Module 2 Chapter 8

Question 1

Extracellular Fluid
1. What is considered extracellular fluid?
2. What electrolytes are found in extracellular fluid?

Answer 1

Extracellular fluid composes about 1/3 of the bodies total fluid. Makes up roughly 20% of a person’s body weight.
1. Any fluid outside the body’s cells. Plasma. Interstitial fluid. transcellular.
2. The most abundant electrolytes found in the ECF are sodium and chloride. Small amounts of calcium, potassium, magnesium, and phosphorous.

Question 2

Intracellular Fluid
1. What is considered intracellular fluid?
2. What electrolytes are found in the intracellular fluid?

Answer 2

Intracellular fluid makes up a total of 2/3 of the bodies total fluid. Makes up roughly 40% of a person’s body weight.
1. All fluids found inside cells in the body are intracellular.
2. The most abundant electrolyte in the body’s cells is potassium. Small amounts of magnesium, sodium, chloride, and phosphorous. Almost no calcium.

Question 3

What are electrolytes?

Answer 3

Substances that dissociate in solution to form charged particles, ions.

Question 4

Cation Vs Anion

Answer 4

Cation - positively charged particle
Anion - negatively charged particle

Question 5

Diffusion
1. Transportation
2. Energy
3. Which way do the particles go?

Answer 5

Movement of particles along a concentration gradient. Considered a passive form of tranportation. Generates energy to transport it’s particles from the constant random collisions going on in the body. Because there are more particles colliding and creating energy in areas of high concentration, diffusion results in particles moving from this higher concentration to an area of lower, less collision area.

Question 6

Concentration Gradient

Answer 6

Difference in the concentration of particles over a distance.

Question 7

Osmosis
1. Which way does water go?

Answer 7

Osmosis is the movement of fluid across a semipermeable membrane.
1. Water diffuses down its concentration gradient. This means water travels from areas of low particles and high-water quantities to areas of high particles and low water quantities.

Question 8

Osmolarity

Answer 8

Osmolarity is the osmolar concentration in 1 L of a solution. Typically refers to substances outside the body.

Question 9

Osmolality

Answer 9

Osmolality is the osmolar concentration in 1 Kg of water. Typically used when describing fluids inside the body.

Question 10

Urine Osmolality Vs Serum Osmolality

Answer 10

Urine osmolality is a reflection of the kidneys ability to dilute or concentrate urine in response to serum osmolality levels. With dehydration (loss of water) the urine osmo would increase as the body attempts to conserve water. Conversely, if the patient has difficulty concentrating their urine (excess of water in the body) then the urine osmo would be low as the body attempts to flush out excess water.

Question 11

Isotonic
1. How does it affect cells placed in this type of fluid?
2. Examples of this type of fluid

Answer 11

Having the same effective osmolality as the intracellular fluid. Cells placed in isotonic fluid neither shrink nor swell. Commonly used examples of isotonic fluid include - N/S and LR

Question 12

What is tonicity?

Answer 12

Property of a solution that measures its ability to make water move in or out of its cells.

Question 13

Hypotonic
1. How does it affect cells placed in this type of fluid?
2. Examples of this type of fluid?

Answer 13

Hypotonic solutions have a decreased tonicity when compared with fluids intracellularly.
1. Cells placed in this type of fluid will swell. This is because the tonicity difference results in a shift of water into the cells. Water likes to go to places where there is higher concentrations of solutes and less solution.
2. Examples of this type of fluid include - .045 n/s

Question 14

Hypertonic
1. How does it affect cells placed in this type of fluid?
2. Examples of this type of fluid?

Answer 14

Hypertonic solutions contain increased amounts of solutes when compared to intracellular levels.
1. Cells placed in hypertonic solutions will result in those cells shrinking as water moves from the area of higher water concentration and lower solute concentration to areas of lower water concentration and higher solute concentration.
2. Hypertonic saline

Question 15

What is third spacing?

Answer 15

This involves fluid amounts in the transcellular parts of the body increasing. When this portion of the extracellular fluid reserve increase, this is referred to as third-spacing because this fluid is not readily available for the body to use.

Question 16

Edema

Answer 16

Palpable swelling produced by expansion of the interstitial fluids. Normally the interstitial fluids can accommodate an additional 10-30L of fluid.

Question 17

What are the 4 major causes of edema? Give an example of each.

