M1 Topic 6: Homeostasis & Control mechanisms

Question 1

Homeostasis

Answer 1

Condition of balance in body’s internal environment which allows us to function optimally as an organism

• All different chemicals in body are within normal concentration ranges
• All states of the body (e.g. temperature) are within a normal range

Question 2

Homeostatic control

Answer 2

Corrective mechanisms to restore balance to internal environment

• Nervous system
• Endocrine system

Question 3

Nervous system

Answer 3

Sends fast, targeted messages (sensory, motor) around the body using electrical impulses

Question 4

Endocrine system

Answer 4

Uses chemical messages called hormones that travel via bloodstream

• Although distributed over body, only some cells have receptors for them so message is still somewhat targeted
• Generally works slowly but can have effect for greater period of time

Question 5

Feedback mechanisms (feedback loops)

Answer 5

Series of events where body monitors part of its environment, detects deviation from norm, corrects this deviation and goes back to monitoring

• Constant loop that keeps part of internal environment in state of homeostasis

Question 6

Variables

Answer 6

Aspects of the body being monitored

• E.g. body temp, blood glucose level, blood pressure

Question 7

Stimulus

Answer 7

Anything that changes a variable

• E.g. hot environment heats up body temp

Question 8

3 main components to feedback systems

Answer 8

• Receptor
• Control centre
• Effector

Question 9

Receptor

Answer 9

• Monitors variable, detects stimuli (changes)
• Once detected, sends info (input) about stimulus to control centre

Question 10

Control centre

Answer 10

• Determines normal range (set point) for each variable
• Sends output message to effected to help bring variable back to normal range

Question 11

Effector

Answer 11

Cell, tissue, organ or system that carries out response according to control centre instructions

Question 12

Feedback loop cycle

Answer 12

1. Monitoring
2. Stimulus disrupts homeostasis
3. Receptors detect disruption, sends input
4. Control centre receives input, processes, sends output
5. Effectors work to correct disruption
6. Return to step 1

Question 13

Negative feedback systems/loop

Answer 13

Reverses (or negates) change to a variable

• Eventual result of process will be opposite of original stimulus

Example = body temp

• If stimulus makes you too cold > body warming back up through skeletal muscles
• If stimulus makes you too hot > body cools down through sweat glands

Question 14

Positive feedback systems/loop

Answer 14

Results in reinforcement of original stimulus

• If original stimulus increases/decreases something, the result will be to increase/decrease even further
• As original stimulus continues to be reinforced, these processes require shut-off mechanism