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Physio II > pressure and flow > Flashcards

pressure and flow Flashcards

1
Q

systemic blood pressure

A

sum total of everything going on in the periphery
but every tissue and organ has the ability to control its own flow

what we know as “systemic blood pressure” is what we know as the combined parts that make up this whole

if one area of the body sees an increase in flow the increased flow to skeletal muscles and to feed the pulmonary circuit you see don’t see a big change in systemic pressure at the level of the organis,

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2
Q

mechanisms for local control

A

acute regulation = vasodilator theory and oxygen demand theory

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3
Q

stress from increased pressure that causes vasodilators to be released is known as what theory of acute flow control

A

vasodilator theory

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4
Q

long term controls of blood flow

A

require the creation of new tissue and take time

muscle cells change the density of mitochondria to more efficiently generate energy

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5
Q

the return of flow to normal is known as

A

autoregulation

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6
Q

myogenic theory

A

suggests that still another mechanism not related to tissue metabolism explains the phenomenon of autoregulation.

.

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7
Q

metabolic theory

A

can be understood easily by applying the basic principles of local blood flow regulation discussed in previous sections. Thus, when the arterial pressure becomes too great, the excess flow provides too much oxygen and too many other nutrients to the tissues and “washes out” the vasodilators released by the tissues. These nutrients (especially oxygen) and decreased tissue levels of vasodilators then cause the blood vessels to constrict and return flow to nearly normal despite the increased pressure.

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8
Q

special mechanisms of acute flow control (kidney)

A

tubuloglomerular feedback in the kidney

When too much fluid filters from the blood through the glomerulus into the tubular system, feedback signals from the macula densa cause constriction of the afferent arterioles, in this way reducing both renal blood flow and glomerular filtration rate back to nearly normal.

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9
Q

special mechanisms of acute flow control in the brain

A

in addition to control of blood flow by tissue oxygen concentration, the concentrations of carbon dioxide and hydrogen ions play prominent roles. An increase of either or both of these ions dilates the cerebral vessels and allows rapid washout of the excess carbon dioxide or hydrogen ions from the brain tissues. This mechanism is important because the level of excitability of the brain itself is highly dependent on exact control of both carbon dioxide concentration and hydrogen ion concentration.

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10
Q

the most important of the endothelial derived relaxing factors is

A

nitric oxide
a lipophilic gas that is released from endothelial cells in response to a variety of chemical and physical stimuli. Endothelial-derived nitric oxide synthase (eNOS) enzymes synthesize NO from arginine and oxygen and by reduction of inorganic nitrate.

limited to that particular blood vessels and a few cm from where that release occurs (very short term regulator)

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11
Q

humoral regulators work on

A

Ca channels

vasoconstrictors and vasodilators

angiotensin II

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12
Q

decreased Ca concentration means

A

vasodilation

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13
Q

arterial pressure is controlled by what mechanism

A

largely through the SNS

(autonomic response of fight or flight)

systemic bp increases
(vasoconstriction)

flow to the muscles increase

flow to the lungs increases (vasodilation)

blood flow to the gut decreases (alimentary canal too i.e dry mouth)

PSNS does the opposite through inhibition

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14
Q

vasomotor center

A

in the medulla with the reticular activating system

mediates vascular tone

responds to cells in the medulla and mediates vascular tone through sympathetic nerve fibers

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15
Q

vasoconstrictor area of the vasomotor center is responsible for

A

The neurons originating in this area distribute their fibers to all levels of the spinal cord, where they excite preganglionic vasoconstrictor neurons of the sympathetic nervous system.

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16
Q

increases in arterial pressure seen during exercise

A

muscles require increase in flow and this occurs through

  1. local vasodilation of the muscle vasculature caused by an increase in metabolism
  2. increase in arterial pressure from sympathetic stimulation

some organs vasoconstrictor and divert blood flow to other areas

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17
Q

total peripheral resistance

A

the total sum of changes in flow

this is what the central controls are trying to regulate

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18
Q

baroreceptor reflex is initiated by

A

stretch receptors

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19
Q

what role does the cortex play in blood flow

A

lived experience and interpretation

“top down” influence

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20
Q

location and trajectory of baroreceptors

A

mesure stretch and strain in the walls of the internal carotid artery (carotid sinus)

