Renal II Flashcards
Filling of the bladder activates stretch receptors initiating the _______ reflex
micturition
What is the more common term for micturition?
Urination
______ undergo continuous rhythmic contractions (pacemaker cells)
Ureters
Movement of fluid from the kidney to the urinary bladder occurs with the help of _____ (standing up) and ________ ______
gravity, rhythmic contractions
Bladder has a thick wall of ______ muscle, specifically ______ smooth muscle which contains ____ junctions in a ______ pattern
smooth, unitary, gap, uniform
_______ muscle: the smooth muscle that makes up the wall of the bladder, makes up most of the wall
Detrusor
The sensory information will not only come the _______ region of the spinal cord, but there will be ______ tracts (spinothalamic tracts), up to the _____, to the ____, then into different regions of the _______ _____ so that you become actively aware that you need to urinate. Then you will have ______ tracts that go from the cortex down to this network to either allow or inhibit urination
sacral, ascending, thalamus, pons, cerebral cortex, descending
_____ sphincter of the bladder: smooth muscle, passively contracted
Inner
_____ sphincter of the bladder: skeletal muscle, stays contracted
External
Arrange these statements according to “Micturition:”
1. Stretch receptors fire
2. Parasympathetic neurons fire. Motor neurons stop firing
3. Smooth muscle contracts. Internal sphincter is passively pulled open. External sphincter relaxes
1, 2, 3
Urge to urinate appears around ___ml
200
Once exceeding ___ml internal sphincter forced open, leading to reflexive opening of external sphincter and loss of voluntary opposition
500
~___ml left in bladder after micturition
10
An increase in the volume of fluid in the bladder leads to an _______ of the wall and an activation of _____ receptors
expansion, stretch
The activation of stretch receptors in the bladder causes an ↑ in ________ activity, a ↓ in __________ activity, and a ↓ in ? activity
sympathetic, parasympathetic, somatic motor neuron
A decrease in sympathetic activity towards the bladder causes a ?
relaxation of the internal urethral sphincter
An increase in parasympathetic activity towards the bladder causes a ?
contraction of the detrusor muscle
A decrease in somatic motor neuron activity towards the bladder causes a ?
Relaxation of external urethral sphincter
The relaxation of the internal urethral sphincter and the contraction of the detrusor muscle combined cause ?
the opening of the external urethral sphincter
The relaxation of external urethral sphincter causes ?
the opening of the external urethral sphincter
The combination of the opening of the internal urethral sphincter and the opening of the external urethral sphincter cause ?
Micturition
What is incontinence?
The inability to control urination voluntarily
What causes incontinence in infants?
Corticospinal connections necessary for voluntary control have yet to be established
What are some other causes of incontinence?
Damage to internal or external sphincter
Spinal cord damage
Aging
- Loss in muscle tone
- CNS problems
- Prostate growth in males
Fluid volume is important because it dictates blood volume which dictates ____ _____
blood pressure
Homeostatic mechanisms for fluid/ electrolyte balance focus on maintaining four parameters: ?
