Chapter 7 - Homeostasis Of Body Temperature And Body Fluids

Question 1

What is the normal body temperature of humans?

Answer 1

36.8°C

Question 2

In a sentence, how does the body achieve a constant body temp?

Answer 2

The heat gained by the body must exactly equal the heat lost from the body.

Question 3

What is thermoregulation?

Answer 3

Maintaining the balance between heat production and heat loss.

Question 4

What is the optimum temp for cellular respiration?

Answer 4

37°C

Question 5

What are two examples of heat inputs and heat outputs?

Answer 5

Heat input

1. Heat from metabolism (especially respiration of the liver and muscle cells)
2. Heat gain from surrounding by conduction and radiation

Heat output

1. Radiation, conduction and convection to surroundings
2. Evaporation of water from skin and lungs, warmed air breathed out, warm urine and faeces.

Question 6

What is metabolic rate?

Answer 6

The rate at which energy is released by the break down of food.

Question 7

What are some factors that contribute to the increase of metabolic rate?

Answer 7

Exercise, stress and body temperature.

Question 8

For each 1°C rise in temperature, the rate of biochemical reactions increase by 10%.

Answer 8

Fun fact

Question 9

What are peripheral thermoreceptors?

Answer 9

Thermoreceptors in the skin and in some mucous membranes.

Question 10

What are the two types of peripheral thermoreceptors?

Answer 10

• Cold receptors, stimulated by environmental temperatures lower than normal
• Heat receptors, stimulated by environmental temperatures higher than normal.

Question 11

What are the four main ways heat can be lost from the skin? (CERC)

Answer 11

1. Conduction
2. Convection
3. Radiation
4. Evaporation

Question 12

What is sweating?

Answer 12

Sweating is the active secretion of fluid by sweat glands and the periodic contraction of cells surrounding the ducts to pump the sweat to the skin surface.

Question 13

What is sweat made of?

Answer 13

Sodium chloride, urea, lactic acidosis and potassium.

Question 14

How does the body prevent body temperature from falling? (5)

Answer 14

• Vasoconstriction (physiological). Blood vessels in the skin constrict causing skin to becomes cooler and allow less heat to go through it.
• Stimulation of the adrenal medulla (physiological ). Sympathetic nerves stimulate the secretion of adrenaline and noradrenaline that bring about an increase in cellular respiration which increases heat production.
• Shivering (physiological and behavioural)
• production of thyroxine (physiological) increases metabolic rate which increases body temperature
• consciously aware of cold conditions (behavioural)

Question 15

What is shivering?

Answer 15

Shivering is a physiological and behavioural response. It increases muscle tone which leads to oscillating, rhythmic muscle tremors at a rate of 10-20per Second. Heat is produced by this metabolic activity and goes towards core body temperature.

Question 16

How does the body prevent body temperature from rising? (4)

Answer 16

• vasodilation (physiological ).increases blood flow through the skin.
• sweating (physiological) temperature above 28°C results in sweating to cool the body.
• Decrease in metabolic rate (physiological). Less heat is produced in the body (decrease in the secretion of thyroxine)
• Consciously aware of warm conditions (behavioural)

Question 17

What is heat stroke?

Answer 17

Heat stroke usually occurs when the weather conditions make it difficult for the body to loose heat through radiation or evaporation.

Question 18

At what temperatures can death occur?

Answer 18

Above 45°C and below 32°C

Question 19

What is the approximate amount of water the human body is made of? (%)

Answer 19

The body is roughly 60% water. Males have an average of 65% of water where as females have an average of 55%.

Question 20

What are the 3 body fluids that contain water?

Answer 20

Intracellular fluid or cytosol 
Extracellular fluid (includes blood plasma and intercellular fluid) 
Intercellular fluid or interstitial fluid or tissue fluid (fluid between cells).

Question 21

What is the average fluid intake per day?

Answer 21

2500mL/day

Food - 700mL
Metabolic water - 200mL
Drink - 1600mL

Question 22

What is the average fluid outtake per day?

Answer 22

2500mL/day
Skin - 500mL
Kidneys (urine) - 1500mL
Alimentary canal (faeces) - 200mL