BME 2101 Test 3

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equation for flow resistance?

(8*mu*L)/(pi*a^4)

diameter of arterioles

10-15 micrometers

diameter of capillaries

5-9 micrometers

mean circulatory filling pressure (MCFP) and systemic filling pressure (Psf) at rest?

7 mm Hg

The normal operating point for the carotid baroreceptors is

90-100 mm Hg

Cholinergic

Acetylcholine using nerves

In an animal experiment to study control of mean arterial pressure, we ligate the glossopharyngeal nerve. If we infuse i.v. fluid to increase blood volume, what compensatory changes will we observe that attempt to return venous storage volume to normal?

Bainbridge reflex

Within 30 sec after a heart attack, which of the following are primary reflex responses?

Decreased MAP causes arterial baroreceptors to release sympathetic inhibition. Hypoxia causes arterial chemoreceptors to stimulate sympathetic tone. CNS ischemia causes cerebral chemoreceptors to stimulate sympathetic tone.

In response to an acute loss of blood volume, which of the following are primary responses?

Decreased MAP causes arterial baroreceptors to release sympathetic inhibition. Hypoxia causes arterial chemoreceptors to stimulate sympathetic tone. Decreased capillary pressure leads to fluid resorption.

Cardiac output increases with age throughout our lifetimes. T or F?

F

By what mechanism does venous pressure (Pv ) determine cardiac output?

Frank-Starling

Cushing reaction

Increase in intracranial pressure causes compression of blood vessels--> baroreceptors are triggered--> reduce the inhibition of sympathetic stimulation/increase in parasympathetic--> less vasodilation and more vasoconstriction--> increase in MAP

equation for net filtration pressure

NFP = Pc - Pif - (PIc - PIif)

Mean arterial pressure is related to cardiac output using what law?

Ohm's Law

When both the hydraulic pressure difference (ΔP = Pc - Pif) and the osmotic pressure difference (Δπ = πp - πif) are taken into consideration, which way does fluid flow across the capillary wall?

Outward, because ΔP > Δπ

What can cause tissue swelling?

Pc increases πp decreases ΔP increases Δπ decreases

The hydraulic pressures acting on fluid near the capillary wall include capillary fluid pressure acting in the outward direction (Pc) and interstitial fluid pressure acting in the inward direction (Pif). Which one is bigger? Which way would fluid flow across the wall on average if no other forces were purshing fluid?

Pc>Pif so fluid would flow outward

When blood volume decreases, as in acute hemorrhage, what is the primary effect the venous return curve?

Psf decreases

After a heart attack, how does reduced MAP due to compromised cardiac function affect the venous return curve (vascular function curve)?

Psf increases

What happens to the venous return (vascular function) curve after increased sympathetic stimulation of veins?

Psf increases, shifts right

write an equation for venous pressure

Pv = MCFP - (TPR/(1 + Cv/Ca))CO

What is most of the interstitial colloid osmotic pressure due to?

The plasma protein albumin

Aortic pulse pressure in a patient is measured to be 90 mmHg. Which of the following could be an explanation?

The pressure pulse is larger than normal because of arteriosclerosis, a condition that decreases vascular wall compliance.

To test your hypothesis that the myogenic theory is responsible for autoregulation when the endothelium is denuded, what could you do to show that smooth muscle contraction is responsible?

Treat with a vasodilator or remove extracellular Ca2+

What is edema caused by?

accumulation of fluid in the interstitium

What is the neurotransmitter released by all preganglionic nerve fibers?

acetylcholine

In the autonomic nervous system, signals usually travel through 2 nerves before reaching the target organ. What is the one exception in which an organ replaces the postganglionic nerve?

adrenal glands

reactive hyperemia

after brief ischemia, blood flow temporarily increases more than normal temporarily (caused by metabolic theory because blood vessels dilate)

One strategy to manage hypertension is to take an ACE inhibitor, which blocks production of which vasoconstricting hormone?

angiotensin II

vasoconstrictors

angiotensin II, norepinephrine, epinephrine, vasopressin, endothelin

direction of blood flow

arteries, arterioles, capillaries, venules, veins

"resistance vessels"

arterioles

Do central or local mechanisms win in skeletal muscle?

