Manipulation of vascular tone

Question 1

What are the roles of ion channels governing VSM tone

Answer 1

Ca channels – mediate contraction/dilation

K channels – mediate hyperpolarisation

Na/K ATPase – provide energy

All pharmacologically exploit BP

Question 2

What are endothelial derived factors that influence vasomotor tone

Answer 2

Nitric oxide – vasodilators

Endothelium-derived hyperpolarising factor (EDHF) - vasodilator

Prostaglandins – vasodilators

Angiotensin II – vasoconstrictors

Endothelins – vasoconstrictors

Question 3

Describe how hydrophobic signalling factors can act directly at nucleus

Answer 3

Hydrophobic signalling factors are lipid soluble so cross lipid bilayer easily & bind to proteins in cytosol

Bind to cytosolic proteins (heat-shock proteins – HSP) to form hormone-receptor complex

Crosses through nuclear membrane & releases hormones which act at nucleus to cause transcription & make more hormone

e.g. testosterone

Question 4

Identify 3 main classes of cell surface receptors

Answer 4

Ligand-gated ion channels e.g. neuron

G protein linked e.g. epinephrine receptor

Enzyme linked e.g. insulin receptor