Chapter 9.3: Cardiac 5 and 6 Flashcards
____ are the vascular components that carry the fluid between the pump and body tissue
vessels
Most populous blood vessel
capillary
physical features of arteries.
Thick, highly elastic walls, large radii
physical features of artieles
highly muscular, well INNERVATED, smaller radii
physical features of capillaries
very thin walled, but LARGE CROSS SECTIONAL AREA
physical features of veins
thin walled compared to arteries, highly distensible, large radii.
Which vessel type is actually innervated by the symp nervous system?
arterioles.
which vessel provides primary resistance of the circulatory system? which vessel determines the distribution of cardiac output?
arterioles for both
Which vessel provides PRESSURE of the circulatory system?
arteries
which vessels are the site of exchange and determines the distribution of ECF between plasma and interstitial fluid?
capillaries
which vessels serve as a blood reservoir?
veins
which vessel has the most elastic fibers? Which vessels has the least amount of smooth muscle? which fiber has the most collagen?
most elastic fibers: artery
LEAST smooth muscle: capillaries
most collagen: veins
all vessels have smooth, flattened ____ cells. What are these cells continous with?
all vessels have endothelium cells that are continuous with the heart’s endocardial lining.
__ ___ give the artery wall elasticity and allows it to withstand the high pressure generated by the heart
elastin fibers.
maximum pressure exerted in arteries is during ____, and minimum pressure in arteries is during ____
maximum pressure exerted in arteries is during SYSTOLE, and minimum pressure in arteries is during DIASTOLE
Why does pressure in arteries never fall to 0?
because the next cardiac contraction occurs.
What is the dichrotic notch?
a small flucutation in pressure between systolic and diastolic pressure as a result of the (closing of the aorta?)
2 main functions of arteries
1) rapid transit passageways for blood from the heart to the tissues
2) a pressure reservoir to provide the driving force for blood when the heart is relaxing.
How do arteries act as a method of rapid transit from heart to tissues?
they have a large radii that offer LITTLE RESISTANCE to blood flow
also less cross sectional area, ensures high velocity from heart to organs.
pressure in the heart is ___ immediately following contraction when it starts to fill again.
pressure in heart is 0
T/F: flow in capillaries is continuous
true. doesn’t fluctuate between systole and diastole, or when the pressure in the heart is 0
During ventricular systole, ____ volume of blood enters the arteries than ___ the arteries. What does this result in?
During ventricular systole, GREATER volume of blood enters the arteries than LEAVES the arteries.
This results in artery expansion. blood cannot leave the arteries as fast as it enters because there is greater resistance in downstream vessels.
What happes to flow rate in arteries? velocity?
flow rate remains the same, but velocity of flow changes.
What is the driving force of continued blood flow in the arteries?
the elastic properties of the arterial walls. Recoil pushes excess blood in arteries into downstream vessels.
Pressure in arteries does fluctuate between systole and diastole.
Why is “upstream pressure” in arteries (to arterioles) always ELEVATED over downstream pressure, and blood flow rate is continuous?
while the heart is relaxing pressurized arteries deflate and push blood downstream (FLOW RATE CONTINUOUS, and relaxed heart has pressure 0, therefore upstream pressure is elevated). As deflating ends, heart contracts and arteries become pressurized.(ELEVATED PRESSURE)
when heart contracts and empties, arteries ___
expand. Occurs during systolic pressure.
When heart relaxes and fills, arteries ___ ___
passively recoil.
an artery branches into numerous ____ near each organ
arterioles.
major functions of arterioles
1) to variably distribute the cardiac output among the systemic organs, depending on the body’s needs
2) to help regulate body-wide arterial blood pressure.
the resistance of the arterioles is reflected in the:
marked drop in local pressure as blood flows through the arterioles.
Why is there so much resistance of arterioles?
because they have very little elastic connective tissue. .
What part of the autonomic nervous system innervates arterioles?
They have a thick layer of smooth muscle that is richly innervated by SYMPATHETIC NERVE FIBERS
In addition to the little elastic connective tissue, why else is there such high resistance in arterioles?
bc sympathetic innervation causes contraction (vasoconstriction) of smooth muscle, resulting in the vessel RADIUS DECREASE, increasing resistance and decreasing flow throughout the vessel.
the sympathetic innervation of smooth muscle maintains ___ ___: a state of partial constriction
vascular tone. This is due to MYOGENIC ACTIVITY and continued release of NE from the sympathetic nerve fibers.
