Physiology 6 Flashcards
tubular fluid entering the distal tubule is __osmotic to plasma
hypo
osmolarity of the plasma?
300mosmol/l
what does the distal tubule empty into?
collecting duct
what hormone controls water reabsorption and what effect does it have on this?
ADH
increases rebasorption
what hormone controls Na reabsorption? what effect does it have on this?
aldosterone
increases it
aldosterone is responsible for secretion of which 2 ions?
H+
K+
what hormone decreases Na reabsorption?
atrial natriuretic hormone
PTH is responsible for the increased reabsorption of __ and the decreased reabsorption of __
calcium ions
PO4
the distal tubule has __ permeability to water and urea
low
where is urea concentrated?
tubular fluid
what part of the distal tubule is responsible for NaCl absorption?
early part
the late collecting duct is permeable to ions T or F
F, has a low ion permeability
plasma half life of ADH?
10-15 mins
how does ADH make the apical membrane more permeable to water?
inserts aquaporins into the membrane
why do you get hypertonic urine when ADH is high?
causes more reabsorption of water via aquaporins -> more concentrated urine
why is water not reabsorbed when there is no ADH?
no aquaporin channels can be created without ADH, so the collecting duct is impermeable
does ADH have an effect on urine volume?
yes, it decreases it
what controls thirst and ADH secretion?
hypothalamus
what effect does ADH have on the blood vessels?
vasoconstricts them
name the 2 kinds of diabetes insipidus
central
nephrogenic
symptoms of diabetes insipidus?
large volumes of dilute urine
constant thirst
Tx of diabetes insipidus?
ADH replacement
decreased atrial pressure -> __ ADH release
increased
nicotine stimulates ADH release T or F
T
alcohol stimulates ADH release T or F
F (need to pee all the time when drunk)
where in the nephron is the tubular fluid at its highest osmolarity?
descending loop of henle
how does aldosterone increase BP?
it causes Na retention which causes high BP and blood volume
where is most K+ normally reabsorbed?
proximal tubule
what component of RAAS is responsible for inducing thirst?
angiotensin II
where is renin released?
granular cells in the juxtaglomerular apparatus
what effect does renin have on the body?
increases salt reabsorption
increases blood pressure
increases ECF/blood volume
how does RAAS know if salt levels are low?
via macula densa cells (salt sensors)
granular cells are directly innervated by what nerves?
sympathetics
why do those with congestive heart failure retain fluid?
RAAS keeps working because it is responding to the low CO + BP patients with CCF get
where is ANP stored?
atrial muscle cells
when is ANP released?
when the atrial muscle cells become stretched by an increased circulating volume
what does ANP do?
decreases Na reabsorption
stops RAAS
vasodilates SM of afferent arterioles
decreases sympathetic nervous system
why does ANP work on the sympathetic nervous system?
sympathetics increases CO and TPR and therefore BP
name the 2 mechanisms that govern the process of urination
micturation reflex
voluntary control
what volume can the bladder hold before the micturation reflex is initiated?
250-400ml
what nerves control contraction of the bladder?
parasympathetics
what controls voluntary control of micturation?
the cerebral cortex and motor nerves
what does osmotic diuresis mean?
water loss
what type of diuresis involves increased excretion of urine and solute?
osmotic diuresis
