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114 Cards in this Set

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  • Back
functions of microcirculation?
-transport of nutrients to tissues.
Site of waste product removal.
Over 10 billion capillaries with surface area of 500-700 square meters 1/8 of a football field
Perform function of solute and fluid exchange
Structure of a capillary wall
-Composed of unicellular layer of endothelial cells surrounded by a basement membrane.
-Diameter of capillaries is 4 to 9 microns.
-Solute and water move across capillary wall via intercellular cleft (fenestrations) (space between cells) or by plasmalemma vesicles
RBC’s are approximately ____ microns in diameter
7.7
Solute and Fluid move Across Capillaries mosty by?
passive diffusion
Most important means by which substances are transferred between plasma and interstitial
fluid is by _________.
diffusion.
________ soluble substances diffuse directly through cell membrane of capillaries (CO2, O2).
Lipid
________ insoluble substances such as H2O, Na+, Cl-, glucose cross capillary walls via intercellular clefts.
Lipid
____________ differences across capillary enhances diffusion.
Concentration
The width of capillary intercellular slit pores is ______ nanometers. (molecues got through, no RBCs)
6 to 7
The permeability of the capillary pores for different substances varies according to their ____________
molecular diameters.
The capillaries in different tissues have extreme differences in their __________.
permeabilities
The width of capillary
intercellular slit pores is _________. (molecues got hrough, no RBCs)
6 to 7 nanometers

6-7 nanos is smaller than albumin
6-7 nanos is about 20X larger than water molecules
In the brain, the pores are _________ and very little gets through.
tight junctions
In the liver the pores are _______ and most substances - including proteins - dissolved in the blood come into contact with hepatocytes
large
G.I tract pores are _______ in size
medium
In kidney glomeruli, small windows ‘fenestrae’ perforate the endothelial cells and allow small molecules and fluid to easily pass into the __________ as filtrate
Bowman’s capsule
muscle capillary pore permeability.....

most permeable to?
least?
most water
least hemoglobin and albumin
As arterioles and caps open and constrict every few seconds, there is a ________ motion of fluid through cellular areas
wave-like
________ levels are the primary controller of vessel dilation and constriction
Tissue oxygen
Space between cells is called
________; fluid in this
space is called _________ fluid.
interstitium
interstitial
Two major types of solid structures in interstitium are _________ and __________.
collagen fibers

proteoglycan filaments (coiled molecules composed of hyaluronic acid).
Almost all fluid in interstitium is in form of _______.
gel (fluid proteoglycan mixtures); there is very little free fluid under normal conditions.
Diffusion of fluid through the gel is easy or hard?
easy and only small fluctuations in conc. will cause molecules to move
______________ enables diffusin from out of the capilary bed.....makes the cell environement jellylike
Proteoglycens
___________ tends to force fluid outward through the capillary membrane.
Capillary hydrostatic pressure (Pc)-
__________ opposes filtration when value is positive.
Interstitial fluid pressure (Pif)-
Determinants of Net Fluid Movement across Capillaries? [4]
Capillary hydrostatic pressure (Pc)-tends to force fluid outward through the capillary membrane.
Interstitial fluid pressure (Pif)- opposes filtration when value is positive.

Plasma colloid osmotic pressure (p c)- opposes filtration causing osmosis of water inward through the membrane
Interstitial fluid colloid pressure (p if) promotes filtration by causing osmosis of fluid outward through the membrane
_________ opposes filtration causing osmosis of water inward through the membrane
Plasma colloid osmotic pressure (p c)-
____________ promotes filtration by causing osmosis of fluid outward through the membrane
Interstitial fluid colloid pressure (p if)
Interstitial Fluid pressure is...
– how much physical pressure is on the interstitial fluid
_________is the pumping force of the heart
Capillary hydrostatic pressure –
Plasma colloidal pressure is –
how ‘salty – is the plasma compared to Interstitial fluid?
Interstitial fluid colloid (osmotic) pressure is...
– how salty is the interstitial fluid compared to plasma?
Normal (and average) Capillary hydrostatic pressure is approximately ___?
17 mmHg.
Interstitial fluid pressure in most tissues is___?