The amount of cardiac output received in a GIVEN ORGAN is determined by the ___ and ___ of the ___ supplying that area. Why not (delta) pressure?
The amount of cardiac output received in a GIVEN ORGAN is determined by the NUMBER and DIAMETER of the ARTERIOLES supplying that area.
Delta P is the SAME for each organ because it relies on arteries, therefore difference is determine by the density of blood vessels (vascularization and resistance)
Two methods to controlling arterioles (typically their radius)
1) intrinsic control: important for matching blood flow to the metabolic needs of the specific tissue
2) extrinsic control: important for diverting blood among organs to where it is needed and also body-wide BP REGULATION
Name some Local metabolic changes (an intrinsic control factor) that relax smooth muscle in arterioles
relaxing smooth muscle = vasodilation = hyperemia (more blood flow)
1) decrease O2
2) increased CO2
3) increase acid
4) increase K+
5) increased osmolarity (salts)
6) ADENOSINE RELEASE
5 factors that intrinsically control the arteriole radius
1) local metabolic changes (ex/ decreased O2)
2) histamine: released from local immune cells in tissues that are injured. Triggers increase in blood flow (swelling)
3) local temp changes
heat= vasodilation
cold = vasoconstriction
4) stretch: myogenically respond to stretch by vasconstricting and vasodilation when theres a reduction in stretch.
5) local vasoactive mediators secreted by ENDOTHELIAL CELLS in response to local chemical and physical changes.
example of a vasoactive intrinsic mediator. What cell secretes vasoactive mediators?
ex/ Nitric oxide, which causes RELAXATION in arteriole by increasing concentration of intracellular cGMP.
endothelial cells secrete intrinsic mediators.
Extrinsic control mechanisms that can influence arteriole radius and “override” intrinsic mechanisms.
1) sympathetic nerve influence
2) adrenal hormone influence
3) parasympathetic nerve influence
4) muscular activity
5) cardiovascular control center (in brain)
6) other hormones
How does sympathetic innervation act as an extrinsic control of arteriole radius? What receptors are involved? which arterioles in the body lack these receptors?
NE released from sympathetic nerve endings combines with ALPHA 1 ADRENERGIC RECEPTORS (Recall 1= excitatory, 2= inhibitory) on arteriole smooth muscle and causes VASOCONSTRICTION.
Brain and alveoli arterioles do not have alpha 1 receptors, so no vasoconstriction happens in these areas.
How does adrenal gland medulla act as an extrinsic control of arteriole radius? which receptors are involved?
epinephrine released from AGM combines with both BETA 2 and ALPHA 1 reecptors, with more affinity for BETA 2.
Epinephrine causes VASODILATION. (2 = inhibitory)
where are beta 2 receptors most abundant?
in heart and skeletal muscle. Kidney and digestive tract only have alpha receptors and therefore undergo vasoconstriction in response to NE or Epinephrine.
epinephrine causes vaso___ whereas NE causes vaso ___
epinephrine causes vasoDILATION (via stimulation of Beta 2) whereas NE causes vaso CONSTRICTION (via stimulation of alpha 1)
how does parasympathetic nerve influence affect arterioles?
barely affects it. arterioles are primarily innervated by SYMPATHETIC SYSTEM
exception: arterioles of mammalian penis and clitoris have abundant parasympathetic innervation, which causes vasodilation by promoting release of NO. ( an intrinsic mediator, vasodilator)
how does skeletal muscle activity cause vasodilation? is this an extrinsic or intrinsic method of regulating arteriole radius?
EXTRINSIC symp system during muscle (LOCOMOTORY ACTIVITY) can vasodilate arterioles of skeletal muscle and heart in anticipation of activity (and vasoconstriction in digestive tract to divert blood to other organs)
beta 1 receptors primarily found in ___ and ___, alpha receptors primarily found in __ and ___
beta receptors primarily found in HEART and SKELETAL MUSCLE, (beta 2 receptors found in smooth muscle of gut) alpha receptors primarily found in KIDNEY and DIGESTIVE TRACT
which hormones can act as extrinsic control of arteriole radius?
vasopressin and angiotensin II, which constricts and is related to fluid balance.