at rest, central vasodilation wins during exercise, local vasodilation wins

Suppose that mean carotid artery pressure increases to 140 mmHg while you are doing a handstand. What mechanism returns mean pressure to normal?

baroreceptor reflex

sympathetic receptor

beta 1 adrenergic

atropine

blocks muscarinic receptor, can be used to treat heart heart failure

curare

blocks nicotinic receptors, signal can't be transmitted to the ganglion

If blood volume decreases, then what happens to venous pressure and cardiac output?

both decrease

If blood volume decreases, then what happens to venous pressure and cardiac output? Draw function curves to help you arrive at an answer.

both decrease

when diameter increases, what happens to resistance? to pressure?

both decrease

What factors are negative inotropic, i.e., shift the cardiac function curve downward?

calcium channel blockers (verapmil, diltiazem, nifedipine), low extracellular calcium, high extracellular sodium, hypertension, arrhythmia, coronary artery blockage, valve disease, hypoxia

A soldier wounded in battle is losing blood volume, and mean carotid artery pressure has dropped to 60 mmHg. What reflex feedback mechanism will be activated to try to return mean pressure to normal?

carotid chemoreceptor reflex

In response to hypoxia, carotid chemoreceptors

cause vasoconstriction.

beta 1 adrenergic receptors

causes increased heart rate and increased contractility

Do central or local mechanisms win in skin?

central vasodilation

+NFP

change in fluid pressure is greater than change in osmotic pressure, fluid pressure inside the capillaries is greater than outside, fluid flows from high pressure to low pressure, so fluid will flow out of capillaries

-NFP

change in osmotic pressure is greater than change in fluid pressure, osmotic pressure inside the capillaries is greater than outside the capillaries, water moves from low pressure to high pressure, fluid will flow into the capillaries

A mountain biker involved in a wipeout hit his head on the ground during the fall. At the ER, the biker is diagnosed with swelling in the brain near the point of impact. Explain two mechanisms that might be at work to maintain blood flow to area of the brain experiencing edema.

chemoreceptor reflex and Cushing reaction

compliance of veins versus arteries

compliance is change in volume over change in pressure Cv=19Ca

alpha 1 adrenergic receptors

constricting arteries and arterioles

If myocardial contractility increases, we expect cardiac output to increase. What happens to venous filling pressure? Draw function curves for yourself to help you arrive at an answer.

decreases

If total peripheral resistance increases, then what happens to cardiac output? Draw function curves to help you arrive at an answer.

decreases

what happens to blood vessel diameter when you increase tone?

diameter increases

Possible pathways for solute transport across capillary walls?

diffusion through intercellular clefts, transcytosis using caveolae, diffusion through fenestrae, diffusion through cell membranes and cells

beta 2 adrenergic receptors

dilates airways and arterioles

how are pressure and resistance related?

directly proportional

The active contraction curve (which is the upper bound of the left ventricle P-V loop) relates the maximum pressure (or force of contraction) that can be generated at a given LV volume. This curve is a representation of

frank-starling

In general, physiological hydrostatic pressure gradients tend to push fluid...?

from the capillaries into the interstitial fluid

Increased venous return stimulates atrial stretch receptors, causing

heart rate to increase (the Bainbridge reflex).

Pressures from highest to lowest? (capillary, arteriole, venular)

highest=ateriolar middle=capillary lowest=venular

metabolic vasodilator theory

if metabolism in the tissue increases or if flow rate through the blood vessel slows down, the cells release a neurotransmitter that will dilate the arterioles, which will increase flow/oxygen delivery

Sympathetic ganglia are mostly located

in a "chain" of cells next to the spinal cord.

increase in blood volume causes what change in venous return graph?

increase in Psf/MCFP, graph shifts right

Bainbridge reflex

increased blood volume in atria--> increase HR

minimizing blood volume affect on MAP

increased blood volume--> vasodilation, decrease in heart rate, decrease in contractility, decrease in MAP

Decreasing arterial wall compliance without changing venous wall compliance would cause

increased cardiac output at a given preload.

