Circulatory Physiology

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Cardiac output at rest: where is the main flow going?

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digestive system, kidneys, muscle, brain

BFlow changes based on metabolism

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Blood Flow + Pressure relationship (gradients)

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High to Low (^ change in P = ^ flow)

inversely proportional to vascular resistance (^ resistance = less flow)

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Left Ventricle creates pressure and flow

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60 Terms

1
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Cardiac output at rest: where is the main flow going?

digestive system, kidneys, muscle, brain

BFlow changes based on metabolism

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Blood Flow + Pressure relationship (gradients)

High to Low (^ change in P = ^ flow)

inversely proportional to vascular resistance (^ resistance = less flow)

\
Left Ventricle creates pressure and flow

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Blood Pressure moving through vessels (high to low)

Aorta

Arteries

Arterioles

Capillaries

Venules

Veins

Vena Cava

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Resistance to BFlow

resistance factor (it -- resistance --)

viscosity ^^

vessel length ^^

radius v^

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@@Radius impact on blood flow + by what factor?@@

smaller radius→ ^ resistance = less flow

@@radius decrease by factor of 2: r@@

@@flow decrease by factor of 16: r^4@@

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What controls BFlow

vasoconstriction + dilation

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effect of viscosity on blood flow

^ viscosity (thick) = less blood flow

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blood doping

example of effect of viscosity: excessive RBC’s will increase viscosity (thick) = decrease blood flow = decrease O2 delivery

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Order of size of vessels

arteries →arterioles → capillaries → venules (dont need to know) → veins

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Layers of Vasculature (blood + lymph vessels)

tunica intima = endothelium (+ areolar connective tissue)

tunica media = muscle + elastin

tunica externa = connective tissue - collagen, elastin

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What layer of vasculature arterioles have the most of

smooth muscle -- tunica media

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what layer of vasculature capillaries are

single endothelium

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what layer of vasculature arteries mainly have

collagen + elastin -- tunica externa

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when there is a large section between arterioles and capillaries… what happens to diffusion?

larger section = more diffusion time/ time for exchange = less speed thru capillaries

**pulse through arterioles to capillaries is non existent for smooth movement

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ARTERIES - fibres? what do they do?

high flow rate + high pressure (pressure reservoir when heart relax)

large radius = low resistance

collagen →strength for tension

elastin →stretch/recoil

pulsate flow

systolic (contract) pressure = 120 mmHg

diastolic (relax) pressure = 80 mmHg

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atherosclerosis

cholesterol build up within arteries

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Atherosclerosis - atheroma

fatty plaques within vessel WALLS

harden into plaques

restrict blood flow… clot

Causes:

  • obesity
  • inactivity
  • smoking + alcohol
  • genetics
  • diabetes

Risk factor for:

  • ischemia, infarct, stroke
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Pulse Pressure

dif btwn systolic + diastolic pressures

increase as age

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ARTERIOLES - main function? applications?

change blood flow + resistance + control flow

smooth out pulsatile flow (from arteries to capill.)

RADIUS:

  • adjusted to distribute CO to organs based on needs
    • @@blood flow to brain stays constant@@
  • - regulate arterial BP

vasoconstrict + vasodilate (triggered by local + central factors)

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vasoconstriction - what is it? what causes it?

narrow vessels

^ resistance = reduce flow

smooth muscle contraction

\
causes:

  • ^ O2 in tissues
  • less CO2 in tissues
  • *endothelin + stretch
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vasodilation - what is it? what causes it?

enlargement of vessel

less resistance = ^ flow

smooth muscle relaxation

\
causes:

  • @@less O2@@ in tissues (want more, so send more blood)
  • @@^ CO2@@ in tissues
  • @@Nitric oxide@@
  • ^ lactic acid
  • ^ K+
  • ^ osmosis
  • ^ adenosine release (coronaries)
  • ^heat
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Vascular tone - what is it? what @@influences@@ it?

contractile activity

  • local influences:
    • metabolic changes
    • histamine release (vasodilate)
    • endothelial factors (protein regulating BVessel constriction) -- nitric oxide (dilate) + endothelin (constrict)
  • local physical influences
    • heat (dilate)
    • cold (constrict)
    • myogenic response to stretch -- reflex contraction
    • constriction of vessel due to pressure
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Arterioles →extrinsic control

maintain Mean Arterial Pressure + redistribute blood

SNS input (vasoCONSTRICT)

