Unit 2 Flashcards
What would you expect to happen to the flow when pressure increases in a vessel?
Flow would increase in a linear fashion, but not within a certain range.
Why does the flow not increase within a certain range when pressure increases? What is this called?
Tissues adjust their resistance to maintain normal blood flow.
Autoregulation
Vascular compliance equation
C = Delta V / Delta P
Change in volume / Change in transmural pressure
Amount the volume of a vessel changes in response to pressure
Vascular compliance
Term referring to the elasticity of a vessel without consideration of volume changes
Distensibility
Veins are _______ times more compliant that arteries
20 times
Why are veins more compliant than arteries
They have a greater elasticity
What causes vasoconstriction in many blood vessels
Sympathetic stimulation
Symnpathetic inhibition causes
Less pressure
Sympathetic stimulation causes
Higher pressure
True/False:
There are no parasympathetic nerves supplying the blood vessels
True
After volume increases and pressure increases, what then happens?
What is this called?
Pressure somewhat decreases as the walls stretch to accommodate the extra volume
Called Delayed compliance
2 factors that affect the pulse pressure
Stroke volume output
Compliance of the arterial tree
Pulse pressure contours:
Upstroke (due to systole)
Incisors (due to aortic valve closure)
Diastolic decline
Abnormal pressure pulse contours
Arteriosclerosis
Aortic stenosis
Patent ductus arteriosus
Aortic regurgitation
Opening in the aorta
Aortic stenosis
Hardening of the arteries, causing them to not expand
Arteriorsclerosis
Increase in systolic pressure but not much change in diastolic pressure.
Arteriorsclerosis
Aortic valve does not close so blood keeps backing up into the ventricle
Aortic regurgitation
The rising pressure in the aorta causes:
A wave of blood flow through the arterial tree
Progressive loss of pulsations upon entering the small arteries -> arterioles -> capillaries
Damping
Damping is directly proportional to:
Resistance and compliance
Pressure in the right atrium because all systemic veins flow into the right atrium
Central venous pressure
Central venous pressure is regulated by :
A balance between the ability of the right side of the heard to pump blood into the lungs, and the tendency for blood to flow into the right atrium
Factors that increase venous return (3)
Increased blood volume
Increased large venous tone
Dilation of arterioles
Smooth muscles constricting veins, increasing venous return rate
Increasing venous tone
Normal right atrial pressure
0 mm Hg
Abnormally high right atrial pressure
Up to 20-30 mm Hg
What causes abnormally high right atrial pressure
Severe heart failure
Excessive blood transfusion
Abnormally low right atrial pressure
-3 to -5 mm Hg
What causes abnormally low right atrial pressure
Heart pumping vigorously
Severe hemorrhage
Large veins with little resistance in general (with an exception) due to
Peripheral venous pressure
Exception of peripheral venous pressure
Vein compression points
Effect of right atrial pressure on peripheral venous pressure:
Increase causes blood back up and increase in peripheral venous pressure
Significant increases only seen in CHF (congestive heart failure)
Pressure collapse in the neck is typically caused by
Atmospheric pressure
Effect of intra-abdominal pressure when increased
Venous pressure increases in the legs
Intracellular-abdominal pressure may increase due to:
Pregnancy
Abdominal tumors
Ascites (excessive fluid in the peritoneal cavity)
Effect of gravitational pressure
Venous pressure above the heart is less that 0 mm Hg
Venous pressure below the heart is greater than 0 mm Hg
Pressure on body at
Head
Abdomen
Feet
Head- -10 mm Hg
Abdomen- +22 mm Hg
Feet- +90 mm Hg
Valves ensure:
One-way movement of blood
Extremity muscles contraction “massages” blood up toward the heard
Muscle pump
Breathing action that massages blood toward the heart
Thoracic pump
Venous valve incompetence causes:
Varicose veins in the legs
Ability to allow vessels to store blood
Blood reservoir
Principle reservoirs
Large abdominal veins Spleen Liver Subcutaneous venous plexus Heart
Microscopic circulation that occurs at the level of the tissues (capillary bed)
Microcirculation
Purpose of microcirculation
To transport nutrients to the tissues and remove cellular waste
Structures in a capillary bed structure (5)
Arteriole
Met arterioles and precapillary sphincters
True capillaries
Preferential (thoroughfare, bypass) channels
Venues
Vessels without any smooth muscles present
True capillaries
Last consctrictor before reaching the true capillaries
Precapillary sphincters
Contraction and dilation of the metarterioles and precapillary sphincters
Vasomotion
Regulation of vasomotion by local tissue conditions (mainly O2)
Autoregulation
What is the mean arterial pressure?
