Renal III Flashcards
Most potassium reabsorption at the proximal tubule is _____
passive
Why is there is no conflict between sodium and potassium reabsorption?
Because in the grand scheme of things its relatively small amounts, there may be some pathological situations where one may drive the other away from homeostasis but that is relatively rare
Potassium acts directly on cells, independent of the _____ system
RAS
_______ is reabsorbed in proximal tubule and ascending limb of loop of Henle
Potassium
At _____ [K+] excretion =10-20% of filtered load (reabsorption is less than filtered)
normal
Low [K+] deceases _______ release, reducing secretion which reduces excretion (2%)
aldosterone
High [K+] stimulates _____ release directly and increases secretion and thus excretion (10-150%)
aldosterone
Aldosterone also plays a critical role in K+ ________ (enhances secretion in P cells)
homeostasis
Plasma (ECF) K+ needs to be maintained within a ____ range (3.5-5 mM). Alterations in body K+ levels affects the ______ membrane potential of all cells
narrow, resting
What are two reasons for why is it important to maintain adequate amounts of potassium?
- Potassium is mainly found intracellularly
- How much potassium that is in the ECF will determine the amount of potassium in the ICF which will determine the resting membrane potential of a cell
During a state of _______ (higher potassium in the ECF) there is a reduced amount of potassium that leaks out of the cell, more is being retained in the cell itself, which causes the resting membrane potential to become depolarized. Causes ______ of the cells
Hyperkalemia, hyperexcitation
During a state of ______ (lower potassium in the ECF) that will facilitate more potassium to leave the cell, which would hyperpolarize the cell and cause a more negative resting membrane potential. Now a stimulus that would normally cause an action potential won’t because now it needs a _____ depolarization to fire
Hypokalemia, stronger
Potassium balance is particularly important in ____ tissues such as the heart or skeletal muscles
excitable
__________ causes muscle weakness because its more difficult for hyperpolarized motor neurons and muscles to fire AP’s (failure of respiratory and cardiac muscles is particularly worrisome)
Hypokalemia
________ more dangerous, initially leads to hyperexcitability. Eventually cells are unable to repolarize and actually become less excitable and can lead to life threatening arrhythmias in the heart
Hyperkalemia
Disturbances in K+ balance may result from _____ dysfunction, eating disorders, loss of K+ in diarrhea or use of ____ that prevent kidneys from properly reabsorbing K+
kidney, diuretics
______ responses are critical in restoring the normal state, particularly when ECF volume decreases or osmolarity deviates.
Behavioral
_______ _____ is normally the only way to replace lost water and eating salt is the only way to raise the body’s Na+ content.
Drinking water
The act of drinking relieves thirst, water does not actually have to be _______
absorbed
Unknown receptors in the _____/______ respond to water by decreasing thirst and decreasing AVP release
mouth/pharynx
The region responsible for both thirst as well as sodium appetite are in the _______, they have osmo-sensitive neurons that respond to increase in osmolarity
hypothalamus
The act of drinking acts as a _______ mechanism assuming that the fluid that you did take in will be adequate to bring osmolarity back down to normal.
feedforward
Thirst comes in ______; this is to prevent swinging too far in the opposite direction
waves
While the RAS also is a stimulus of thirst, _______ is considered the main driver
osmolarity
_______ behaviors help prevent dehydration
Avoidance
Increased aldosterone and ANGII increases _____ appetite
sodium
Increased [Na+] of blood plasma, cerebrospinal fluid, post-ingestive signals from the gut sensed via the vagus nerve, and circulating & CNS peptide hormones/neuromodulators cause a _______ in sodium appetite
decrease
The ___ system responds to changes in blood volume and pressure, the _____ system responds to changes in blood volume and/or ________ and ______ mechanisms respond to both
CV, renal, osmolarity and behavioral
Normally volume and osmolarity can be kept within a narrow range but under certain circumstances becomes out of _____. Osmolarity and blood volume can change _________ resulting in different scenarios.