- Fluid volume
- Osmolarity
- Concentrations of individual ions
- pH
One of the main goals for fluid electrolyte balance is ____ ______ – maintaining a relatively constant stable value for the 4 parameters
mass balance
Kidneys can only adjust what is already in the body, so when we need _____ adjustments that’s when behavioral mechanisms play an essential role
external
The body is in a state of constant _____. We ingest ~ 2L of fluid containing 6-15 grams of _____ and we take in ______ amount of other ions (K+, H+, Ca2+, HCO3- and phosphate ions)
flux, NaCl, varying
Whatever comes in must be excreted if not needed, this is known as ____ ______ and the ______ are the primary route. There are _____ amounts lost in feces and sweat and the ______ lose water and help remove H+ and HCO3- by excreting CO2
mass balance, kidneys, small, lungs
Behavioral mechanisms also play an essential role in ______ and _____ _______
thirst, salt appetite
We concerned with homeostasis of these substances for the following reasons:
1. H2O and Na+ determine ECF ______ and _______
2. K+ balance can cause problems with ______and ______ function
3. ____ is involved in many processes in the body
4. H+ and HCO3- determine the body ____
- volume, osmolarity
- cardiac, muscle
- Ca2+
- pH
ECF osmolarity affects cell _____
volume
Maintaining osmolarity in the body is important because water can cross most cell membranes freely due to _______ channels
aquaporin
Extracellular fluid is usually ______
isotonic
Its important to maintain normal osmolarity to maintain most normal cell volumes and hence normal cell _______
functioning
Some cells have independent mechanisms for maintaining cell volume:
- _____ ______ cells are constantly exposed to hypertonic ECF and produce organic solutes such as sugar alcohols and amino acids to match their intracellular osmolarity to the ECF
- Some cells use changes in cell volume to initiate ______ _______, liver cells beginning protein and glycogen synthesis (swell)
Renal tubule, cellular responses
In a hypotonic solution, the cell becomes ____
In a isotonic solution, the cell becomes _______
In a hypertonic solution, the cell becomes _______
lysed, normal, shriveled
Fluid and electrolyte balance is an integrative process involving the ________, _________ and _____ systems as well as ________ responses
respiratory, cardiovascular, renal, behavioral
True or False: there is overlap between the pathways that integrate fluid and electrolyte balance?
True
_________ and ________ systems are under neural control and are quite rapid, _____ responses occur more slowly because kidneys are primarily under endocrine and neuroendocrine control
Cardiovascular, respiratory, renal
A decrease in blood volume causes a decrease in blood pressure, which trigger?
Volume receptors in atria and carotid/aortic baroreceptors
The volume receptors in atria and carotid/aortic baroreceptors trigger _______ reflexes
homeostatic
After the homeostatic reflexes are triggered, it activates the:
__________ system: ↑ CO, vasoconstriction
________: ↑ thirst, ↑ water intake, ↑ ECF and ICF volume
These combined ____ blood pressure
______: conserve salt and water to minimize further volume loss
Cardiovascular, Behavior, ↑, Kidneys
________ receptors: low pressure baroreceptors that exist primarily in the atria as well as a few different areas and they respond to atrial filling and its an indicator of overall blood volume
Volume
Water makes up ___-___% of our body weight, 2/3 is ____ and 1/3 ____
50-60, ICF, ECF
Water intake must match _______
excretion
Under normal conditions water loss in urine is a _______ mechanism, other mechanisms become significant during conditions like ______ ______ and ______
regulated, excessive sweating, diarrhea
The primary _____ source of water is through our digestive tract while the main _____ source is urine and can be regulated
input, output
Fecal water loss and insensible water loss is normally relatively _____
stable
Our autoregulatory systems only work in response to ______ not _______
hypertension, hypotension
The concentration, or osmolarity, of urine is a measure of how much water is ______ by the kidneys
excreted
When removal of excess water required, the kidneys produce ____ volume of _____ urine. If the kidneys need to conserve water, ____ volume of _______ urine is produced
large, dilute, low, concentrated
_______: removal of excess urine
Diuresis
The kidneys control urine concentration by varying the amounts of water and Na+ reabsorbed in the _____ nephron (distal tubule and collecting duct)
- To produce dilute urine the distal nephron must reabsorb solute without allowing ? by osmosis aquaporins
- To produce concentrated urine, the distal nephron must reabsorb water and little ______.
distal, water to follow, solute
The ______ limb is only permeable to water but not to solutes (water will be reabsorbed), while the ________ limb is mainly permeable to solutes but not water (solutes will be reabsorbed)
descending, ascending
________ controls water reabsorption
Vasopressin
How do the distal tubule and collecting duct alter their permeability to water?
