manipulation of vascular tone

Question 1

what are the 3 main classes of cell surface receptors

Answer 1

• ion-channel(neurons)/ligand-gated(peptides)
• G-protein linked (pheremones, hormones, neurotransmitters, cAMP and IP3)
• enzyme linked (trnasmembrane element and activates intracellular enzyme)

receptor kinetics determines how drugs and hormones work (how quickly how theyre cleared etc.)

Question 2

how do hydrophobic signalling factors act at directly at the nucleus

Answer 2

• they do not like water
• they bind to receptors that solubilise them in water and move them around the body
• when released, can easily move across cell membranes (as cell has lipid bilayer)
• in cell, further proteins trnasport to nucleus
• examples: steroids are lipid solluble and cross the bilayer easily to bind to proteins in the cytosol

Question 3

describe the main ultrastructural features of a vascular smooth muscle cell

Answer 3

main elements in a VMSC:
- actin filaments
- gap junctions
- myosin
- elastic elements (collagen and elastin)
- sarcoplasmic reticulum

forms a functional syncytium to allow for coordinated vasoconstriction/vasodilation. this makes it so when one cell changes conformation the rest will do the same in order to streamline the process

Question 4

why do arterioles have lots of vascular smooth muscle cells

Answer 4

they control flow and need to constrict/dilate accordingly

Question 5

the aorta has lots of elastic tissue. why?

Answer 5

it is under very high pressure and does not need to be under constrictive/dilatory control. elastic tissue decreases resistance to make sure there is a non-stop flow of blood.

Question 6

what are the roles of Ca channels in governing vascular smooth muscle cells

Answer 6

mediate contraction/dilation

Question 7

what are the roles of K channels in governing vascular smooth muscle cell control

Answer 7

mediate hyperpolarisation

Question 8

what are the roles of Na/K ATPase in governing vascular smooth muscle cells

Answer 8

provides energy

Question 9

give examples of endothelial derived factors that influence vasomotor tone and describe their cellular signalling mechanisms

Answer 9

endothelin:
- peptide on cell surface
- G-coupled receptors (multiple second messenger systems)
- usually vasoconstrictors)

angiotensin II
- peptide on cell surface
- controls vaso tone
- RAAS
- multi organ response to defend BP
- G-protein coupled receptors (various according to site in body)

Noreprinephrine/eprinephrine (alpha adrenergic receptors
- cell surface glycoprotein

nitric oxide
- eNOS
- enymatic linked receptor
- cGMP
- tonic vasodilator releases shear stress (helps keep vessels open)
- inhibits platelet aggregation

prostoglandins
- G proteins
- cAMP

Question 10

what are the mechanisms that operate locally to regulate arteries and veins

Answer 10

local blood flow is determined by relative open/closed state of arterioles
- poiseuilles law states that cross sectional area is related to blood flow (reduced diameter=increased resistance=reduced blood flow
- in basal state, <10 % of capillaries are dilated.
- capillary recruitment when required to increase local blood flow
- all vasoactive factors/drugs will affect all endothelium
- low oxygen=increased build up of metabolites, which decreases O2 supply inducing vasodilation.
- reactive hyperaemia clears built up metabolites