Circulatory Physiology

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60 Terms

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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)

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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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vaso**constrict**ion - what is it? what causes it?
narrow vessels

^ resistance = reduce flow

smooth muscle **contrac**tion

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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

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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

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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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Things contributing to MAP (flow chart)
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

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less SNS:

→vasodilation →less TPR →less BP

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

→ venodilation →less VR →less SV →less CO →less BP
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
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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
everything increase EXCEPT PNS + baroreceptors firing

\
^ SNS: 

→vasoconstriction →^ TPR →^ BP 

→^ contractility →^ SV →^ CO →^ BP

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

^HR

TPR: total peripheral resistance
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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
\*\*BP increases, everything else decreases
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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)