitirol transport in circulation
bound to plasma protein
calcitirol stimulus for synthesis
decrease calcium indirectly via PTH
calcitirol tager cells or tissues
intestine, bone and kidney
calcitirol target receptor
nuclear
calcitirol whole body reaction
increase plasma calcium
calcitonin chemical nature
32-amino acid peptide
calcitonin biosynthesis
typical peptide
calcitonin transport in circulation
dissolved in plasma
calcitonin half-life
less than 10 mins
calcitonin factors affecting release
increase plasma calcium concentration
calcitonin target cells or tissues
bone and kidney
calcitonin target receptor
G protein-coupled membrane receptor
calcitonin whole body or tissue action
prevents bone reabsorption, enhances kidney excretion
calcitonin action at molecular level
signal transduction pathways appear to vary during cell cycle
