BIOL 1051H Study Guide - Winter 2018, Comprehensive Midterm Notes - Urine, Osmotic Concentration, Hormone
12 Oct 2018
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BIOL 1051H
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Water Balance
• Water is 45-75% of total body weight
• ICF; intracellular – 65%
• ECF; extracellular – tissue, blood plasma lymph and transcellular – 45%
• Intracellular: in the cells
• Interstitial fluid - between cells
• When you have water, you take it in by drinking, absorbed by digestive tract and
moved into bloodstream and then it moves into tissues/tissue fluids and water
moves by osmosis
• Osmosis - what drives that movement of water? Concentration gradient of solutes in
fluid, low to high solute concentration
• Drink water - water content goes into bloodstream osmolarity of bloodstream
decreases, and as a result water osmolarity is lower than tissues, so water moves
into tissues, etc. If too much fluid moves into tissue - that is captured by lymph, and
it will take it back up to heart and put it back into bloodstream
• Question - edema is the swelling of tissue, excess of water in tissues, so in water
would accumulate in tissues, issue with drainage through lymph (wasn't able to take
it) might contribute
Regulation of Fluid intake
• Osmoreceptors respond to AngII and rising osmolarity of ECF
• What regulates fluid intake and output? Thirst, Not separate processes
• Taking in food - governed by thirst, that probably means we are dehydrated,
Osmoreceptors - receptor in brain that sense osmolarity of fluid,
Renin-Angiotension-Aldosterone (RAAS) System
• A system of hormones that helps control blood pressure an filtration in the kidneys
• Angiotensin
- Potent vasoconstrictor raising BP
- Constricts efferent arteriole raising kidney filtration
- Stimulates adrenal cortex to secrete aldosterone which promotes Na+ and H2o
reabsorption
- Stimulates posterior pituitary to secrete ADH which promotes H2O reabsorption
- Simulates thirst
- Summary - Kidney's job = to filter, if blood pressure is too low, it can't filter
properly. So activates renin. Angiotensin stimulates hypothalamus
Osmoreceptors. Aldosterone - taking Na+ from filtrate, fluid within nephron, and
helps reabsorption of Na+ in bloodstream = osmolarity will go up and water will
follow
ADH/AVP
• Secreted by posterior pituitary in response to
- Dehydration
- Loss of blood volume
- Raising blood osmolarity
• Actions of ADH
- Increases permeability of collecting duct in kidney to water. Water renteners the
bloodstream rather than being lost in urine
find more resources at oneclass.com
find more resources at oneclass.com
• Video - Hormonal communication generally begins with a part of the
neuroendocrine receiving sensory information and reacting by issuing a
command to the body, in the form of a hormone. Ex - dehydration is
detected by the Osmoreceptors in the hypothalamus which then directs
or stimulates posterior pituitary gland to release ADH, now hormone
needs to transported to the targeted tissues, typically done via
bloodstream to the kidneys and blood vessels. When hormone
molecules reach target cells they bind to matching binding receptors on
those cells and the hormone receptor complexes on those cells will
trigger changes in target cells, causes kidneys to reduce water volume
by causing increased water retention and in blood vessels - increased
vasoconstriction leads to a higher blood pressure and thus countering
the lower blood pressure caused by dehydration
Aldosterone – the “salt-retaining hormone”
• Steroid hormone secreted by the adrenal cortex
• Triggers for aldosterone secretion:
1) Low blood Na+ concentration
2) High blood K+ concentration
3) Drop in blood pressure → renin release → angiotensin II formation →
stimulates adrenal cortex to secrete aldosterone
• Functions of aldosterone
- Acts on thick segment of nephron loop, DCT and cortical portion of
collecting duct
o Stimulates reabsorption of Na+ and secretion of K+
o Water and Cl- follow the Na+
o Net effect is that the body retains NaCl and water. Helps maintain
blood volume and pressure.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Water balance: water is 45-75% of total body weight, ecf; extracellular tissue, blood plasma lymph and transcellular 45, when you have water, you take it in by drinking, absorbed by digestive tract and. Thirst, not separate processes: taking in food - governed by thirst, that probably means we are dehydrated, Osmoreceptors - receptor in brain that sense osmolarity of fluid, Renin-angiotension-aldosterone (raas) system: a system of hormones that helps control blood pressure an filtration in the kidneys, angiotensin. Stimulates adrenal cortex to secrete aldosterone which promotes na+ and h2o reabsorption. Stimulates posterior pituitary to secrete adh which promotes h2o reabsorption. Summary - kidney"s job = to filter, if blood pressure is too low, it can"t filter properly. Aldosterone - taking na+ from filtrate, fluid within nephron, and helps reabsorption of na+ in bloodstream = osmolarity will go up and water will follow. Adh/avp: secreted by posterior pituitary in response to. Raising blood osmolarity: actions of adh.
