Chapter 10 Homeostasis

Question 1

Describe the function of part C (sweat gland) in temperature regulation [3] (2012/A3)

Answer 1

Part C is the sweat gland. [1]
When there is an increase in the body temperature, the sweat gland produces more sweat that is brought to the surface of the skin.[1]
When the sweat evaporates, latent heat is lost, allowing the body temperature to be brought
down to normal. [1]

Question 2

Suggest an explanation for the fall in body temperature from 2400h and 0600h. (Shown in diagram) [2] (2012/A3)

Answer 2

Between 24.00 and 6.00, the person is in a cold or air-conditioned room. This causes a drop in body temperature.
The person’s metabolic activity is also reduced at night since the person is likely to be sleeping. This reduces the
amount of heat released (during respiration).

Question 3

Fig 2.1 shows the body temperature of an insect rising at the same rate as the air temperature

State two conclusions that could be drawn from fig 2.1 [2] (2015/A3)

Answer 3

1. As the air temperature increases, the body temperature of the insect also increases.
2. Insects are unable to regulate/maintain a constant
   body temperature.

Question 4

Describe the role of sweat glands in body temperature regulation [3] (2015/A3)

Answer 4

1. When the body temperature increases, the blood temperature increases. As the blood temperature increases above normal, sweat glands become more active and more sweat is produced; [1]
2. More water in sweat evaporates and more latent heat of vapourisation is removed [1], decreasing the blood temperature back to normal. [1]
3. As the blood temperature decreases below normal, sweat glands become less active and less sweat is produced, less water in sweat evaporates and less latent heat of vapourisation is removed, increasing the blood temperature back to normal.

Question 5

Define the term homeostasis [2] (2017/A1a)

Answer 5

Homeostasis is the maintenance of a constant internal environment through [1] negative feedback mechanism to allow the
organism to function optimally. [1]

Examples include:
- thermoregulation in the skin or
- osmoregulation in the kidneys regulated by ADH levels or
- glucose regulation in the pancreas regulated by insulin and glucagon levels

Question 6

Name the chemical process which produces heat in the body [1] (2013/B8)

Answer 6

Respiration (Reject: metabolism)

Question 7

The human body has processes to prevent overheating. Describe how the body prevents overheating. [3] (2013/B8)

Answer 7

• Vasodilation of arterioles and constriction of shunt vessels allow more blood to flow through blood capillaries near the surface of the skin.
  More heat is lost by conduction, convection and radiation.[1]
• Sweat glands become more active, increasing sweat production. As more water in the sweat evaporates, more
  latent heat of vaporisation is lost. [1]
• Decreased metabolic rate to reduce the production of heat. [1]

Question 8

describe the 4 stages of the negative feedback loop [4] (self)

Answer 8

Stimulus
a change in the internal environment deviating from the normal range
Receptor
detect the stimulus and sends signals to the control centre
Effector
Bring about a corrective mechanism
Response
Condition decreases or increases to return to normal

Question 9

explain what happens when the body and external temperatures drop. [6] (self)

Answer 9

Drop in temperature:
● Thermoreceptors in the skin detect the decrease in temperature of the environment and are stimulated, while a change in the blood temperature is detected by the hypothalamus in the brain which is stimulated. The brain transmits nerve impulses to effectors to carry out responses that restore normal body temperature.
● Skeletal muscles contract and relax repeatedly called shivering, resulting in the release of heat energy due to increased rate of respiration.
● Sweat glands are less active and produce less sweat to reduce further loss of body heat through the evaporation of water in sweat, less latent heat of vapourisation is
removed.
● Vasoconstriction of arterioles and shunt vessels dilate resulting in less blood flowing to the blood capillaries on the skin surface so that less heat is lost through conduction, radiation and convection.
● Metabolic rate increases and more heat energy is released via respiration.
● Blood temperature increases and core body temperature returns to normal.

Question 10

describe the role of the hypothalamus in a negative feedback loop [3] (self)

Answer 10

1. detects changes in blood temperature
2. stimulated and generates nerve impulses
3. Nerve impulses are transmitted to the effectors to carry out responses to bring the blood temperature back to the norm

Question 11

What are the three layers of the skin? [3] (self)

Answer 11

1. Epidermis
2. Dermis
3. Subcutaneous fat

Question 12

Name the three layers of the epidermis. [3]

Answer 12

1. Cornified layer
2. Granular layer
3. Malpighian layer

Question 13

What is the structure and function of the cells in the cornified layer? [4] (self)

Answer 13

Structure
Flattened and dead keratinised cells

Function
- Protects the body from water loss
- Protects the body from invasion by microbes
- Protects the body from mechanical, thermal & chemical damage

Question 14

What is the granular layer made of? [1] (self)

Answer 14

New cells undergoing cell division

Question 15

What is the structure and function of the cells in the Malpighian layer? [2]

Answer 15

Structure
Pigment cells
Function
- To replace dead cells from the cornified layer
- Brown pigment, melanin shields genetic material from UV radiation.

Question 16

what is the function of the sebaceous glands on the skin?

Answer 16

to secrete sebum to act as a lubricant and to prevent the skin from drying out

Question 17

What controls the position of
the hair? either upright or
flattened

Answer 17

hair erector muscles

Question 18

what kind of tissue does the subcutaneous layer have and what is its function?

Answer 18

Adipose tissue
Insulating layer reducing heat loss