  1. the wall of the aortic arch

carotid sinus
transmitted throughout small hering’s nerve fibers
then to the glossopharyngeal nerves in the high neck then to the NTS in the medulla

aortic arch are transmitted to the vagus nevrve to the nts

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21
Q

chemoreceptor reflex

A

like baroreceptors unlike baroreceptors do not respond to stretch they

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22
Q

bainbridge reflex

A

An increase in atrial pressure also causes an increase in heart rate, sometimes increasing the heart rate as much as 75 percent.
A small part of this increase is caused by a direct effect of the increased atrial volume to stretch the sinus node; such direct stretch can increase the heart rate as much as 15 percent. An additional 40 to 60 percent increase in rate is caused by a nervous reflex called the Bainbridge reflex.

signal of stretch is transmitted through the vagus nerve to the medulla and efferent signals are sent back through the sympathetic nerves

this is a very local reflex

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23
Q

cushing reaction

A

The so-called Cushing reaction is a special type of CNS ischemic response that results from increased pressure of the cerebrospinal fluid around the brain in the cranial vault.

For instance, when the cerebrospinal fluid pressure rises to equal the arterial pressure, it compresses the whole brain, as well as the arteries in the brain, and cuts off the blood supply to the brain. This action initiates a CNS ischemic response that causes the arterial pressure to rise.

When the arterial pressure has risen to a level higher than the cerebrospinal fluid pressure, blood will flow once again into the vessels of the brain to relieve the brain ischemia. Ordinarily, the blood pressure comes to a new equilibrium level slightly higher than the cerebrospinal fluid pressure, thus allowing blood to begin to flow through the brain again.

The Cushing reaction helps protect vital centers of the brain from loss of nutrition if the cerebrospinal fluid pressure ever rises high enough to compress the cerebral arteries.

24
Q

abdominal compression reflex

A

when a baro or chemo receptor reflex is elicited nerve signals are sent through skeletal nerves to skeletal muscles particularly to abdominal muscles

Muscle contraction then compresses all the venous reservoirs of the abdomen, helping to translocate blood out of the abdominal vascular reservoirs toward the heart. As a result, increased quantities of blood are made available for the heart to pump. This overall response is called the abdominal compression reflex.

The resulting effect on the circulation is the same as that caused by sympathetic vasoconstrictor impulses when they constrict the veins: an increase in both cardiac output and arterial pressure. The abdominal compression reflex is probably much more important than has been realized in the past because it is well known that people whose skeletal muscles have been paralyzed are considerably more prone to hypotensive episodes than are people with normal skeletal muscles.

25
Q

skeletal muscle reflex control on flow

A

compression of the blood vessels tighten muscles and compress vessels, translocating blood

26
Q

Indeed, an increase in arterial pressure in the human of only a few mm Hg can double renal output of water, a phenomenon called ____________ as well as double the output of salt, which is called ______________

A

Indeed, an increase in arterial pressure in the human of only a few mm Hg can double renal output of water, a phenomenon called pressure diuresis, as well as double the output of salt, which is called pressure natriuresis.

27
Q

calculation of MAP

A

diastolic pressure + 1/3 of pulse pressure

provides an assessment for the average strain on vasculature

28
Q

why do you want to be weary of medicating elderly pts with love diastolic pressure

A

diastolic pressure is necessary for cardiac profusion

170/50 has a MAP of 90

you don’t want to medicated this person because they are going to fall down

remember diastolic is when cardiac arteries are filling

29
Q

why do we see wide pulse pressure?

A

loss of elasticity in the aorta

aortic calcification or aortic stenosis

when the aorta is stiff we see the inability to control

30
Q

RAAS as it pertains to flow

A

conversion of the angiotensinogen to angiotensin I through the presence of renin enzyme

–> ACE enzyme allows for the production of angiotensin II which leads to the release of ADH and aldosterone

31
Q

Essential HTN and idiopathic HTN can be due to

A 
adrenal hormone secreting tumor 
hormone imbalance
coarctation of the aorta 
goldbaltt 
toxemia 
neurogenic
32
Q

goldbaltt

A

normal blood volume but constricted blood flow to the kidney

GFR down activates RAAS and leads to HTN

33
Q

coarctation of the aorta

leads to idiopathic HTN

A

constriction or narrowing of the aorta anywhere along the arch

if it occurs before the bifurcation with brachial artery you have two different blood pressures

you will see a dramatic difference in blood pressure on the right arm or the left arm

34
Q

why would you want to take a blood pressure on a different arm in a young person with abnormally high bP

A

coarctation of the aorta before the bifurcation

35
Q

essential HTN

A

seen in 90-95% of pts with high bp

MAP increases 40-60%

36
Q

What are the two special forms of autoregulation?