If total peripheral resistance decreases, then what happens to cardiac output?

increases

how does arterial vasoconstriction affect VR curve?

increases resistance, flatter VR curve slope

In response to increased mean arterial pressure, baroreceptors

inhibit sympathetic stimulation

what is autoregulation

keeping flow rate constant over a range of pressures

why is the rate of diffusion of solutes faster in the kidneys than in the brain?

leaky junctions vs tight junctions

Do central or local mechanisms win in brain and heart?

local vasodilation

is oxygen a vasoconstrictor or vasodilator?

locally, for example during exercise, oxygen is a vasodilator, but if oxygen concentration gets low enough, the central control system takes over and oxygen becomes a vasoconstrictor

chemoreceptor signaling

low pressure--> hypoxia--> chemoreceptors in aortic arch or carotid sinus detect the change in pressure due to stretch--> afferent nerves (Hering's nerve, glassopharyngeal nerve) --> vasomotor center (medulla)--> efferent nerves --> peripheral vasoconstriction (to preserve oxygen content in brain and heart)

why do feet swell on plane?

lymph pump isn't working to drain interstitial fluid

how to measure rate of solute diffusion across capillaries

mass flux Fick's 1st Law J=-P*delta c (mass flux = permeability * concentration gradient)

Baroreceptor Signaling

mean arterial pressure increases--> baroreceptors in aortic arch or carotid sinus detect the change in pressure due to stretch--> afferent nerves (Hering's nerve, glassopharyngeal nerve) --> vasomotor center (medulla)--> efferent nerves --> vasodilation, HR decreases, contractility decreases

The pressure that would exist everywhere in the peripheral circulation due to filling it with a normal volume of blood is called the

mean systemic filling pressure

adrenergic neurons

most sympathetic post-ganglionic neurons

parasympathetic receptor

muscarinic

What increases lymph flow?

muscle pump activity, increased interstitial fluid pressure, coordinated contraction waves of smooth muscle in the wall of lymphatic vessels

While watching TV, your dog is resting his head on your arm. After a while, you feel like your arm fell asleep and the dog needs to move. When the dog moves his head, you notice that the spot on your arm where he was resting turns red for a few minutes. What is happening? (check all that apply)

myogenic response vasodilation reactive hyperemia

In a rat experiment to study blood flow regulation in skeletal muscle, you accidentally scrape the endothelium on the inside of the artery with your catheter. However, you notice that when you increase the pressure inside the artery, it maintains its diameter anyway. What mechanism maintains the diameter?

myogenic theory

general nerve signaling pathway

nerve cell body in central nervous system--> pre-ganglionic nerve--> peripheral ganglion--> post-ganglionic nerve--> target organ

acetylcholine

neurotransmitter for all pre-ganglionic nerves, sympathetic and parasympathetic also the post-ganglionic nerve for all parasympathetic nerves

preganglionic receptor

nicotinic

how do endothelial cells act on smooth muscle cells to cause vasodilation?

nitric oxide (second messenger)

vasodialator that acts directly on smooth muscle, doesn't require endothelial cells

nitropresside, it mimics NO

Sodium nitroprusside is a vasodilator that acts directly on vascular smooth muscle cells to cause them to relax. In the presence of nitroprusside, what effect would endothelial cell release of nitric oxide have?

no effect

sympathetic post-ganglionic neurotransmitter

norepinephrine

overall, does water move into or out of capillaries? Is this filtration or absorption?

out of capillaries because fluid pressure is greater than osmotic pressure, so NFP will be positive. this is called filtration

parasympathetic nerve signaling pathway

post-ganglionic nerve= in or near the target organ, vagus nerve is the pre-ganglionic nerve

sympathetic nerve signaling pathway

post-ganglionic nerve= sympathetic chain/paravertebral, exception: adrenal gland, no post-ganglionic nerve, directly to blood stream

Atropine blocks muscarinic cholinergic receptors, which leads to increased heart rate and contractility. Which nerve signals are blocked by atropine?

