Homeostasis

Question 1

What is homeostasis?

Answer 1

Maintenance of a stable internal state e.g. body temperature, body sugar levels

Dynamic process requiring constant physiological adjustments

Essential for survival of the organism

Question 2

Claude Bernard

Answer 2

Appreciated the importance of maintaining constant internal state

Question 3

What is negative feedback?

Answer 3

To keep the internal state constant organisms need to detect the changes in the external/internal environment and respond accordingly

Physiological response in OPPOSITE direction to detected change - e.g. cool environment induces shivering, which generates heat

Question 4

How does negative feedback occur?

Answer 4

Negative feedback occurs due to a change from a set point (narrow range of a variable e.g. body temp)

Question 5

Define the following
Sensor
Integrator
Effector

Answer 5

Sensor: detects change in external environment
- Integrator: compares detected change with set-point of system
- Effector: induces response to restore system back to set-point

Question 6

How is negative feedback controlled?

Answer 6

Negative feedback is controlled by automatic physiological response apps and voluntary which acts as an effectors
(E.g. panting vs seeking shade on hot day)

Question 7

Disadvantages of negative feedback

Answer 7

Delay in stopping reponse once set point is re-established
-overshoot beyond set point

Question 8

Adaptations in negative feedback

Answer 8

ANTICIPATION
Predicts external change before it occurs (e.g. skin defects change in room temp before body temp changes)

Question 9

Adaptations in negative feedback

Answer 9

ACCLIMATISATION

Adaptation that alters negative feedback gradually in new environment - adding fat layer / thicker fur in the autumn to keep warm over winter - increased blood cell production (more O2) at higher altitude

Question 10

How can set points be altered?

Answer 10

Set points can be altered under certain circumstances e.g. temporary (fever, temporary increase in set point to fight infection)
Permanent e.g. puberty

Question 11

What is positive feedback?

Answer 11

Mechanism to create a rapid, temporary change from set-point
Change detected causes further change in SAME direction (i.e. opposite to negative feedback)
E.g. Oxytocin during labour
- causes uterine contractions
- pressure on cervix causes more
oxytocin release
- results in more uterine
contractions (and so on)