Lecture 1: Homeostasis, body fluids, pH and temperature

Question 1

What is the definition of homeostasis?

Answer 1

Physiological process by which the internal systems of the body such as water, temperature and pH balance are maintained at equilibrium

Question 2

What is the percentage of water in a standard 70kg male?

Answer 2

60%

Question 3

What are the body compartments where fluids accumulate?

Answer 3

Intracellular fluid, interstitial fluid and plasma

Question 4

What is the difference between water balance in males and females?

Answer 4

As males have lower percentage of body fat than females, males have more total body water than females. A normal adult male has 60% TBW while females have 50% TBW.

Question 5

What is the difference between water balance in early life and in older populations?

Answer 5

Infants have the highest percentage of TBW while elderly has the least

Question 6

What are the differences between dehydration and water toxicity?

Answer 6

Dehydration is due to insufficient water while water toxicity is due to too much water.

Question 7

How does a negative feedback loop work?

Answer 7

A stimulus is detected by a sensor in the body, and that information is sent to the control centre, which then gives commands to the effector to counter that change. This loop continues until the stimulus has been reversed and the sensor detects it, sending the information to the control centre which then gives commands to the effector to stop.

Question 8

How does a positive feedback loop work?

Answer 8

A change occurs, initiating the feedback cycle. The body reacts and the product of that reaction leads to an increase in that reaction. This continues until the initiator ceases.

Question 9

What is the importance of acid-base balance for normal human physiology?

Answer 9

There is a very narrow range of pH that is compatible with life (pH 7.35 - 7.45). If blood pH falls below 7.35, acidosis occurs and if it increases above 7.45, it is alkalosis. If it falls below 6.8 or increases above 8.0 for a significant period of time, death is likely.

Question 10

What is the normal range of pH in blood?

Answer 10

7.35 - 7.45

Question 11

What is the normal range of pH in gastric juice in the stomach?

Answer 11

1 - 2.5

Question 12

What is the normal range for core body temperature?

Answer 12

36.5 - 37.5 degrees C

Question 13

What is the mechanism that regulates pH in blood?

Answer 13

Infusion of bicarbonate solution can help to control the concentration of carbon dioxide in blood which is acidic, hence controlling pH of blood

Question 14

What is the mechanism that regulates pH in cells?

Answer 14

Sodium phosphate buffering system is used to regulate intracellular pH and transport systems

Question 15

What is used to regulate pH if heartburn symptoms occur?

Answer 15

Antacids which contain weak basic salts can neutralize the acidic pH, such as aluminum hydroxide, magnesium hydroxide and calcium salts. Aluminum hydroxide are preferred as they are milder, long acting and have fewer side effects as it is insoluble.

Question 16

What are the mechanisms that regulate core body temperature when it is too low?

Answer 16

Mechanisms that increase body temperature:

• shivering
• curling up
• piloerection
• vasoconstriction

Question 17

What is the process of oedema?

Answer 17

When water is consumed too quickly, body fluids become diluted and there is a reduction of sodium concentration in the extracellular fluid that causes a shift in osmotic pressure, making cells and tissues swell.

Question 18

What are the mechanisms that regulate core body temperature when it is too high?

Answer 18

Mechanisms that decrease body temperature:

• vasodilation
• sweating
• pilorelaxation
• stretching out

Question 19

What are the pH values of venous and arterial bloods?

Answer 19

Venous blood has more CO2 so more acidic, pH 7.35 while arterial has less so pH 7.45

Question 20

What reagent of choice should we use to detect sugars?

Answer 20

Periodic acid-Schiff Reagent

Question 21

What happens if core body temperature is higher than the normal range?

Answer 21

37.6 - 40: Fever - pale sweaty skin, cramps in stomach, arms and legs
40 - 46: Heat stroke - flushed dry skin, hot to touch, strong bounding pulse
> 46: Heat exhaustion - unconsciousness, confused, seizures, headache, dizziness

Question 22

What happens if core body temperature is lower than the normal range?

Answer 22

32 - 37.4: Mild hypothermia - shivering, fatigue, slurred speech, confusion, muscle stiffness
28-32: Severe hypothermia - shivering stops, muscles become rigid, slow and weak pulse, drowsiness, reduction in response levels
<26: No vital signs - unconsciousness, dilated pupils, pulse undetectable, appear dead (not dead until warm and dead)

Question 23

What is the proportion of water in the extracellular space?

Answer 23

Extracellular 1/3 of total water
Interstitial space - 25% of extracellular fluid
Plasma - 75% of extracellular fluid