Tissues 8 (Signalling between cells)

Question 1

What are the types of signalling?

Answer 1

• Autocrine (signalling molecule acts on same cell)
• Paracrine (hormone acts on adjacent cell)
• Endocrine (hormone travels via blood & acts on distant target cell)
• Membrane attached proteins (plasma membrane proteins on adjacent cells interact)

Question 2

What type of signalling is glucagon involved in?

Answer 2

Endocrine: acts on liver cells promoting gluconeogenesis and glycogenolysis

Question 3

What type of signalling is insulin involved in?

Answer 3

• Endocrine: inhibits gluconeogenesis and glycogenolysis in liver
• Paracrine: inhibits glucagon synthesis by nearby α-cells

Question 4

What is an example of signalling between membrane attached proteins?

Answer 4

T lymphocyte engages with MHC molecule through T cell receptor activation

Question 5

What is an example of autocrine signalling?

Answer 5

Activated T lymphocytes have IL-2 receptors and secrete IL-2

Question 6

Describe the signalling that takes place at neuromuscular junctions.

Answer 6

The action potential propagates along the axon and the depolarisation causes the opening of VGCCs
Ca2+ influx
Vesicle exocytosis
Acetylcholine diffuses across the synaptic cleft and binds to sarcolemmal nicotinic receptors that lead to depolarisation of the postsynaptic membrane
Acetylcholine is broken down by cholinesterase and recycled

Question 7

What are the physiological functions of cell signalling?

Answer 7

1. Process information- from sensory stimulus
2. Self preservation - spinal reflexes and sympathetic nervous system
3. Voluntary movement - daily activities
4. Homeostasis - thermoregulation and glucose