Encapsulated organs have ________ interstitial pressures
-3mmHg

positive (+5 to +10 mmHg).
Negative interstitial fluid pressure is caused by _______?
pumping of lymphatic system.
Colloid osmotic pressure is caused by_________?
presence of large proteins.
Presence of negative ions on proteins _________ the colloid osmotic effect of proteins–Donnan effect.
increases
Plasma colloid osmotic = ___ mmHg
Plasma protein conc. = ___ mg/dl
28mmHg

7.3mg/dl
The __________ of capillaries quantitates the amount of protein that is reflected away from the capillary membrane.
reflection coefficient
Reflection coefficient of 1 means all proteins are _______ and ____ pass through pores
reflected

none
reflection coefficient of 0 means membrane is ________ to all proteins.
permeable
causes of edema? [4]
low albumin
eneropathies
Hight art pressure
High interstitial pressure
___% of the total colloid osmotic pressure of plasma results from the presence of albumin and __% is due to globulins.
75

25
Interstitial protein conc. is approx.______
The interstitial colloid osmotic pressure is normally______
3gm/dl

8mmHg
Filtration rate = net filtration pressure (NFP) multiplied by the filtration coefficient
Filtration coefficient (Kf) is a product of surface area times the hydraulic conductivity of membrane
xxxxxxx
Forces tending to move fluid outward from arteriole ind of the capillary [3]
Capillary pressure 30
Negative interstitial free fluid pressure 3
Interstitial fluid colloid osmotic pressure
Force tending to move fluid inward at arteriole end of the capillary.
Plasma colloid osmotic pressure 28
what force tends to move fluid inward at the venous end of the capillary?
Plasma colloid osmotic pressure 28
what Forces tend to move fluid outward at the venous end of the capillary? [3]
Capillary pressure 10
Negative interstitial free fluid pressure 3
Interstitial fluid colloid osmotic pressure
Starling says – fluid’s almost in _________. Only a tiny amount of fluid remains in the tissues and that gets drained by the lymphatics
equilibrium
Lymphatic System [5]
-An accessory route by which fluid and protein can flow from interstitial spaces to the blood
-Important in preventing edema
-Lymph is derived from interstitial fluid that flows into the lymphatics
-A major route for absorption of nutrients from the GI tract
-Plays important role in the immune system
Determinants of Lymph Flow [2]
-The degree of activity of the lymphatic pump (smooth muscle filaments in lymph vessel cause them to contract
external compression also contributes to lymphatic pumping)
-Interstitial fluid hydrostatic pressure
hassall's corpuscle?
in thymus
Each tissue controls its own blood flow in proportion to _______.
its needs
Tissue needs include: [5]
1) delivery of oxygen to tissues
2) delivery of nutrients such as glucose, amino acids, etc.
3) removal of carbon dioxide, hydrogen and other metabolites from the tissues
4) transport various hormones and other substances to different tissues
5) maintain normal fluid concentrations
Flow is closely related to ______ rate of tissues.
metabolic
Acute Control of Local Blood Flow
Increases in tissue metabolism lead to increases in blood flow.
Decreases in oxygen availability to tissues increases tissue blood flow.
Two major theories for local blood flow are:
1) The vasodilator theory
2) Oxygen demand theory
Decreases in oxygen availability to tissues ____ tissue blood flow.
increases
Vasodilator theory
– as cells metabolize ATP, adenosine is released into the interstitial fluid and causes cap.s and arterioles to dilate. Other possible dilators – CO2, histamine, K+ ions and H+ ions from lactic acid
Oxygen lack theory
– or nutrient lack – smooth MM contraction in the cap. Sphincters and meta-arterioles, require Ox to sustain the contraction. As Ox drops, the sphincters begin to lose strength and open. Other dilators – drop in glucose, vitamin deficiency Bs esp: niacin, thiamine, riboflavin will cause dilation.
As arterial oxygen drops, blood flow___?
increases
As tissue Ox decreases - pneumonia, high altitude, CO poisoning, cyanide poisoning – flow ______?
increases
Vasodilators:[7]
Adenosine, CO2, Lactic acid, ADP compounds, Histamine, K ions, H ions
Active hyperemia – tissue is metabolically active and blood flow is ?
high.
Reactive hyperemia – Blood flow is occluded for a time, then restored, flow to the tissue is...
high, long enough to reduce the tissue debt
ability of a tissue to maintain blood flow relatively constant over a wide range of arterial pressures is?
Autoregulation -
Blood Flow Autoregulation Theories [3]
Metabolic theory suggests that as arterial pressure is decreased, oxygen or nutrient delivery is decreased resulting in release of a vasodilator.
Myogenic theory proposes that as arterial pressure falls the arterioles have an intrinsic property to dilate in response to decreases in wall tension.
Certain tissues have other mechanisms for blood flow control. Kidneys have a feedback system between the tubules and arterioles. The brain blood flow is controlled by carbon dioxide and hydrogen ion conc.
Kidneys have a feedback system between the
tubules and arterioles. Juxtaglomerular apparatus and distal convoluted tubular cells.
The brain blood flow is controlled by
carbon dioxide and hydrogen ion conc- from lactic acid - or any acid accumulation
Long-term regulatory mechanisms which control blood flow are _____ effective than acute mechanism.
more
Long-term local blood flow regulation occurs by changing the degree of
vascularity of tissues (size and number of vessels).
______ is an important stimulus for regulating tissue vascularity.
OxygenAngiogenesis
_____ is the growth of new blood vessels.
Angiogenesis
Autogenesis occurs in response to angiogenic factors released from: [3]
1) ischemic tissue
2) rapidly growing tissue
3) tissue with high metabolic rates
Most angiogenic factors are ___ ?
small peptides such as vascular endothelial cell growth factors (VEGF), fibroblast growth factor (FGF), and angiogen.
Humoral regulation of blood flow
[2]
Vasoconstrictors
Vasodilator agents
Vasoconstrictors [5]
Norepinephrine – powerful vaso constrictor
Epinephrine – can be a dilator in cardiac MM
not as powerful a constrictor
Angiotensin II – constricts areas. Esp small arterioles
Vasopressin (ADH) – can greatly raise BP esp after trauma
Endothelin – released after BV damage, causing vessel spasm
Vasodilator agents
Bradykinin – arteriole dilation and cap permeability
Histamine – “ “
Prostaglandins – “ “
Nitric oxide – as Endothelial Derived Relaxing Factor – as press in cap.s h sheer forces on endoth cells cause release of EDRF
And vessel dilates
Nervous Regulation of Circulation * Autonomic * [4]
Redistribution of blood flow
Increasing pumping activity of the heart
Rapid control of arterial pressure
Regulates via the autonomic nervous system
Arterial Pressure can be increased by: [3]
Constricting almost all arterioles of the body which increases total peripheral resistance.

