Physiology of the Peripheral Circulation

__ pressure is the measure between the 2 ends of a blood vessel

axial

__ pressure is the measure across the wall of a blood vessel

transmural

general resistance equation is

dP = QR

systemic circulation resistance equation is

BP - RAP = CO x SVR

organ circulation resistance equation is

BP - RAP = Organ Q x Organ VR

v = ___

Q / A

Poiseuille’s law shows ___ changes in r results in ___ changes in vascular R

small, large

resistances in series is

R total = R1 + R2 + R3

resistances in parallel is

1/Rtotal = 1/R1 + 1/R2 + 1/R3

large arteries are ___ vessels

elastic

large arteries ___ when blood pumped into aorta to accommodate SV

stretch

large arteries ___ when aortic valve is closed, to maintain P for perfusion of organs

recoil

what blood vessel has many elastic fibers in media, facilitating expansion and recoil

large arteries (aka elastic vessels)

__ are resistance vessels

arterioles

major site of vascular resistance

arterioles

__ are important in regulation of BP and control distribution of CO

arterioles

__ are made of prominent media and do ocntraction/relaxation of smooth muscle to change vascular resistance

arterioles

__ are exchange vessels

capillaries

__ are where O2 and nutrients are exchanged for CO2 and other metabolic waste products

capillaries

__ wall only has intima layer, facilitating diffusion of gases and solutes

capillaries

__ are capacitance vessels

venules and veins

__ hold a large capacity (60-70% of blood volume at rest)

venules and veins

__ are important in regulating return of blood to heart

venules and veins

__ control contraction/relaxation of smooth muscle for changes in storage capacity

venules and veins

pulse pressure =

SP - DP

compliance =

dV / dP

arterial compliance =

SV / PP

if increase SV, PP ___

increases

if decrease arterial compliance, PP ___

increases

if increase inotropic state, PP ___

increases (because faster, more forceful ejection)

__ is the main site of SVR and organ VR

arterioles

vascular resistance is innervates by the ___ division of the ANS

sympathetic

if arteriole resistance (Ra) increased, what happens to BP and capillary hydraulic pressure?

increases BP, decreases Pc (because if you increase arteriole resistance, more energy dissipated as it goes through resistance vessels → less pressure in capillaries)

if increase sympathetic tone to veins (alpha-1) → ___ venous capacitance → ___ volume of blood in veins → ___ venous return → ___ preload

decrease, decrease, increase, increase

SKM contraction → ___ venous return → ___ preload

increase, increase

inspiration → ___ intrathoracic P → ___ RAP → ___ venous return → ___ preload

decrease, decrease, increase, increase

expiration → ___ intrathoracic P → ___ RAP → ___ venous return → ___ preload

increase, increase, decrease, decrease

if increase sympathetic tone to heart → ___ PP

increase

___, ___, and ___ are the different types of capillaries

continuous, fenestrated, discontinuous

__ capillaries are the most common, least leaky

continuous

__ capillaries are much more permeable to water, small solutes than continuous

fenestrated

__ capillaries are most leaky

discontinuous

transcapillary exchange is ___

passive

solutes and gases ___ across capillary wall while water ___ across capillary wall

solutes and gases diffuse across capillary wall while water flow across capillary wall

diffusion of solutes is driven by a ___

concentration gradient

diffusion of gases is driven by a ___

partial pressure gradient

water flow is driven by ___

filtration pressure gradient

lipophilic solutes/gases diffusion vs lipophobic solutes diffusion

lipophilic solutes/gases can readily diffuse across a capillary wall while lipophobic solutes need pores to diffuse across capillary wall (much slower)

pores for small lipophobic solutes in continuous capillaries are ___

water-filled channels in ICCs

pores for small lipophobic solutes in fenestrated capillaries are ___

water-filled channels in ICCs and fenestrae

__ prevents large lipophilic solutes from accessing ICCs and fenestrae

Glycocalyx

endothelial cells have ___ for carrier-mediated solute transport

membrane proteins

brain capillaries need ___ to transport essential lipophobic solutes across endothelial cells

specific carrier proteins

Fick’s law is the ___

rate of solute diffusion at a specific point along a capillary

Fick principle is the ___

rate of total solute exchange between a and v ends of capillary network perfusing an organ

