5.14 Homeostasis

Question 1

Conditions in your body need to be kept within a narrow range. Why is this important?

Answer 1

So that enzyme-controlled metabolic reactions that take place in your cells continue at an appropriate rate. It can be dangerous for your health if conditions vary too much from normal levels.

Question 2

Define homeostasis

Answer 2

Homeostasis is the regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions.

Question 3

What type of systems do our body use in order to maintain a constant internal environment?

Answer 3

Automatic control systems

Question 4

What do automatic control systems do?

Answer 4

They recognise when there is a change from optimal conditions and then send a signal to reverse that, so that the levels go back to normal.

Question 5

What 3 main components are automatic control systems made up of?

Answer 5

• Receptors: to detect a change
• Coordination centres (such as the brain or spinal cord): which interpret that change and decide what needs to be done about it
• Effectors: carry out the change (muscles or glands)

Question 6

Some effectors involved in homeostasis are antagonistic. What does this mean?

Answer 6

They work in opposition to each other (e.g. once increases a level and another decreases it)

Question 7

What are the three things in the body that are kept steady in the body during homeostasis?

Answer 7

• Blood glucose (sugar) concentration - you need to make sure the amount of glucose in your blood doesn’t get too high or too low.
• Water content - you need to keep a balance between the water you gain (in drink, food and from respiration) and the water you urinate, sweat and breathe out.
• Body temperature - you need to make sure it doesn’t get too high or low

Question 8

What temperature do the enzymes in the human body work best at?

Answer 8

37 degrees celsius

Question 9

Describe how negative feedback is used to control body temperature (4)

Answer 9

1) Receptors in the skin and hypothalamus detect when the temperature is too high or too low.
2) The hypothalamus then processes the information and communicates via the nervous system with effectors, e.g. erector muscles in the skin or swear glands
3) The effectors respond to counteract the change - bringing the temperature back to normal.
4) Negative feedback helps to keep conditions in the body within certain limits - it usually keeps body temperature between 0.5 degrees and 37 degrees.

Question 10

Where are the coordination centres located in the body?

Answer 10

• Spinal cord
• Brain

Question 11

Name the two types of effectors and state what they do

Answer 11

They two types of effectors are muscles and glands. Muscles contract when stimulated, whilst glands release hormones.