Vascular Physiology Flashcards
blood
-mostly made of water
-if you were to put blood in a test tube and let it sit, you would see the blood cells fall to the bottom that are called the hematocrit
-above it is the water which makes up a large % of the plasma as well as proteins like albumin, globulin, and fibrinogen
-RBC, WBC, and platelets
hemodynamics
-pressure = flow x resistance or delta P = Q x R where Q is the heart when it squeezes (cardiac output), R is the vessels constricting or dilating, and P is the blood pressure
cardiac ouput
stroke volume x heart rate and it defines the heart squeezing or relaxing
anatomy of the cardiovascular system
comprised of the heart, pulmonary circulation, and systemic circulation
pulmonary circulation
-heart pumps blood —> lungs —> comes back oxygenated
-heart pumps red blood —> body —> comes back deoxygenated
-blood flow, gas exchange, and one of the carriers of gas exchange is the hepatic vein
what is gas exchange and where does gas exchange occur?
occurs across capillaries and it is when blue blood loses CO2 and gains O2 in the lungs
gas exchange
-oxygen enters the lung into grape-like structures called alveolus
-oxygen diffuses across the alveoli and goes into the blood
oxygen and hemoglobin
oxygen gets dissolved in water at low level but combines with hemoglobin at higher level —> RBCs diffuse
systemic circulation
-blood flow of oxygenated blood
-LV pumps oxygenated blood to the tissues of the body
-O2 is unloaded by the RBCs
oxygen transport
oxygen in air —> lungs —> blood —> peripheral tissues
vascular histology
blood vessels all have the same 3 layers but depending on where you are in body, some may have more of one layer compared to another
3 layers of vessels
- adventitia
- media
- intima
intima
endothelial cells with internal elastic lamina
media
-in the middle of the vessel walls
-smooth muscle cells with external elastic lamina
adventitia
-outside of the vessel
-composed of smooth muscle cells and connective tissue
Ex. strong, powerful arteries have a lot of smooth muscles where the media is big but weak veins have only a little bit of smooth muscle
different types of vessels
arteries, capillaries, and veins
arteries
-deliver blood to the periphery
-on a graph showing the bp vs the different types of vessels, you see the biggest drop in BP across the arterioles
-arteries, particulary arterioles, regulate blood flow into the capillaries
arterioles
very small blood vessels that branch off of arteries and carry blood from heart to peripheral tissues
capillaries
-thin-walled vessels with pores
-diffusion and gas exchange occurs across them
-red blood from heart and blue blood to heart with the connection being the capillaries
-BP is continuing to drop as you go from left to right
what happens as you go from left to right in capillaries?
-from left, you have the fluid being pushed out like water and the ions go with it
-as the blood gets closer to the venuoles the fluid and waste products come in
what two principles does fluid move across the capillaries?
hydrostatic pressure and oncotic pressure
hydrostatic pressure
pressure pushing the fluid out
oncotic pressure
when water gets drawn out against the concentration gradient, a lot of the proteins are left in the capillary with less water so this pressure causes the water to get sucked back in
what type of movement of fluid do you have at the start of the capillary and at the end?
net movement
starling’s law
-the heart stroke’s volume increases as the volume of blood in the ventricles increases
-the hydrostatic and oncotic pressure gradients must be equal and opposed
what happens as we travel left to right in capillaries?
O2 is going to tissues because you have a lot of oxygen in the beginning and flows down the gradient then at the end there is a lot of CO2 in the tissues
peripheral arterial disease
-this occurs when the blood vessels narrow
-less blood gets delivered to the leg —> less O2, glucose, and nutrients and you have waste buildup
-must have an operation to deliver the blood
veins
-transport blood from the periphery back to the heart
-venuoles converge to become veins, which becomes one large vena cava
-2/3 of blood supply sit in veins and move back
venous disease
if the veins do not work, the blood builds up in the legs and backs up the capillaries —> skin in legs starts to slowly break down
lymphatic system
-collects waste
-when fluid flows out of capillaries to tissues, it has to go somewhere and it goes to this sewage system
-vessels that drain out of tissues and empty to bloodstream
-thin-walled, easily damaged vessels
how does the lymphatic system work?
-as the heart pumps blood out and the fluid leaks out of capillaries, it gets picked up by lymph nodes
-while the nodes are collecting waste and water, they’re also collecting pathogens and viruses
filaraisis
-small worm can infect people through a mosquito bite
-goes into the lymphatic system and blocks it —> if you get it in your leg, it can swell from backup
regulation of blood flow
-blood vessels are always relaxing and dilating at the same time
-forces that are vasodilating and vasoconstricting are opposing each other
what are the three parts of regulating blood flow?
- brain- neuronal
- kidney- hormonal
- arterioles- local
integrated regulation of blood flow
- sensors —> brain —> nerves —> heart and blood vessels
- sensors —> kidney —> hormones —> heart and blood vessels
- sensors —> tissues —> local factors —> heart and blood vessels
blood flow for brain
receptors —> afferent nerves —> brainstem —> efferent nerves —> vascular response
how does the brain control blood flow?
