Homeostasis

Question 2

Define: autocrine

Answer 2

Communication with the same cell

Question 3

Define: paracrine

Answer 3

Communication with neighbouring cells

Question 4

Endocrine

Answer 4

Communication with distant cells

Question 5

What systems in the body need to remain stable? give some examples

Answer 5

1. Nervous and endocrine system
2. body temp, pH, electrolytes, BP, body weight, glucose, hormones

Question 6

What 4 elements to regulate a parameter does the negative feedback loop need?

Answer 6

1. Sensor to detect parameter
2. Internal standard or set point
3. Output signal in response to change in parameter
4. Output activates an effector and removes stimulus

Question 7

What is a diurnal rhythm and what hormone has it?

Answer 7

Changes throughout the day, cortisol

Question 8

What adaptations occur in negative feedback loops?

Answer 8

1. Short term adaptations (override set point) e.g. during exercise baroreceptors are re-set in response to rising BP
2. Long term adaptations (acclimatisation)
   e.g. living at high altitidue (low O2)

Question 9

What is a positive feedback loop?

Answer 9

A physiological change that leads to an even greater change in the same direction.

Activation of the sensor/mechanism amplifies the response rather than reducing it

Question 10

Give examples of positive feedback loops

Answer 10

• Action potentials: Na channels opening and allowing Na influx
• Haemostasis: adhesion of platelets to site of injury leads to fibrin activation and strengthening of the clot
• Menstrual cycle
• Breastfeeding