About 100 mmHg
What type of of velocity of blood flow is in the arteries
High
Arteries are (THIN/THICK) walled, with a diameter range of:
Thick
Diameter range- 0.1 mm - 25 mm
Arteries consist of:
Endothelium Elastic tissue (lots of) Smooth muscle (lots of) Fibrous tissue Collagen (lots of)
Arterioles consist of:
Small endothelium
Smooth muscle
Capillaries consist of
Endothelium only
Venules consist of
Endothelium and fibrous tissue
Veins consist of
Endothelium
Elastic tissue
Smooth muscle
Fibrous tissue
What controls flow into capillaries?
Arterioles
Arterioles are the most important determinant of:
Peripheral resistance
Arterioles are ____ walled relative to diameter
Thick
Arterioles can change:
Diameter
Function of capillaries
To exchange fluid, nutrients, electrolytes, hormones, etc. to tissue cells
Venules and veins have (LOW/HIGH) pressure
Low
Venules and veins have _____ walls that are:
Thin
Dispensable
Valve ensure:
One way flow
What changes venous volume? Why is this important
Capillary inflow Venous tone (smooth muscle)
Important for venous return
Where is most of the blood volume located?
In the venous system
Veins, venules and venous sinuses are considered to be the:
Blood reservoir
Sum of the individual cross sectional areas of each blood vessel category
Total cross sectional area
What has the largest combined cross sectional area?
Capillaries
As total cross sectional area increases, what happens to blood flow velocity?
It decreases
Pressure in the arteries is:
High
Average pressure in the capillaries
About 17 mm Hg
Pressures in the venous system is:
Low
Ohm’s law
Q = Delta P / R
Volume of blood that passes a given point per unit of time
Blood flow (Q)
Cardiac output (CO) :
Q for entire systemic circulation
Is typically about 5 L/min
Flow in layers that is generally quiet
Laminar flow
Laminar has a ______ shape of velocities
“Parabolic”
Flow where layers are disrupted by some partial obstruction, or excessive velocity. It is noisy
Turbulent
Carotid Bruit:
Artherosclerotic plaques partially occulting an artery. Causes a turbulent flow
In measuring blood, _____ sounds are created by pulsatilla blood flow through the compressed artery.
Cuff pressure at this time is approx
Korotkoff
80-120 mm Hg
Approx cuff pressure (in measuring BP) when the cuff is silent and the artery is no longer compressed
Less than 80
Reynold’s number equation
Re = (VDP)/viscosity
V= mean velocity of blood flow
D: Vessel diameter
P = density
Poiseulle’s Law
Can be constructed substituting R in the basic flow equation with the variables in the resistance equation.
Equation for Poiseuille’s
Q = (delta P * Pi * r^4)/(8 * mue* l)
Series resistance
The total resistance of vessels in series is equal to the sum of their individual resistances
Rtotal = R1 + R2 + R3…..
Aortic pressure is (HIGHER/LOWER) than left ventricular pressure
About the same, if not a little higher
Between aorta and left ventricle, which has a larger pressure increase?
left ventricle (goes from 0 to 120ish)
Amount of pressure in the left atrium
little to none.
