Pack 7 – Thermoregulation and Homeostasis

Question 1

Homeostasis

Answer 1

The maintenance of a stable internal environment, using physiological processes to maintain stable conditions such as pH, temperature, water concentration etc.

Question 2

Thermoregulation

Answer 2

The maintenance of body temperature within a set range

Question 3

How does the body control conditions and ensure they stay within certain ranges?

Answer 3

• The body uses negative feedback loops to maintain all of these conditions around a set, or norm, value
• Homeostatic mechanisms act to return this value to the norm should it deviate from it

Question 4

Homeostasis process:

Answer 4

• Receptors detect deviations from the norm
• Message sent to control centres in the brain via the nervous or hormonal system
• Control Centres (e.g. Hypothalamus) receive message and send out message to effectors
• Effectors are turned on or off to bring conditions back to the norm value

Question 5

How does the body react to a drop in temperature?

Answer 5

• Drop in temperature detected by thermoreceptors in the skin and hypothalamus
• Nerve impulses sent to heat gain centre in hypothalamus

Question 6

What does the heat gain centre initiate in reaction to a drop in temperature?

Answer 6

• Inhibition of sweat glands - sweat reduction to decrease energy loss from the skin
• Vasoconstriction – arterioles constrict meaning that blood flows further from skin so less heat energy is lost
• Rapid, involuntary contraction of skeletal muscles– shivering increases heat production

Question 7

How does the body react to a rise in temperature?

Answer 7

• Rise in temperature detected by thermoreceptors in the skin and hypothalamus
• Nerve impulses sent to heat loss centre in hypothalamus

Question 8

What does the heat loss centre initiate in reaction to a rise in temperature?

Answer 8

• Vasodilation – arterioles dilate meaning that blood flows closer to the surface so more heat energy is lost
• Relaxation of skeletal muscles – no shivering
• Liver decreases metabolic rate - decreases heat production by cells

Question 9

Hyperthermia

Answer 9

The internal body temperature rises too high

Question 10

Cause of hyperthermia

Answer 10

An increase in CBT (core body temperature) above 40.5oC

Question 11

Symptoms of hyperthermia:

Answer 11

Sweating, flushing, nausea, fatigue, seizures

Question 12

Physiological responses to hyperthermia:

Answer 12

• Vasodilation and sweating to reduce body temperature
• Irreversible neuronal damage above 40oC

Question 13

Hypothermia

Answer 13

The internal body temperature falls too low

Question 14

Symptoms of hypothermia:

Answer 14

Shivering, hypotension, muscle disfunction, coma

Question 15

Burns

Answer 15

The surface of the body is exposed to extreme heat

Question 16

Burn cause:

Answer 16

Dry heat (such as a hot pan)

Question 17

Scald cause:

Answer 17

Wet heat (such as hot oil)

Question 18

Symptoms of burns:

Answer 18

Blistering, red and peeling skin, swelling, white and charred skin

Question 19

Body’s response to a burn:

Answer 19

• In the local area, some tissue is irrevocably lost and surrounding tissue can recover provided the blood supply isn’t destroyed

Question 20

Frostbite

Answer 20

The surface of the body is exposed to extreme cold

Question 21

The body’s response to frostbite:

Answer 21

• In the local area, some tissue is irrevocably lost (site of the damage), and surrounding tissue can recover provided the blood supply isn’t destroyed
• At the site of the damage, cells die off (undergo necrosis – A5) turning the area black
• Systemic responses include inflammation, oedema (building up of tissue fluid), drip in cardiac output, shock