Sodium

Question 1

What is the major source of sodium in the Western diet?

Answer 1

Table salt

Salt is extensively used in food processing and manufacturing

It is estimated that processed foods account for nearly 75% of total sodium consumed (by Americans)

Question 2

How much of the salt we eat is naturally occurring?

Answer 2

~10% (meat, eggs, milk, most vegetables)

Question 3

How much of the salt we eat is added at the table?

Answer 3

~15%

Question 4

How much of sodium is absorbed?

Answer 4

95-100%

The remaining 0-5% is excreted in the feces

Note: there is not a lot of regulation going on at the absorption level

Question 5

What are the 3 basic pathways for sodium absorption?

Answer 5

1. Sodium/Glucose Cotransport System
2. Electroneutral Sodium and Chloride Cotransport System
3. Electrogenic Sodium Absorption Mechanism

Question 6

Explain the Na/Glucose Cotransport System

Answer 6

Na & Glucose get pumped into the enterocyte together. Glucose diffuses across the membrane, while Na must be pumped out through the Na+/K+ ATPase Pump (requires ATP), as K+ is pumped in.

Sodium does not need any transport protein in the blood.

Question 7

Explain the Electroneutral Na+/Cl- Cotransport System.

Answer 7

Mechanisms are still a little unclear, this is a hypothetical model:

Na+ will be pumped in, while H+ is pumped out

Cl- will be pumped in, while HCO3 (bicarb) is pumped out

Synergetic mechanism appears that the presence of CHLORIDE improves Na+ absorption.

Cl- diffuses across the membrane

Na+ requires the Na+/K+ ATPase Pump to cross into circulation.
Then Na+

Question 8

Explain the Electrogenic Transport of Sodium.

Answer 8

3rd mechanism of Na+ absorption

This is expressed in the COLON (rather than the SI like the other 2 mechanisms).

This electrogenic pump which is an ION pump will generate a CHARGE FLOW, as a result.

So, we see Na+ entering through the channel and flowing through the enterocyte, and will be pumped out through the same Na+/K+ ATPase pump

Question 9

(TRUE/FALSE)

Sodium requires a transport protein to circulate in the blood.

Answer 9

FALSE ***

Question 10

What is the serum concentration of sodium?

Answer 10

~135-145 mEq/L is the normal range

It is maintained within a fairly narrow range

Question 11

If sodium is absorbed and not needed, where is it excreted?

Answer 11

90% will leave through the URINE, most lost in SWEAT, even less in SKIN CELLS (exfoliation)

Question 12

Sodium that is not absorbed, will be excreted where?

Answer 12

FECES

Question 13

Nephron

Answer 13

A working unit of the kidney

Each kidney has millions of nephrons

Question 14

What are the main functions of sodium? ***

Answer 14

1. Maintenance of Fluid Balance & maintaining osmotic pressure
2. Nerve transmission/impulse conduction
3. Muscle contraction

Question 15

What does excess sodium cause?

Answer 15

Sodium excretion through the kidneys

An increased sodium load, that increases ECF volume and increase blood pressure (causing us to retain water)

Question 16

What causes the release of Aldosterone?

Answer 16

A decrease in BP, due to loss of blood volume, injury, extreme sweating, etc.

Question 17

Aldosterone***

Answer 17

Is released from the adrenal gland, in response to the Angiotensin-Renin system

ACTS at the kidney, causing an INCREASE OF NA2+ AND WATER REABSORPTION (in an effort to INCREASE blood volume and BP).

Question 18

Renin

Answer 18

Responsible for the production of angiotensin

Question 19

Angiotensin

Answer 19

Causes the release of ALDOSTERONE from the adrenal glands

Question 20

Vasopressin

Answer 20

aka ADH or Antidiuretic Hormone

Hormone secreted by the hypothalamus, that functions similar to aldosterone, by targeting the kidney to INCREASE SODIUM AND WATER REABSORPTION (in an effort to increase blood volume)

Question 21

What is the main cause of “sodium deficiency?”

Answer 21

Excessive sweating (loss of >3% body weight)

or in extreme diarrhea or vomiting episodes

Question 22

What are symptoms of sodium deficiency?

Answer 22

Muscle cramps, N/V, lethargy, dizziness, shock, confusion, coma, even death

Question 23

AI for sodium

Answer 23

1,500 mg for adults daily

Question 24

UL for sodium

Answer 24

2,300 mg for adults

Question 25

What is the average consumption of sodium?

Answer 25

3,000 to 5,000 mg daily