For blood vessels arranged in parallel, more vessels means:
more avenues for blood flow and reduces resistance
1/Rtotal = 1/R1 + 1/R2 + 1/R3……
Reciprocal of resistance =
conductance
Ratio of volume of RBC to the total blood volume
hematocrit (HCT)
How is the HCT usually checked?
centrifution
What does the centrifuge separate, top to bottom?
Plasma
WBC and platelets
RBC
Normal HCT for males?
Females?
Male: 42-52%
Female: 37-47%
Possible causes of increased HCT
Erythrocytosis (increased due to illness or an external situation)
Polycythemia (bone marrow disorder)
Severe dehydration
Possible causes of decreased HCT
Anemia
Renal disease (decreased EPO)
Leukemia
Overhydration
What causes delayed compliance to happen?
This is due to the stretch-relaxation response of the smooth muscle cells.
Capillary wall types (3)
Continuous
fenestrated
Discontinuous/Sinusoidal
Continuous walled capillaries have:
They are found in:
Continuous endothelial layer and basement membrane
Found in muscle, nervous tissue, heart, lung, and skin
Fenesterated capillaries have:
They are found in:
continuous basement membranes but fenestrations in the endothelial layer. They are highly permeable
Found in intestinal vili, chordi plexus, glomeruli, and endocrine
Discontinuous/sinusodial capillaries have:
a larger diameter
incomplete basement membrane and larger gaps in the endothelial layer
found in liver, bone marrow, spleen
Types of movement through capillary walls
Intercellular clefts (slit-pores) Transcytosis (plasmalemmal vesicles, caveolae, vesicular channels) Fenestrae (permanent pores through the membrane)
Capillary characteristics of the brain
continuous capillaries with tight junctions that only allow small molecules to pass (water, oxygen, CO2)
Capillary characteristics of the liver
Discontinuous capillaries with wide intercellular clefts that allow all dissolved substances including plasma proteins to pass through.
Capillary characteristics of the GI tract
Fenestrea that allow absorption through the capillary wall
Capillary characteristics of glomerulus (kidney)
Numerous fenestrae to allow large amounts of filtration
How can lipid soluble substances pass through the capillary membrane
they diffuse directly through the membrane
size of capillary pores
about 6-7 nm in diameter- too small for most plasma proteins or blood cells to pass through
components of the interstitium
collagen fiber bundles
proteoglycan filaments
interstitial fluid
These form a gel
Interstitial fluid is derived by:
filtration and diffusion from the capillaries
most interstitial fluid is trapped:
in the gel, but some “free” fluid is found in the interstitium
Composition
the same as plasma but with less protein
Starling’s forces, AKA
bulk flow
ultrafiltration
4 different forces that determine movement of fluid between the capillary and the interstitium
IMPORTANT
Capillary pressure (Pc)
Interstitial fluid (Pif)
Plasma colloid osmotic pressure (PIp)
Interstitial colloid osmotic pressure (PIif)
Increased pressure (hydrostatic) forces causing movement out of the capillary
Capillary pressure (Pc)
Negative pressure inwardly directing force, pushing movement into the capillary
Interstitial fluid (Pif)
Pressure caused by water coming in. Due to colloids (protein and fluids) being permiable to water. Pulls movement inward
Plasma colloid osmotic pressure (PIp)
Colloid in extracellular fluid causing water to leave, so pressure is pulled outward
Interstitial colloid osmotic pressure (PIif)
The actual direction of fluid movement in a capillary is:
the summative effects of all 4 forces
Capillary End where there is net filtration
Arterial end
Capillary End where there is net reabsorption
Venous end
Which force is greater at the arterial end?
Outward force
Which force is greater at the venous end?
Inward force
An accessory route for the return of fluid and protein from the interstitial space to the blood.
Lymphatic system
Lymphatic structures (6)
Lymph capillaries Lymph vessels Lymph nodes Cisterna Chyli Thoracic duct right lymphatic duct
Amount of fluid that leaves the blood capillaries that enters the lymph capillaries
1/10
Lymph capillaries are _____ ended. They are lined with:
Along with lymph channels, there are:
Blind
Lined with endothelial cells that overlap to form simple valve-like structures
valves
Lymph flow increases in the:
interstitial pressure
Factors that increase Pif for lymph flow.
