Final - Sodium

Question 1

What is the major source of Na+?

Answer 1

NaCl (salt) - 40% Na

It is a major component in food processing 75% of total

Naturally occurring ~10%

Table salt (cooking and at the table) ~15%

Salt in water supplies (water softeners) 10%

Question 2

Where is salt naturally occurring?

Answer 2

Meat, eggs, milk and most vegetales

10% of total Na consumed

Question 3

What is the adequate intake of salt?

Answer 3

1,500 mg

Question 4

How is sodium absorbed?

Answer 4

Three basic pathways:
Na+/glucose co-transport (small intestine)
Electroneural Na +and Cl- co transport (Small intestine poximal colon)

Electrogenic/ colonic Na+ absorption (colon)

Question 5

How is sodium pumped into the blood?

Answer 5

Absorbed sodium is pumped out across the basolateral membrane by a Na/K ATPase pump
-This maintains the energy gradient to drive uptake

Question 6

How does the electroneural sodium transport work?

Answer 6

Na+/Cl- co-transport

Requires the presence of chloride

Na+/H+ exchange works in concert with a Cl-/HCO3 mechanis

Allows for the uptake of both NA ad CL- into the cell

Question 7

How does the Electrogenic / colonic sodium transport work?

Answer 7

Electrogenic sodium absorption

Na+ is the only ion moving transcellularly, allowing for transport to be monitored electronicall

Na enters the colon throug Na+ channels/concentration graident
-Accompanied by water and anions

Question 8

How is sodium excreted?

Answer 8

Renal excretion and retention is controlled by aldosterone

Question 9

How is aldosterone released?

Answer 9

It is released in response to low Na+ or high K+ concentrations

Question 10

What is the function of aldosterone?

Answer 10

It promotes the retention of Na+ and the excretion of K+

Question 11

Reabsorption of Na+

Answer 11

Highly selective
Active transport process that requires ATP
-promotes the retention of Na+ and the excretion of K+

Question 12

What happens in response to sodium retention?

Answer 12

The osmolarity of the plasma is increased, which is accompanied by water retention

Question 13

What are the functions of sodium?

Answer 13

Maintains fluid balance (osmotic pressure)
Nerve transmission
Impulse conduction
Muscle contraction
Acid base balance

Absorption of other nutrients (co-transport)

Question 14

Symptoms of sodium deficiency

Answer 14

Does not normally occur (serum levels are tightly maintained?

Excessive swelling
Muscle cramps
nausea
lethargy
vomiting
dizziness
shock
confusion
coma
possibly death

Can occur during episodes of extreme diarrhea or vomiting

Question 15

How does the sodium / glucose co-transport work?

Answer 15

it is carrier mediated; located on the apical membrane throughout the SI

sodium and glucose bind to the protein carrier –> carrier shuttles them across the membrane into the cell

Absorbed sodium is pumped out across the basolateral membrane by Na+/K+ ATPase pump (maintains energy gradient to drive uptake)

Glucose diffuses across the membrane by facilitated transport

Co transport can also occur with amino acids, di- and tripeptides and many b vitamins

Question 16

What is sodium’s role in the cell?

Answer 16

sodium is the major extracellular cation

Question 17

What causes sodium deficiency?

Answer 17

Excessive sweating (loss of >3% of total body weight) can result in hyponatremia (decreased sodium)

• some athletes have a greater sodium need because they lose more sodium in sweat

Question 18

What is the toxicity of sodium?

Answer 18

It is non toxic in healthy adults because it is readily excreted

Elevated Na levels suppress RAAs

Also associated with hypertension and adema

Also a risk factor for osteoporosis because sodium can increase urinary calcium losses

Question 19

What is sodium deficiency called?

Answer 19

Hyponatremia