Chapter 10 part 1: Homeostasis

Question 1

what is homeostasis?

Answer 1

• homeostasis is the maintenance of a constant internal environment.

Question 2

what is the internal environment of an organism consisted of?

Answer 2

• the internal environment of an organisms consists of the blood, and tissue fluid that surrounds the cells in the body.

Question 3

what are the examples of homeostasis in humans?

Answer 3

• regulating body temperature.
• regulating water potential of blood and tissue fluid.
• regulating blood glucose concentration.

Question 4

what is an advantage of homeostasis of an organism?

Answer 4

• homeostasis allows an organism to survive wihtout being affected by changes in the external environment.

Question 5

what is the negative feedback process and how does it take place?

Answer 5

• the negative feedback is a process that takes place when changes in the internal environment of the body are detected, so the body reacts to bring about an opposite effect to the changes detected, and then restores the body to its original state.

Question 6

what are the requirements for negative feedback to take place?

Answer 6

1. normal level/set point:
   - the normal condition of the internal environment to be maintained.
2. stimulus:
   - the change in the internal environment.
3. receptors:
   - sense organs that detect any changes and send signals to the control centre of the body.
4. corrective mechanism:
   - reverses the effect of the stimulus.

Question 7

what happens when the set point is reached?

Answer 7

• when the set point is reached, feedback is sent to the receptor to stop the corrective mechanism.

Question 8

what are the general stages in negative feedback?

Answer 8

first version: increase then decrease
1. normal (set point)
2. stimulus (condition rises above normal)
3. receptor detects stimulus
4. signal sent to control centre to brain and thought process
5. corrective mechanism
6. condition decreases
7. back to normal (set point)

second version:
1. normal (set point)
2. stimulus (condition decreases below normal)
3. receptor detects stimulus
4. signal sent to control centre to brain and thought process
5. corrective mechanism
6. condition rises
7. back to normal (set point)

Question 9

what is the homeostasis control of blood water potential when it rises above normal levels?

Answer 9

1. first type of stimulus: blood water potential rises above normal level. (e.g. due to large intake of water)

RECEPTOR AND CONTROL CENTRE:
- hypothalamus of the brain is stimulated.

CORRECTIVE MECHANISM:
- less ADH is released by pituitary gland into the bloodstream.
- less ADH is transported to the kidneys.
- cells in the walls of collecting ducts become less permeable to water.
- less water is reabsorbed into the bloodstream
- more water is excreted.
- urine is more diluted.
- more urine is produced.

RESULT:
- blood’s water potential drops to normal level.

Question 14

what is the homeostasis control of blood water potential when it falls below normal levels?

Answer 14

1. second type of stimulus: blood water potential falls below normal level. (e.g. through profuse sweating)

RECEPTOR AND CONTROL CENTRE:
- hypothalamus of the brain is stimulated.

CORRECTIVE MECHANISM:
- more ADH is released by pituitary gland into the bloodstream.
- more ADH is transported to the kidneys.
- cells in the walls of collecting ducts become more permeable to water.
- more water is reabsorbed into the bloodstream
- less water is excreted.
- urine is more concentrated.
- less urine is produced.

RESULT:
- blood’s water potential rises to normal level.