4.5: Homeostasis And Feedback Loops

Question 1

The body must be able to monitor its ____ conditions at all times

Answer 1

Internal

Question 2

What are set points? (2)

Answer 2

• Values for various physiological conditions that the body tries to maintain
• this set point has a normal range for which it can fluctuate

Question 3

Temperature is an example of how there is a set point, but has a normal range. How?

Answer 3

• set point: 98.6 F

- normal range: 97 F to 99 F

Question 4

What is homeostasis? (3)

Answer 4

• the state of relatively stable internal conditions
• organisms detect and respond to a stimulus
• think of it like balance

Question 5

What allows the body maintain homeostasis?

Answer 5

Feedback loops

Question 6

What are the two types of feedback loops?

Answer 6

Negative and positive

Question 7

What is a stimulus? Give three examples

Answer 7

• a variable that will cause a response

- ex. Light, heat pain

Question 8

What is a receptor/sensor? Where is this info sent to?

Answer 8

• sensory organs that detect a stimulus

- this information is sent to the control centre (brain)

Question 9

What is an effector? (3)

Answer 9

• muscle or glands that will respond
• glands always secrete materials, such as the liver
• muscle include skeletal, smooth, cardiac

Question 10

What is a response?

Answer 10

Changes (increases or decreases) the effect of the stimulus

Question 11

Is positive or negative feedback the most common feedback mechanism?

Answer 11

Negative

Question 12

What is a negative feedback mechanism?

Answer 12

This type of feedback reduces the effect of the stimulus
Ex. Sweat, blood sugar, breathing rate
Note: see Patrick diagram on page 26

Question 13

What is a positive feedback mechanism?

Answer 13

Increases the effect of a stimulus
Ex. Child labour, blood clotting, fruit ripening
See childbirth diagram on page 26

Question 14

There are many reasons for why the body may not be able to regulate homeostasis. Give 3 examples

Answer 14

• genetic disorders
• drug or alcohol abuse
• intolerable conditions (ie. extreme heat or cold)

Question 15

What occurs in disease?

Answer 15

The body is unable to maintain homeostasis.

Question 16

Cancer and diabetes are two examples of diseases. We know that diseases occur when the body is unable to maintain homeostasis. In cancer and diabetes, why is homeostasis not achieved?

Answer 16

Cancer - the body cannot regulate cell growth

Diabetes - the body cannot regulate blood glucose levels

Question 17

Since we need feedback loops to maintain homeostasis, what else do we need to maintain homeostasis? How? (2)

Answer 17

• cells in multicellular organisms must be able to communicate
• communication is done through a signal transduction pathway