Renal L5: Fluid balance (Na+)

Question 1

What are the 4 steps of the reabsorption process?

Answer 1

1. Isosmotic fluid leaving the proximal tubule becomes progressively more concentrated in the descending limb
2. Removal of solute in the thick ascending limb creates hyposmotic fluid
3. Hormones control distal nephron permeability to water and solutes
4. Urine osmolarity depends on reabsorption in the collecting duct

Question 2

What is step 1 of the reabsorption process?

Answer 2

Isosmotic fluid leaving the proximal tubule becomes progressively more concentrated in the descending limb

Question 3

What is step 2 of the reabsorption process? (after fluid becomes more concentrated in the descending limb)

Answer 3

Removal of solute in the thick ascending limb creates hyposmotic fluid

Question 4

What is step 3 of the reabsorption process? (after the ascending limb creates hyposmotic fluid)

Answer 4

Hormones control distal nephron permeability to water and solutes

Question 5

What is step 4 of the reabsorption process? (after hormones control permeability)

Answer 5

Urine osmolarity depends on reabsorption in the collecting duct

Question 6

What are the 2 reasons why the kidney controls reabsorption?

Answer 6

maintain:

1. ECF volume
2. blood pressure

Question 7

What is Na+ important?

Answer 7

one of main solutes of blood- contributes to osmotic activity

Question 8

_______ and _____ anions (specifically _____ - + _______) contribute 90% of the ECF osmotic activity

Answer 8

Na+; ECF; HCO3; Cl-

Question 9

Under normal conditions, the ECF can “retain” enough water to maintain osmolarity at _______ mOsm/L

Answer 9

300

Question 10

Add more salt to ECF —> retain _____ (more/less) water = 300 mOsm/L. As a result, this _____ (increases/decreases) ECF volume (blood volume) & blood pressure

Answer 10

more; increases

Question 11

Add more salt to ECF —> _____ (gain/lose) water = 300 mOsm/L. As a result, this _____ (increases/decreases) ECF volume (blood volume) & blood pressure

Answer 11

lose; decrease

Question 12

ECF volume and blood pressure are _______ (directly proportional/inversely proportional)

Answer 12

directly proportional

Question 13

If the average salt input is 10.5g/day, how much of it is lost from obligatory loss in sweat and faeces?

Answer 13

0.5g

Question 14

If the average salt input is 10.5g/day, how much of it is lost from controlled excretion in urine?

Answer 14

10.0g

Question 15

How is the majority of Na+ loss in the body?

Answer 15

controlled excretion in urine

Question 16

With Na+ reabsorption, ______ (nearly all/none) of Na+ is reabsorbed from the _________

Answer 16

nearly all; filtrate

Question 17

Why is Na+ reabsorption for other molecule reabsorption?

Answer 17

Na+ absorption creates a gradient and helps create the absorption for other molecules

Question 18

Order from most to least % of Na+ being reabsorbed: proximal, Loop of Henle and distal tubule and collecting duct.

Answer 18

Proximal tubule > Loop of Henle > Distal tubule and collecting duct

Question 19

What is the function of the proximal tubule?

Answer 19

Aids reabsorption of glucose, amino acids, water, Cl- and urea

Question 20

What is the function of the Loop of Henle?

Answer 20

Allows production of urine of varying concentrations (for osmotic gradient)

Question 21

What is the function of the distal tubule and collecting duct?

Answer 21

Regulates ECF volume (hormonally controlled)

Question 22

To maintain a constant salt load, salt intake must equal salt ______.

Answer 22

output

Question 23

_________ is the only place Na+ is not reabsorbed.

Answer 23

Descending limb of loop of Henle

Question 24

8% of Na+ reabsorption is _____ controlled. Where does this occur?

Answer 24

hormonally Distal convoluted tubule & collecting duct

Question 25

What are the 2 hormones which control Na+ reabsorption?

Answer 25

1. Renin-angiotensin-aldosterone system (RAAS) 2. Natriuretic peptides

Question 26

How does Renin-angiotensin-aldosterone system (RAAS) control Na+ reabsorption? What does it do to blood volume and pressure?

Answer 26

Reabsorbs Na+ (increases blood volume & pressure)

Question 27

How does Natriuretic peptides control Na+ reabsorption? What does it do to blood volume and pressure?

Answer 27

Inhibits Na+ reabsorption (decreases blood volume & pressure)

Question 28

What is the response to a decrease in Na+ load?

Answer 28

Question 29

What if there is a large drop in blood pressure (eg. Haemorrhage)?

Answer 29

The baroreceptor response causes the constriction of the afferent arteriole which decrease GFR

Question 30

Na+ reabsorption in the distal tubule & collecting duct is controlled by the hormone \_\_\_\_\_\_\_

Answer 30

aldosterone

Question 31

Where does aldosterone control Na+ reabsorption?

