Pressure Gradients
drive flow from high pressure to low pressure
bulk flow
Flow due to pressure gradients =
Heart
_____ creates pressure gradient for bulk flow of blood
circulatory system
A gradient must exist throughout __________ to maintain blood flow
Mean Arterial Pressure (MAP)
Pressure in aorta (90 mmHg)
Central Venous Pressure (CVP)
Pressure in vena cava (0 mmHg)
Aorta
Largest artery
Vena Cava
Largest vein
lower
There is a _____ resistance in the pulmonary circuit
Arterioles
______ have the greatest drop in blood pressure
Systemic circuit
Pressure gradient in _______ is much greater
Resistance in the Cardiovascular System
Flow through both circuits is equal
Flow = DP/R
1. Radius of vessel (arterioles and small arteries - can regulate radius)
2. Length of vessel
3. Viscosity (thickness) of fluid
Factors affecting resistance to flow:
proteins
Blood viscosity dependent on amount of RBC's and ________ in blood.
Vasoconstriction
Decrease radius --> increase resistance
Vasodilation
Increase radius --> decrease resistance
Pulmonary Circuit
lower pressure gradient
cardiac output (CO)
Flow =
mean arterial pressure (MAP)
Delta P =
total peripheral resistance (TPR))
R =
CO
______ = MAP/TPR
Baroreceptors
stretch receptors
Arterial Baroreceptors
High pressure baroreceptors
Sinoaortic baroreceptors
Carotid Sinus, Aortic Arch
We want this on the carotid because this goes directly to the brain
Location of Arterial Baroreceptors:
Hemorrhage
Decrease in blood volume, drop in MAP, baroreceptors reflex quickly which compensates for the changes in blood pressure --> this doesn't correct the problem it just shunts blood away from that area
renal (kidney)
Long term hemorrhage regulation occurs through _________ regulation of blood volume
Kidney
regulates fluid output and puts fluid back into the blood stream to try to compensate instead of putting fluid into the urine after a hemorrhage
Arteries
relatively large, branching vessels that conduct blood away from the heart
Arterioles
small branching vessels with high resistance
Capillaries
site of exchange between blood and tissue
Venules
small converging vessels, have valves
Veins
relatively large converging vessels that conduct blood to the heart
Heart >Arteries >Arterioles > Capillaries > Venules >Veins >> Heart again
Closed system:
Elastic Arteries
Walls of smooth muscle and elastin, expand when the pressure of the blood rises, and acts as recoil system when ventricles relax
Pulse
Alternate expanding and recoiling of the arterial wall that can be felt
Aneurysms
Weakness in arterial wall: ballooning, can be caused by a tear in the lining, aortic and cerebral = most common
Throbbing, sudden "worst headache" of your life, death 99% of the time
Symptoms of Aneurysms:
Wait and watch, surgery with stents
Treatments of Aneurysms:
Cerebral Aneurysm
Circle of Willis, nothing you can do
Arterioles
Contain highest % of smooth muscle, greatest pressure drop and resistance to flow, vascular resistance regulated through changes in radius, respond to changes in Oxygen (active hyperemia), temperature, and hemorrhage
heat
temperature that increases blood flow
cold
temperature that decreases blood flow
Active Hyperemia: Steady State
O2 delivered as fast as consumed, CO2 removed faster than being removed
Active Hyperemia: Increased Metabolic Rate
O2 consumed
CO2 produced
Active Hyperemia: Response to low O2 and high CO2
Vasodilation (which increases blood flow)
Active Hyperemia: Increased blood flow
Delivers more O2
Removes more CO2
indirectly
Pressure in brachial artery is measured ______
Estimating Aortic Pressure
Use sphygomanometry (blood pressure cuff) and auscultation, listen for sounds due to turbulent flow through brachial artery
120/80
Normal blood pressure:
Increase in: blood volume, heart rate, stroke volume, blood viscosity, and TPR
Factors influencing Arterial Blood Pressure
cardiac output and peripheral resistance
Controlling ____________ regulates blood pressure
Hypertension
Blood pressure in excess of normal range for age and gender, above 120/90 mmHg,
Primary or essential Hypertension
result of a complex or poorly understood process
Secondary Hypertension
result of a known disease (such as kidney disease)
Essential Hypertension