Constricting large veins thereby increasing venous return and cardiac output.

Directly increasing cardiac output by increasing heart rate and contractility.
Sympathetic nervous system
is important in control of circulation by controlling ______.
vessel diameter.
Parasympathetic nervous system is important in regulating ?
heart function esp. rate.
Sympathetic nerve fibers
innervate all vessels except
capillaries and precapillary sphincters and some metarterioles – primarily controlled by local tissue demands.
Innervation of small arteries and arterioles allow sympathetic nerves to ________ vascular resistance.
increase
Large veins and the heart are also _________ innervated.
sympathetically
Parasympathetic nervous system is mainly important in control of heart rate via
the vagus nerve. Lowers hrt rt and contractility.
Sympathetic Vasoconstrictor System
Vasoconstrictor area bilaterally on the anterior medulla – excite pre-gang fibers throughout the CNS
Vasoconstrictor fibers are distributed throughout all segments of the circulation.
Distribution is greater in kidneys, gut, spleen, and skin.
Less potent in skeletal muscle and the brain.
The ________ transmits impulses downward through the cord to almost all blood vessels.
VMC
The Vasomotor Center (VMC)
The VMC transmits impulses downward through the cord to almost all blood vessels.
VMC is located bilaterally in the reticular substance of the medulla and the lower third of the pons.
The VMC is composed of a vasoconstrictor area, vasodilator area, and sensory area.
Functions of the Vasomotor Center (Part I)
Vasoconstrictor area of VMC transmits signals continuously to sympathetic nerve fibers called sympathetic vasoconstrictor tone. These impulses maintain partial state of contraction in blood vessels called vasomotor tone.
Lateral and superior portions of VMC control heart activity by increasing heart rate and contractility. Excitatory
Medial and inferior portions of VMC transmit signals via vagus nerve to heart to decrease heart rate.
VMC Affects Vessel Function via Neurotransmitters
The neurotransmitter for the vasoconstrictor nerves is norepinephrine. Alpha adr. receptors

Adrenal medulla secretes both epinephrine and norepinephrine which constricts some blood vessels via alpha adrenergic receptors.