Adding or removing water pores in the apical membrane under the direction of the posterior pituitary hormone vasopressin (AVP), aka antidiuretic hormone (ADH)
If water levels are high then there is ____ release of AVP in the body, and in response to that, the channels will be removed from the apical membrane which then prevents water _______
low, reabsorption
With ______ vasopressin, the collecting duct is freely permeable to water. Water leaves by osmosis and is carried away by the vasa recta capillaries. Urine is concentrated
In the ______ of vasopressin, the collecting duct is impermeable to water and the urine is dilute
maximal, absence
Within the _____ layer of these cells you’d have multiple types of aquaporin channels. But on the _____ membrane, you have a different subtype of aquaporin channels known as AQP2, the APQ2 channels are under ______ control
basolateral, apical, hormonal
Vasopressin will be driven in response to ____ osmolarity, ____ blood volume, and ____ blood pressure. Vasopressin will be secreted in response to “we need to _____ more water”
high, low, low, reabsorb
Vasopressin receptor: ___ receptor
V2
Vasopressin release is not an “?” response its constantly ______-
all or none, adjusted
Vasopressin is released from the _______ pituitary, go the collecting duct cells, and will act upon a vasopressin receptor on the _______ layer (V2 receptor). This is a g-protein coupled receptor that uses the ________ pathway (converts ATP to cAMP), cAMP results in the activation of proteins kinases that will go and phosphorylate proteins on vesicles that are stored within the cell and contain _____ channels that cause exocytosis across the apical membrane, now water can cross the apical membrane
posterior, basolateral, adenylcyclase, APQ2
Insertion of AQP2 is graded, depends on the amount of ____ _____
AVP present
Vasopressin causes the insertion of water pores into the ____ membrane
apical
What stimuli control vasopressin secretion?
Blood volume, pressure and osmolarity
Increased ______ is the most potent stimulus of AVP secretion
osmolarity
AVP secretion also shows a ______ ______
circadian rhythm
Decreased blood pressure would decrease activity in your high-pressure baroreceptors (carotid and aortic baroreceptors) information feeds into your ________ and can affect ________ release
hypothalamus, vasopressin
? : very large neurons that have a cell body that exist within the hypothalamus with long axons that extend down to the posterior pituitary
Magnocellular neurosecretory cells (MNC)
Vasopressin is a peptide hormone, meaning ?
its produced in the cell body itself
MNCs have been proposed to be osmo-sensitive, meaning they will ? . They do that by stretch activated ion channels that are linked to the actin filaments within the cell that close when the cell gets _____
change their level of activity in response to a change in osmolarity around them, stretched
MNCs are stretch sensitive neurons that increase their firing rate as ______ increases (shrink)
osmolarity
Under ______ Basal VP secretion there would be some fluid that would leave the cell, reduced tension on the cell membrane, which would open some of these channels causing an influx of cations (sodium, calcium)
normal
In response to _______ in osmolarity, fluid would flow into the cell, it would swell, and the stretching of the cell membrane would close most of these ion channels, this would reduce the level of activity, reduce the level of VP secretion
reductions
In response to _______ solutions that would cause a lot of water to leave the cell, cause a shrinkage of the cells, open a lot more of the osmo-sensitive channels, resulting in a greater depolarization, increased exocytosis of VP, leads to increased water reabsorption
hyperosmotic
AVP is important for water reabsorption out of the nephron, but the high osmolarity within the _______ _______ is absolutely necessary to create the concentration gradient for osmotic movement of water out of the or collecting duct.
medullary interstitium
What two mechanisms create the hyperosmotic interstitium?
- Countercurrent exchange system
- Urea
What is the general definition for a countercurrent system?
They classically involve arterial and venous blood flowing past each other in proximity of each other that allows the exchange of substances (solutes, heat, etc.). These systems don’t prevent heat loss, they just minimize unnecessary heat lost and conserve what can be conserved
What is a crucial role in classical countercurrent exchange systems?
Prevent cold blood coming back to the body
What is exchanged in the context of countercurrent systems in the kidneys?
Kidneys transfer water and solutes instead of heat
In the renal countercurrent exchange system, is flow in the same or opposite directions?
opposite
In the countercurrent system in the kidneys there is 2 components, there is not just one set of tubes (like in a heat exchange system): ?
