L21 Flashcards by Hayley 1234

in a Low K diet what segments of the nephron will be reabsorbing K

all the segments of the nephron will be reabsorbing K

How well did you know this?

Not at all

Perfectly

in a normal to high K diet what is the nephron doing

A normal to high the upper parts of the nephron will still do reabsorption and the lower parts will do secretion

How well did you know this?

Not at all

Perfectly

What is the concentration of K+ in the ICF and the ECF?

ICF - generally 150 mM

* ECF ~ 4 mM

How well did you know this?

Not at all

Perfectly

what is hyperkalemia

–ECF > 5 mM = hyperkalemia (High K+ blood)

How well did you know this?

Not at all

Perfectly

what is hypokalemia

–ECF < 3.5 mM = hypokalemia (Low K+ blood)

How well did you know this?

Not at all

Perfectly

Why is high K+ in the
ICF important?

there’s 5

maintain cell volume
regulation of pH
controlling cell enzyme function

• controlling DNA and
protein synthesis

• controlling cell growth, cell cycling and cell proliferation

How well did you know this?

Not at all

Perfectly

Why is low K+ in the
ECF important?

theres 2

• maintain the steep K+
gradient across the
membrane to maintain the potential of cells

• Low K+ prevents problems with excitation and
contraction
– action potential
– muscle contraction
– cardiac rhythmicity

How well did you know this?

Not at all

Perfectly

what is a low extracellular K effect on the membrane potential

it makes the MP more -ive theefore the cell is less excitable

this would be the opposite if the ECF conc of K was high

How well did you know this?

Not at all

Perfectly

what is ataxia and what causes it

Ataxia leads to tremors and loss of fine motor control which is what happens when you have high K in extracellular fluid

How well did you know this?

Not at all

Perfectly

what is the intracellular effect of K on the volume of the cell

net loss of intracellular K = cell shrinks

gain of K = cell swells

How well did you know this?

Not at all

Perfectly

what is the intracellular effect of K on the pH of the cell

loss of K = cell acidosis

gain of K = alkalosis

How well did you know this?

Not at all

Perfectly

what is the P wave?

Atrial depolarisation

How well did you know this?

Not at all

Perfectly

what is the QRS wave?

Ventricular

depolarisation

How well did you know this?

Not at all

Perfectly

what is the T wave?

Ventricular

repolarisation

How well did you know this?

Not at all

Perfectly

repolarisation of a cardiac myocyte is dependent on how many K channels

How well did you know this?

Not at all

Perfectly

what is the effect of an ECF conc of K of 2.5mM (hypokalemia) on an ECG

low T wave

high U wave

low ST wave

the ecg looks very different therefore you have altered cardiac function

what is the effect of an ECF conc of K of 10mM (hyperkalemia) on an ECG

initially
prolonged PR interval, depressed ST segment and high T wave

auricular standstill/intraventricular black

ventricular fibrillation = death

Which of the following statements is TRUE?

A. A typical diet does not contain the proper amount of daily K+.

B. Low ICF K+ is very important for proper enzyme function.

C. K+ is the most abundant cation in the body.

D. K + is not invoved in the nerve action potential.

C is correct

how do we get K into our bodies

then what happens

through our diet where it is absorbed through the intestine and absorbed into the blood

from her it goes into the ECF where it is either stored in the tissues via insulin, adrenaline or aldosterone (extra renal)

or excreted into the urine via ADH or aldosterone (and plasma conc)

How does your body respond to changes in K+ to maintain K+ homeostasis?

external factors

• Extrarenal - to increase K+ uptake into cells (skeletal muscle, bone, liver, red blood cells)
– epinephrine
– insulin
– aldosterone
Occurs rapidly to prevent hyperkalemia (stops it by “hiding” the K away)

How does your body respond to changes in K+ to maintain K+ homeostasis?

internal factors

• Intrarenal - regulation of reabsorption and
secretion of K+ along the nephron
Occurs over several hours

what are the extrarenal effects of Epinephrine,Insulin, and

Aldosterone on uptake of K+

acute rise in plasma conc causes Epinephrine,Insulin, and Aldosterone to increase Na/K ATPase activity in some way

The mussle cells have an insulin and adrenaline receptor in the membrane and a aldosterone receptor intracellularly

adrenaline is produced in the chromaffin cells of the adrenal medulla.