95% of population, increase in TPR is a universal characteristic (cholesterol plaque hardening), Sustained high stress vis SNS (sympathetic nervous system) and high Na+ intake act together in development of hypertension, adaptive response= thickening of a
Silent killer, asymptomatic until substantial vascular damage occurs, increases workload of heart (congestive heart failure), damage to cerebral blood vessels (stroke)
Dangers of Hypertension:
Stop smoking, alcoholic moderation, weight loss, reduction of salt intake, diuretics, and ACE inhibitors
Treatments of Hypertension
Angiotensin II
synthesized from angiotensinogen (precursor)
stimulates aldosterone which conserves Na+ (vasoconstriction, and increases TPR)
Angiotensin II
Angiotensinogen --(renin)--> Angiotensin I --(ACE)--> Angiotensin II
Capillaries
smallest blood vessels, 1 endothelial cell thick, provide direct access to cells, permits exchange of nutrients and wastes, regulated by precapillary sphincters
Kidney: glomerulus and vasa recta
Liver: for nutrient processing
Anterior Pituitary: for releasing/inhibiting hormones from hypothalamus
3 organs with portal circulation: have 2 capillary beds before entering heart
Capillaries
Have greatest total cross-sectional area, have slowest velocity of blood flow, enhances exchange
Precapillary Sphincters
Rings of smooth muscle that surrounds capillaries on the arteriole end
Precapillary Sphincters
Contract/relax in response to local factors only, contraction = constriction = decrease blood flow, relaxation = increased blood flow, metabolites cause relaxation
Capillary BP
Capillary hydrostatic pressure =
positive
net filtration pressure =
38 mmHg
arteriole end =
16 mmHg
venous end =
0-1 mmHg
interstitial hydrostatic pressure =
hydrostatic pressure
Standing on feet increases _____________
capillaries damaged and leak fluid and protein
histamine increases capillary permeability to proteins --> swelling
Injuries from filtration and absorption across capillaries:
Liver disease
disease causes decrease in plasma proteins (site of most plasma protein manufacture)
Kidney Disease
increase blood volume and thus blood pressure, decrease in plasma protein
hydrostatic and osmotic pressures
Forces for bulk flow:
Osmotic pressure
osmotic force exerted on water by non-permeating solutes
proteins
Only non-permeating solute =
oncotic pressure
osmotic force of proteins
colloid (protein) oncotic pressure
draws water back into capillary - proteins have a negative charge, reason for negative charge on plasma membrane
Edema
Excessive accumulation of tissue fluid
May result from: high arterial blood pressure, leakage of plasma proteins into interstitial fluid, decreased plasma protein (kidney and liver disease), and obstruction of lymphatic drainage (parasitic infection or ly
Lymphadema
Often result of breast cancer surgery, removal of sentinal lymph nodes under arm may prevent drainage, swelling in affected arm, no injections or BP taken using arm on side with breast cancer
Venules
Formed when capillaries unite, very porous
Veins
little smooth muscle or elastin
Capacity Vessels (blood reservoirs)
60% of blood volume in veins, contain 1-way valves ensure blood flow to the heart
Venous return
The rate of ______ is dependent in part on the action of skeletal muscle pumps
veins
Skeletal muscles contract, forcing flood out of the _____ toward the heart
Skeletal muscle contracts
Squeezes on veins increasing pressure, blood moves toward heart, blood cannot move backwards due to valves
Skeletal muscle relaxes
blood flows into veins between muscles
Respiratory Pump
Inspiration, Pressure on veins in abdominal cavity creates gradient that favors blood movement to thoracic cavity (increases central venous pressure and increases venous return)
Inspiration
Decrease pressure in thoracic cavity
Increase pressure in abdominal cavity
Varicose Veins
breakdown of valves
"Spider Veins
St. Fiacre
Patron Saint of Hemorrhoid sufferers
Hemorrhoid Treatment
Rectal rocket, rubber band ligation, and surgery
Lymphatic System
System of vessels, nodes and organs
Vessels involved in returning excess filtration to circulation
Vessels form open system starting at capillaries
Pick up lipids from small intestine to by-pass capillaries
Also part of the immune system
Collecting Ducts
RIght lymphatic duct drains lymph from upper right side of body
Thoracic duct