These factors may lead to _____ if flow can’t keep up with____
Elevated capillary pressure
Decreased plasma colloid osmotic pressure
Increased interstitial fluid colloid osmotic pressure
Increased permeability of the capillaries
May lead to edema if flow can’t keep up with lymph formation
What can facilitate lymph flow? What are some sources?
compression
Sources: Contraction of surrounding skeletal muscle Movement of body parts Pulsation of adjacent arteries Compression forces from outside the body
Functions of the lymphatic system (5)
Works as an “overflow” system for capillaries
Controls concentration of protein in the IF
Controls volume of the IF
Controls the Pif (keeps it negative in most tissues)
Immune function
Tissues need:(6)
Oxygen Nutrients (glucose, amino acids, fatty acids) CO2 removal Acid removal Electrolyte balance Hormone delivery
Blood flow can be redistributed by altering the:
arterial resistance
Blood is diverted from:
high to low resistance arterioles
Blood flow rate is just enough to supply:
Unless:
oxygen and nutrients a tissue needs
unless the tissue functions as a blood conditioner
Mechanisms of blood flow control
Short term (acute, metabolic)/ Autoregulation
Long term
Short term control / autoregulation
rapid changes of blood flow over seconds to minutes using vasomotion
Long term control
Slow changes of blood flow over days, weeks, or months by changing the number of capillaries in a tissue
Short term: as blood flow increases, what happens to metabolism rate?
it increases
Short term: as blood flow increases, what happens to arterial oxygen saturation?
It increases
Mechanisms of short term control
Vasodilator theory
Oxygen lack theory
Vasodilator theory:
The greater the metabolic rate of a tissue, or lack of oxygen, the more vasodilator substances are secreted, which then affext pre-capillary sphincters, metarterioles, and arterioles
Oxygen lack theory
Lack of O2 causes smooth muscle to relax
Dilates the pre-capillary sphincters, metarterioles and arterioles
Important local vasodilators
Adenosine Carbon Dioxide Histamine Potassium ions Hydrogen ions (from lactic acid, for ex)
An increase in the quantity of blood flow to a tissue or body part
Hyperemia
Normal autoregularion to increase blood flow due to metabolic need
Active hyperemia
Response to temporary interruption of blood flow to pay back O2 debt
Reactive hyperemia
Response of smooth muscle to contract with excessive pressure; generally over-ridden by metabolic control of blood flow
Myogenic response
Tubuloglomerular feedback
Blood flow In the kidney
Composition of fluid in the distal tubule is sensed by special cells (macula densa), which then regulates the afferent arteriole.
Blood flow in the brain
The concentrations of CO2 and H+ are as important as O2 to normal brain function. Astrocytes regulate blood low
In the skin, blood flow is closely linked to ___ ____ ______, and is controlled largely via ______ ______
body temperature regulation
sympathetic innervation
An endothelial derived relaxing factor:
Nitric oxide (NO)
NO is released by:
endothelial calls in small arteries in response to shear stress (as would occur when there is rapid blood flow into the capillary bed
NO causes ______ in small arteries. This causes:
vasodilation
Causes them to reduce wall stress and improves flow into downstream capillary
Products needed to produce NO
Calmodulin
NADPH
BH4
with L-Arginine
Main determining factor of long term blood flow
Oxygen
Main vascular growth (______)
factors:
Angiogenetic
Vascular endothelial growth factor
Fibroblast growth factor
Angiogenin
Vacoconstrictors:
Norepinephrin and epinephrine
Angiotensin II
Vasopressin
Endothelin
Vasocontrictors from sympathetic nervous system and adrenal medulla