When it binds to the receptor it increases intracellular cAMP which activates Na/K ATPase to get more K into the cell

insulin is produced by the b cells in the pancreas and when it binds to its receptors in acts on Na/K ATPase as well

Aldosterone also increases Na/K ATPase activity produced from zonular glomerulosa cells of the adrenal cortex

how can we calculate the intrarenal effects of an increase in K

If we know the Glomerular Filtration Rate (GFR), we can calculate the daily filtered load of K+

GFR x [K+]plasma = Daily filtered load

eg
[K+]plasma = 4 mmol/L
180 L/day x 4 mmol/L = 720 mmoles/day
(filtered)

how can you figure out the filtered load of an ion (eg K)

GFR x [K+]plasma = Daily filtered load

the proximal tubule reabsorbs what % of the K+ filtered load

67% this is where majority is absorbed

in the PT is mainly reabsorbed through what mechanism

the paracellular pathway (because of the leaky absorptive epithelium and local environmental voltage)

what causes K in the PT to be mostly reabsorbed through the paracellular pathway

local environmental voltage

the thick ascending limb reabsorbs what % of the filtered load of K

20%

how is K reabsorbed in the thick ascending limb

through NKCC2 (transcellular) and paracellular pathways

the cortical collecting duct contains 2 kinds of cells these are the intercalated cells and the principal cells what is their roles in terms of K

• Intercalated cells (~30% of the cells) – K+ reabsorption (9% of K filtered load via K/H ATPase) • Principal cells (~70% of the cells) – Na+ reabsorption – K+ secretion

what transporters are located in an intercalated cell of the collecting duct

reabsorbs K in a low NA diet These are tight absorbitive epithelial cells Contain H ATPase and K/H exchanger (also ATPase) in apical membrane Basolateral = Cl bicarbonate exchanger and K/Cl channel and Na/K ATPase Carbonic anhydrase and K/H exchanger is for pH regulation

how do the principal cells and the late distal tubule secrete K

in a high K diet you get K+ secretion (luminal K+ channel ROMK) under the influence of aldosterone and the K+-Cl- cotransporter (electroneutral) aldosterone increases the activity of these channels via increasing more ENaC into the apical membrane, this brings more Na into the cell increasing the activity of the Na/K ATPase which makes the inside of the cell more positive (more K inside the cell) which increases the driving force of K across the apical membrane

If you have a low K+ diet, which statement is TRUE? A. Your body would increase K+ secretion by the collecting duct cells. B. Your body would reduce insulin release to reduce uptake of K+ into cells. C. Your body would increase the release of epinephrine to increase uptake of K+ into cells. D. Your body would decrease the amount of aldosterone

A. you wouldn't increase secretion in a low K diet C. decrease the release D. aldosterone is not secreted actively in response to K it is so Na is reabsorbed and loss of K is just a byproduct maybe???

what regulates K excretion/secretion

* high plasma K+ concentrations * aldosterone * flow rate of the filtrate

how does an increase in K concentration in the plasma (hyperkalemia) increase K excretion

increase in plasma K is detected by the adrenal gland which causes aldosterone to be secreted which acts on the kidney to increase K secretion

what is the effect of Aldosterone on K+ secretion by the | LDT and CD

there is an increase in activation and amount of the epithelial sodium channel (ENaC) which brings more Na into the cell increasing the Na driving force for the Na/K ATPase an increase in the amount and activity of the Na+-K+-ATPase; entry of K+ across basolateral membrane entry of Na+ makes the cell potential more positive enhancing the driving force for K+ exit across the apical membrane (K+ secretion)

what is the effect of flow of tubular fluid on K secretion

Low K+ diet = low flow rate = K+ secretion is low • Normal or High K+ diet then K+ secretion is high when compared at a single flow rate flow is about 5nL/min