Body fluids

Question 1

What is homeostasis?

Answer 1

The relative dynamic constancy of the “milieu interieur”, or internal environment

Question 2

What is the difference between the internal environment and the external environment in the body?

Answer 2

The internal environment is where the cells are located and must remain relatively constant/balanced, while the external environment can vary in terms of pressure, temperature, etc.

Question 3

Who is the father of physiology? What were his two major observations?

Answer 3

Claude Bernard. He said that:
1. The environment surrounding individual cells is vastly different from the external environment.
2. The internal environment remains relatively constant under conditions of health.

Question 4

What is responsible for maintaining homeostasis in the body?

Answer 4

Organ systems (and their functional activities) are responsible for maintaining homeostasis and detecting any changes in order to adjust.

Question 5

What happens if homeostasis is not maintained?

Answer 5

Normal function is disrupted and disease results.

Question 6

What is the most abundant body fluid? What proportion of the body does it make up?

Answer 6

Water. It can make up anywhere from 45%-75% of the total body mass.

Question 7

Name 2 reasons why body water is important at the micro scale.

Answer 7

1. It is the medium in which solutes are dissolved.
2. It is where metabolic reactions take place.

Question 8

Name 5 larger scale reasons why body water is important to the functioning of the individual.

Answer 8

1. Regulates body temperature
2. Lubricates joints
3. Moistens tissues in the mouth, eyes, and nose
4. Protects body organs and tissues
5. Helps prevent constipation
6. Lessens the burden on the kidneys and liver by flushing out waste products
7. Helps dissolve minerals and other nutrients to make them accessible to the body
8. Carries nutrients and oxygen to cells

Question 9

Name the main 5 sources of body water and whether they are high or low in body water. Which ones vary significantly between individuals?

Answer 9

Tissues high in body water: skin, muscle, organs (heart, liver, brain, kindney). They all have around 70-80% water.

Tissues low in body water: bone (25%), fat (10%).

Only fat varies significantly between individuals.

Question 10

Explain why body water as a proportion of mass varies so much between individuals.

Answer 10

While solids in the body do not vary much between individuals, fat does. Fat (adipose tissue) is the main reason why body water varies so much as a proportion of body mass. It is low in water, so individuals with more fat have a lower proportion of total body water than individuals with less fat.

Question 11

Does body water vary among individuals? Explain why or why not.

Answer 11

Body water as a proportion of total body mass varies among individuals because the amount of fat they have will increase or reduce the proportion of water in their bodies. But water content as computed as a fraction of lean body mass, meaning with fat excluded, does not vary significantly among (similar) individuals.

Question 12

Who is the physiological reference individual?

Answer 12

A 21 year old, white male with a 70 kg weight.

Question 13

Name 3 factors that affect water content in the body and explain the trends they cause.

Answer 13

Age: Newborns have low amounts of fat and therefore a high body water %. As a child ages they add fat, decreasing their body water %. As we age, tissues become drier because we lose muscle mass in favour of connective tissue, which is drier. So as we get older, the proportion of body water goes down.

Sex: After puberty, females deposit more fat than males in the breast and buttocks region, leaving them with a lower body water proportion than males.

Weight: An overweight individual will have more fat and therefore a lower proportion of body water.

Question 14

What is the formula to calculate the absolute amount of water an individual has in their body?

Answer 14

Absolute amount of water = (mass (kg) x % water)/100 = ?? kg = ?? L

Question 15

Would you expect a female to have a higher or lower absolute amount of water in her body than male? Why?

Answer 15

She would have less water, since females have a higher proportion of fat.

Question 16

Why is it important to know how much total body water we have?

Answer 16

It is necessary to properly administer water-soluble medication.

Question 17

If you want to administer a water soluble medication in a proportion of 10 mg/7 kg to a 70 kg male with 60% body water, what concentration of medication will end up in his system?

