Signalling Between Cells

Question 1

4 reasons why cells need to communicate?

Answer 1

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

Question 2

What happens during hypoglycaemia?

Answer 2

1. Glucagon is secreted by alpha cells in Islets of Langerhans
2. Stimulates glycogenolysis and gluconeogenesis

Question 3

What is ENDOCRINE SIGNALLING?

Answer 3

Hormone secreted from one place, travels in the blood to reach its target cell elsewhere

E.G. insulin, adrenaline

Question 4

What happens during hyperglycaemia?e

Answer 4

Beta cells secrete insulin
This has a PARACRINE EFFECT
Inhibits glucagon secretion from alpha cells

Question 5

What is PARACRINE SIGNALLING?

Answer 5

Hormone or signal fro one cell targets adjacent cells

E.G. nitric oxide produced by endothelial cells
Osteoblasts activate factors produced by adjacent osteoblasts

Question 6

What is MEMBRANE ATTACHED PROTEIN SIGNALLING?

Answer 6

Protein on one cell is complementary to receptor on another cell

E.G. MCH molecule on APC presenting an antigen to a receptor on a T lymphocyte

HIV GP120 glycoproteins binds to CD4 receptor on T
Bacterial cell wall bind to toll-like receptor on haematopoietic cells

Question 7

What is AUTOCRINE signalling?

Answer 7

Ligand produces by the same cell that it targets

Activating T lymphocytes :

1. Produce interleukin 2 receptor
2. Produce interleukin 2
3. Binds to receptor

E.G. acetylcholine binds to muscarinic receptor
Growth factors from tumour

Question 8

What is NEUROMUSCULAR SIGNALLING?

Answer 8

1. Voltage gated sodium channels open - DEPOLARISATION
2. Voltage gated potassium channels open - REPOLARISATION
3. Calcium influx
4. Vesicles exocytose
5. Acetylcholine binds to sarcolemmal nicotinic receptors
6. Metabolised by cholineesterase

Question 9

What are IONOTROPIC RECEPTORS?

Answer 9

1. Ligand binds to receptor
2. Configurational change
3. Pores open
4. Ions flow through

Question 10

Nicotinic acetylcholine receptor

Answer 10

On skeletal muscle in neuromuscular junction

Can be found in brain as well

Question 11

GABA

Answer 11

Found on cells in the CNS
Opens chloride pores allowing INFLUX
If blocked = CNS gets too excited

Question 12

G protein receptor

Answer 12

1. Ligand binds to 7TM receptor
2. Heterotrimer binds to 7TMR
3. GDP—> GTP
4. Beta and gamma chain break off
5. Alpha and GTP bind to target protein
6. GTP—> GDP
7. Unwinds from target protein and heterotrimer reforms

Question 13

Name the three types of Galpha subunits

Answer 13

G alpha S
G alpha I
G alpha Q

Question 14

G alpha S example?

Answer 14

Stimulates adenyly cyclise
Converts ATP —> cAMP
Produces PKA

E.G. beta 1 adrenegic receptor