Answer 31

distal tubule & collecting duct

Question 32

How does aldosterone control Na+ reabsorption?

Answer 32

Aldosterone promotes the insertion of additional Na+ channels and pumps in the tubular cell membrane

Question 33

Aldosterone is _______ type hormone and is ____ (hydrophillic/phobic) which means it ____ can/can't cross a membrane and go into the cell

Answer 33

lipid; hydrophobic; can

Question 34

What are the 5 steps of aldosterone in Na+ reabsorption?

Answer 34

1. Aldosterone combines with a cytoplasmic receptor 2. Hormone-receptor complex initiates transcription in the nucleus. 3. New protein channels and pumps are made 4. Aldosterone-induced proteins modify existing protein 5. Result in increased Na+ reabsorption and K + secretion

Question 35

What is step 1 of aldosterone in Na+ reabsorption?

Answer 35

Aldosterone combines with a cytoplasmic receptor

Question 36

What is step 2 of aldosterone in Na+ reabsorption? (after combined with a cytoplasmic receptor)

Answer 36

Hormone-receptor complex initiates transcription in the nucleus.

Question 37

What is step 3 of aldosterone in Na+ reabsorption? (after initiation of transcript in the nucleus)

Answer 37

New protein channels and pumps are made

Question 38

What is step 4 of aldosterone in Na+ reabsorption? (after protein channels and pumps are made)

Answer 38

Aldosterone-induced proteins modify existing protein

Question 39

What is step 5 of aldosterone in Na+ reabsorption? (after proteins modify existing proteins)

Answer 39

Result in increased Na+ reabsorption and K + secretion

Question 40

RAAS is stimulated by cells of the \_\_\_\_\_\_\_\_\_\_

Answer 40

juxtaglomerular apparatus

Question 41

RAAS begins with the secretion of _____ by the _____ cells

Answer 41

renin; granular

Question 42

What is the function of juxaglomerulus apparatus?

Answer 42

Helps to control glomerular filtration rate

Question 43

What are 3 factors that renin secretion is stimulated by?

Answer 43

1. decreased stretch of the granular cells (ie. decreased blood pressure in the afferent arteriole) 2. decreased NaCl in the distal tubule (detected by macula densa cells) 3. Baroreceptor reflex (sympathetic stimulation of granular cells)

Question 44

Renin secretion is stimulated by _____ (increased/decreased) stretch of the _____ cells (ie. \_\_\_\_\_\_\_(increased/decreased) blood pressure in the ____ arteriole)

Answer 44

decreased; granular; decrease; afferent

Question 45

Renin secretion is stimulated by _____ (increased/decreased) NaCl in the ______ (proximal/distal) tubule, which is detected by _______ cells

Answer 45

distal; macula densa

Question 46

What are other factors related to fluid balance which also bring out changes? List the 6 steps

Answer 46

1. Granular cells secrete renin 2. Renin activates angiotensinogen into angiotensin I – Angiotensinogen is a plasma protein (high concentrations but inactive) 3. In lungs: Angiotensin I converted into angiotensin II by angiotensin-converting enzyme (ACE) 4. Angiotensin II triggers release of aldosterone (hormone) from adrenal cortex 5. Aldosterone stimulates Na+ reabsorption from distal tubule and collecting duct 6. Water follows Na+ into ECF to restore blood volume & pressure

Question 47

Apart from triggering the release of aldosterone (hormone) from the adrenal cortex, what else can the angiotensin II do?

Answer 47

can also increase thirst and vasopresin (increase water reabsorption= increase blood volume )

Question 48

What is the function of Natriuretic peptides (NP)?

Answer 48

Stimulates Na+ &water excretion (more Na+ into the urine) to lower blood volume & pressure

Question 49

Natriuretic peptides (NP) is produced by ________ in the _______ and \_\_\_\_\_\_\_.

Answer 49

cardiomyocytes; atria; ventricle

Question 50

What is atrial natriuretic peptide - ANP?

Answer 50

normal physiology

Question 51

What is brain natriuretic peptide – BNP?

Answer 51

heart failure; isolated in the heart

Question 52

NP release is triggered by stretch of the (\_\_\_\_ (increase/decrease) blood volume & pressure)

Answer 52

increase; heart chamber (atria, ventricle)

Question 53

What happens when there is an increase in NaCl, ECF volume and atrial blood pressure?

Answer 53

Question 54

The initial response to a drop in blood pressure involves the ______ system, when there is a Car accident with severe blood loss (10%) and a drop in blood volume &blood pressure. ECF osmolarity is normal

Answer 54

cardiovascular

Question 55

The long term response to a drop in blood pressure involves the _____ system

Answer 55

renal