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S2 MAP II > Nervous Regulation of Circulation > Flashcards

Nervous Regulation of Circulation Flashcards

1
Q

what are the two theories of how local control of blood flow to the tissues occurs?

A

O2 lack theory

vasodilator theory

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2
Q

how does ANS regulation of blood flow compare with local blood flow control
-characteristics of this type of control

A

more global in effect

  • redistributes blood to different areas of body prn
  • affects heart rate
  • can rapidly change arterial blood pressure
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3
Q

which part of the ANS is the primary nervous system influence in regulating circulation
-what does the other one do?

A

SNS

PSNS assists in regulation of heart function

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4
Q

sympathetic vasomotor nerves

  • leaves spinal cord where
  • pass into…
  • continue as…
A 
leave through thoracic and 1st 1 or 2 lumbar spinal nerves
pass into sympathetic chain
continue into
-sympathetic nerves
-spinal nerves
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5
Q

SNS

-innervates which vessels

A

innervates all vessels except

  • capillaries
  • precapillary sphincters
  • metarterioles
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6
Q

SNS innervation of small arteries and arterioles

-allows…

A

allows stimulation to vasoconstrict

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7
Q

SNS influence on veins

-what occurs with blood loss

A

stimulation decreases their volume
with blood loss
-reflexes elicited from aortic bodies and carotid sinus
-stimulates sympathetic nerve impulses to the veins
-result: blood goes towards the heart

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8
Q

significant blood loss - clinical pathologies

-can result from…

A 
circulatory shock
-condition in which blood vessels are inadequately filled and blood can't circulate normally
can lead to...
-hypovolemic shock
-vascular shock
-cardiogenic shock
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9
Q

hypovolemic shock

A

loss of blood volume
can be due to burns
-partly due to edema formation
reduction in BP

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10
Q

vascular shock

A

due to massive vasodilation

  • allergic response (release of histamine)
  • septicemia (large bacterial infection that travels through the blood)
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11
Q

cardiogenic shock

A

heart failure

due to tissue damage to the heart

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12
Q

SNS control

-sympathetic nerves carry many _____ and few _____

A

many vasoconstrictor fibers and few vasodilator fibers

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13
Q

SNS vasoconstrictor fibers

  • where are they distributed
  • where is the largest distribution
  • less distributed to…
A

distributed to all segments of circulation
largest distribution to kidneys, intestines, spleen, and skin
less distributed to skeletal muscles and brain

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14
Q

SNS vasoconstriction: CNS control

A

vasomotor center

  • in the medulla
  • regulates diameter of vessels and controls blood pressure
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15
Q

vasomotor center areas

A

vasoconstrictor area
vasodilator area
sensory area

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16
Q

vasoconstrictor area of vasomotor center

-what does it do?

A

sympathetic vasoconstrictor tone

  • maintains normal vasomotor tone
  • contributes to maintenance of BP
17
Q

what can happen if sympathetic vasoconstrictor tone is lost

A

vasodilation

-can lead to vascular shock

18
Q

how does the vasoconstricor area work?

A

neurons in area secrete norepinephrine
causes excitation of SNS vasoconstrictor fibers
SNS transmits signals through the spinal cord and peripheral sympathetic nerves to almost all blood vessels of body

19
Q

vasodilator area of vasomotor center

  • neuronal fibers project towards _____
  • function
A

project up toward vasoconstrictor area

inhibit the vasoconstrictor area

20
Q

sensory area of vasomotor center

  • sensory nerve impulses received from…
  • function
A

impulses received from circulatory system via vagus and glossopharyngeal nerves
sensory area output helps control vasoconstrictor and vasodilator areas

21
Q

adrenal medulla

  • when does it receive SNS stimulation
  • result
  • function
A

receives SNS stimulation simultaneously as blood vessels
result
-medullae secrete norepinephrine and epinephrine into blood system
primarily causes vasoconstriction
epinephrine occasionally causes vasodilation in some tissues