NOT NO, which is an intrinsic factor and is a paracrine
____ branch extensively to bring blood within reach of every cells
capillaries
What is the equation of Ficks capillary law and state it.
Rate of diffusion (Q) = (CxAxD)/ (X)
Diffusion is proportional to the surface area, concentration gradient and diffusion rate, and inversely proportional to the distance the molecule has to travel from the blood to the surrounding cells.
why is the rate of diffusion really fast in capillaries?
recall Ficks equation
A= area. capillaries have a lot of surface area due to their numbers, and diffusion is directly related to area
C= concentration. Blood composition and PERFUSION enhance the capillary-tissue concentration gradient.
- blood has high conc of O2, so O2 will move to tissues naturally
- Perfusion is regulated by constriction/dilation capillary and this alters concentration gradietns.
X= diffusing molecules have only a hsort distance to travel between the blood and surrounding cells. Capillary walls are very thin, so O2 doesn’t have to travel very far.
The shorter the distance between blood and tissue, the FASTER the rate of diffusion.
what is perfusion?
passage of blood through circulatory system
what is a metaarteriole
a vessel that runs between an arteriole and a venule.
capillaries typically branch either directly from an ___ or from a __
capillaries typically branch either directly from an ARTERIOLE or from a METAARTERIOLE
metarterioles are surrounded by wisps of smooth muscle cells to form ___ ___.
PRECAPILLARY SPHINCTERS. each consisting of a ring of smooth muscle around the entrance to a capillary as it arises from a metarteriole.
T/F Precapillary sphincters are innervated
false, but they have a high degree of myogenic tone such that most are CLOSED
___ and __ ___ both regulate perfusion
arterioles and precapillary sphincters.
T/F: blood flows quickly through capillaries
false. blood flows much more slowly in them than else where in the circulatory system, allowing more time for diffusion to occur.
Velocity of blood flow is inversely proportional to the __ __ __ of all the vessels at any given level of the circulatory system.
flow rate (VOLUME/time within an area) is the ___, but velocity of flow ____
Velocity of blood flow is inversely proportional to the CROSS SECTIONAL AREA of all the vessels at any given level of the circulatory system.
flow rate (VOLUME/time within an area) is the SAME, but velocity of flow CHANGES (as area (of capillary ) increases, the velocity decreases)
___ __ is a passive intermediate between blood and cells
interstitial fluid
What is bulk flow?
when constituents of the fluid move together in bulk with the fluid itself.
purpose of bulk flow to cells
determines the DISTRIBUTION of the ECF volume between the vascular and interstitial fluid compartments.
Ultrafiltration occurs when the pressure inside the capillary is ____ than pressure outside
GREATER than pressure outside. causes fluid to be pushed out through PORES of the capillaries into surrounding cells/area
Reabsorption occurs when inward-driving pressures ___ outward-driving pressures across a capillary wall. What happens to fluid during reabsorption?
Reabsorption occurs when inward-driving pressures EXCEEDS outward-driving pressures across a capillary wall.
Fluid thus moves back into capillaries through pores.
bulk flow from capillaries occurs because of differences in the ____ and __ ___ pressures between the plasma (in capillaries) and interstitial fluid.
bulk flow from capillaries occurs because of differences in the HYDROSTATIC and COLLOID OSMOTIC pressures (both from capillary/plasma and insterstitial fluid)
4 factors influencing bulk flow
1) capillary blood pressure
2) plasma collois osmotic pressure
3) interstitial fluid hydrostatis pressure
4) interstitial fluid colloid osmotic pressures
Capillar blood pressure forces fluid ____ (out of/into) capillaries. What is capillary blood pressure?
OUT OF. CBP is The hydrostatic pressure exerted on the INSIDE of the capillary walls by the blood
Plasma-colloid osmotic pressure causes ___ movement ____ (into/outof) capillaries by ____ . What is this type of pressure?
Plasma-colloid osmotic pressure causes WATER movement INTO (into/outof) capillaries FROM INTERSTITIAL FLUID by OSMOSIS.
