Lecture 10: Intercellular Signalling Flashcards
why do cells need to communicate with each other
- adapt or change metabolism
- induce or decrease growth, eg wound healing
- respond to danger signals eg in immune system
- stem cells for proliferation and diferentiation
which molecules are involved in signalling
- proteins eg interferon and insulin
- peptides eg glucagon and growth hormone produced by cleavage of proteins
- small chemicals eg steroids, estradiol and cortisol
- dissolved gases like nitric oxide
what can signals do and how fast is it
- alter protein function (fast)
- alter cytoplasmic machinery (fast)
- alter protein synthesis (slow)
where are receptors found
- mostly found on cell surface
- some receptors for small molecules like nitric oxide and hydrophobic molecules like thyroxin and steroid hormones are found in the cytosol or nucleus
what effects does adrenaline have
- contracts smooth muscle in blood vessels supplying the gut, as it has alpha adrenergic receptors
- relaxes smooth muscle in blood vessels supplying the muscles, due to beta adrenergic receptors
what effects does acetylcholine have
- triggers secretion in salivary gland cell as it activates muscarinic 1 receptor
- decreases rate of contraction of heart pacemaker cell as it activates a muscarinic 2 receptor
- triggers skeletal muscle contraction when activated by nicotinic-type Na+/K+ channel
what sort of hormone is cortisol and where is its receptor
steroid that binds to a glucocorticoid receptor in the nucleus
what effect does cortisol have
- can activate gene expression to produce metabolic response
- can suppress gene expression to produce anti-inflammatory response
what are synthetic hormones that activate the glucocorticoid receptor
- hydrocortisone
- prednisolone
- dexamethasone
what are the corticoid hormones used to treat
- autoimmunity eg psoriasis and ulcerative colitis
- allergic reactions eg hives
- asthma
what are paracrine signals
- low concentrations of hormones target neighbouring cells
- some hormones can be paracrine but have systemic effects if produced in large quantities
examples of paracrine signalling molecules
- cytokines
- platelet derived growth factor
- histamine
- nitric oxide
what is NO involved in (mechanism)
- acetylcholine stimulates endothelial cells
- NO produced from arginine and diffuses into nearby smooth muscle cells
- binds to guanylyl cyclase
- leads to GTP being converted to cGMP
- causes smooth muscle relaxation, so increased blood flow
- cGMP quickly hydrolysed to GMP by phosphodiesterase
which drug can be used to relieve angina and how
nitroglycerin, as mitochondrial aldehyde dehydrogenase converts it to NO which will improve blood flow in coronary arteries
what is dopamine important in
fine-tuning of motion, low levels seen in Parkinson’s disease