NE and epinephrin
Ex of vessels that vasodilate from NE and epinephrin
Coronary arteries
Angiotensis II is formed by:
It causes:
Formed by a cascase initiated by renin release from the kidneys
causes arteriole constriction to increase total peripheral resistance and increases blood pressure
Vasopressin, AKA __ ____
it is released from:
It increases:
Antidiuretic hormone
Released from the posterior pituitary gland
Increases water reabsorption by the kidneys, and peripheral resistance and blood pressue
in increased amounts ca ncause arteriolar vasoconstriction
Edothelin’s release is triggered by:
Its function:
Endothelial damage
Prevents excessive bleeding
Bradykinin is formed by:
It causes:
A cascade initiated by tissue inflammation
Causes arteriolar dilation and increased capillary permeability
Histamine is derived from:
Its function:
Mast cells and basophils
Causes vasodilation of arterioles in inflammatory reactions
Also an important mediator in allergic reactions
Increased calcium causes:
vasoconstriction by stimulating smooth muscle
Increased Potassium and magnesium causes
vasodilation by inhibiting smooth muscle
Increased hydrogen ions cause
dilation by lowering the pH
The autonomic nervous system is used for more global control such as:
Redistributing blood flow to different areas
Regulation of the heart
Rapid control of arterial pressure
Somatic motor neurons branch from:
They release:
Ventral horn of the spinal cord
ACh which causes contraction of skeletal muscle
Autonomic motor neurons branch from:
They consist of:
They release:
Intermedial lateral horn of the spinal cord
Preganglionic neurons and postganglionic neurons
After preganglionic they release ACh
After postganglionic they release ACh OR NE
Location of sympathetic neurons (pre and post synaptic)
Thoraco-lumbar
Location of Parasympathetic neurons (pre and post synaptic
Cranio-sacral (3 cranial an 2 sacral)
neurons with adrenergic postganglion target cells:
Smooth muscle cells and cardiac cells
Neurons with cholinergic postgangion target cells:
Secretory cells like sweat glands
sympathetic neurons with no postganglion target cells:
Chromaffin cells in adrenal medulla
Cholinergic
Neuron secretes acetylcholine
adrenergic
neuron secretes norepinephrine
What happens to the pacemaker cell when stimulated by sympathetic neuron
Norephinephrine stimulates Beta1 receptor
Activates G protein by Alphasubunits
Adenylyl cyclase converts STP into cyclic AMP (cAMP)
G protein connects with cAMP, releasing PKA (protein kinase A)
Ca channel is phosphorylated by ATP
allowing Ca++ to enter
What happens to the pacemaker cell when stimulated by parasympathetic neuron
AcH receptor is M2
G protein with alpha subunit is released
Opens potassium channel, causing the cells to become more negative, slowing down the rate.
How does a symphathetic neuron affect force of contraction in an ordinary cardiac muscle
Same as pacemaker,
except then Ca++ binds to troponin
How does the sympathetic neuron affect a smooth muscle such as the tunica media?
Alpha receptor stimulated
G protein released and binds to Phospholipase C
Releases IP3 (inasopholtriphosphate) which binds to ER opening a Ca channel there
Ca++ binds to calmodulin causing a contraction
Sympathetic nerves innervate:
All vessels (except capillaries, pre-capillary sphincters and merarterioles) and the heart
Vasoconstriction fibers highly innervate:
Why?
Kidneys
gut
spleen
skin
Takes blood flow from these during fight or flight
for sympathetic, Vasoconstriction fibers lightly innervate:
Why?
Skeletal muscle and brain
All muscles NOT being used for fight or flight will not need as much blood, so more will go to muscles being used.
