Control of Blood Flow Flashcards
What are blood vessels used for?
- delivery of nutrients
- removal of waste
How do blood vessels deliver nutrients?
microvascular exchange
What is the total volume of capillaries?
4.8 liters
What is the blood volume in capillaries?
1.8 liters
What is the relationship between blood volume and total volume in capillaries?
blood volume in capillaries is less than total capillary volume
Where is the blood velocity the lowest?
in capillaries
What is the difference in speeds of blood velocity throughout the body?
fast in major arteries> slows down in capillaries> fast towards heart> slow in lungs
Where is blood volume the most?
in veins
Veins are known as what?
capacitance vessels
Arterioles are known as what?
resistance vessels
What is the function of arterioles?
regulate systemic vascular resistance
What do arterioles respond to?
- tissue demand
- flow and pressure inside the vessel
- neurogenic stimuli
- hormones, drugs, other chemical stimuli
What is the regulation of arteriolar tone?
Ca comes into smooth muscle muscle and causes contraction
How does the sympathetic nervous system control arteiolar tone?
- releases norepinephrine
- alpha receptors on vascular smooth muscle cells cause constriction
- IP3 causes Ca release from sarcoplasmic reticulum
How does the parasympathetic nervous system control arteiolar tone?
- Ach binds to muscarinic receptors on endothelial cells
- activates eNOS: nitric oxide diffuses to VSMC> soluble GC> cGMP> dilation
What is the process of preparation of autoregulation of blood flow?
- endothelium NOT involved
- myogenic response eliminated by treatment with nitrates
- VSMC alone is required
What is included in the autoregulation of blood flow?
- pressuere is raised/lowered equally t both ends
- vessel diameter can b edtermined precisely using microscopy
- endothelial cells can be removed mechanically or chemically
What is the myogenic hypothesis of autoregulation?
vascular smooth muscle contracts in repsonse to an increase in pressure
increased transmural pressure> increased stretch> constriction
What is active hyperemia?
increased metabolic activity creates byproducts that induce and increase blood flow
example: doing multiple reps at gym
What is reactive hyperemia?
buildup of waste products induce reactive hyperemia once blood flow is reestablished
example: having boulder fall on arm and taken off some time after
What is the mtabolic hypothesis of autoregulation?
lack of O2> metabolic byproducts> vasodilation
What is the flaw of the metabolic hypothesis?
flawed when attempting to explain what happens when blood flow increases
What is the flaw of the metabolic hypothesis?
flawed when attempting to explain what happens when blood flow increases
What is the flaw in the myogenic hypothesis?
does a poor job of explaining how metabolic activity or increased flow leads to dilation
What occurs with pressure with flow-induced vasodilation?
pressure is increased on one side and lowered on the other equally
increased flow without changing pressure
What is the endothelial regulation of blood flow?
senses mechanical forces and stimulates vasodilation in response to an increase in flow by producing an “endothelial-derived relaxing factor” (nitric oxide)
What is the summary local control of blood flow?
- metabolic autoregulation -> metabolism
- myogenic autoregulation -> pressure
- endothelial-dependent control of arteriolar tone -> flow
- autonomic nervous system
What are the 3 types of blood capillaries?
- continuous: cell-cell junctions (allows least amount of things through)
- fenestrated: fenestrae (only fluid)
- sinusoidal: caveolae
Are blood capillaries permeable?
YES
What is blood vessel permeability is required for?
- bathing tissues in nutrients and removal of wastes
- maintaining basal permeability to prevent edema
- inflammatory responses: increased vascular permeability is the first step in inflammation
- regulating the transmigration of immune cells to fight infection/resolve inflammation
What are the 4 R’s of inflammation?
- tumor: swelling
- rubor: redness
- calor: hot
- dolor: pain
How does material leave the capillaries?
by convection (filtration) or diffusion (osmosis)
What is Ernest Starlings hypothesis on the law of filtration?
fluid is filtered from the arterial side of the capillary bed and 90% is reabsorbed on the venous side
What is the formula for Ernest Starling’s hypothesis?
Jv/s = Lp [(Pc-Pi) - sigma (pi c - pi i)]
Why was Ernest’s theory incorrect?
becuase vessels cannot both filter and reabsorb fluid
If Jv/s is negative then…
more fluid flows in
If Jv/s is positive then…
mroe fluid flows out, high hydrostatic, low oncotic
What the formula of Fick’s first law of diffusion?
Js = PS change in C= PS (Cc - Ci)
What is Fick’s first law of diffusion?
molecules move from the higher conc. to the lower conc.
What is the process of lymphatic vasculature?
- lymphatic vessels begin in tissues as bilnd ended sacs that absorb big cells
- large/immune cells merge into collecting lymphatic vessels
- lymphatic vesslels take immune cells to lymph nodes -> immune reactions
- lymph nodes -> thoracic duct -> left subclavian vein
What is tissue fluid homeostasis?
removal of excess fluid from tissue
What is the role of lymphatic vessels during tissue fluid homeostasis?
- actively pump
- regulate endothelial permeability
How do lymphatic vessle prevent edmea?
- increased tissue pressure drives lymph flow, which clears excess fluid
- being permeable
must have hydrostatic pressure
What is the largest lymphatic and empties all lymph into left subclavian vein?
thoracic duct
What is responsible for 85% of osmotic pressure gradient and is removed from tissues by lymphatic vasculature?
albumin
What is lymphedema?
occurs when lymphatic vessels fail to remove fluid and interstitial fluid builds up
What does increased lymphatic vessel permeability lead to?
adipose deposition and obesity
Cholesterol removal from atherosclerotic plaques depend on what?
lymphatic vessels
