4 - Arterioles
CO2 is a powerful ________ (location) vasodilator
-cerebral -blood flow to the brain decreases when you hyperventilate (breathing out a lot og CO2)
What is the function of prostacyclin?
-coats blood vessels to stop inhibits platelet activation and thus prevent blood clots from forming -also an effective vasodilator
What is the important part regulated by tissues for autoregularion of bloodflow?
RESISTANCE
Why breath into a paper bag?
To increase their CO2 levels
How would H2CO3 potentially work to increase blood flow?
-Through acidification (decreased pH) -Carbonic acid is dissolved CO2 in water -When pH decreases, you have a lot of H+ around which can open up K+ channels in smooth muscle This is also possibly how Lactic acid can be a vasodilator?
One of the first signs you see for diabetic cardiovascular dysfunction is the effect on _______ cells.
endothelial cells -They don't make nitric oxide like they used to.
What is the importance of arteriole tone?
establishes baseline for arteriole resistance
What is the receptor highly expressed on smooth muscle that the sympathetic system acts on?
Alpha 1
Why would you suspect you would see reactive hyperemia?
Because the cells deprived of oxygen are still generating ATP through anerobic pathways, they will be generating lots of enproduct vasodiatlors, thus causing an increased flow when the occlusion is removed
Why are arterioles known as resistance vessels?
Because they are going to regulate the amount of blood that goes into the capillary beds, through the contraction and relaxation of the smooth muscle in their walls can change their diameter.
flow in capillaries =
MAP / Resistance
With a decrease in activity, there is _______ local oxygen, and ______ perfusion.
MORE, LESS
You want to match blood flow to _______ _______.
Metabolic need *you don't need to have 100% blood flow to every organ at all times
How does the body match blood flow to metabolic need?
Metabolic vasodilation
What is an example drug of a nitrovasodilator?
Nitroglycerin
The nitric oxide produced by nitroglycerin medication can dilate coronary arteries and also veins which reduces ____
PRELOAD
How can the body change the flow in capillaries?
By changing resistance (vascular smooth muscle)
Arterioles are _______ muscular
HIGHLY
Define metabolic vasodilation
coupling tissue activity to blood flow
Nitrovasodilators work by:
donating or increasing production of nitric oxide
Active hyperemia starts with
increased metabolic activity in an organ
Histamine results in an _______ response to injury
inflammatory
When would reactive hyperemia occur?
it would occur following the removal of a tourniquet, unclamping an artery during surgery, or restoring flow to a coronary artery after recanalization (reopening a closed artery using an angioplasty balloon or clot dissolving drug).
Flow is inversely proportional to
resistance
The arterioles is the major control for:
resistance
Neural (extrinsic) control of the arterioles is established through __________ influence on arteriole smooth muscle
sympathetc
How can a tissue can regulate its own blood flow by the level of its own activity?
The MORE metabolites the INCREASED vasodialation the GREATER the blood flow
How do endothelial cells modulate blood flow and vascular resistance?
They can release substances that can control the smooth muscle causing contraction and relaxation.
When there is INCREASED O2 will there be vasodialtion or vasoconstriction?
Vasoconstriction
When there is DECREASED O2 will there be vasodialtion or vasoconstriction?
Vasodilation
Sildenafil is what
Viagra
When is histamine released?
When bodily injury from a pathogen, chemical or physical trauma occurs.
Arterioles exhibit TONE, this allows their smooth muscle
be in a state of partial contraction
Local factors effecting blood flow
Endothelial cells & Histamine
How can CO2 work as a metabolic vasodilator?
-it can rapidly diffuse from tissues into VSM
Hoes does metabolic vasodilation work?
1) As you have metabolic activity you use metabolic fuels like oxygen and glucose, you give off metabolites (waste products like CO2 & lactate) 2) The metabolites accumulate in the extra-cellular space 3) The metabolites act also as vasodilators! 4) Blood flow increased But it is a cycle because as you increase blood flow you will have LESS metabolites thus causing VASOCONSTRICTION and DECREASING blood flow
term-54What do endothelial cells release to CONTRACT VSM?
1) Endothelin 2) Thromboxane
What are the steps of histamine release?
1) Mast cells detect injury to nearby cells and release histamine, initiating inflammatory response 2) Histamine increases blood flow to the wound sites. 3) This brings phagocytes and other immune cells that neutralize pathogens 4) The blood influx causes the wound to swell, redden, and become warm and painful
What do endothelial cells release to RELAX VSM?
1) Nitric oxide (very powerful vasodilator) 2) Prostacyclin
Active vs Reactive Hyperemia
1) decreased flow of blood to a tissue allows for accumulation of vasodilators 2) transient rebound in flow (4-7 times the average)
What are the results of metabolic vasodiolation?
Active hyperemia, reactive hyperemia
What are metabolic vasodilators?
Adenosine, CO2,
How does histamine activate vasodilation?
Causes the release of nitric oxide by acting on endothelial cells
Define angina pectoris
Chest pain resulting from an insufficient myocardial blood flow (oxygen demand that is not met by adequate oxygen supply) seen in patient with myocardial ischemia
When levels of CO2 _________ you get an increase of blood flow, especially in the brain.
INCREASE
Histamine ________ capillary permeability?
INCREASES
How does adenosine work as a metabolic vasodilator?
If there is not a lot of oxygen (hypoxic) to create ATP from adenosine fast enough, you will have a lot of Adenosine around which will act as a vasodilator to bring more oxygen in and create more ATP
How can NE release effect muscle vasoconstriction and vasodilation?
If you release more NE = increased tone = increased constriction If you release less NE = decreased tone = decreased constriction
What is autoregulation?
The ability of a tissue to keep bloodflow within a defined average intensity despite fluctuations in pressure. The tissue responds by adjusting resistances to bring the flow to optimal level.
What organ is adenosine thought to be an important vasodilator?w
The heart <3, because it needs a lot of energy!
How do the arterioles maintain tone?
Through constant output of NE from the sympathetic terminals
What is the purpose of syncope?
To get your brain on the same perfusion level as the heart, to enhance cerebral blood-flow
Is it really CO2 that is the vasodilator? Or is it simply ______
acidification
active hyperemia vs reactive hyperemia
active - blood flow is proportional to metabolic activity reactive - increase in flow after a period of occlusion to flow
Active hyperemia is also known as
functional hyperemia
What are the 4 classic signs of inflammation?
heat, redness, swelling, pain
Mast cells release
histamine
metabolic vasodilation is part of a localized ______ feedback mechanism
negative
There are local control and neural control factors of arterial blood flow. The local controls can _______ the neural controls.
override
Vascular smooth muscle requires ________ to sustain contraction
oxygen
There is almost no ______ innervation to arterioles.
parasympathetic (except for reproductive organs)
Flow is proportional to
pressure
What is the function of thromboxane?
produced when there is endothelial damage -vasoconstrictor -promotes platelet aggregation platelet aggregation to get the platelets to clot
define active hyperemia
the increase in tissue blood flow due to increased tissue metabolic activity
What is hypoxic vasodilation?
the prompt vascular response to increased local demand for oxygen because of a change in metabolic activity in the absence of injury or disease
Define metabolic activity
utilization of energy
Is nitric oxide a vasodilator or vasoconstrictor?
vasodilator