balance, independently
1- Ingestion of hypertonic saline: ↑ volume, ↑ osmolarity: may occur with ? and ? at the same time, net results= ingestion of hypertonic saline (salt>water). You need to therefore ? to match what was taken in
eating salty foods, drinking liquids, excrete the solute and liquid
2- Ingestion of isotonic saline: ↑ volume, no change in osmolarity: if salt and water ingested is equivalent to ______ solution
isotonic
3- Drinking larg amount of water: ↑ volume, ↓ osmolarity: simply drinking pure water without ?. The kidneys cannot excrete pure water, so some solute would be lost in this situation, compensation is ______
ingesting solute, imperfect
4- Eating salt without drinking water: No volume change, ↑ osmolarity: eating salt without ?, increases ECF osmolarity shifting water from cells to ECF, This triggers intense ____ and kidneys make _______ _____
drinking water, thirst, concentrated urine
5- Replacement of sweat loss with plain water: No change in volume, ↓ osmolarity: water and solutes would be lost in sweat but only _____ is replaced. This can lead to ______ or ________. Sports drinks help to replace fluid and solutes lost
water, hypokalemia, hyponatremia
6- dehydration: ↓ volume, ↑ osmolarity: dehydration could be due to ____ _____ (water loss from lungs can double, sweat loss can increase from 0.1-5 L) or ______ (excessive fluid loss in feces). This can result in inadequate _____ (decreased blood volume) and cell _______. Increases ____ intake
heavy exercise, diarrhea, perfusion, dysfunction, water
7- hemorrhage: ↓ volume no change in osmolarity: _______, need blood transfusion or ingestion of ______ solution.
hemorrhage, isotonic
8- Incomplete compensation for dehydration: ↓ volume, ↓ osmolarity: may result from incomplete compensation for _______, but is uncommon
dehydration
Of the 8 possibilities between, which is the most common?
6, increase in osmolarity, with a decrease in volume. AKA dehydration
Pathological hyponatremia, causes an increase in _____ secretion
aldosterone
Severe dehydration results in a loss of ECF volume, decrease in blood pressure and an increase in osmolarity, the ________ _____ aim to restore these three factors
compensatory mechanisms
Severe dehydration has compensatory mechanisms aim to restore a loss of ECF volume, decrease in blood pressure and an increase in osmolarity by:
- Conserving fluid to prevent additional loss
- Trigger cardiovascular reflexes to increase blood pressure
- Stimulate thirst so normal fluid volume and osmolarity can be restored
Four compensatory mechanisms with redundant overlap overcome the symptoms of dehydration:
- Cardiovascular mechanisms
- Renin-angiotensin system
- Renal mechanisms
- Hypothalamic mechanisms
During severe dehydration, decreased ECF volume (blood pressure) would signal to increase ______ release but at the same time an increased ______ inhibits aldosterone release
aldosterone, osmolarity
Osmolarity control in severe dehydration situation reigns and aldosterone is not secreted, if it were that would cause ____ _______ which would worsen the already high osmolarity
Na+ reabsorption
Carotid and aortic baroreceptors signal CVCC
a. Heart rate goes up as SA node control shifts from _______ to _______
b. Force of ventricular contraction increases from sympathetic stimulation, increases _____ ______. Causes an increase in ____
c. Sympathetic input to arterioles ______ peripheral resistance, increases ___
d. Sympathetic ________ of afferent arterioles in kidney decreases GFR, conserving fluid
e. Increased _______ activity at granular cells increases renin secretion
a. parasympathetic to sympathetic
b. stroke volume, CO
c. increases, BP
d. vasoconstriction
e. sympathetic
Decreased blood pressure directly decreases ____
GFR
Paracrine feedback at macula densa cells causes granular cells to release _____
renin
______ cells respond to decreased blood pressure by releasing renin
Granular
Decreased blood pressure, volume, increased osmolarity, and increased ANGII all stimulate ________ and the thirst centers of the _______. ANG II reinforces ___ response
vasopressin, hypothalamus, CV
Decreased blood volume and pressure results in:
____ attempt by the CVCC to maintain blood pressure
Restoration of volume by ____ conservation and fluid intake
Restoration of normal osmolarity by decreased ___ ______ and increased water reabsorption and intake.
Rapid, water, Na+ reabsorption
The pH of a solution is a measurement of its ?
