Homeostasis & Control Systems - Lecture 3

Question 1

Homeostasis

Answer 1

Maintenance of a constant internal environment

Question 2

Negative feedback control

Answer 2

○ Maintain a controlled variable at its set point
○ Change in variable -> sensor -> integrating centre -> effector

Question 3

Diurnal body temperature changes

Answer 3

Body temperature fluctuates throughout the day with the lowest during sleep

Question 4

Positive feedback

Answer 4

○ Not as common
○ Initial stimulus causes a response which reinforces itself
○ Examples:
- Ovulation
- Blood clotting
- action potential in nerves

Question 5

Nervous vs Endocrine

Answer 5

○ Rapid, short term effects
○ long-term effects

Question 6

Sympathetic Nerves

Answer 6

○ Active in stressful situations
○ Origin: thoracic & lumbar
○ Short preganglionic
○ Long postganglionic
○ Ganglionic transmitter: Acetylcholine -> N2 receptor
○ Neuroeffector transmitter: norephinephrine -> α or β

Question 7

Parasympathetic nerves

Answer 7

○ Active in vegetative situations
○ Origin: cranial & sacral
○ Long preganglionic
○ Short postganglionic
○ Ganglionic transmitter: acetylcholine -> N2 receptor
○ Neuroeffector transmitter: acetylcholine > muscaranic receptor

Question 8

Cortisol hormonal control

Answer 8

○ Negative feedback
○ CRH → ACTH → Cortisol

Question 9

Milk production control

Answer 9

○ Positive feedback
○ Suckling → Oxytocin → Milk