PNB Vasculature

• will capillary bed receive blood (carry blood to tissue)
• determines MAP by effect on TPR

spontaneous contraction of smooth muscle in tunica muscle.

• contract smooth muscle more-->VASOCONSTRICTION
• relax of smooth muscle-->VASODILATION

• GREATER the friction
• BIG increase in flow
• Friction-main factor in resistance (R)

• R-inverseley proportional to radius (exponential) R=1/r4
• -SMALL Decrease radius=BIG increase in resistance=BIG decreased flow=BIG increase pressure
• -SMALL Increase radius=BIG decrease in resistance=BIG increase in flow=SMALL decrease in pressure

• -local control 
• -neural (reflex) contol
• -Hormonal Control

• -local control, no nerves, no hormones
• -Active Hyperemia: blood flow adjusted to meet tissue needs
• -arterioles radius will increase if it needs more O2 from release of chemical signals

• -decreased O2
• -increased CO2
• -increased H+
• -decreased pH
• -metabolites (K+), increase osmolarity
• DO NOT REGULATE MAP

increase Radius of arterioles, metarterioles and pre-capillary sphincters

*make sure tissues get blood/O2 they need

EPI- beta2- relax and opens smooth muscle

• local/intrinsic control of arteriolar radius
• -decreased BP in organ-->arteriolar DILATION restores blood flow

• several...
• decreased O2
• increased metabolites

• *IMPORTANT IN MAP REGULATION*
• -SYMP STIMULIS-release of NE, bind to alpha-receptors -->mass vasoconstriction of arterioles-->increased TPR-->increased MAP
• -Sympathetic stimulus: adrenal medulla release EPI-->alpha-adrenergic receptors AND BETA2 RECEPTORS-->
• EPI will cause vasodilation (in arterioles, most skeletal muscles, heart, lungs brain)

-mass vasoconstriction-->inc. TPR-->inc MAP

-parasympathetic stim-less important

strong vasoconstrictor

MAP regulation

regulation of MAP

NEURAL controls will override local to make sure we stay alive

• -transport via difussion, (between blood and interstitial fluid)
•        -lipid-soluble, ion polar molecules-    
•           endothelial cell membrane
•        -glucose: carrier mediated diffusion
• -RBC squeeze through in single file, so volume decreases and more time for exchange

*not leaky, carrier-mediated diffusion plays larger roles

ONE THIN capillary wall (tunica intima) and basement membrane

• formed by capillarys
• metarteriole: connects arteriole with venule, true capillarys branch off metarteriole-

ultime control if blood enters capillary/tissue

regulated by local/neural control

35-40 mmHg

15-20 mmHg

• SLOW compared to rest of vascular system (due to so many capillaries), slows down rate of  flow
• -slow rate of travel allows for COMPLETE EXCHANGE

fluid moving out of the capillary/blood

back to the blood (into capillary)

• hydrostatis pressure (capillary BP) force driving fluid out. (filtration) *plasma protein can not diffuse*
• Colloid osmotic pressure of blood-caused by (reabsorbsorption)
•    -caused by impenetrable non-plasma    
•      penetrating proteins

• filtration varies over time (beg-high, end-decrease)
• absorption (remains constant due to colloid osmotic presure

• Beginning:
• Hydrostatic BP-INCREASE
• colloid OP- DECREASE
• Net filtration pressure (BP-CoP=NFP) MORE filtration

• End:
• BP: lower 
• CoP: remains the same (BUT HIGHER THAN BP NOW)
• NFP= negative (reabsorption)

• BP= 15 (high
• CoP=

NFP= BP-CoP

ex: BP-32 (-) CoP-22 (=) NFP-10

• midway through capillary where both are balance
• -BP pushing out- 22mmHg
• -CoP reabsorbing- 22mmHg

did not reabsorb all fluid we filtered out earlier

-filtered out 10 mmHg, only gained 70% back.... (bc NFP=-7)