H+ concentration
The H+ concentration of normal arterial plasma is very ____ compared to other ions, Na+ is usually expressed on a ______ pH scale of 0-14
small, logarithmic
pH of 7 is _____, if a solution is below 7.0 the H+ concentration is greater than 1x10-7M and considered ____. If a solution is above pH of 7.0 it has a [H+] below 1x10-7 M and is considered _____ (basic)
neutral, acidic, alkaline
Normal pH of the body is ____, slightly ______
7.40, alkaline
A change of 1 pH unit represents a ___-fold change in H+ concentration
10
Commonly look at ____ pH when considering ECF and whole body pH
______: 7.38-7.42
plasma, Normal
The only time we see ______ of the norm is looking at areas that are technically considered “outside the body” or a “continuation of the external environment” like the GI tract
deviations
pH changes can _____ proteins
denature
pH is closely ____, intracellular proteins such as enzymes and membrane channels sensitive to pH changes. The function of these proteins depend on their normal three-dimensional ______
regulated, structure
Very low pH (excess H+) can result in ______:
CNS depression, confusion, coma
acidosis
Changes in H+ concentration results in disruptions in ____ ____ altering the structure
hydrogen bonds
High pH, low H+ can result in _______:
hyperexcitability in sensory neurons and muscles, sustained respiratory muscle contraction
alkalosis
In day to day functioning the body is challenged by intake and production of _____ more than _____
acids, bases
Acid input is a result of ____ as well as acids produced during ______. The largest source of acid on a daily basis is ____ from aerobic metabolism
diet, metabolism, CO2
pH homeostasis depends on three mechanisms: ?
Buffers (first line of defense)
Ventilation (handles 75% of disturbances)
Renal regulation of H+ and HCO3- (slowest)
Buffers only function in the _____ range of pH, but when they go ______ of it that’s when the other two mechanisms kick in
normal, outside
_____ systems include proteins, phosphate ions and HCO3-
Buffer
A ______ is a molecule that moderates, but does not prevent changes in pH by combining with or releasing H+
buffer
In the absence of a buffer adding acid to a solution causes a _____ change in pH, but in the presence of buffers the H+ added is bound and pH change is slightly ______ or may even be unnoticeable
sharp, moderated
Buffers are found within cells and in the plasma. ________ buffers include cellular proteins and phosphate ions
Intracellular
We measure pH generally of the _____
ECF
HCO3- , the most ______ extracellular buffer system
important
According to law of ____ _____ any change in amount of CO2, HCO3- or H+ in solution causes reaction to shift until new equilibrium is reached
mass action
Increasing CO2 shifts equation to ______ creating one H+ and one HCO3-
right
Adding H+ (through a metabolic source i.e. lactic acid) shifts the equation to the _____, HCO3- acts as buffer creating carbonic acid
left
Because of the already _____ concentration of bicarbonate, you need to either gain/lose a significant amount for it to affect the equilibrium
high
_______ compensates for pH disturbances
Ventilation
_______ and _____ chemoreceptors sense changes in plasma PCO2 and/or H+ and signal to the respiratory control center to adjust ventilation accordingly
Peripheral, central
Alterations in ventilation can correct disturbances in acid-base balance as well as cause them:
__________: right shift
__________: left shift
Hypoventilation, Hyperventilation
In response in increased CO2, increased pH, you would have an increase in ____ and _____ of breathing so you would increase the _______ of CO2, which would cause levels of CO2 in the plasma to ____ and H+ to drop
rate and depth, exhalation, drop
When you have low levels of H+ in plasma, you’d have lower levels of ____ as well, ____the rate and depth of breathing which would bring the pH back down to normal
CO2, reduce
_____ use ammonia and phosphate buffers
Kidneys
The kidneys handle the remaining ____ of pH disturbances slowly through two mechanisms
25%
Kidneys handle the remaining 25% of pH disturbances slowly through two mechanisms: ?
- Directly, by altering the rates of excretion or reabsorption of H+
- Indirectly, by changing the rate at which HCO3- buffer is reabsorbed or excreted.
