week 2 quiz review Flashcards
review of negative feedback loop
stimulus will produce a change in normal homeostasis; this is detected by sensors and this input travels along the afferent pathway to the control centre; control centre creates an output which is sent along the efferent pathway to an effector; the response of the effector decreases the original stimulus, thus maintaining homeostasis
stimulus
a change great enough to disrupt normal homeostasis conditions
receptors
contain sensors that detect the stimulus and create generators or receptors potentials; this information is sent along the afferent pathway to the control centre
bladder at rest
motor neurons are firing, detrusor muscle is relaxed, and internal and external sphincters are contracted
what parts of the bladder are controlled by the parasympathetic system?
the detrusor and the internal sphincters
what parts of the bladder are controlled by the somatic system?
the external sphincter
where is the micturition centre located?
the sacral spinal cord
what is the smooth muscle of the bladder
detrusor muscle and internal urethral sphincter
what does the contraction of the detrusor muscle do?
makes the bladder small, thus increasing pressure inside the bladder
what are the motor neurons synapsing with during bladder at rest?
the sphincter muscles, causing these structures to stay contracted
bladder when full
sensory receptors detect stretch and send this sensory input to sacral spinal cord; this causes two motor pathways to be stimulated by the parasympathetic system, the first is for the detrusor muscle to contract and the second is the relaxation of the internal sphincter; also during this time the firing of motor neurons ceases
what is the stimulus for ADH secretion?
high blood osmolarity and when water reabsorption is low
where and what are the receptors for ADH feedback loop?
the osmoreceptors in the hypothalamus
what releases ADH?
posterior pituitary gland which is controlled by the hypothalamus
where does ADH act?
in the late DCT and collecting ducts
what does ADH bind to?
V2 receptors on the basolateral membrane of collecting duct cells
what cells does ADH act on?
principal cells
result of ADH feedback loop
decreased plasma osmolarity and increased facultative water reabsorption
what produces renin?
the juxtaglomerular apparatus
what detects low blood pressure
JGA and baroreceptors in the carotid sinus
what is renin?
an enzyme that causes the conversion of angiotensinogen to angiotensin I
where is aldosterone released from?
the adrenal cortex
ANG II effects
increased sympathetic activity, vasoconstriction, increased Na and H20 reabsorption, ADH secretion via posterior pituitary gland, and aldosterone secretion
why is ANG II associated with sympathetic system?
because this systems helps to increase blood pressure by increasing heart rate and blood pressure by vasoconstriction; sympathetic system also causes the release of norepinephrine when ANG II binds to AT1 receptors, causing vasoconstriction
when happens when blood pressure conditions are normal?
blood vessels are dilated and intrinsic controls override extrinsic controls
what does ANG II bind to?
AT1 receptors
how does ANG II cause increased tubular reabsorption of Na and Cl?
through increasing Na, Cl, and K channels in the CT; also causes increased activity of the Na/H antiporter, as well as the Na/Cl symporter
what does aldosterone do in simple terms?
causes increased activity of the principal cells of the collecting ducts; increases Na, Cl, and K channels here
what does aldosterone bind to?
mineralocorticoid receptors within the cell cytoplasm
afferent vs efferent arteriole during normal conditions
afferent is typically larger in diameter than the efferent
afferent and efferent arterioles if BP needs to increase
afferent will constrict, allows decreased GFR
afferent and efferent arterioles if BP needs to decrease
efferent will constrict, allows increased GFR
what kind of hormone is aldosterone?
a steroid hormone
where does aldosterone act?
mainly in the CT (principal cells)
what is the primary purpose of aldosterone?
to increase the activity of the Na/K pump; but also increases sodium, potassium, and chloride channels
ANP
released when blood pressure is high from the atria of the heart; functions to inhibit renin and therefore decreased sodium reabsorption
what is a diuretic?
a type of drug that causes the kidneys to make more urine, decreasing blood volume and pressure as a result
transport proteins involved in aldosterone mechanism?
Na/K pump, Na channels, K channels, Cl channels, and aquaporins
where do osmotic diuretics work?
in the PCT
how do osmotic diuretics work?
by blocking the sodium-glucose symporter on the apical surface through using mannitol (similar structure to glucose)
what water reabsorption are osmotic diuretics associated with?
obligatory
where do thiazide-type drugs work?
in the DCT
how do thiazide-type drugs work?
through blocking the Na and Cl symporter on the apical side in the DCT
what water reabsorption are thiazide-type diuretics associated with?
facultative
where do loop diuretics work?
in the ascending limb
how do loop diuretics work?
block the Na-K-2Cl symporter on the apical side
what water reabsorption are loop diuretics associated with?
facultative
where do potassium-sparing diuretics work?
in the CT
how do potassium-sparing diuretics work?
they limit the activity of K channels, also causing the Na/K pump to cease; cause the tubule cells to retain more potassium and secrete more sodium
what water reabsorption are potassium-sparing diuretics associated with?