Epinephrine can dilate some vessels through a potent Beta2 receptor.
Adrenal medulla secretes both and which constricts some blood vessels via alpha adrenergic receptors.
epi and morepi
The neurotransmitter for the vasoconstrictor nerves is
norepinephrine. Alpha adr. receptors
Many higher centers of the brain such as the _____ and _________can exert powerful excitatory or inhibitory effects on the Vasomotor Center.
hypothalamus and thalamus
The nervous system can increase AP within seconds by:
constricting almost all arterioles of the body which increases total peripheral resistance
constricting large veins thereby increasing venous return and cardiac output
directly increases cardiac output by increasing heart rate and contractility
Arterial Baroreceptor Reflex
Important in short term regulation of arterial pressure.
Reflex is initiated by stretch receptors called baroreceptors located in the walls of the large systemic arteries.
A rise in pressure stretches baroreceptors and causes them to transmit signals to the VMC and feedback signals are sent via the automonic nervous system to the circulation to reduce AP back to normal.
Baroreceptors are ‘spray’ type nerve endings located in
the walls of the carotid bifurcation called the carotid sinus and in the walls of the aortic arch.
Signals from the carotid sinus are transmitted by the ______ nerve to the ______ nerves and then to the_______ of the medulla.
Hering’s

glossopharyngeal

nucleus tractus solitarius (NTS)
Signals from the arch of the aorta are transmitted through the _____ into the Solitary Nucleus.
vagus
Response of the Baroreceptors to Arterial Pressure
Carotid sinus baroreceptors respond to pressures between 60 and 180 mmHg.
Baroreceptors respond to changes in arterial pressure.
Baroreceptors reflex is most sensitive at a pressure of 100mmHg.
As pressure increases the number of impulses from carotid sinus increases which results in:
1) inhibition of the vasoconstrictor
2) activation of the vagal center
the _________ maintains relatively constant pressure despite changes in body posture.
baroreceptors
___________ are unimportant in long term control of arterial pressure because they adapt.
baroreceptors
Carotid and Aortic Chemoreceptors
Chemoreceptors are chemosensitive cells sensitive to oxygen lack, CO2 excess, or H ion excess.
Chemoreceptors are located in carotid bodies near the carotid bifurcation and on the arch of the aorta.
Activation of chemosensitive receptors results in excitation of the vasomotor center.Chemoreceptors are not stimulated until pressure falls below 80mmHg.
Chemoreceptors are chemosensitive cells sensitive to
oxygen lack, CO2 excess, or H ion excess.
Activation of chemosensitive receptors results in _______ of the vasomotor center.Chemoreceptors are not stimulated until pressure falls below 80mmHg.
excitation
CNS Ischemic Response
CNS Ischemic response is activated in response to cerebral ischemia.
Reduced cerebral blood flow causes CO2 buildup which stimulates vasomotor center thereby increasing arterial pressure.
CNS Ischemic response is one of the most powerful activators of the sympathetic vasoconstrictor system.
CNS Ischemic Response
CNS Ischemic response is not activated until pressure falls below 60mmHg; greatest activation occurs at pressures of 15-20mmHg.
Cushing reaction is a special type of CNS ischemic response. When rising CSF pressure equals art. pressure, art.s collapse and blood flow to brain is reduced. Then art. pressure is elevated to be above CSF pressure
Prolonged CNS ischemia has a depressant effect on the vasomotor center.
_______ is a special type of CNS ischemic response. When rising CSF pressure equals art. pressure, art.s collapse and blood flow to brain is reduced. Then art. pressure is elevated to be above CSF pressure
Cushing reaction
Prolonged CNS ischemia has a _______ effect on the vasomotor center.
depressant
what helps maintain constant normal pressure when atria are stretched?
‘Low pressure receptors’ in atria and pulmonary
Atrial and Pulmonary Artery Reflexes
‘Low pressure receptors’ in atria and pulmonary arteries lower arterial pressure in response to increases in blood volume.
They help maintain constant normal pressure when atria are stretched.
Increases in blood volume activate low pressure receptors which in turn lower arterial pressure.
Stretch of atria also activate of low pressure receptors which increase afferent art. diameter. Volume reflex
Stretch of atria also activate of low pressure receptors which increase afferent art. diameter. Volume reflex, which is...[5]
-Increase filtrate production
-Decreasing rate of antidiuretic hormone
-Increasing glomerular filtration rate
Decreasing Na reabsorption
- Reduces body fluid volume
Bainbridge Reflex
Prevents damming of blood in veins, atria and pulmonary circulation.
Increase in atrial pressure increases heart rate by stretching S.A. node.
Stretch of atria sends signals to VMC via vagal afferents to increase heart rate and contractility.