4 - Arterioles

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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


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