Countercurrent Multiplier: the loop of Henle
Countercurrent Exchanger: peritubular capillaries
When we are looking at creating a hyperosmotic interstitial space in the medulla we are focusing on the _________ nephrons and the _____ _____
juxtamedullary, vasa recta
Filtrate entering the descending limb becomes progressively more ______ as it loses water
concentrated
Blood in the vasa recta removes ______ leaving the loop of Henle
water
The ascending limb pumps out NA+, K+, and Cl-, and filtrate becomes ______
hyposmotic
The descending limb of the loop of Henle allows water to follow its osmotic gradient into the increasingly ______ interstitium but does not allow solutes to be transported; while the ascending limb of the loop of Henle ______ transports solutes (Na+, Cl- and K+) into the interstitium
hypertonic, actively
The _____ surface of the ascending is not permeable to water. Active reabsorption of ions in this region creates a dilute filtrate in the lumen
apical
Although majority of reabsorption takes place in the ______ tubule, about 25% of Na+ and K+ reabsorption occurs in the _______ limb of the loop of Henle
proximal, ascending
NKCC transporter on ______ membrane uses energy stored in the Na+ concentration gradient to move Na+, K+ and 2 Cl- into the ________ cells
apical, epithelial
Na+ is actively transported against concentration gradient on _______ membrane
basolateral
NKCC is target of loop diuretic drugs for treatments of ______ and ____ (prevents generation of hyperosmotic medulla)
hypertension, edema
Because of the _______ of chloride and sodium against its concentration gradient into the cell, now it can just flow down its concentration gradient into the interstitial space
accumulation
_____ _______: used for the treatment of hypertension as well as edema to get rid of excess fluid and they primarily target these transporters in the loop of Henle, the prevent the transporter from functioning, which will prevent the generation of hyperosmotic medulla interstitial space, prevents water reabsorption, causes excess urination of fluid, brings down ECF volume, potentially bring down blood volume to get rid of hypertension
Loop diuretics
Why doesn’t the water entering interstitium via the descending limb dilute the hyperosmotic medulla?
The opposite direction loop of the vasa recta picks some solute up and loses some water as it travels by the ascending limb creating hyperosmotic blood
The main job of the _______ is to create the hypertonic interstitium, while the main job of the ________ is to prevent the washout (dilution) of the hypertonic interstitium
multipler, exchanger
There is so much solute that is being pumped from the ascending limb that as blood flows in the opposite direction it picks up a lot of solute so that when water does start to move into the interstitial space, there will be ?
a further gradient
____ ____ maintains the hyperosmotic interstitial space, it prevents the washout from water coming in either via the descending limb or through the collecting duct
Vasa recta
There is high amounts of ____ in the medulla that contribute to the medulla interstitial that contributes to this _______ state
urea, hyperosmotic
About ____ the solute in the medulla interstitium is urea
half
A large amount of urea is reabsorbed in the ____ portion of the nephron and creates a _______ loop
distal, recycling
The ability to selectively reabsorb water depends on:
1. An ______ _______, depends on the interstitial space in the medulla being hyperosmotic
2. _________ mediated insertion of water pores in the collecting duct
osmotic gradient, Vasopressin
High AVP increases AQP2 insertion = ________ reabsorption
Low AVP results in decreased AQP2 = ________ reabsorption
increased, reduced
North American diet high in NaCl ~ __g or ___ milliosmoles of Na+ and ___ milliosmoles of Cl- each day
9, 155, 155
Our plasma Na+ concentration is ___-___ milliosmoles/L, Na+ is distributed freely between plasma and interstital fluid thus representing our ___ [Na+]
135-145, ECF
If we ingested NaCl+ increasing the ECF [NaCl] to 155 mosmol/L how much water do we need to keep the [Na+] at 140 mosmol/L
155 mosmol/x liters = 140 mosmol/liter
x = 1.1 liters
Normal ECF volume 14L that would be a 10% gain and would cause a large increase in blood pressure
How would adding that NaCl affect osmolarity if we did not consume any water?