A

Tubuloglomerular feedback in the kidneys, 2] Reflexive washout in the brain

37
Q

Describe autoregulation in most tissues

A

Increased pressure causes rise in flow which resolves after about 1 minute, The organ will adjust based on metabolic demand

38
Q

anatomy of an artery

3 layers

A

1] Tunica intima - made up of simple squamous (aka endothelium)
2] Tunica media - smooth muscle
3] Tunica adventia - connective tissue layer, connects vasculature to surrounding tissues

39
Q

Describe the steps involved in the release of Nitric oxide from the tunica intima

A

1] endothelial tissues release NO in response to stress,
2] NO diffuses from the tunica intimata to the tunica media,
3] causes smooth muscle to relax leading to reduced sheer stress on the vessels with increase in volume/pressure

40
Q

Describe the MOA of nitric oxide

A

NO works through guanylate cyclase cascade.

2nd messenger makes cGMP, cGMP affects its changes in smooth muscle walls to relax allowing the vessel to dilate

41
Q

Describe angiotensin II effect on blood flow

A

Ang II works through a G protein, inositol cascade, which causes the release of Ca, and a influx of Ca from outside the cell into the cytoplasm which causes muscle contraction, resulting in vasoconstriction.

42
Q

Describe leptin effect on blood flow

A

Leptin works through JAK & STAT cascade to cause endothelial cells to release NO, causing vasodilation, probably by limiting intracellular Ca levels

43
Q

List the effects of ions of blood flow

A

Ca, Caffeine, cortisol - vasoconstrictor,

K, Mg, H+, anions, CO2, serotonin, oxytocin - vasodilators

44
Q

What regulates the ANS control of the blood pressure?

A

Vasomotor center, located in the pons and medulla, which transmitts parasympathetic signals via the vagus nerve, and sympathetic signals via the spinal cord

45
Q

What centers control the Rapid increase in arterial pressure

A

vasoconstrictor and cardioaccelerator centers

46
Q

What three changes result in the Rapid increase in arterial pressure via the ANS system

A

1] Most arterioles of the systemic circulation are constricted, increasing TPR, increasing arterial pressure

2] Veins are strongly constricted, increasing venous return of blood

3] heart increases in heart rate and contractility via the cadioaccelerator center through sympathatic signal

47
Q

two theories of local autoregulation

A

metabolic–> washout of vasodilators flow to great too many good things

myogenic–> stretch causes reflexive contraction

48
Q

pathway of baroreceptors

A

info from the arch of aorta is carried on vagus nerve,

info from carotid vessels are carried on the glossopharyngeal n. (hering’s n.)

49
Q

response zines in the carotid sinus

A

carotid baroreceptors have different response zones.

the carotid sinus baroreceptors are not stimulated at all by pressures between 0 and 50 to 60 mm Hg, but above these levels, they respond progressively more rapidly and reach a maximum at about 180 mm Hg.

50
Q

response zones in the aorta

A

The responses of the aortic baroreceptors are similar to those of the carotid receptors except that they operate, in general, at arterial pressure levels about 30 mm Hg higher.
Action

51
Q

Describe the Bainbridge effect (atrial reflex) in response to high blood pressure

A

increase in volume to atria, stretch in atrial wall detected by stretch receptors, atrial reflex will cause vasodilation within the kidneys via ANP, increasing diuresis, which leads to drop in blood volume to relieve that stretch; heart will feedback on itself, stretch in atrium leads to increase in HR and more efficient pumping by heart to deal with increase pressure & volume.

52
Q

Describe the central ischemic response

A

receptors in the brainstem near the cardiac and vasomotor centers, detect lack of nutritional support in the brain and metabolites and then induce elevation in BP

53
Q

In which situation would the CSF increase pressure?

A

Meningitis, tumor, hydrocephalus

54
Q

What is MAP is considered HTN?

A

110

55
Q

all the different types of hTN (6)

A 
1] Hormone imbalance, 
2] Goldblatt HTN
 3] Coarctation of aorta
4] Toxemia (pregnancy/preclampsia)
 5] Neurogenic
 6] Essential
56
Q

goldblatt

A

HTN from constriction of a renal artery which leads to reduced blood flow to the renal arteriole, stimulating RAAS system leading to increased blood volume and pressure

Physio II (18 decks)

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