how to calculate solute exchange

Vs = Q x (Ca_s - Cv_s)

to increase transcapillary exchange, ___ Q

increase

to increase transcapillary exchange, ___ metabolic rate

increase (increase Δc)

to increase transcapillary exchange, ___ A and ___ T

increase, decrease

__ recruitment can be used to increase transcapillary exchange

capillary

during exercise, ___ are dilated by metabolites and by circulating ___ (NT) acting at ___ receptors → ___ number of well-perfused capillaries

arterioles, EPI, beta-2, increasing

flow of water across the capillary wall is driven by a ___ → ___

filtration pressure gradient, net filtration pressure

what contributes to the net filtration pressure

capillary hydraulic pressure, interstitial fluid pressure, plasma oncotic pressure, interstitial oncotic pressure

net filtration pressure =

(Pc - Pi) - (π_p - π_i)

Pc → capillary hydraulic pressure (pushes fluid out of capillary)

Pi → interstitial fluid pressure (pushes fluid into capillary)

π_p → plasma oncotic pressure (holds fluid in capillary)

π_i → interstitial oncotic pressure (pulls fluid out of capillary)

fluid movement from capillary → interstitium = ___

filtration

fluid movement from interstitium → capillary = ___

absorption

for a perfect barrier, σ = ___

1

for an imperfect barrier, σ = ___

< 1

to calculate net filtration pressure for an imperfect barrier =

(Pc - Pi) - σ(π_p - π_i)

if increase Ra → ___ Pc

decrease

If increase Rv → ___ Pc

increase

net filtration pressure ___ along capillary

decreases

concentration gradient is defined by Fick’s law of diffusion which is ___

Js = (DA/T) ΔC

filtered fluid is returned to circulation via ___

lymphatics

lymphatics main function is to collect fluid filtered from ___ to ___

capillaries, interstitium

regulation of SVR and venous capacitance impacts regulation of ___

BP

regulation of organ VR impacts regulation of ___

organ Q

by blocking sympathetic tone to resting SKM → ___ in blood flow

increase

describe what happens to arterioles when loss of blood volume

volume loss → decreased BP → BRR → increased sympathetic tone to arterioles (vasoconstriction) → increased SVR → restores BP

describe what happens to veins and venules when loss of blood volume

volume loss → decreased BP → BRR → decreased venous capacitance → increased venous return → increased preload → increased CO → restores BP

if have increased core temperature → ___ sympathetic tone to cutaneous blood vessels → vaso___ → decreased body heat

decreased, vasodilation

systemic neural control of SVR and venous capacitance includes ___

NE (alpha 1 vasoconstriction) and EPI (alpha 1 vasoconstriction, beta 2 vasodilation)

systemic hormonal control of SVR and venous capacitance includes ___

RAS (Ang II), Nartriuretic peptides, vasopressin (antidiuretic hormone)

local regulation of organ VR includes ___ and ___ response

myogenic, metabolic

myogenic response is an active response of vascular SM to changes in ___

vascular P

for myogenic response, if P ___ then ___

increases, contraction

for myogenic response, if P ___ then ___

decreases, relaxation

myogenic response of vascular control requires ___

Ca++

myogenic response is ___ by Ca++ channel blockers

blocked

metabolic vasoactive factors include:

[K+]_ISF, acidosis, hypoxia, adenosine

vasoactive effect of increased [K+]_ISF

vasodilation (because increased interstitial K+, hyperpolarizes the SM cell → relaxation)

vasoactive effect of acidosis

vasodilation

vasoactive effect of hypoxia

vasodilation

vasoactive effect of adenosine

vasodilation

autoregulation = change in BP causes ___ in organ Q if organ’s metabolic activity (organ Vo2) remains constant

no change

how does BP relate to CBF?

BP = CBR x CVR

kidneys have a ___ blood flow at rest

high (due to excreting wastes and regulating body fluids)

if flow (Q) below typical resting values, what happens?

BRR response to low BP → increases sympathetic tone → increases organ VR

__ flow is the most common pattern of flow in circulation

laminar (arteries, arterioles, venules, veins)