Blood Vessels Flashcards
Describe the basic vessel architecture.
- outer layer
- middle layer
- inner layer
- lumen
What is the outer layer of a vessel?
connective tissue / fat (adventitia)
What is the middle layer of a vessel?
smooth muscle & elastic tissue (media)
What is the inner layer of a vessel?
primarily endothelium (intima)
What is the lumen?
small central space in vessel through which blood/fluid flows
What are arterioles?
‘resistance’ vessels
In what state are arterioles at rest?
partially constricted
What does smooth muscle of arterioles do?
causes vasoconstriction and vasodilation of arterioles
What is the blood flow through arterioles determined by?
constriction or dilation from nerves and hormones
What do arterioles play a critical role in?
controlling blood pressure
- flexibility in blood pressure control
How is blood pressure maintained?
systemic vascular resistance (SVR)
- blood is pumped from heart into closed loop of collapsible tubes
- pressure in this circuit is determined largely by:
(1) volume of blood in arterioles
(2) how relaxed (dilated) or contracted (constricted) arterioles are
What determines vasoconstriction and vasodilation of arterioles?
neural control of arteriolar diameter – SNS
PSNS is insignificant
What determines vasoconstriction of arterioles?
(SNS)
noradrenaline – from sympathetic nerves going to different organs
What determines vasodilation of arterioles?
(SNS)
adrenaline – from adrenal gland on top of kidney
Noradrenaline Pathway for Vasoconstriction in Vascular Smooth Muscle Cells
–
Adrenaline Pathway for Vasodilation in Vascular Smooth Muscle Cells
–
What are the vasoactive hormone constrictors? (2)
- angiotensin II (AII) – from kidney
- arginine vasopressin (AVP) – from brain
What is the vasoactive hormone dilator?
atrial natriuretic peptide (ANP) – from heart
What is an example of a vasoactive mechanism?
metabolic regulation of blood flow
What is metabolic regulation of blood flow?
tissue metabolites are released by active cells, and cause local vasodilation
ie. decrease O2, increase CO2, increase adenosine, increase K+
How is coronary circulation regulated?
largely due to metabolic regulation of blood flow
When is coronary circulation diminished? Why?
diminished in systole due to mechanical contraction – more in left ventricle than right
What happens when there is insufficient blood supply (and O2) to cardiac muscle?
chest pain (angina)
ischemia (↓ O2) goes to afferent nerve endings, then to brain, is perceived as painful stimuli, results in heart attack
What causes insufficient blood supply (and O2) to cardiac muscle?
- coronary artery spasm (drugs/alcohol)
- coronary artery narrowing (plaque formation)
How is cerebral circulation regulated?
large amount of metabolic regulation of blood flow
- very responsive to low O2 tension
- ie. if O2 drops, vasodilation allows more oxygenated blood to travel to that area and take away metabolites
What is regional cerebral circulation linked to?
brain activity
ie. neurons being used a lot in a certain area produces lots of CO2, and uses lots of O2
Where do fibrous plaques develop?
in intima with necrotic core of cholesterol
How does plaque impact blood flow?
- plaque may project into lumen, reducing blood flow
- plaque can rupture, sending embolus downstream and resulting in complete occlusion
What is an angioplasty/stenting?
opening a narrowed vessel
What is a coronary artery bypass graft (CABG)?
replacing a narrowed or blocked artery
