regulation of blood flow and pressure Flashcards
What are the main structural layers of a blood vessel?
tunica intima, tunica media, and tunica externa
what vessel type has the greatest pressure
large systemic arteries
what vessels have lowest pressure
larger systemic veins
what type of cells are found in the tunica intima
endothelial cells
what makes up the tunic media
smooth muscle
what makes up the tunic externa
connective tissue and collagen
sympathetic nerve fibres embed in the collagen
what makes veins and venules unique
they have valves
valves are used to prevent
back flow of blood
what do veins and venules lack
elastic layers
what modulates diameter
arteries and arterioles
name the 4 hormones that regulate vasomotor tone
nitric oxide
EDHF
endothelin-1
angiotensin II
what cells produce nitric oxide
endothelial cells
is nitric oxide a vasodilator or vasoconstrictor ?
vasodilator
How is nitric oxide (NO) produced in endothelial cells?
activation of eNOS
What role does calcium play in the production of nitric oxide?
When intracellular Ca²⁺ levels rise, they bind to calmodulin, which then activates eNOS, leading to increased production of NO.
Describe the process by which NO causes vasodilation.
NO diffuses from endothelial cells into the adjacent smooth muscle cells in the vessel wall. Inside smooth muscle cells, NO activates guanylate cyclase, increasing cyclic guanosine monophosphate (cGMP) levels. cGMP then triggers a cascade that results in smooth muscle relaxation, leading to vasodilation.
What is the role of cyclic GMP (cGMP) in NO-mediated vasodilation?
activates protein kinase G to reduce intracellular Ca promoting relaxation of smooth muscle = vasodilation
What role does nitric oxide play in preventing platelet aggregation and thrombosis?
helps prevent blood clot formation
What is the impact of oxidative stress on nitric oxide function?
reactive oxygen species can reduce NO availability
What is EDHF (Endothelium-Derived Hyperpolarizing Factor)?
released from endothelial cells contribute to vasodilation
through the hyperpolarization of vascular smooth muscle cells, leading to relaxation and decreased vascular tone
What is the primary mechanism by which EDHF regulates vascular tone?
EDHF induces hyperpolarization of vascular smooth muscle cells, which inhibits calcium influx and reduces the contraction of smooth muscle cells, leading to vasodilation and decreased vascular tone.
What is Endothelin-1 (ET-1)?
potent vasoconstrictor peptide produced by endothelial cells
How does ET-1 contribute to vasoconstriction?
ET-1 induces vasoconstriction primarily through ET_A receptors on vascular smooth muscle cells, leading to calcium influx, which stimulates smooth muscle contraction and raises vascular tone.
ET-1 inhibits ______ and reduces __________ availability
eNOS
nitric oxide
