Electrolyte and pH balance (Ch. 26 Part II)

Question 1

Na+ Balance and aldosterone

Answer 1

Body tries to hang onto Na+, reabsorbs it in kidneys and that helps us reabsorb water too 65% in PCT (majority of reabsorption occurs in PCT, filtrate volume decreases a lot) 25% in loops of Henle,

High [aldosterone]: The rest (10%) is absorbed in the DCT & CD,

Low [aldosterone]: Na+ is not actively reabsorbed- lost to urine, water follows

Question 2

aldosterone’s effects on K+ balance

Answer 2

since Na+ gets reabsorbed in higher amounts with aldosterone due to more Na-K pumps, K+ goes the other way and we urinate it out

Question 3

ANP’s effects at kidney

Answer 3

opposite of aldosterone, increases urine output, decreases BP because it increases urine output to bring BV down

eliminates sodium from the body, water follows

[effect on GFR as it relates to contractile activity of glomerular mesangial cells]

Question 4

estrogen

Answer 4

• High [aldosterone]:
• The rest (10%) is absorbed in the DCT & CD
• Low [aldosterone]:
• Na⁺ is not actively reabsorbed- lost to urine, water follows

Question 5

Progesterone

Answer 5

• Progesterone decreases Na⁺ reabsorption (blocks aldosterone)•
• Promotes Na⁺ and H₂O loss

Question 6

K+’s importance in APs and RMP

Answer 6

affects RMP and generation APs in neurons and muscle cells (so does sodium and calcium)

Question 7

hyperkalemia

Answer 7

high ECF [K+] causes depolarization & hyperexcitability, RMP closer to threshold potential, too many APs quickly fired during period of hyperexcitability, so reduced excitability follows and can lead to cardiac arrhythmia → arrest

Question 8

reversal potential review

Answer 8

charge difference at which you start reversing the flow of potassium because the cell is so negative inside that for every K+ that exits, another is pulled in (-90 for K+, +55 for Na+)

Question 9

hypokalemia

Answer 9

very dangerous because can easily lead to unresponsiveness and sudden cardiac arrest

Question 10

Regulation of K+ Balance

Answer 10

K⁺ balance is controlled in cortical collecting ducts by regulating amount secreted into filtrate

• Most important factor affecting K⁺ secretion is its concentration in ECF, which is determined by diet
• K⁺ controls its own ECF concentration via feedback regulation of aldosterone release

Question 11

how can acidosis lead to hyperkalemia

Answer 11

lots of hydrogen ions moving into cell, H+ wants to bind to P-, potassium leaves cell to balance charge, hyperkalemia

Question 12

PTH (parathyroid hormone)

Answer 12

released from parathyroid gland in response to Ca2+ dropping, because we need to get more Ca2+ into blood

Question 13

3 ways PTH increases Ca2+ in blood

Answer 13

increase osteoclast activity in bone to cause Ca2+ and PO43- release into blood, increase Ca2+ reabsorption in kidney tubule, higher activation of vitamin D by kidney which increases Ca2+ absorption from food in small intestine

Question 14

where each buffer plays its biggest role

Question 15

understand bicarbonate buffer system intimately

Question 16

3 ways to rid body of acid

Answer 16

chemical buffering systems, lungs can eliminate volatile acids, kidneys can eliminate nonvolatile fixed acids/bases

Question 17

You are examining a patient’s bloodwork, which indicates the following:

pH: 7.4

P_CO2: 4.1 mm Hg

HCO₃^-: 20 mEq/L

a. Is this patient’s condition acidosis or alkalosis? b.Is the source of this condition respiratory or metabolic? Is compensation occurring (yes or no)?

normal ranges are pH: 7.35-7.45

pCO2: 4.7-6

HCO3: 22-24

Question 18

Laxix (Furosemide) is a loop diuretic that is commonly prescribed to patients with hypertension or congestive heart failure. These patients are at an increased risk of cardiac arrhythmias and/or arrest. Why? Hint: think movement of charged ions into/out of cell

Question 19

change pco2 to 7 on question 24 of study guide

Question 20

Hypersecretion of aldosterone results in hypokalemia, which causes …

Answer 20

hyperpolarization of neurons and the need for a stronger than normal stimulus to trigger an action potential

Question 21

Mr. Heyden’s low blood pressure will trigger certain compensatory mechanisms. Which statement below best reflects the changes in hormone levels that will occur?

Answer 21

Mr. Heyden’s ADH, aldosterone, and renin will increase.

Question 22

would hypokalemia make it easier or harder to generate an AP?

Answer 22

harder, because less ECF K+ makes the difference between RMP and threshold too great

Question 23

Which of these combinations of values would indicate that a patient was suffering from metabolic acidosis?

Answer 23

Increased blood HCO3- levels and decreased pH

Question 24

Which of the hormones results in increased sodium reabsorption (and therefore water reabsorption also)?

Answer 24

aldosterone

Question 25

ANP's effects on BP through kidneys' granular cells

Answer 25

atrial cells detect high BP and release ANP; ANP makes its way to the kidneys' granular cells to tell them to decrease secretion of renin → less angiotensin II → more vasodilation → lower BP

Question 26

ANP's effects on BP through CD

Answer 26

ANP from atrial cells → hypothalamus and posterior pituitary → stimulate ADH release → kidneys' CD has fewer aquaporins → less water reabsorption → higher urine output → lower BP; OR directly to CD to decrease Na+ & therefore water reabsorption

Question 27

ANP's effect on BP after it reaches the adrenal cortex

Answer 27

decrease aldosterone release → inhibit CD in kidney → lower Na+ reabsorption, more Na+ lost in urine, water follows, lower BV → lower blood pressure

Question 28

Na+ and estrogen & progesterone

Answer 28

**Estrogen** Increases NaCl reabsorption (like aldosterone)••Leads to H₂O retention during menstrual cycles and pregnancy **Progesterone** Progesterone decreases Na⁺ reabsorption (blocks aldosterone)••Promotes Na⁺ and H₂O loss

Question 29

would hyperkalemia make it easier or harder to generate an AP?

Answer 29

easier, because extra K+ in ECF is more positive, so the difference between RMP and threshold is less

Question 30

Explain how acidosis can lead to hyperkalemia

Answer 30

acidosis → more H+ ions in ECF move down their gradient into cells → K+ leaves cells to balance that charge → more K+ in ECF

Question 31

What happens to K+ levels with alkalosis?

Answer 31

ECF K⁺ levels fall with alkalosis, hypokalemia

Question 32

how is K+ balance controlled

Answer 32

high circulating K+ → stimulate aldosterone release in kidneys → more Na-K⁺ pumps in cortical collecting ducts → more Na+ absorbed and more K+ secreted in urine

Question 33

how is K+ balance controlled

Question 34

ECF and ADH

Answer 34

An increase in ECF osmolality prompts ADH release by stimulating the hypothalamic osmoreceptors.

Question 35

What happens when the body senses decreased stretch in afferent arterioles?

Answer 35

Granular cells of kidneys release renin → convert angiotensin I-II

Question 36

what does angiotensin II activate/target (name 4 things)

Answer 36

→ thirst mechanism, adrenal cortex, posterior pituitary, systemic arterioles