It would increase total body osmolarity from 300 – 307 mOsM, this would draw water from cells disrupting normal function
Our homeostatic mechanisms maintain ____ ____
mass balance
The _____ are responsible for most Na+ excretion, very little is lost during perspiration and in feces
kidneys
Although we talk about ingesting and excreting NaCl, only Na+ _______ is regulated, Cl- tends to follow through the __________ gradient set up by Na+ movement or co-transported with Na+
absorption, electrochemical
Aldosterone helps control ___ balance
Na+
Regulation of blood Na+ levels takes place through a complicated endocrine pathway: ?
the renin-angiotensin-aldosterone system
Aldosterone is a steroid hormone responsible for altering ___ reabsorption, and ___ secretion and excretion
Na+, K+
Aldosterone targets the last third of the _____ tubule and the portion of the ______ duct located in the cortex of the kidney
distal, collecting
In the last ~third of the distal tubule and the initial portion of the collecting duct you have fine tuning of _____ _____
sodium balance
Aldosterone acts on _____ cells
principal
In ____ ______ phase to aldosterone binding receptor apical Na+ and K+ channels increase their open time through an unknown mechanism
early response
Principle cells are stimulated by aldosterone to increase sodium ______ and increase potassium ______
reabsorption, secretion
Order these statements according to “Aldosterone acts on principal cells:”
1. Translation and protein synthesis makes a new protein channels and pumps
2. Aldosterone combines with a cytoplasmic receptor
3. Aldosterone-induced proteins modulate existing channels and pumps
4. Result is increased Na+ reabsorption and K+ secretion
5. Hormone-receptor complex initiates transcription in the nucleus
2, 5, 1, 3, 4
When aldosterone is released in higher amounts from the adrenal cortex will cause two different responses:
Early phase response and late phase response
____ phase response: you get stimulation of apical potassium and sodium channels (leak channels, they still have gates, they’re just open most of the time, they can flicker open and close) remain open for longer periods of time which facilitates increased sodium and potassium entry into the cell, increase sodium reabsorption, and increased potassium secretion in response. This phase will affect channels that are already in the membrane but also cause the insertion of channels
Early
____ phase response: production of new channels, slow response because it takes a little bit of time. Aldosterone-receptor-hormone-complex will translocate to the nucleus where it will increase transcription of the production of more ENaC and ROMK channels, and sodium-potassium pumps which will insert into the apical and basolateral membrane and also increase sodium reabsorption as well as potassium secretion
Late
Both early and late phase responses ultimately drive an increase in sodium _____and an increase in potassium ______
reabsorption, secretion
On the apical membrane, we are mainly focused on the _____ channels and _____ channels, which are leak channels
On the basolateral membrane, we have the ?
ENaC, ROMK, sodium-potassium ATPase
The receptor for aldosterone is a ______ receptor, meaning it just exists in the cytoplasm and it’s a _________ receptor that becomes bound by aldosterone
cytoplasmic, mineralocorticoid
? translocate into the cell nucleus, binds to hormone response elements that increase transcription of apical Na+ channels, basolateral Na/K+ pumps and possibly apical K+ channels further enhancing Na+ reabsorption and K+ excretion
Hormone ligand complex,
Early response can take _______; while the late response can take ____
minutes, hours
What drives aldosterone production?
- High levels of ___
- Increased _______
K+, secretion
________ blood pressure will increase aldosterone production, which increases sodium reabsorption
Decreased
I. K+ acts directly on the adrenal cortex protecting the body from ______
hyperkalemia
II. Decreased blood pressure usually controls aldosterone secretion initiating a pathway that results in the production of ________ ___ which triggers aldosterone release
angiotensin II
Two additional (primary) modifiers of aldosterone release exist:
-Increased ______ acts directly on the adrenal cortex during ______ to inhibit release
-Abnormally large drops in _____ ____ can directly stimulate aldosterone ______
osmolarity, dehydration, plasma Na+, secretion
? : a multi-step pathway for maintaining blood pressure
Renin-angiotensin-system (RAS)
The RAS helps to facilitate an increase in blood pressure in response to _______.
