Cellular communication

Question 1

Define Paracrine

Answer 1

A hormone that acts on cells in close proximity to the gland that secreted it.

E.g eicosanoid

Question 2

Define Prostaglandin

Answer 2

A paracrine hormone that is rumoured to be released by all mammalian cells that cause:

• Smooth muscle contraction
• Platelet aggregation
• Smooth muscle uterine contractions during childbirth
• Inflammation

e.g. thromboxane, PGE2

Question 3

Define Cytokine

Answer 3

Chemical messengers produced from proteins

• may act as autocrine, paracrine or endocrine hormones
• primarily used in immune response

Question 4

Define Autocrine

Answer 4

Chemical messengers that act on the cell that secreted them

very quickly destroyed

Question 5

Define neuroendocrine

Answer 5

A hormone such as noradrenalin or ADH which are secretted by nerve cells into the circulation

Question 6

Define endocrine

Answer 6

A chemical messenger that is produced and secreted by an endocrine cell into the bloodstream -> target cell.

Question 7

What is the difference between nicotinic and muscarinic cholinergic receptors and how they ultimately bring about a change in membrane potential of their respective target cells?

Answer 7

Nicotinic: Ach receptor = Ligand-gated ion channel for Na+K+

• Ach binds-> Gate opens -> cations move down ECG
• > depolarise post synaptic membrane

Muscarinic: G-Prot Dissociation -> Phospholipase C->

Increase Diacylglycerol + Inositol Phosphate 3

DAG= Activates Protein Kinase C -> phosphorylation of protein

IP3= Releases intracellular Ca2+-> activation of Ca2+ dependent events.