22
Q

cardiac center

  • adjacent to…
  • function
  • what are the centers?
A 
adjacent to part of the vasomotor center
adjusts rate and force of heart contraction to meet needs of the body
centers
-cardioaccelerator
-cardioinhibitory
23
Q

cardiovascular center

  • combo of what centers?
  • how do these work together
A

cardiac center + vasomotor center
stimulation of vasomotor center under normal conditions also stimulates cardiac centers
-therefore, control heart heart function and vascular function simultaneously
–get increased vasoconstriction with increased HR
-get vasodilation with decreased HR

24
Q

rapid control of arterial pressure by nervous system - BP regulation
-how fast?

A

nervous system control of BP most rapid of responses
can increase BP within seconds
2-fold increase within 5-10 seconds
decrease to 1/2 normal can occur in 10-40 seconds

25
Q

increase in arterial pressure

  • simultaneous stimulation of…
  • reciprocal inhibition of…
  • results
A

simultaneous stimulation of vasoconstrictor and cardioaccelerator
reciprocal inhibition of PSNS vagal signals to the heart
results
-must arterioles constrict
-veins and other large vessels constrict
-SNS stimulation of heart

26
Q

mechanisms to maintain normal arterial pressure

A

baroreceptors

27
Q

baroreceptors

  • what are they
  • how do they work
A

neural receptors in the carotid sinuses, aortic arch, and walls of nearly every large artery in the neck and thorax
pressure sensitive: respond to stretch or lack of stretch in vessel walls
stretch sends rapid impulses to the vasomotor center and cardiac center
decline in MAP initiates reflex vasoconstriction and increases CO - BP rises

28
Q

sequence of events concerning baroreceptors when blood pressure rises

A
  • baroreceptors in carotid sinuses and aortic arch stimulated
  • inhibit vasomotor center
  • sympathetic impulses to heart decline (decreased HR)
  • decreased CO and R
  • rate of vasomotor impulses declines, allows vasodilation
29
Q

baroreceptor functions

A

protect circulation against acute changes in BP: “pressure buffer system”
-carotid sinus reflex
-aortic reflex
variation in BP minimized
ineffective with prolonged pressure changes - adapt

30
Q

baroreceptor example with hypertension

A

baroreceptors will “reset” at higher set point with prolonged pressure change, which limits their long term response to perceived higher pressure

31
Q

chemoreceptor control of arterial BP

  • respond to…
  • location
  • function
  • important at…
A

respond to changes in O2, CO2, and H+
chemoreceptors located in carotid bodies and aortic bodies
stimulate nerve fibers traveling to the vasomotor center
important at low arterial pressures (<80 mmHg)

32
Q

chemoreceptor MOA

A

in contact with arterial blood
senses low O2 or high levels of CO2 or H+ that results with a drop in arterial pressure
initiates reflexive vaso/venoconstriction

33
Q

atrial reflexes

  • location
  • types or receptors
A

within walls of atria: respond to change in pressure
types
-low-pressure receptors (stretch receptors)
–minimize arterial pressure changes
-bainbridge reflex

34
Q

bainbridge reflex

A

with increased arterial pressure, will get an increase in HR and strength of contraction to prevent blood from “backing up” into system

35
Q

what can reduce the effective response of the atria to pressure changes

A

damage to atria

36
Q

CNS ischemic response

A

occurs when blood flow to vasomotor center severely decreased - compromises nutritional accesss = cerebral ischemia
get strong reaction of vasoconstrictor and cardioaccelerator centers
large rise in systemic arterial pressure

37
Q

CNS ischemic response

  • can raise ____ to _____ for _____
  • how strong is it?
A

can raise the MAP to 250 mmHg for up to 10 minutes

most powerful activator of SNS vasoconstrictor system

38
Q

Cerebral ischemic response flowchart

A
  • massive decrease in BP
  • decreased cerebral blood flow
  • increased PCO2, increased H+
  • activation of VMC
  • increased smypathetic
  • increased HR, increased TPR
  • restores BP

S2 MAP II (17 decks)

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