10 - Signalling between cells I

Question 1

Why do cells need to communicate?

Answer 1

• to process information - sensory stimuli e.g. light
• self preservation - reflexes and the SNS
• voluntary movement
• homeostasis - thermoregulation and glucose homeostasis

Question 2

How is glucose concentration maintained in hypoglycaemia?

Answer 2

• glucagon is secreted by the alpha cells in the islets of Langerhans
• this stimulated gluconeogensis and glycogenolysis in the liver

Question 3

What type of signalling occurs in response to hypoglycaemia?

Answer 3

endocrine

Question 4

define endocrine signalling

Answer 4

hormones travel in the blood and act on a distant target cell

Question 5

Give some other examples of endocrine signalling

Answer 5

• insulin

- adrenaline acting on the trachea and bronchi

Question 6

How is glucose concentration maintained in hyperglycaemia by the action of hormones on local cells?

Answer 6

• insulin is secreted by the beta cells in the islets of Langerhans
• this inhibits glucagon secretion by nearby alpha cells

(its endocrine effect is glycogenesis)

Question 7

What type of signalling occurs in response to hyperglycaemia?

Answer 7

the action of insulin on the nearby alpha cells is a paracrine effect
insulin also has an endocrine effect

Question 8

Give some other examples of paracrine signalling

Answer 8

• NO produced by endothelial cells in blood vessels

- osteoblast activating factors produced by adjacent osteoblasts

Question 9

Give some examples of autocrine signalling?

Answer 9

• activated T lymphocytes secrete IL-2, which binds to the IL-2 receptor on its own surface
• ACh binds to presynaptic muscarinic receptors
• growth factors from tumour cells can lead to mitogenesis in the tumour cell

Question 10

What is juxtacrine signalling?

Answer 10

the secreted product acts on the directly adjacent cells