PCO pressure is a force caused by the colloidal dispersion of plasma proteins. (proteins in the plasma/capillaries are in high conc, ATTRACTS WATER)
Institial fluid hydrostatic pressure forces fluid ___ capillary. What is this type of pressure?
forces fluid INTO capillary from interstitial site. This is fluid pressure exerted on the OUTSIDE OF THE CAPILLARY WALL by the ISF
Interstitial fluid-colloid osmotic pressure results from:
How are these returned to blood?
Does this type of pressure have a big effect on bulk flow?
interstritial fluid colloid osmotic pressure results from a few plasma proteins that leak across the capillary walls into the ISF (shouldn’t usually happen)
These proteins are returned to the blood through the lymphatic system
this type of pressure DOES NOT have a bid effect on bulk flow because there are not many plasma proteins in the ISF to bein with, so the pressure is close to 0.
by combining hydrostatic and colloid osmotic forces, a ___ net pressure exists at the ___ of the capillary that allows for ____
by combining hydrostatic and colloid osmotic forces, a POSITIVE net pressure exists at the BEGINNING of the capillary that allows for ULTRAFILTRATION
What end of the capillary has more pressure? Why?
the arterial end hs more pressure, and by the time the venular end of the capillary is reached, outward pressure has dropped becuase CAPILLARY BLOOD HYDROSTATIC PRESSURE HAS DROPPED
BULK FLOW is extremely important in regulating the ____ of ___ between the plasma and interstitial fluid
bulk flow is important in regulating the distribution of the ECF between the plasma and the interstitial fluid.
Blood leaves capillary beds and enter into ___ and then ___
enter into venules and then veins
2 main functions of venules and veins
1) passage back to heart
2) blood resevoir.
Why do systemic veins have a capacity for blood storage? What characteristics lead to this?
because they can easily stretch and not recoil.
key characteristics:
1) they have more collagen fibers than elastin= far less elasticity (no recoil)
2) less smooth muscle that has little myogenic tone
3) valves prevent backflow.
The velocity of blood flow ___ as the blood approaches the heart despite the lower pressure. Why?
INCREASES. compared to capillaries (where the blood was just at), the veins have smaller cross sectional area and thus it needs to flow faster in order to maintain flow rate.
venous capacity
the volume of blood that the veins can accommodate
what does venous capacity depend on
the distensibility of the vein ( ability to stretch)
and the influence of any externally applied pressure squaazing inwardly.
How do changes in venous capacity influence the magnitude of venous return?
if the venous capacity increases, there is less blood going to the heart to continue circulating.
6 short term control measures of venous retunr and 1 long term measure
SHORT TERM
1) venous valves: mechanically prevents backflow of blood
2) cardiac suction effect
3) pressure imparted to blood by cardiac contraction
4) sympathetic vasocontrictor activity
5) skeletal muscle pump
6) respiratory pump
LONG TERM
1) blood volume
SEE DIAGRAM!!! for explanation
Pressure within the chest cavity averages 5 mmHg ___ than atm pressure.
LESS than atm pressure.
What is the respiratory pump?
it is the difference in pressure between the chest cavity (less pressure in chest) and the rest of the body that enhances the flow from the lower veins to the chest veins (bc blood flows from higher to lower pressures), which promotes increased venous return.
Integrated cardiovascular function involves regulation of : (3 things)
1) cardiac output
2) vascular resistance
3) fluid volume and blood viscosity.
How does the integrator monitor BP?
via a baroreceptor reflex
baroreceptor reflex is an ____ reflex. What is the sense organ? Where are these receptors located?
Autonomic reflex.
Uses arterial baroreceptors: STRETCH RECEPTORS that respond to changing pressure.
Located in the carotid sinus and aortic arch
Info from baroreceptors travel to the ___ ____ center in the ___
cardiovascular control center in the medulla
Increased arterial BP will cause an ____ in ____ of afferent APs from baroreceptors
INCREASED in FREQUENCY
Increased BP = increase baroreceptor stimulation =
____ sympathetic activity and ____ parasymp activity, causing ____ HR and ___ SV, and ____ output to arterioles and veins.
What does this result in?
Increased BP = increase baroreceptor stimulation =
DECREASED sympathetic activity and INCREASED parasymp activity, causing LOWER HR and LOWERSV, and DECREASED output to arterioles and veins.
Results in decrease cardiac output and peripheral resistance and decreased BP