In general, during _____ excess H+ is buffered by ammonia within tubule cells or enters lumen and is buffered by phosphate ions. H+ is not filtered, enters tubule via _____ only
acidosis, secretion
The kidney secretes H+, which is buffered in the urine by _______ and ________ _____. It reabsorbs bicarbonate to act as an extracellular buffer
ammonia, phosphate anions
The ____ tubule secretes H+ and reabsorbs HCO3-
proximal
Hydrogen is secreted through a ?
sodium-hydrogen exchanger
______ reabsorption drives all transport within the proximal tubule
Sodium
There are no bicarbonate transporters on the _____ membrane, so the secretion of hydrogen allows to conversion of bicarbonate back to CO2 so that it can get into the ______ tubule cells
apical, proximal
Another mechanism for bicarbonate creation and reabsorption as well as a potential buffer for hydrogen would be the use of _______ within proximal tubule cells
glutamine
Order these statements for “proximal tubule secretion:”
1. CO2 diffuses into cell
2. HCO3- is reabsorbed with Na+
3. NHE secretes H+
4. Glutamine is metabolized to ammonium ion and HCO3-
5. CO2 combines with water to form H+ and HCO3-
6. H+ in filtrate combines with filtered HCO3- to form CO2
7. NH4+ is secreted and excreted
8. H+ is secreted again
3, 6, 1, 5, 8, 2, 4, 7
The _____ nephron controls acid excretion
distal
Initial portion of the _______ ____ plays a significant role in the fine regulation of acid-base balance
collecting duct
_______: type B intercalated cells in collecting duct function in this. HCO3- and K+ are excreted; H+ is reabsorbed
Alkalosis
Type B has the same transporters as Type A but on the ______ membrane, which means that the ______ is switched
opposite, polarity
Type __: hydrogen-ATPase on apical, and bicarbonate-chloride transporters and potassium leak channels on the basolateral membrane
Type __: hydrogen-ATPase on basolateral, and bicarbonate-chloride transporters and potassium leak channels on the apical membrane
A, B
_______: type A intercalated cells in collecting duct function to increase H+ secretion and HCO3- reabsorption is usually accompanied by an increase in K+ reabsorption (hyperkalemia)
Acidosis
______: type B intercalated cells in collecting duct function to increase H+ reabsorption and HCO3- secretion is usually accompanied by increase K+ secretion (hypokalemia)
Alkalosis
Acid-base disturbances may be _____ or ______
respiratory, metabolic
Three compensatory mechanisms (buffers, ventilation and renal excretion) take care of most ______ in plasma pH
variations
Acid-base disturbances are classified both by the ______ of the pH change (acidosis or alkalosis) and by the _______ ____ (metabolic or respiratory)
direction, underlying cause
By the time an acid-base disturbance causes a change in plasma pH the body’s buffers are _______ leaving ______ and _____ compensation to alleviate the change in pH
ineffective, respiratory, renal
_______ _____: occurs when alveolar hypoventilation results in CO2 retention and elevated plasma CO2. -Due to ______ origin, compensation must occur via _____ mechanisms (excrete H+, reabsorb HCO3-)
Respiratory acidosis, respiratory, renal
What are some examples of respiratory acidosis?
-Pulmonary fibrosis
-Skeletal muscle disorders: Muscular dystrophy
_______ ______: much less common, occurs as a result of hyperventilation in the absence of increased metabolic CO2 production. Compensation occurs via _____ HCO3- excretion and H+ reabsorption
Respiratory alkalosis, renal
In respiratory alkalosis:
In clinic: usually caused by excessive artificial _______
Physiological: anxiety induced ___________
respiration, hyperventilation
______ _______: occurs when dietary and/or metabolic input of H+ exceeds H+ excretion
Metabolic acidosis
What are two examples of metabolic acidosis?
Lactic acidosis
Ketoacidosis
______ acidosis as a result of anaerobic metabolism
________ from excessive breakdown of fats and some amino acids
Lactic, Ketoacidosis
________ ______: can also occur from excessive HCO3- loss (diarrhea), H+ enters blood, HCO3- enters intestine. -rarely seen clinically, usually resolved by respiratory (increased ventilation) and slow renal compensation (HCO3- reabsorbed, H+ excreted)
Metabolic Acidosis
________ ______: two common causes; excessive vomiting of acidic stomach contents or excessive ingestion of bicarbonate-containing antacids
Metabolic alkalosis
_____ ______: usually rapidly resolved by a decrease in ventilation, but effectiveness is limited because it can cause hypoxia. There is a renal response: HCO3- excreted, H+ reabsorbed
Metabolic alkalosis
