Signalling between Cell I

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 homeostasis

Question 2

What happens during hypoglycaemia?

Answer 2

1. Glucagon is secreted by alpha cells in Islets of Langerhans 2. Glucagon travels out of pancreas in blood vessels. Stimulates glycogenolysis and gluconeogenesis in the liver, increasing blood glucose levels

Question 3

What is ENDOCRINE SIGNALLING?

Answer 3

Hormone travels via the blood and acts on a distant target cell

Question 4

What are some other examples of endocrine signalling?

Answer 4

Insulin: acts on liver, muscle cells and adipose tissue
Adrenaline: produced in the adrenal gland acting on the trachea

Question 5

What happens during hyperglycaemia?e

Answer 5

Insulin secretion by beta cells in the islets of langerhans

Insulin has PARACRINE effects such as inhibiting glucagon secretion from alpha cells

Question 6

What is PARACRINE SIGNALLING and give other examples?

Answer 6

Hormone acts on an adjacent cell.
E.g Endothelin-1 produced by the endothelial cells within blood vessels
Osteoclast activating factors produced by adjacent osteoblasts.

Question 7

What is MEMBRANE ATTACHED PROTEIN SIGNALLING?

Answer 7

Interaction between membrane proteins from two different cells.
Protein on one cell is complementary to receptor on another cell E.G.T-cell receptor interacting with MHC class II molecule.
The HIV GP120 glycoprotein interacting with the CD4 receptor.
Bacterial cell wall components binding to toll-like receptors on haematopoietic cells

Question 8

What is AUTOCRINE signalling?

Answer 8

Signalling molecules act on same cell

1. Activated T lymphocyte has a IL-2 receptor on surface.
2. Activated T lymphocyte secretes 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 effecting the cell wall.

Other example:

• Acetylcholine binds to presynpatic M2 muscarinic receptors
• growth factors from tumour cells can lead to mitogenesis in the tumour cell.

Question 9

What is NEUROMUSCULAR SIGNALLING?

Answer 9

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

Calcium acts as a second messenger

Question 10

What are IONOTROPIC RECEPTORS?

Answer 10

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

Question 11

Explain, with examples, modes of intercellular signalling.

Answer 11

Endocrine: Glucagon or Insulin from the pancreas
Paracrine: Insulin within the pancreas
Autocrine: IL-2 on T-lymphocytes
Signalling by membrane attached proteins: Antigen-presenting cells and T-lymphocytes

Question 12

What are the three types of signalling?

Answer 12

Autocrine Paracrine Endocrine

Question 13

What type of signalling is glucagon involved in?

Answer 13

Endocrine – it acts on liver cells promoting gluconeogenesis and glycogenolysis

Question 14

What type of signalling is insulin involved in?

Answer 14

Endocrine – inhibits gluconeogenesis and glycogenolysis in the liver Paracrine – inhibits glucagon synthesis by nearby alpha cells

Question 15

Give an example of signalling between membrane attached proteins.

Answer 15

GP120 and CD4 between HIV and T lymphocyte

Question 16

Give an example of autocrine signalling.

Answer 16

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

Question 17

Describe the signalling that takes place at neuromuscular junctions.

Answer 17

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 18

What are the four types of Signal Receivers?

Answer 18

Ionotropic Receptors

G-protein linked receptors Enzyme-linked receptors Intracellular Receptors