Principles of Tubular Transport Flashcards

1
Q

What are the 3 processes in urine formation?

A

Ultrafiltration
Reabsorption
Secretion

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2
Q

What is usually never found in urine?

A

Proteins

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3
Q

How does water move throughout the nephron?

A

Passive transport. There are no active transport processes for water.

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4
Q

What processes use facilitated diffusion?

A

Glucose transport into RBCs

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5
Q

What processes use active transport?

A

Active Na resorption and endocytosis for protein transport and requires the use of ATP.

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6
Q

What processes use secondary active transport?

A

Requires an indirect energy source in an ion gradient and it can be saturated as it is limited by carriers (Tm)

Examples are Na+-H+ exchangers

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7
Q

What is the transcellular pathway?

A

Uses a specific pump such as an Na/K-ATPase pump

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8
Q

What is the paracellular pathway?

A

Movement of ions via solvent drag and it occurs with ions like Ca2+, Mg2+ and K+

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9
Q

What is CaO2 - CvO2?

A

It is the O2 extraction from the blood

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10
Q

How does the (CaO2 - CvO2) change as O2 demand and O2 supply both increase in the heart?

A

No change in CaO2 - CvO2

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11
Q

How does the (CaO2 - CvO2) change as O2 supply decreases and O2 demand remains constant in the skeletal muscle?

A

The CaO2 - CvO2 will increase, indicating increased extraction of O2 from the blood

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12
Q

How does decreased O2 supply affect the kidney?

A

In the kidney, it will decrease the O2 demand with no change in CaO2 - CvO2. This means as blood flow decreases to the kidney, it requires less O2.

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13
Q

What is the normal handling of glucose in the kidney?

A

Normally 100% of the glucose is reabsorbed

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14
Q

What is the reabsorption of glucose equal to in an equation?

A

R = F - E

S = 0

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15
Q

When can the tubular transport maximum (Tm) be calculated?

A

Only when the Tm is exceeded

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16
Q

What is the Tm for glucose equal to?

A

Tm (glucose) = (Pa GFR) - (UV)

17
Q

What is the renal plasma threshold (RPT) of glucose?

A

The RPT is the point where glucose first appears in urine.

18
Q

Describe the normal handling of PAH.

A

Normally over 90% of PAH is secreted

19
Q

What is the equation for the secretion of PAH?

A

S = E - F

R = 0

20
Q

What is the Tm for PAH equal to?

A

Tm (PAH) = (UV) - (PaGFR)

21
Q

What is the RPT of PAH defined as?

A

The RPT of PAH is the point where the secretion slope of PAH first decreases

22
Q

What is diuresis?

A

It is a urine flow greater than 1 mL per minute

23
Q

What is the function of mannitol?

A

It acts as an osmotic diuretic

24
Q

What is the fate of mannitol in the nephron?

A

It is filtered but not reabsorbed

25
Q

How does mannitol function as an osmotic diuretic?

A

It holds excess water in the tubule by osmotic forces which leads to increased urine flow.

26
Q

How can glucose function as an osmotic diuretic?

A

Normally glucose is 100% reabsorbed but if some is left in the tubule, it will hold excess water by osmotic forces and leads to increased urine flow. It will also cause dehydration and thirst.