Answer 17

1. Increased capillary pressure - as the capillary pressure increases, the amount of fluid going into the interstitial fluid increases as well. This is seen with heart failure where there is generalized fluid overload which increases the capillary pressure.
2. Decreased capillary colloidal osmotic pressure - plasma proteins are large molecules that exert a good amount of osmotic pressure, which works to keep fluid in the vascular space. Decreased amounts of proteins leads to fluid being drawn into the interstitial space. Severe liver disease, albumin loss, burns.
3. Increased capillary permeability - increased pore size or pore damage in the capillaries allows plasma proteins to leak into the interstitial space. This decreases the osmotic pressure in the vascular space and increases it in the interstitial space leading to edema.
4. Obstruction of lymph flow - lymphedema. Removal of lymph nodes. Malignant involvement cutting off circulation.

Question 18

Increased capillary pressure

Answer 18

As the capillary pressure increases, the amount of fluid going into the interstitial fluid increases as well. This is seen with heart failure where there is generalized fluid overload which increases the capillary pressure.

Question 19

Decreased capillary colloidal osmotic pressure

Answer 19

Plasma proteins are large molecules that exert a good amount of osmotic pressure, which works to keep fluid in the vascular space. Decreased amounts of proteins leads to fluid being drawn into the interstitial space. Severe liver disease, albumin loss, burns.

Question 20

Increased capillary permeability

Answer 20

Increased pore size or pore damage in the capillaries allows plasma proteins to leak into the interstitial space. This decreases the osmotic pressure in the vascular space and increases it in the interstitial space leading to edema.

Question 21

Obstruction of lymph flow

Answer 21

Lymphedema. Removal of lymph nodes. Malignant involvement cutting off circulation.

Question 22

The difference between fat and skeletal muscle for holding water.

Answer 22

Fat is essentially water free - it only holds about 10%.
Skeletal muscle holds 75%.

Question 23

Where is sodium most abundantly found?
Why is sodium found here?

Answer 23

Sodium is most abundantly found in the extracellular space.
The cell membrane is relatively impermeable to sodium. The sodium that gets in is transported out via the Na+/K+ pump.

Question 24

What is sodium’s main function in the extracellular space?

Answer 24

Water follows sodium. Sodium works to maintain adequate amounts of extracellular fluid.

Question 25

How much sodium is needed by the body every day?

Answer 25

The body requires roughly 500mg/day. The average salt intake is 6-15g a day, well over the required amount.

Question 26

How is sodium levels controlled in the body?

Answer 26

1. Diet
2. The kidneys - they are extremely efficient at regulating sodium concentrations based on the fluid status of the body.

Question 27

What tells the kidneys to excrete or hold onto sodium?

Answer 27

The effective circulating volume (the vascular bed that perfuses the body). A decreased amount of fluid circulating in the body alerts the kidneys to increase sodium retention. An increased amount of circulating fluid in the body tells the kidneys to excrete.

Question 28

How does the body know how much effective circulating volume there is in the body? Where are they located?

Answer 28

The body has baroreceptors located in key locations. These baroreceptors monitor the degree of stretch placed on the blood vessels which correlates to the amount of effective circulating volume.

Baroreceptors are located in the blood vessels and in the kidneys.

Question 29

How does the sympathetic nervous system help regulate water elimination in the body?

Answer 29

Baroreceptors detect decreased effective circulating volume. This alerts the SNS which responds by adjusting the rate of filtering by the glomerular structures. This reduced rate of filtration results in water and sodium retention which increases the effective circulating volume. An increase in effective circulating volume stops the baroreceptors from triggering this negative feedback loop.

SNS activation also increases reabsorption of sodium and water in the renal tubules and releases renin.

Question 30

ANP

Answer 30

Atrial natriuretic peptide - released from the atrial cells in the heart in response to overstretching of the atria.

ANP causes the kidneys to increase sodium excretion which reduces the effective circulating volume which reduced the amount of stretch on the atria.

Question 31

SNS releases renin in response to baroreceptors detecting low circulating volume. What happens next with renin?

Answer 31

Renin circulates until it finds angiotensinogen. It converts this into angiotensin 1.

Question 32

What is renin? Why is it released?

Answer 32

Renin is a small protein that is secreted by the kidney in response to arterial pressure, GFR, and the amount of sodium in the tubule fluid. It then circulates in the blood until it finds angiotensinogen.

Question 33

What is angiotensin 1? What happens to it? Where?

Answer 33

Angiotensin 1 is the byproduct of renin and angiotensinogen. It is rapidly converted into angiotensin 2 by the angiotensin-converting enzyme in the blood vessels of the lungs.

Question 34

What is angiotensin 2? What does it do?

Answer 34

Angiotensin 2
1. Acts on renal tubules, increases sodium reabsorption.
2. Constricts renal blood vessels to slow down the GFR - less blood filtered is more sodium in the circulation.
3. Powerful regulator of aldosterone.

Question 35

What is aldosterone? Where does it come from?

Answer 35

Aldosterone is a hormone secreted by the adrenal cortex. Acts on the collecting tubules to increase sodium reabsorption and increase potassium excretion.