urinary 3 Flashcards
RAA
renin-angiotensin-aldosterone system
angiotensin
inactive plasma protein, not doing anything because theres no renin in the blood stream
-becomes angiotensin 1
angiotensin 1
proteins that acts as a precurser molecule for angiotensin 2
angiotensin 2
protein that acts directly on blood vessels for constriction and raising blood pressure
renin
enzyme that helps control your BP
release of renin triggers
cascade of activations resulting in angiotensin 2
how renin is secreted
many pathways but all start with decreased plasma volume (carries water, salts, enzymes)
aldosterone
balances the levels of sodium and potassium
detection of plasma volume
baroreceptors/stretch
detection of 0
osmoreceptors
ANP atrial natriuretic peptide
small peptide secreted by the heart when there is atrial stretch or high systemic blood pressure
plasma volume - osmolarity
decreased PV - Incresed O
increased PV- decreased O
osmolarity
the concentration of a solution expressed as the total number of solute particles per litre
ANP secretion leads to
- increased sodium excretion
- will increase urine output as water follows sodium, decreasing blood volume via plasma volume
-more filtration and secretion
- can also decrease the release of vasopressin
vasopressin/ antidiuretic
regulates blood pressure and increases reabsorption of water from the kidneys. conserving body water and defending against dehydration
hormonal regulation- vasopressin
- both volume and concentration of urine output are variables
- excess h20 ingested leads to →decrease vasopressin secretion and → increased H20 excretion (diluted urine)
- decreased plasma volume leads to → increased vasopressin secretion→decreased H20 excretion (concentrated urine)
concentrated urine
- vasopressin high, greater water reabsorption, excretion low volume concentrated urine
- associated with dehydration because vasopressin will try and absorb as much water as possible (19.8% water reabsorbed)
dilute urine
- vasopressin low, collecting duct relatively impermeable to water ; excretion high volume dilute urine
- diuresis : elevated urine flow rate (diuretic - substance that cause increase urine)
vasopressin -aquaporin channels
- number of aquaporin water channels variable in latter part of tubules
- mostly in distal tubule and collecting duct
-presence of aquaporins virtually absent in collecting ducts unless vasopressin present
-vasopressin causes insertion of aquaporins on apical membrane
inhibiting vasopressin
- caffeine, alcohol inhibit secretion of vasopressin
- Diabetes insipidus : failure to synthesize, release or respond to vasopressin (can reach urine output of 25L/day)
facultative water reabsorption
- adapting to need
- normal hydration - 19% water reabsorbed
- dehydration -19.8% water reabsorbed; increase number of aquaporins (APQ)
- overhydration - as low as 0% water reabsorbed; decrease number of aquaporins
sweat
- loss of both electrolytes (like sodium) and water
- salt appetite : hedonistic and regulatory (humans little regulatory)
- severe sweating will lead to increased plasma aldosterone →which lowers Na+ secretion
and
-increased vasopressin which will lead to → decreased H2O excretion
thirst -water appetite
- kidney minimizes losses but really need ingestion to replace losses
- stimulating thirst centre in hypothalamus is key
- thirst a subjective feeling stimulated by several paths (plasma osmolarity most important) → increased plasma osmolarity detected by →osmoreceptors→signal thirst
-receptors for thirst similar to vasopressin secretion
-also psychological and conditioned responses for thurst
hyponatremia
- problem with large losses of both electrolytes and water, but only replacing the water
- hyponatremia involves decreased Na+ concentration of interstitial fluid and plasma
- leads to decreased osmolarity of interstitial fluid and plasma
- leads to osmosis of water from interstitial fluid into intracellular fluid
- leads to water intoxication or hypotonic solution (cells swell)
- endurance performance - consuming large amounts of plain water, minor levels give mental confusion and dizziness
movement from kidney to urinary bladder
via Ureter
-smooth muscle contraction (peristalsis), hydrostatic pressure, gravity contribute to movement to urinary bladder
-once passed renal tubules = urinary excretion (filtered +secreted - reabsorbed)
urinary bladder
storage till voiding
urethra
exit passage to external environment
urinary bladder - filling
- distensible sac with a capacity ~ 700-800 mL where urine is stored prior to voiding/micturition
- At a certain point filling triggers sensation of fullness (~ 200-400 mL) and signal sent to spinal cord (initiating micturition reflex a spinal reflex)
- conscious awareness of desire to urinate before micturition reflex
muscle - innervation
during filling
detrusor (smooth muscle) → innervated by Parasympathetic inhibited (relax)
internal urethral sphincter (smooth muscle) → sympathetic stimulated (contract)
external urethral sphincter (skeletal muscle) → innervated by somatic motor stimulated (contract)
urinary bladder - micturition reflex
- micturition reflex signal comes back
- involuntary :
detrusor→ contract
both sphincters→ relax → voiding/micturition
voluntary control
- learn to initiate and stop micturition
- external urethral sphincter control (maintain stimulation and contraction)
- signal from cerebral cortex can over ride for limited period of time