facultative
3 major fluid compartments
intracellular fluid, interstitial fluid, and intravascular fluid
order of fluid compartments holding the most fluid to the least
intracellular fluid > interstitial fluid > intravascular fluid
solute concentrations higher in the interstitial fluid and blood plasma
Na, Cl, and Ca
solute concentrations higher in the cell
K, HCO3, Mg, HPO4, and SO4
what is released by the kidneys when there are high calcium levels?
calcitonin; causes more bones to be built
what is released by the kidneys when there are low calcium levels?
calcitriol; causes more absorption of calcium from foods in the GI tract
negative feedback loop associated with PTH
PTH released from parathyroid gland when calcium levels are low; this causes osteoclasts to degrade bone matrix and also for kidneys to release calcitriol
where is calcitonin released from?
parafollicular cells
water input breakdown
60% beverages, 10% metabolism, 30% foods
water output breakdown
60% urine, 28% insensible losses, 8% sweat, and 4% feeces
thirst mechanism
increased plasma osmolarity (and dry mouth) will activate osmoreceptors in the hypothalamus which will activate the hypothalamic thirst centre; ingestion of water will cause mouth and throat to moisten and for intestines to stretch, allowing for water to be reabsorbed from the GI tract, decreasing plasma osmolarity
excess hydration
causes ECF osmotic pressure to drop (lower concentration of solutes), causing water to move into the cells and swelling them
dehydration
cells will shrink and ECF osmolarity increases, causing water to move into ECF from cells
acids
have higher concentrations of H+ and tend to donate H+
bases
have higher concentrations of OH- and tend to donate OH-
example of a strong acid
HCl
example of a strong base
KOH
pH scale
1-14; it is a log scale so moves up a factor rather than in a linear fashion
buffer systems
these convert strong acids and bases into weak ones
what is a buffer?
a solution that can resist pH change upon the addition of acid or base components; usually consist of weak acids or bases with a salt
is HCO3- weak or strong?
it is a weak base
is H2CO3 weak or strong?
it is a weak acid
do strong acids and bases dissociate easily or not?
easily
example of buffer system with Na and why does this work?
HCl + NaHCO3 > H2CO3 + NaCl; this works because bicarbonate is a weak base that reacts with a strong acid to produce a weak acid and a salt, thus increasing the pH
how do salts form?
when an acid reacts with a base in a neutralisation reaction; ex. HCl + KOH > H20 + KCl
low pH 2 pathways
either involves Na/H antiporter and HCO3 carrier in the PCT or H pump and HCO3/ Cl antiporter in the CT (intercalated cells) on apical surface; brings H+ into urine and HCO3 into bloodstream
high pH pathway
involves CT and intercalated cells and proton pump is located on the basolateral side and send protons into the bloodstream; at the same time HCO3/ Cl antiporter moves HC3O into the urine and Cl into the cell
what is HCO3 usually cotransported with?
Cl
negative feedback loop for low blood pH
chemoreceptors in the medulla and heart send signals to the inspiration centre in the medulla; causes the diaphragm to contract and thus more CO2 to be exhaled
why does exhaling CO2 increase blood pH?
the less CO2 in the blood, the less H2CO3 will form, and thus less H+ in the blood
does HCO3 move in or out of blood when low pH?
into the blood
carbonic anhydrase
enzymes that allow for the bicarbonate shift reaction to occur
what is a strong acid?
one that 100% dissociates
how would a strong acid be neutralised?
by combining with a weak base; this will cause it to form a weak acid, along with a salt
what is the result of a strong acid being neutralised?
the pH will increase
example of a strong acid being neutralised
HCl + NaHCO3 > NaCl + H2CO3
how would a strong base be neutralized?
by combining with a weak acid; this will cause it for form a weak base, along with a salt
what is the result of a strong base being neutralised?
the pH will decrease
example of a strong base being neutralized
NaOH + H2CO3 > NaHCO3 + H20
receptors for low blood pH feedback loop
central chemoreceptors in the medulla oblongata and peripheral chemoreceptors in the carotid and aortic bodies
control centre for low blood pH feedback loop
inspiration centre in the medulla oblongata
the more CO2, the more acidic or basic?
acidic
chloride shift
HCO3 and Cl usually move through this in opposite directions; assists with blood pH changes
how does a proton pump work?
takes ATP, breaks it down to ADP + inorganic phosphate; this energy moves the proton from the inside to the outside of the cell
why do we use the HCO3/Cl shift?
because the negative charge being taken out needs to be replaced; negative charges inside the cell are important for neuron functioning
how is H+ buffered in the urine
they either combine with NH3 to form NH4+ or combine with HPO4– to form H2PO4-
what does increased blood osmolarity do in regards to the thirst mechanism and how are these signals transferred to the CNS
creates dry mouth and decreased saliva activity; these signals are transferred to the CNS by sensory receptors in the mouth/pharynx
how is the RAAS system related to thirst mechanism
decreased blood volume and pressure activate ANG II; in which this activates the thirst mechanism to cause us to drink more water