-excess fluid from capillary bed is absorbed by lympathic system

• 1-way vessels drain into systemic venous circulation-thus regaining loss fluid and levels staying equal
• (Lympatic veins-->lymphatic trunks-->lymphatic ducts-->subclavian veins to superior vena cava)

• resembles plasma without the protein
• looks more like interstitial fluid

• always return blood to heart
• systemic vein: leaves capillary bed with 15mmHg, pressure drops, but it must suffice to get blood ALL the way back to right heart

• -large diameters
• -small resistance to flow
• -valves (prevent backflow) *esp important in lower limbs*
• -large lumens
• -high compliance can be DECREASED to stiffen wall

• weak/loss elasticity in venous walls
•    -veins widen and stretch
•    -valves don't close (leading to back flow)

• low pressure conduit back to heart
• pressure reservoir (high compliance-easy to stretch walls)

elastic arteries/veins: tolerate large increase of volume with little increase of pressure

veins

VENOUS RETURN (impacting stroke volume and CO)

• -skeletal muscle pump
• -respitory pump, 
• -decrease compliance
• -stiffening wall
• -increase venous pressure

• -compression of veins by skeletal muscle contraction--raises venous pressure; valves prevent back flow
• -blood forced towards heart

HEART AND THORACIC CAVITY (negative) gLESS THAN ATMOSPHERIC PRESSURE

--inhalation drops atmospheric pressure and explands lungs and cardiac channel (exercise effect)

venous return

• low pressure system:
• capillaries-->O2 blood venules-->4 pulmonary veins

25/1

25/8

diastolic 8 + 1/3 (17) = 14 mmHg

• increased viscosity
• blood vessel length
• decrease radius

• r=radius
• R=resistance

VERY small changed in r --> BIG changes in R

FRICTION

T (tension/force) ALPHA R (radius) * P (pressure in vessels)

the tension/force stretching vessel is PROPORTIONAL to vessel diameter (or radius) * blood pressure

*=multiply

• LESS tension on walls of SMALL vessels
• more tension of walls of LARGE vessels (this is why aneurisms tend to occur in large vessels)

C= increase in V/increase in P

HIGH compliance can accomodate LARGE increase increase in volume with SMALL increase in pressure

(and vise versa) 

low compliance (stiff vessels)-->small increase in volume--> large increase in pressure

• enter: appx 93 mmHg (MAP)
• exit: appx 20 mmHg
• enter veins: 10 mmHg

• EXTRINSIC
• EPI: vasoconstrictor, a1-adrenergic receptors
•        vasodilator, vessels with B2-adrenergic        
•        receptors
• Angiotension II: strong vasoconstrictor, part of RAAS (renin-angitotensin-aldosterone system)

80

0

• CONDUCTIVE ARTERY: get blood to tissue without losing too much energy.
• 2.5-1.5 cm in diameter (aorta/pulm trunk)
• high compliance, easy to stretch

• DISTRIBUTE ARTERIES
• 1cm-3mm in diameter
• more smooth muscle 
• dilate/constrict lumen
• large lumem

small resistance to flow of blood. energy used for blood flow to small arteries

smooth flow (quiet)

blocking off, allows hearing

EDEMA: unable to p/u extra fluid 

• failure due to:
• Filariasis (tropical parasite)
• chemotherapy
• surgery
• radiation

• low resistance flow back to RIGHT heart
• blood reservoir (due to high compliance of venous walls, veins can accomodate large volumes of blood with relatively little increase in pressure)
• venous pressure determines venous return

high compliance of venous walls, veins can accomodate large volumes of blood with relatively little increase in pressure

venous return

• total blood vol-->pressure-->VR
• compliance-->(normally high) can be stiffened
• sympathetic stim-->increase stiffness-->dec. compliance-->VP
• valves
• large lumen
• skeletal muscle pumps
• respiratory muscle pumps