postganglionic parasympathetic

You set up another artery experiment in which you are sure that the endothelium is intact. You hypothesize that the metabolic theory is responsible for autoregulation in the artery. You temporarily occlude the feed artery and then release the occlusion. The flow rate after you release the occlusion increases temporarily then settles to an intermediate value. What is this phenomenon called?

reactive hyperemia

paracrine

released by a cell and acting on its neighbor

autocrine

released on a cell and acting on itself

when pressure decreases, what happens to resistance to keep flow rate constant?

resistance decreases (F=deltaP/R)

A good measure of venous return is

right atrial pressure or another measure of preload

If we want to relate venous return to preload, then what is a good clinical measure of preload?

right atrial pressure, venous pressure, LVEDV, LVEDP, RVEDV, RVEDP

vasodilators that act on endothelial cells, which then act on smooth muscle cells

sheer stress from pressure in arterioles, acetylcholine, histamine, bradykinin, adenosine, carbon dioxide, potassium ions, hydrogen ions, lactic acid, prostaglandins

net filtration rate equation

starling hypothesis net filtration rate = Kf * NFP

Normal cardiac output and right atrial pressure occur where the cardiac function curve and the venous return curve intersect. This point is known as (two different names)

steady-state operating point or equilibrium point

What is the response to brain ischemia?

strong sympathetic stimulation--> vasoconstriction--> increase in HR and contractility hypoxia--> chemoreceptors--> increase in sympathetic Cushing reaction: increase in intercranial pressure--> baroreceptors--> de-inhibit sympathetic stimulation--> increase pressure in capillaries to prevent them from collapsing

If total peripheral resistance increases and, as a result, venous pressure decreases, what mechanism would enable cardiac output to return to normal?

sympathetic stimulation to increase cardiac contractility

What factors are positive inotropic, i.e., shift the cardiac function curve upward?

sympathetic stimulation, adrenergic agonists (NE, epi), cardiac glycosides (digitalis), high extracellular calcium, low extracellular sodium, hypertrophy

During a heart attack (myocardial infarction), part of the ventricular muscle is damaged and does not contribute to pump function. What is the instantaneous effect on the cardiac function curve?

the curve shifts down

what prevents edema?

the fluid is taken in by the lymph vessels and returned to the circulation

What is Starling's Law of filtration?

the rate of fluid movement across the capillary wall as a function of the balance between hydrostatic and osmotic pressures

If venous return to the heart increases, then

the slope of the cardiac function curve does not change.

function of capillaries

to exchange of materials such as oxygen & carbon dioxide between plasma and interstitial fluid

myogenic theory

transmural pressure (difference in pressure from inside artery walls to outside) increases--> smooth muscle contracts/SM tone (state of contractility) increases--> vasoconstriction

equation used to show osmotic pressure

vant hoff's law pi = phi * i * c * R * T

What are effects of sympathetic stimulation?

vasoconstriction--> more resistance--> venous return curve gets flatter cardiac output curve shifts right--> Psf increases

if blood volume is increased and arterial stretch increases, what are the main results?

vasodilation, decrease in contractility, decrease in MAP, HR stays constant, increase in urine volume

Volume reflex

vasodilaton in kidneys--> increase in capillary pressure downstream--> increase in filtration--> increase in urine volume decrease in anti-diuretic hormone (ADH)--> increase in urine volume increase in atrial natriuretic peptide (ANP)--> increase in urine volume

"blood volume storage vessels"

veins

According to the Frank-Starling mechanism (also known as Frank-Starling law of the heart), cardiac output increases as

venous return increases

flow resistance is most sensitive to which parameter?

vessel radius radius increases, flow decrease radius decreases, flow increases

metabolic oxygen demand theory

when metabolism goes up (oxygen concentration goes down=hypoxia), the vessels dilate

what is the continuous smooth muscle layer?

wraps around arterioles to regulate vessel diameter vasodilation or vasoconstriction

The osmotic pressures acting on fluid near the capillary wall include plasma osmotic pressure inside the capillary (πc) and interstitial fluid osmotic pressure outside the capillary (πif). Which one is bigger? Which way would fluid flow across the wall on average if no other forces were pushing fluid?

πp > πif, so fluid would flow inward


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