exam 2 Flashcards
____ carry blood away from heart, ___ carry blood towards the heart
- arteries branch and vessel diameters get smaller as go away from heart
- veins merge and vessel diameters get larger as go back to heart
arteries; veins
_____ experience higher BP, greater fluctuations in pressure than veins
Arteries closest to the heart experience the greatest blood pressure and fluctuations
* Affects composition and thickness of vessel walls → concentric layers or “tunics” around vessel lumen (note: the names for types of arteries give you clues to this!)
arteries
_______ must carry blood back towards the heart
under low pressure
Blood below the level of the heart must also be moved
against gravity → need assistance to keep blood flowing towards the heart, prevent the backwards flow of blood
veins
Differences in vessel composition correspond largely to differences in _____
pressure
Thicker vessel wall (especially tunica media), elastic membranes, and elastic facilitate the functions of _____
arteries
As vessel diameter decreases, resistance to flow ______
increases
As we move toward the heart (i.e., through veins) the diameter ______.
increases
_______ reduces resistance, increases flow
Vasodilation
_____ increases resistances, reduces flow
vasoconstriction
As blood moves away from the heart through arteries, arteries branch, lumen diameter ______ and composition of the vessel wall changes
decreases
_______ (elastic, large) arteries are the first to receive blood from the heart → experience highest pressure
- Contain alternating thin layers of smooth muscle, collagen, and elastic fibers
- Relatively inactive in vasoconstriction (i.e., routing blood flow to/away from areas of the body)
Serve as pressure reservoirs for smooth blood flow
Conducting
Adjusting blood flow to meet tissue/organ demands: changing ____ _____ (amount of blood pumped by a ventricle in 1 minute, mL/min)
cardiac output
center of medulla (sympathetic)
Cardioacceleratory center
center of medulla
(parasympathetic)
* Vagal tone
* Affect potassium outflow to get less
frequent depolarization
Cardioinhibitory center
accelerate contraction, ventricular filling, and relaxation -> increase heart rate
Epinephrine and norepinephrine accelerate depolarization
These are in the carotid arteries and aorta, there are different baroreceptors in the walls of the atria that when overstretched activate a reflex arc that increases heart rate (atrial reflex)
baroreceptors
affect heart rate
Chronotropic agents (time)
affect the contractility (contractile strength at a given length)
inotropic agents (affect stroke volume)
caffeine is both chornotropic and inotropic that increases both heart rate and cardiac output
study slide 11
degree of stretch of the heart muscle
* Cardiac muscle at rest is at a suboptimal length (stretching moves it towards the optimal length)
* Makes stroke volume proportional to end diastolic volume (Frank-Starling Law)
Preload
pressure that must be overcome to eject blood (back pressure arterial blood)
- Should be relatively constant
- Issue in patients with
hypertension
Afterload
Vasodilationreducesresistance, _____ flow
increases
Vasoconstriction increases resistance, _____ flow
reduces
- Length of blood vessels explains blood pressure changes as children grow, relatively constant in adults
- Blood viscosity affected by hydration, RBC production
- Turbulence caused by damage to vessels, atherosclerosis
Other factors that affect resistance are not adjustable in the moment
- Localized, near-instantaneous adjustments
- From within the organ or tissue itself
- Signals typically have short-term effects on precapillary sphincters, can also affect arterioles
- Local regulation (autoregulation or intrinsic regulation):
- Want to ensure pressure and volume within the system maintained when:
- Tissue demands shift (for e.g., rest vs exercise)
- Something affects fluid balance in the body (for e.g., hydration levels) * There is blood loss (hemorrhage)
- Nervous and/or endocrine system involved
- Systemic (central or extrinsic) regulation:
Too high – affects workload on heart, stress on ____ _____ in maintaining BP
blood vessels
Too low – affects ____ ____ in maintaining BP
tissue perfusion
- _____ signaling affects water loss in urine, blood pressure (via effects on cardiac output and blood vessels), and red blood cell formation
endocrine
- Need pressure to decrease to prevent damage to fragile capillaries
- Increase in resistance due to decreasing luminal diameter of blood vessels helps accomplish this
- Need to allow sufficient time for resources to be exchanged
- Blood velocity decreases at capillaries due to increase in total cross-sectional area -> gives time for exchange!
- Need to ensure resources go into tissues once they reach the associated capillaries
As we near the capillaries, we encounter different challenges
- diffusion through plasma membrane (lipid-soluble substances)
- movement through intercellular clefts (water-soluble substances)
- movements through fenestrations (water-soluble substances)
- transport via vesicles or caveolae (large substances)
mechanisms by which substances are exchanged btw capillaries and interstitial fluid
Blood proteins remain in _____ (blood colloid osmotic pressure)
capillaries
Along the length of the capillary:
* Capillary hydrostatic pressure (CHP) pushes fluid out of the capillary lumen
*Blood colloid osmotic pressure (BCP) pulls fluid back in
Net movement of fluid (and direction of that movement) determined by the difference between hydrostatic and osmotic pressure
Direction of fluid movement relative to capillaries is determined by net filtration pressure
*Anything that affects ____ and ___ can alter delivery of resources, waste removal at capillaries
CHP, BCOP
T/F Fluid leaves capillaries at the arteriole end and returns at the venule end
Fluid that is not reabsorbed is returned to the cardiovascular system by lymphatic vessels
T
Can you explain how each of the following would affect the net movement of fluids at the capillaries AND why?
1. Plasma albumin deficiency.
2. Obstructed lymphatic drainage.
Plasma albumin deficiency decreases oncotic pressure in capillaries, reducing fluid reabsorption and leading to edema as more fluid remains in the interstitial space.
Obstructed lymphatic drainage prevents excess interstitial fluid and proteins from being cleared, causing fluid accumulation and swelling (lymphedema).
flow is directly or indirectly proportional to the pressure gradient and is inversely proportional to resistance
directly
resistance is directly or inversely proportional to the 4th power of the vessel radius
inversely —- vessels further from the heart contribute more to resistance (and flow) than those near the heart
