Circulatory Physiology

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

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

digestive system, kidneys, muscle, brain

BFlow changes based on metabolism

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

Blood Pressure moving through vessels (high to low)

Aorta

Arteries

Arterioles

Capillaries

Venules

Veins

Vena Cava

Resistance to BFlow

resistance factor (it -- resistance --)

viscosity ^^

vessel length ^^

radius v^

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

What controls BFlow

vasoconstriction + dilation

effect of viscosity on blood flow

^ viscosity (thick) = less blood flow

blood doping

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

Order of size of vessels

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

Layers of Vasculature (blood + lymph vessels)

tunica intima = endothelium (+ areolar connective tissue)

tunica media = muscle + elastin

tunica externa = connective tissue - collagen, elastin

What layer of vasculature arterioles have the most of

smooth muscle -- tunica media

what layer of vasculature capillaries are

single endothelium

what layer of vasculature arteries mainly have

collagen + elastin -- tunica externa

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

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

atherosclerosis

cholesterol build up within arteries

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

Pulse Pressure

dif btwn systolic + diastolic pressures

increase as age

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)

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

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

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

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

CAPILLARIES --

gas exchange

thin wall = less diffusion distance

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

^ SA

Pre-capillary Sphincters

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

relax sphincter = open capill. bed

metarteriole - btw arteriole + venule

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

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

pressure of capillary end close to arteries

high BP inside

lower osmotic pressure outside

more want to move out

pressure of capillary end close to veins

low BP inside

higher osmotic pressure outside

more want to move in

what is the lymphatic system? functions?

network of open-ended vessels

drains fluid from tissues

return of excess filtered fluid

defense against disease

• lymph nodes + phagocytes

transport absorbed fat

return filtered protein

lymph vessels

similar structure to veins

lower pressure

have valves

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

venules

capill. beds uniting

porous + allow fluids and WBC into tissues

larger ones have 1+ smooth muscle cell layers

VEINS - main purpose? characteristics?

return to heart

low pressure

larger radius

low resistance to BFlow

slow flow

blood reservoir

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

venous valves + skeletal pump - functions?

VV: prevent backflow

SP: pushes blood upward

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

SP relax - bottom valve open, top closed

SP contract - bottom closed, top open

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

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

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

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

Ways to asses stroke

EEG + CT + MRI

Angiogram (measure blood vessel)

doppler flow (flow thru blood vessels)

Ways to treat a stroke

anticoagulants →less clotting

hypertensive meds →lower BP

carotid endarterectomy →scrape fat

change diet + exercise

BP - main causes

CO

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

mean arterial pressure = CO x total peripheral resistance

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

Things contributing to MAP (flow chart)

Baroreceptors

fast + cardiovascular

pressure receptors (exp. in blood)

• send input to cardiovascular center

• output to heart + vessels

^ BP = stimulated

low BP = inhibited

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

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

Renal Regulation

long term BP control by altering BVolume

kidneys

• direct renal

• indirect renal (renin-angiotensin)

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 ^

Indirect Renal Mechanism in Renal Regulation

Renin-angiotensin

• controls BV + arterioles

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

Renin-Angiotensin System with ^ BP

**BP increases, everything else decreases

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*

Hypertension

HIGH BP

Above 140/90 (systolic/diastolic)

KNOW: (on other cards)

• primary

• secondary (only 10% of cases)

• complications

• treatments

Primary Hypertension Causes

salt

hormones

arterioles abnormalities

poor kidney function (renin-angiotensin system)

age + genetics

smoking / diet / obesity

stress

Secondary Hypertension Examples

10% of cases

happens secondary to other primary problems

EX.

• renal

• endocrine

• neurogenic hypertension

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)

Treatments of Hypertension

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

beta blockers

Ca blockers

Diet + exercise (salt)