Hormones

  • Alpha 1 receptors
    • norepi
    • vasoCONSTRICT
  • Beta 2 receptors
    • epi
    • heart/skeletal muscle
    • vasoDILATE
  • Angiotensin II
    • vasoCONSTRICT
    • ^ BP

\

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CAPILLARIES --

gas exchange

thin wall = %%less diffusion distance%%

small radius = slow velocity of BFlow = large cross-sectional area = ^ gas exchange time

^ SA

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Pre-capillary Sphincters

constrict sphincter = close capill. bed (@rest are often closed)

relax sphincter = open capill. bed

metarteriole - btw arteriole + venule

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Types of Capillaries

Continuous

  • common
  • least permeable
  • muscle, lungs, brain, CT

Fenestrated

  • pores
  • kidneys (bc filter blood), small intestine

Sinusoids

  • large for RBC + proteins
  • liver, bone marrow, spleen
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Capillary Bulk Flow - Causes

GIST: hydrostatic pressure (cap) + osmotic pressure (tissue) regulate bulk flow

\
Starling Forces (physical forces) determine fluid flow btwn capillaries + tissues: PRESSURE GRADIENTS

\

  • capillary BP
    • Hydrostatic pressure: regular pressure of fluids
    • encourage fluid flow into tissue
  • interstitial fluid hydrostatic pressure
    • pushes things out + opposes hydrostatic capill. pressure
  • plasma colloid osmotic pressure
    • encourage fluid into capillaries
  • interstitial fluid colloid osmotic pressure
    • opposes plasma colloid osmotic pressure
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pressure of capillary end close to arteries

high BP inside

lower osmotic pressure outside

more want to move out

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pressure of capillary end close to veins

low BP inside

higher osmotic pressure outside

more want to move in

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what is the lymphatic system? functions?

network of open-ended vessels

drains fluid from tissues

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return of excess filtered fluid

defense against disease

  • lymph nodes + phagocytes

transport absorbed fat

return filtered protein

\

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@@lymph@@ @@vessels@@

@@similar structure to veins@@

lower pressure

have valves

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edema

swelling of tissues

too much interstitial fluid

\
Causes:

  • less concentration of plasma proteins = less osmotic pull/ pressure
  • ^ permeability of capill walls
  • ^venous pressure
  • blockage of lymph vessels
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venules

capill. beds uniting

porous + allow fluids and WBC into tissues

larger ones have 1+ smooth muscle cell layers

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VEINS - main purpose? characteristics?

return to heart

low pressure

larger radius

low resistance to BFlow

slow flow

blood reservoir

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Venous Return: Increased and Decreased by…?

Decrease:

  • venous compliance (stretch)

Increase:

  • pressure from cardiac contraction
    • ^ venous pressure = ^ pressure gradient
  • SNS venoconstriction
    • ^ vein pressure = ^ pressure gradient = less venous capacity
  • skeletal muscle movement
    • ^ venous pressure = ^ pressure gradient
  • venous valves impact
  • respiratory activity
    • less pressure in lung veins = ^ pressure gradient
  • cardiac suction
    • less pressure in heart = ^ pressure gradient

\
\
increase venous return = ^ EDiastolicV = ^ SV = ^ CO

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venous valves + skeletal pump - functions?

VV: prevent backflow

SP: pushes blood upward

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Skeletal muscle contract + relax - top + bottom valves what?

SP relax - bottom valve open, top closed

SP contract - bottom closed, top open

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Embolism

blockage of a blood vessel, sometimes sudden

ex. scuba diving + nitrogen

locations: pulmonary, cerebral, cardiac

… i dont think we have to know this one

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STROKE:

less blood supply to brain

  • ISCHEMIC: thrombus or embolus or plaque blockage
  • HAEMORRHAGIC: bleeding - weak wall rupture

TIA’s: Transient Ischemic Attacks

  • mini strokes (transient) temporary

CVA: Cerebrovascular accidents

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Stroke symptoms

depend on area of brain

\

  • drooping face + drooling
  • confusion
  • dizziness
  • loss of consciousness
  • poor coordination / paralysis
  • weak arms
  • sudden headache
  • difficulty with speech
  • loss of vision
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controllable and non controllable risk factors of stroke

80% strokes are preventable

controllable:

  • smoking/alcohol
  • high-fat diet / obesity
  • lack of exercise
  • high BP
  • diabetes

non controllable:

  • age, gender, ethnicity, genetics
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Ways to asses stroke

EEG + CT + MRI

Angiogram (measure blood vessel)

doppler flow (flow thru blood vessels)

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Ways to treat a stroke

anticoagulants →less clotting

hypertensive meds →lower BP

carotid endarterectomy →scrape fat

\
change diet + exercise

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BP - main causes

CO

total peripheral resistance (all vessels together… force against flow)

\
mean arterial pressure = CO x total peripheral resistance

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Short + Long Term control for BP

short: seconds

  • baroreceptors (relay info from BP in ANS)
  • cardiovascular system (epi, change HR, contract… etc.)

long: mins-hrs

  • kidneys
  • **blood volume
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<p>Things contributing to MAP (flow chart)</p>

Things contributing to MAP (flow chart)

\

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Baroreceptors

fast + cardiovascular

pressure receptors (exp. in blood)

  • send input to cardiovascular center
  • output to heart + vessels

\
^ BP = stimulated

low BP = inhibited

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HIGH BP response

everything decrease EXCEPT PNS + baroreceptors firing

\
less SNS:

→vasodilation →less TPR →less BP

→less contractility →less SV →less CO →less BP

→ venodilation →less VR →less SV →less CO →less BP

<p>everything decrease EXCEPT PNS + baroreceptors firing</p>
<p>\<br />
less SNS: </p>
<p>→vasodilation →less TPR →less BP </p>
<p>→less contractility →less SV →less  CO →less BP</p>
<p>→ venodilation →less VR →less SV →less CO →less BP</p>
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LOW BP response

everything increase EXCEPT PNS + baroreceptors firing

\
^ SNS:

→vasoconstriction →^ TPR →^ BP

→^ contractility →^ SV →^ CO →^ BP

→ venoconstriction →^ VR →^ SV →^ CO →^ BP

^HR

TPR: total peripheral resistance

<p>everything increase EXCEPT PNS + baroreceptors firing</p>
<p>\<br />
^ SNS: </p>
<p>→vasoconstriction →^ TPR →^ BP </p>
<p>→^ contractility →^ SV →^ CO →^ BP</p>
<p>→ venoconstriction →^ VR →^ SV →^ CO →^ BP</p>
<p>^HR</p>
<p>TPR: total peripheral resistance </p>
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Renal Regulation

long term BP control by altering BVolume

kidneys

  • direct renal
  • indirect renal (renin-angiotensin)
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Direct Renal Mechanism in Renal Regulation

change BV indep. of hormone

  • ^BP or BV
    • ^ filtration
    • eliminate ^ urine
    • THEREFORE reduce BP
  • decrease BP or BV
    • kidney preserve water + fluid retention
    • less filtration
    • less urine
    • BP ^
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Indirect Renal Mechanism in Renal Regulation

Renin-angiotensin

  • controls BV + arterioles
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Renin-Angiotensin System with less BP

less arterial BP →

release renin →

trigger production of angiotensin II → (vasoconstrictor)

aldosterone + ADH secretion →

conserve fluid→

\
**BP decreases, everything else increases

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Renin-Angiotensin System with ^ BP

**BP increases, everything else decreases

<p>**BP increases, everything else decreases</p>
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Hypotension

LOW BP

Below 100/60 (systolic/diastolic)

  • too little blood to fill vessels
  • heart is too weak to drive blood

*not a condition in the list we need to know*

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Hypertension

HIGH BP

Above 140/90 (systolic/diastolic)

\
KNOW: (on other cards)

  • primary
  • secondary (only 10% of cases)
  • complications
  • treatments
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Primary Hypertension Causes

salt

hormones

arterioles abnormalities

poor kidney function (renin-angiotensin system)

age + genetics

smoking / diet / obesity

stress

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Secondary Hypertension Examples

10% of cases

happens secondary to other primary problems

EX.

  • renal
  • endocrine
  • neurogenic hypertension
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Complications of Hypertension

congestive heart failure (muscle doesn’t pump as good)

stroke / heart attack

spontaneous hemorrhage

renal failure

retinal damage (blood vessels in eyes)

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Treatments of Hypertension

ACE inhibitors (ANG I to II) (prevents blood vessel narrowing)

beta blockers

Ca blockers

Diet + exercise (salt)