Answer 17

Amount of water in his body: 70 kg x 0.60 = 42 L = 42,000 ml water
Amount of medication: 70 mg/7 kg x 70 kg = 100 mg medication
Final concentration: 100 mg/42,000 mL = 0.0024 mg/mL

Question 18

The water in our body is in a state of dynamic constancy. Explain how this is the case.

Answer 18

The amount of body water must remain constant to stay in good health, but there is water turnover every day through exchanges with both the internal and external environment. But we overall must maintain our water balance.

Question 19

How do individuals remain in water balance?

Answer 19

Their intake of fluids must equal their output of fluids, including both sensible and insensible outputs.

Question 20

Name our major sources of water intake and explain them.

Answer 20

1. Oral fluid: drinking water
2. Oral intake as food: intake of the water that is in food
3. Oxidative water from metabolism: production of 6 molecules of water as a byproduct for every molecule of glucose broken down to produce energy

Question 21

What is the difference between a sensible and an insensible output of water? Give two examples of each.

Answer 21

A sensible loss of water is when we can feel/are conscious off the loss. For example, urination and defecation.

An insensible loss of water is when we are not aware of the loss and cannot feel it. For example, water loss of exhalation and through the skin.

Question 22

What is the difference between obligatory and facultative water loss?

Answer 22

Obligatory water loss is the minimum amount of water that needs to be lost every day for the water to remain healthy. This loss, around 1.5 L per day, will take place regardless of water intake.
Facultative water loss takes care of any excess water that needs to be excreted through the kidneys (urination), allowing us to remain in water balance. The quantity lost varies with intake.

Question 23

Are insensible perspiration and sweating the same? Give 4 reasons why or why not.

Answer 23

No. They are not the same because:
1. IP consists of the release of pure water, while sweat contains electrolytes (salt)
2. IP is a passive process affected by temperature and relative humidity, while sweating requires activity.
3. IP takes place over the entire skin surface (not just sweat glands), while sweating occurs only through sweat glands
4. IP is continuous, while sweating is activated by heavy work or high temperatures

Question 24

When an individual is in water balance, what proportion of the body weight is turned over in adults and in infants? What accounts for the difference?

Answer 24

3-4% of total body weight in adults and 10% of body weight in infants. It is much higher in infants because they have a higher surface to mass ratio than adults, meaning that the water molecules are more easily released. They also have less mature kidneys, meaning that they have less of a chance of losing water through electrolytes.

Question 25

Why shouldn’t you give water to newborns?

Answer 25

They are very susceptible to water loss because of their high surface to mass ratio and because their electrolyte concentration can easily be diluted, since their kidneys are developing and cannot process very much water.

Question 26

Name 2 reasons why it is important to maintain a constant body water volume.

Answer 26

1. It helps maintain solute concentrations
2. It helps maintain normal blood volume and pressure

These both ensure that an adequate amount of oxygen reaches tissues.

Question 27

What are the two ways in which water balance can be thrown off?

Answer 27

You can have a negative water balance if water loss > water intake or water intoxication if water intake > water loss.

Question 28

Name the 5 ways in which a negative water balance could happen.

Answer 28

1. Reduce intake (not drinking enough)
2. Excessive loss from gut (diarrhea or vomiting)
3. Excessive sweating (exercising without replacing the lost water)
4. Excessive loss in expired air (i.e. dry air at high altitudes)
5. Excessive loss in urine

Question 29

Name the 2 ways in which water intoxication can occur.

Answer 29

1. Excessive water intake (kidneys can get overwhelmed)
2. Renal system failure

Question 30

Between a 70 kg male, a 70 kg female, and a 70 kg elderly person, who would you expect to require the biggest and the smallest dose of water-soluble medication? Why?

Answer 30

You would expect the elderly person to require the most, then the female, then the male. This is because water soluble medication dose is mg/mL, and since the elderly person will have the lowest amount of water, the dose will be highest. The opposite is the true for the younger male, since he will have less fat than the female and thus a higher proportion of body water.