hypotension
Cardiovascular responses (the baroreceptor reflex in response to hypotension) is usually a temporary response where you need ______ mechanisms to bring blood volume back up to normal
additional
The RAS system is a more comprehensive system that assists the ______ _____ and solves the underlying problem of low blood pressure (which is usually low blood volume)
baroreceptor reflex
RAS works in unison with the ? and will influence the cardiovascular control center to help facilitate bringing blood pressure back up to normal
cardiovascular control center
Main stimulus for this RAS is a decrease in ____ _____
blood pressure
Renin is considered a hormone, but it acts as an _____
enzyme
The first step of the RAS pathway is the _____ secretion in response to a decrease in blood pressure
renin
There are three stimuli that begin renin secretion:
i. ___ blood pressure in renal arterioles causes granular cells to secrete renin
ii. _______ neurons activated by CVCC when blood pressure decreases terminate on granular cells and stimulate renin secretion
iii. _____ feedback (prostaglandins) from macula densa cells signal to the granular cells to secrete renin
low, sympathetic, paracrine
_____ cells are specialized smooth muscle cells that exist on the afferent arteriole, also secrete renin, also innervated by sympathetic neurons
Granular
Renin’s main role is to ?
convert an inactive plasma protein, angiotensinogen, into angiotensin I
Angiotensin I is then converted to angiotensin II by an enzyme produced in blood vessel enothelium (especially in the lungs) known as ?
angiotensin converting enzyme (ACE)
ANGII then travels to the adrenal cortex and stimulates production of _______, which increases _____ reabsorption
aldosterone, sodium
Angiotensin II receptor (AT 1 and 2) are ? receptors
g-protein coupled
Why, if blood pressure is low, is it important to increase sodium production?
Because generally if blood pressure it low, you want to increase solute reabsorption and you want to increase fluid reabsorption to make sure everything remains isosmotic
ANGII has many effects:
1. ANG II increases _____ secretion
2. ANG II stimulates _____
3. ANG II is one of the most potent _________ in the body
4. ANG II receptors activated in CVCC increase _______ output to heart and blood vessels
5. ANG II increases ______ tubule Na+ reabsorption
vasopressin, thirst, vasoconstrictors, sympathetic, proximal
ANG II reinforces ____ output and _____ activity
cardiac, sympathetic
ANGII acts on ______ to increase the desire to drink water (thirst)
hypothalamus
Pharmaceutical companies now use ACE inhibitors for the treatment of _______, preventing the conversion of ANGI to _____ leads to relaxation of the vasculature and lower ____ ______
hypertension, ANGII, blood pressure
The main stimulus is a decrease in blood pressure, that acts via three different mechanisms to increase renin production:
- Reduces _____ _____ in response to decreased blood pressure cause reduced NaCl uptake by macula densa cells
- A direct effect where less distension on the _____ arterioles results in granular cells increasing their production and secretion of renin
- Increased sympathetic output into the ________ cells via baroreceptor reflex
glomerular filtration, afferent, juxtaglomerular
Atrial natriuretic peptide (ANP) promotes ___ and _____ excretion
Na+, water
After discovering aldosterone and vasopressin increase Na+ and water reabsorption scientists speculated there may be hormones that cause a loss of Na+ (_______) and water (_______)
natriuresis, diuresis
ANP is a peptide hormone produced and secreted by specialized ______ cells primarily in the atria of the heart
myocardial
Increased blood volume causes increased stretch of the atria, causing the specialized myocardial cells to _____ ANP
release
A second type of natriuretic peptide is produced in the cardiac ventricles and in some neurons in the brain; ? `
which has less of a physiological role, used as a biological marker
brain natriuretic peptide (BNP),
ANP receptor is an ? receptor acting through cGMP second messenger system
enzymatic membrane bound
Atrial myocytes release ANP in response to stretch:
- Kidney: relaxes ______ arterioles (increases GFR), reduces ____ release from granular cells (reduces aldosterone and ANG II), and reduces Na+ ______ at the collecting duct
- Hypothalamus: reduces ___ release
- Adrenal cortex: inhibits _____ release
- Medulla: acts on the CVCC to _____ blood pressure
afferent, renin, reabsorption, AVP, aldosterone, decrease