In sympathetic vasoconstriction, Norephinephrin release binds to
alpha receptors
for sympathetic, Vasodilator fibers innervate
the heart and some skeletal muscles
in sympathetic vasodilation, norephinephrine release binds to
beta receptors
Parasympathetic nerves innervate;
the heart, but not the peripheral circulation
For parasympathetic, what causes decrease in heart rate and a decrease in force of contraction?
acetylcholine
Location of vasomotor center (control of blood vessels)
Reticular substance in the medulla and pons
In vasomotor center, what does the vasoconstrictor area do?
excites the vasoconstrictor neurons of the sympathetic nervous system
In vasomotor center, what does the vasodilator area do
inhibits the vasoconstrictor area
In vasomotor center, what does the sensory area (tractus solitarius) do?
receives sensory input from baroreceptors (blood pressure receptors)
Aortic baroreceptors transmit signals via:
the vagus nerve
The carotid sinus transmits signals via
Glossopharyngeal nerves
Vasomotor center and the heart- what does the lateral area control
sympathetic activity to the heart
Vasomotor center and the heart- what does the medial area contol
Parasympathetic activity to the heart via the vagus nerve
What has higher control of the vasomotor center?
Motor cortex, limbic system and reticular substance
What controls the long term regulation of BP?
How?
the kidneys by controlling fluid and salt balance (Pressure diuresis and pressue natriuresis)
Renal function curve demonstrates:
the relationship between arterial pressure and urinary output (fluid loss)
As urinary output goes up, what happens to arterial pressure?
it goes up
water balance is determined by:
Renal output of water and salt
and dietary intake of water and salt
Infinite gain principle
when blood pressure increases or decreases, kidney output changes to restore equilibrium
Equilibrium point
water and salt intake matches water and salt output, and BP is normal
What can change the equilibrium point
Changing the level of water and salt intake
alteration of kidney function or pathology
Increased blood volume (INCREASES/DECRESES) CO and BP
Increases
Increased CO causes:
vasoconstriction, increased total peripheral resistance and arterial BP
Increased BP (INCREASES/DECREASES) urine output vis:
Increases
via pressure diuresis and natriuresis
Increased salt intake (INCREASES/DECREASES) blood osmolarity. This causes:
increases
stimulates the thirst center of the brain (hypothalamus)
Increased osmolarity stimulates
ADH secretion from the post. pituitary gland, which increases water reabsorption in the kidneys
Salt is cleared (FASTER/SLOWER) from the body than water
slower
Renin is secreted by:
In response to:
Juxtaglomerular cells of the kidney
in response to low BP
Renin catalyzes what reaction?
Angiotensinogen -> Angiotensin I
What catalyzes this reaction?
Angiotensin I -> angiotensin II
Angiotensin convertin enzyme (lung)
Effects of angiotensin II
Vasoconstriction- increased perioheral resistance and BP
Increased sodium retention by kidneys (therefore fluid retention)
Stimulates release of aldosterone from adrenal cortex
Aldosterone increases:
sodium retention and potassium excretion by the kidneys
Mean arterial pressure (MAP) equation
1/3 Pulse pressure (systolic pressure-diastolic pressure) + diastolic pressure
So, if BP is 120/80, MAP will be:
40/3 + 80 = 93.3 mmHg
Hypertension can cause damage to:
heart, kidneys, brain and other organs
Hypertensive patients are at a higher risk for:
congestive heart failure coronary artery disease renal damage strokes aneurysms
Stage 1 of hypertension BP
Systolic 130-139
or
Diastolic 80-89
Stage 2 of hypertension BP
systolic >140
or
diastolic >90
Primary hypertension, AKA
essential hypertension
idiopathic hypertension
percentage of americans with hypertension that have primary hypertension
95%
treatments of primary hypertension
lifestyle modification
antihypertensive drugs
Secondary hypertension is due to
A known cause that has lead to HT. Treat the underlying disease, HT will improve
Ex of disorders that have HT as a symptom
Primary hyperaldosteroneism
Hypersecretion of renin
renal failure
pheochromocytoma (adrenal medulla tumor)
Non-pharmacologic interventions for primary HT
Weight loss ( ~ 1mmHg for every 1 kg of weight lost) Healthy diet Avoid excess sodium Get enough potassium physical activity moderation of alcohol possibly chiropractic
Anti-hypertensive drug classes
Diuretics ace inhibitors vasodilator drugs beta blockers calcium channel blockers
common substances that can elevate BP
Alcohol amphetamines some antidepressants caffeine some decongestants NSAIDS Cocaine
