E3 L17: The vascular system - arterioles

When there is an increased demand for metabolism what is the change in arterioles

Increased radius and flow, decreased resistance

Local enviornment

Cells being perfused

Local factors

things that influence the arteriole eg. oxygen

Two major functions of arterioles

Match the demand for blood flow of the local tissue

Maintain MAP by TPR cooperation

Conflicts in arterioles examples

Excersising on a hot day

Heat stroke case

Which organs lose and win when supply cannot keep up with deman

Which part of the vascular system has the highest amount of pressure

Arterioles

Because arterioles are the greatest site of of vascular resistance, they contribute the most to...

TPR

MAP equation including TPR

MAP = CO x TPR

What is a conditioning organ

Tolerant to a BF reduction, receive excess of BF usually

What is a flow dependent organ

No tolerance for ischemia

Examples of conditioning organs

Kidneys

Intestines

Skin

Examples of flow-dependent organs

Brain and Heart

During exercise, skeletal muscles ______

Vasodilate

Skin arterioles _______ to cool the core temperature

Vasodilate

Active hyperemia

decrease in O2 due to increased metabolic activity, CAUSES increased BF

Flow autoregulation

Increased arterial pressure CAUSES arteriole to constrict to prevent rupture of caps

How does Ca influx cause smooth muscle contraction

Ca binds to calmodulin, phosphorelates XB,

Reactive hyperemia

occlusion upstream CAUSES a rebound of high BF downstream in arteriole

Local control

vasoactive metabolites or factors within the local interstitial fluid surrounding caps and cells

Levels of what cause vasodilation

Low O2 and pH

High CO2, ECF K, Adenosine

Levels of what cause vasoconstriction

Low CO2, ECF K, adenosine

High O2 and pH

Two different forms of controls for arterioles

Local controls and extrinsic controls

What do local controls entail

Matching blood flow to demand

What do extrinsic controls entail

Protect MAP

What receptor does NE bind to

a1

What receptor does Epi bind to

B2

NE binding to a1 causes

vasoconstriction

Epi binding to B2 causes

vasodilation

Epi binding to a1 due to extrinsic input causes

vasoconstriction (epi)

What kind of input can innervate the vasculature

sympathetic

NE

binds to a1, vasoconstrict

Nitric oxide

Vasodilate

Epi in high amounts

a1, vasoconstrict

Angiotensin II

Vasoconstrict

ADH/vasopressin

vasoconstrict

Epi in low concentration

B2, vasodilate

ANP

vasodilate

Most potent vasoconstrictor

endothelin-1

Coronary flow occurs during

Diastole, when SL are closed

Flow to the heart is mainly controlled by what

local factors(adenosine), and flow autoregulation

At any given time what percent of blood is in the caps

5%

What makes capillaries efficient

one endothelial layer thick, pores

Pre-capillary sphincters

most local of the local control

Metarteriole

small smooth muscle content that allows for local bipass or shunting of blood due to temp

Flow in L/min is...

always the same, 5 L/min

Velocity is in

cm/sec, variable

How is velocity related to cross-sectional area

inversely

Low velocity indicates

large area

high velocity indicates

small area

Why is the plasma different than the ISF

plasma proteins cannot cross through pores

Filtration

fluid moving out of the blood

Absoarbtion

fluid moving into the blood

Bulk flow/net result

relies on pressure gradients to distribute fluid, NOT DIFFUSION

Pc

hydrostatic pressure out, filtration

Pif

IF hydrostatic pressure, reabsoarbtion

πc

osmotic force due to plasma proteins, filtration

πc

osmotic force due to capillary proteins, reabsorption

Net filtration equasion

Pc + πif - Pif - πc

If NFP is positive

Net filtration

If NFP is negative

Net reabsoarbtion

Pressure at the beginning of the capillary bed

35 mmHg

Pressure at the end of the capillary bed

15 mmHg

Functions of veins (2)

return blood to the heart, storage vessel

Characteristics of veins

low resistance, high capacitance, very compliant, less elastic

Four main factors that assist in venus return

Sympathetic innervation, skeletal muscle pump, inhalation movements, BV

How much lymphatic fluid is collected per day

4 L

What does lymph contain

absorbed fats and proteins

Four mechanisms to enhance lymph flow

Increased capillary filtration

Smooth muscle contraction

Sympathetic stimulation to a1 receptors

skeletal muscle and inhalation pump