4 reasons why cells need to communicate?
- Process information- from sensory stimulus
- Self preservation - spinal reflexes and sympathetic nervous system
- Voluntary movement - daily activities
- Homeostasis - thermoregulation and glucose
What happens during hypoglycaemia?
- Glucagon is secreted by alpha cells in Islets of Langerhans
- Stimulates glycogenolysis and gluconeogenesis
What is ENDOCRINE SIGNALLING?
Hormone secreted from one place, travels in the blood to reach its target cell elsewhere
E.G. insulin, adrenaline
What happens during hyperglycaemia?e
Beta cells secrete insulin
This has a PARACRINE EFFECT
Inhibits glucagon secretion from alpha cells
What is PARACRINE SIGNALLING?
Hormone or signal fro one cell targets adjacent cells
E.G. nitric oxide produced by endothelial cells
Osteoblasts activate factors produced by adjacent osteoblasts
What is MEMBRANE ATTACHED PROTEIN SIGNALLING?
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
What is AUTOCRINE signalling?
Ligand produces by the same cell that it targets
Activating T lymphocytes :
- Produce interleukin 2 receptor
- Produce interleukin 2
- Binds to receptor
E.G. acetylcholine binds to muscarinic receptor
Growth factors from tumour
What is NEUROMUSCULAR SIGNALLING?
- Voltage gated sodium channels open - DEPOLARISATION
- Voltage gated potassium channels open - REPOLARISATION
- Calcium influx
- Vesicles exocytose
- Acetylcholine binds to sarcolemmal nicotinic receptors
- Metabolised by cholineesterase
What are IONOTROPIC RECEPTORS?
- Ligand binds to receptor
- Configurational change
- Pores open
- Ions flow through
Nicotinic acetylcholine receptor
On skeletal muscle in neuromuscular junction
Can be found in brain as well
GABA
Found on cells in the CNS
Opens chloride pores allowing INFLUX
If blocked = CNS gets too excited
G protein receptor
- Ligand binds to 7TM receptor
- Heterotrimer binds to 7TMR
- GDP—> GTP
- Beta and gamma chain break off
- Alpha and GTP bind to target protein
- GTP—> GDP
- Unwinds from target protein and heterotrimer reforms
Name the three types of Galpha subunits
G alpha S
G alpha I
G alpha Q
G alpha S example?
Stimulates adenyly cyclise
Converts ATP —> cAMP
Produces PKA
E.G. beta 1 adrenegic receptor
