Physiology - Plasma Regulation

Question 1

hyperkalemia is defined as what?

Answer 1

1. high K+ levels above 5.0 mM
2. decreass outwardly directed K+ gradient
3. depolarized resting membrane potential
4. may cause hyperexcitable muscle contraction
5. may cause metabolic acidosis

Question 2

hypokalemia is defined as what?

Answer 2

1. low K+ levels, below 3.5 mM
2. increases outwardly directed K+ gradient
3. hyperpolarizes resting membrane potential
4. may cause hypoexcitability - weakened muscle contraction
5. may cause metabolic alkalosis

Question 3

describe the cellular mechanisms relating to the H+ - K+ exchange, with increased cellular uptake of H+ (acidemia) ? with decreased cellular uptake of H+ (alkalemia)

Answer 3

increased H+ cell uptake blocks the (Na/K/Cl) and Na/K ATPase transporters- the inhibition lowers the K+ uptake into the cell, increasing K+ in plasma (may lead to hyperkalemia)

alkalemia (decreased H+ cell uptake) stimulates (Na/K/Cl) and Na/K ATPase transporters, K+ pulled into cell even more - hypokalemia may result

Question 4

describe the role of aldosterone on K+ secretion

Answer 4

aldosterone acts in the distal nephron, results in simultaneous Na+ reabsorption and K+ secretion

Question 5

describe generally hypernatremia?

Answer 5

it is an increase in sodium concentration (Na) to a level above normal range 135 - 145 mEq/L. Caused by inadequate water consumption or an increase in water excretion

Question 6

A person comes in with hypernatremia, what are their symptoms?

Answer 6

lethargy, weakness and irritability, sever cases - seizure and coma

Question 7

what can cause hypovolemic hypernatremia?

Answer 7

Due to 1. inadequate water consumption 2. extreme sweating 3. severe diarrhea 4. polyuria ( excess renal excretion of h20)

Question 8

excessive renal excretion may result from central diabetes insipidus, describe this disorder?

Answer 8

central diabetes insipidus - low release of ADH/AVP from posterior pituitary in response to increased plasma osmolarity

Question 9

excess renal secretion can also cause nephrogenic diabetes insipidus, describe it?

Answer 9

nephrogenic diabetes refers to an inability of the collecting tubule/duct to respond to ADH/AVP -

Question 10

what can cause hypervolemic hypernatremia?

Answer 10

excessive hypertonic fluid consumption (seawater), or IV infusion of hypertonic saline, hyperaldosteronism (high levels of aldosterone – inappropriate Na+ reabsorption and volume expansion )

Question 11

describe hyponatremia generally?

Answer 11

characterized by a decrease in plasma sodium concentration below normal range 135 - 145 mEq/L. Due to a gain of water in excess of solutes in the plasma, dilutes plasma Na+ concentration

Question 12

name two causes of general hyponatremia

Answer 12

1. extreme excess consumption of water (polydipsia) 2. an inappropriate increase in free water rebasorption by kidney (SIADH syndrome - too much ADH release )

Question 13

describe hypervolemic hyponatremia

Answer 13

Leads to an inappropriate reabsorption of water, which increases plasma volume, and dilutes plasma Na+

Question 14

describe hypovolemic hyponatremia

Answer 14

1. Leads to extreme plasma reduction ( hemorrhage, diuretic drug therapy) , water consumption/reabsorption not enough to correct depleted volume, but can decrease plasma Na+ 2. Addisons disease (hypoaldosteronism/adrenal insufficiency) 3. severe vomiting or diarrhea

Question 15

what do ECF volume barorecpetors sense?

Answer 15

they sense changes in pressure and effect changes in ECF volume, including effective circulating volume – can be increased or decreased depending on pressure

Question 16

where are central vascualar sensors of BP for low pressure located ?

Answer 16

these sensors are located in the atria and the pulmonary vasculature

Question 17

Aldosterone - where is it secreted from and what does it regulate?

Answer 17

aldosterone is a mineralocorticoid, it is secreted from the adrenal cortex, it increases Na+ reabsorption and increases K+ excretion, acts in the distal nephron

Question 18

What are some of the actions of Angiotensin II?

Answer 18

1. stimulates aldosterone release 2. acts on hypothalamus - increase thirst and release of ADH/AVP 3. potent vasoconstrictor 4. increases Na+ reabsorption

Question 19

which two substances lead to sodium retention

Answer 19

its promoted by Angiotensin II in proximal tubule (Na+ H+ exchange) and Aldosterone in the distal tubule and collecting duct

Question 20

what is the most important factor controlling Angiotensin II levels in the plasma?

Answer 20

renin release! from the JGA cells.

Question 21

AVP/ADH - how does this act?

Answer 21

acts by increasing water reabsorption

Question 22

how does atrial natriuretic peptide work? with decreased effective circulating volume , how does ANP work?

Answer 22

it causes Na+ to be excreted in the urine. it is inhibited wuth decreased effective circulating volume

Question 23

how does the body get rid of excess Na+?

Answer 23

the body can only decrease Na+ reabsorption, renal handling does not include secretion

Question 24

describe the cellular actions of aldosterone

Answer 24

Aldosterone diffuses easily into the cell from the blood, it creates a Aldo-MR complex that stimulates transcription, and results in synthesis of Na+ channels, mitochondrial enzymes, and Na-K pumps.

Question 25

describe positive water balance

Answer 25

when the gain of water exceed the loss of water, and total body water increases (TBW)

Question 26

describe negative water balance

Answer 26

when loss of water is greater than its gain, TBW decreases

Question 27

excretion of water by the kidney depends on whether

Answer 27

the plasma is hypo-osmotic or hyper-osmotic