Lecture 2 - Blood Vessels and Pressure Flashcards
What are the five blood vessels in the body?
artery, arteriole, capillary, venule, vein
What is the relative mean diameters of each of the five blood vessels in the body?
artery- 4mm
arteriole - 30 um
capillary - 8 um - can fit on rbc
venule - 20 um
vein - 5mm
What do all blood vessles have?
an endothelial layer of cells
What blood vessles have a layer of smooth muscle?
arteries, arterioles, (NOT capillaries or veins smaller than 30 micrometers)venules and veins
What is a metaarteriole?
an arteriole with less smooth muscle which has precapillary sphincters which are smooth muscle which can constrict or dilate to cause blood flow to certain capillaries
What is arteriovenous anastomosis?
stagnant blood in the capillaries due to precapillary sphincters being constructed
What is vasodilation and vasoconstriction?
vasodilation - smooth muscle of arterioles is relaxed
vasoconstriction - smooth muscle of arterioles is constricted
What prevents a blood vessel from rupturing?
the connectuve tissue in the blood vessles which is made of collagen and it is thicker outside of arteries than veins because arteries are the pressure reserve while veins are the volume reserve of blood
What is laplace’s equation?
the wall tension (or force pulling walls apart) is proportional to the pressure inside the vessels times the radius of the vessels
What blood vessels is most likely to burst?
arteries because they have biggest radius and wall tension
What is an aneurysm?
when an artery inflates
What happens in a subarachnoid hemmorhage?
the pressure in the subarachnoid space wil surpass that of the brian and the blood will flow into the brain and cause it to start dying
What is the pressure change in systemic circulation?
there is a continual drop in pressure that deeper you go into the vascular system
What does the pressure in the left ventricle fluctuate between?
0 and 120 because it is less elastic than the arteries and can completely relax between systole (isovolumic contraction) and diastole
What does the pressure fluctuate between in the large arteries?
-the large arteries have a lot of connective tissue surrounding them making them more elastic so the pressure only fluctuates between 120 and 80 - this is pulsing
Why does the greatest pressure drop happen in the arterioles?
bceause they have the smallest diameter and are surrounded by the most smooth muscle so they can vasodilate causing less resistance and the pressure drops
Is there pulsing in the capillaries?
no
What is the pressue in the vena cava?
a bit above zero so it can fill the right atrium which is at zero
What is the pressure in the right ventricle?
fluctuates between 0 and 30mmHg
What is the pressure in the pulmonary arteries?
fluctuates between 20 and 30
What is the pressure in the small arteries and arterioles?
begins to falls due to vasodilation of arterioles
Is there pulsing in the pulmonary capillaries?
no
What is the pressure in the pulmonary vein?
a bit above zero so it can fill the left side of the heart
What of the arteries dampens pressure pulses?
elasticity and compliance
What is elasticity?
the tendency of the arteries to return back to their original shape after distortion
What is compliance?
the ease of distortion by applied force the inverse of stiffness
What is arteriosclerosis?
reduces the elasticity and compliance of arteries
What is the subtype of arteriosclerosis?
atherosclerosis and this is caused by atheromatous plaques (fatty) (cause a problem in brain and heart)
What is the compliance and elasticity extent of arteries?
moderately compliant and highly elastic
Why is aortic pressure never zero?
due to elasticity of the arteries
What can cause arteriosclerosis?
stiffening of arteries due to calicum deposits via osteoblasts or crystals
What can cause hypotension?
dehydration
What can cause hypertension?
high sodium diet retain more water in blood due to osmotic gradient
What are the three things that can regulate arteriolar resistance?
- myogenic autoregulation (stretch activated calcium channels)
- local and circulating hormones
- autonomic regulation via sympathetic
What three chemicals cause vasoconstriction?
-norepinpehrine via alpha receptors
-vasopressin
-angiotensin II
What is the role and source of the NT norepinephrine?
baroreceptor reflex; sympathetic neurons
What is the role and source of the neurohormone vasopressin?
increases bp in a hemorrhage and is released by the post pit
What is the role and source of the hormone angiotensin II?
it increases the blood pressure and it is a plasma hormone
How does norepinephrine act in alpha receptors?
it binds to them and causes vasocontriction which increases the TPR and in response to the barorecepotr reflex so you do not pass out when you stand up
What is another term for vassopressin and how doe it increase blood pressure in a hemorrhage?
ADH, released from the post pit, has the kidney retain water to increase blood volume and correct for hyperosmolarity by dehydration
How does angiotensin II increase blood pressure as a blood plasma hormone?
causes vasoconstriction
What are the seven vasodilators?
epinephrine (binding to beta receptors)
acetylcholine (via NO)
NO
adenosine
low oxygen high CO2 and high H+ and high extracellular potassium
histamine
natriuretic peptides like ANP
What is the role and source of the neurohormone epinephrine?
increases blood flow to the skeletal muscle heart liver and is from the adrenal medulla
What is the role and source of the NT acetylcholine?
from parasympathetic neurons and it causes erection of the clitoris or penis
What is the role and source of the paracrine molecule NO?
it is a paracrine mediator secreted by the endothelium in blood vessels
What is the role and source of the paracrine hormone adenosine?
increases blood flow to match metabolism and is released from hypoxic cells
What is the role and source of the paracrine signals of low oxygen and high CO2 and high H+ and high K+?
increases blood flow to match metabolsim and comes from cell metabolism
What is the role and source of the paracrine molecule histamine?
is secreted from mast cells and increases blood flow
What is the role and source of the hormone or NT of natriuretic peptides lilke ANP?
reduce blood pressure and are from the atrial myocardium or the brain
How does epinephrine cause vasodilation and increase blood flow to the skeletal muscle liver and heart?
it binds to beta 2 receptors and is a neurohormone whcih increases blood flow to the skeletal muscle heart and liver not the skin and not digestive organs or reproctive organs organs
How does acetylcholine cause the erection of the penis and clitoris?
the cornoary arteries of the heart have parasympathetic innervation whcih causes the release of Ach and this causes the production of NO and this is a gaseous paracrine hormone which is repsonsible for erections but the vasodilation and the blood flowing into the erectile sex organs is responsible into sex organs
Where does adenosine come from?
breakdown of ATP to ADP to AMP to adenosine so hypoxic metabolically active cells
How does NO cause vasodilation in the heart?
it will be produced by their endothelial cells of coronary arteries increasing blood flwo to the heart via vasodliation (nitroglycerin tablets for people with chest pain or anginia)
How does histamine work?
released from mast cells and they are nonsepcific immune cells and this mediate inflmmation. by causing more blood flow to an inflammed area - acts locally
What are natriuretic peptides and what do they do?
hormones or NTs and they are released from the heart atria and this stimulated sodium excretion so water follows it and this reduces the blood pressure and atrial muscle cells secrete this
-cause sodium excretion overall
