10- Signalling Between Cells 1

Question 1

Why do cells need to communicate

Answer 1

Process Information
Sensory stimuli - e.g. light
• Self Preservation
Spinal reflexes
Sympathetic nervous system
• Voluntary Movement
• Homeostasis
Thermoregulation Glucose homeostasis

Question 2

Give an example of endocrine signalling

Answer 2

Hypoglycaemia
Glucagon is secreted by the alpha cells in the islets of Langerhans
Stimulates gluconeogenesis and glycogenolysis in the liver

Question 3

Give an example of paracrine signalling (on adjacent cells)

Answer 3

Insulin is secreted by the beta cells in the islets of Langerhans Insulin has PARACRINE effects It inhibits glucagon secretion by nearby alpha cells
Insulin also has ENDOCRINE effects on liver cells

Question 4

Give examples of autocrine signalling

Answer 4

Activated T lymphocyte will initiate a cascade of reactions within the cell
• Activated T lymphocyte has a IL-2 receptor on surface
• Activated T lymphocyte secretes IL-2
• IL-2 can bind to the IL-2 receptor on its
own surface thus having an effect on the
cell
Other examples of autocrine signalling:
• Acetylcholine binds to pre-synaptic muscarinic receptors
• Growth factors from tumour cells can lead to mitogenesis in the tumour cell

Question 5

What is juxtacrine signalling

Answer 5

instead of acting on a cell that is two cells down, the secreted product acts on the immediately adjacent cell

Question 6

Give examples of membrane attached protein signalling

Answer 6

Blood borne virus is detected in the blood stream by an APC
• APC digests the pathogen an expressed MHC class II on the surface
• Circulating T-lymphocyte engages with the MHC
molecule through TCR interaction

Also HIV GP120 glycoprotein binds to CD4 receptors on T lymphocytes
Bacterial cell wall components bind to toll-like receptors on haematopoietic cells