-does this through the autonomic nervous system — > involuntary control
-autonomic is divided between the sympathetic and parasympathetic nervous systems
-driven by brain sending out nerves to body
-center in the brainstem called the vasomotor center, which sends out messages to all parts of the body
-brain gets messages from the body about blood pressure and other sensors to control blood flow
baroreceptor regulation of blood flow
-baroreceptors sense pressure
-BP goes up —> carotid sinus baroreceptor senses it —> afferent nerves —> brain —> autonomic nervous system —> efferent nerves —> decrease the vasoconstriction and HR and contractility —> decrease in BP
patient in ER with high BP
touch the carotid arteries to fool them into thinking the BP is high and turns on the parasympathetic nervous system and brings down BP
chemoreceptor regulation of blood flow
aorta, carotid, or medulla —> decreased O2 or increased CO2 —> chemoreceptors —> brain —> ANS —> vasoconstrict, increase the HR, and increase respiration
hormonal regulation of blood flow
vasoconstrictors and vasodilators
vasoconstrictors
substances that cause blood vessels to narrow or constrict
Ex. adrenal gland- epinephrine and cortisol, kidneys- renin, and pituitary- vasopressin (ADH)
vasodilators
open blood vessels and allow blood to flow more easily through the body
Ex. tissues (local regulators) like hypoxia, CO2, adenosine, bradykinin, histamine, and serotonin
kidney’s function in regulating blood flow
-kidney senses BP is down —> releases hormone
-kidney releases renin —> angiotensinogen —> renin acts on angiotensinogen to create angiotensin I —> angiotensin-converting enzyme from the lungs acts on angiotensin I to form angiotensin II, a potent vasoconstrictor
role of angiotensin II
acts directly on blood vessels and adrenal gland to stimulate the release of aldosterone, which tells the kidneys to urinate less and save water/salt long-term
local mediators of vessel tone
-divided between vasodilators and vasoconstrictors
-vasodilators are nitric oxide (NO) and tissues
-vasoconstrictors are peptides like endothelins and angiotensin as well as arachadonic acid like EDHP and thromboxane
local regulation of blood flow: vasodilation
metabolic demands —> decreased O2, increased CO2, adenosine, and other mediators —> vasodilation
local vasodilation
-endothelial cells control vasodilation
-NO diffuses out of cells into media and activates mediators that cause relaxation like cGMP
-NO is a free radical, highly reactive with a short half-life and diffuses across membranes
what does NO do?
binds to other oxygen radicals and is made by the enzyme nitric oxide synthase
-amino acid and oxygen —> another amino acid and NO, which is made by ripping off electrons on NADPH and dumping them
-if you have endothelial cells that don’t work, then you have issues with vasodilation since NO is a vasodilator
NO is a vasodilator for the smooth muscle cell
-NO enters muscle cells and turns on a signalling cascade
NOS —> NO —> activates guanylate cyclase, which makes cGMP leading to kinases that make the smooth muscle cell relax
NO protects vessels
-NO is a vasodilator, anti-thrombotic, and anti-inflammatory
-acts on platelets, smooth muscle, and lymphocytes
physiological role of NO
-produced by blood vessels and drugs
-dilates blood vessels
-protects blood vessels from disease
-loss of NO predisposes to atherosclerosis
local regulation of blood flow: vasoconstriction
metabolic demands —> endothelin, angiotensin II, superoxide, EDHF, and thromboxane —> vasoconstriction
hemorrhage
-heart rate is up, BP is down, and your vessels constrict to keep BP up (resistance would increase)
-mechanisms by which body senses BP is down and tries to get it up
-less blood in heart —> cardiac output goes down
what do baroreceptors do when the body senses BP is down?
they send messages to the brain and the brain tells vessels to constrict (increase resistance) and kidney kicks in and makes angiotensin leading to alderosterone
hypotension
when the BP is really low and the body can’t compensate
what can cause hemorrhages?
-loss of blood
-heart not working from heart attack
-issue with brain
-sepsis
sepsis and NO
-NO kills pathogens like viruses, bacteria, atypical bacteria, fungi, and parasites
-NO acts an immune effector by killing the bacteria
-need tons of NO to kill the bacteria but a large amount can cause vasodilation (decreases resistance) and BP goes down
hypertension
-brain and kidney have determined that normal BP is 120/80
-in hypertension, the kidney has gone rogue and decided that the BP should be higher than 120/80
-senses that the normal BP is low so kidney releases angiotensin and aldosterone —> kidney holds on to more salt and water then BP goes up
atherosclerosis
-disease of the arteries
-high cholesterol can lead to this which can lead to heart attacks
-damaging epithelial cells can lead to damaging the blood vessels
endothelial disfunction in atherosclerosis
endothelium is damaged and becomes inflamed —> white blood cells adhere to it then inflammatory cells come in and suck up the cholesterol —> vessels wall off by scarring —> inside of blood vessels fills up with lipids and if it ruptures the vessels become blocked
