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Organ Systems > Vascular pt 3 > Flashcards

Vascular pt 3 Flashcards

1
Q

What effect does decreasing resistance in one organ have on the MAP of the entire system?

A

A decrease in resistance means a decrease in MAP of the entire system.

MAP must be maintained, therefore it is restored by baroreflexes the elicit vasoconstriction and increased cardiac output.

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2
Q

What two primary mechanisms regulate MAP?

A

Cardiovascular (baroflex): fast, short term response

Renal: slow, long term response

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3
Q

Where are baroreceptors found?

What do they respond to?

A

In the aortic arch and carotid sinus.

They respond to the change in tension of the carotid artery and aortic arch b/c of changes in blood pressure.

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4
Q

What is a baroreceptor reflex to an increase and decrease in blood pressure?

A

(inverse relationship)
Increase elicits a decrease in heart rate and blood pressure
Decrease elicits an increase in heart rate and blood pressure

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5
Q

Baroreceptor afferents project to where? And where do they project excitatory activity to?

A 
Solitary Nucleus (NTS) 
- the caudal ventrolateral medulla and the nucleus ambiguus
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6
Q

What do the baroreceptors of the caudal ventrolateral medulla inhibit?

A

the rostral ventrolateral medulla (RVLM)

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7
Q

What is the role of the RVLM baroreceptor pathway?

A
  • Acts as a pacemaker for the basal sympathetic activity

- Projects to sympathetic preganglionic neurons in the spinal chord

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8
Q

What is the role of the nucleus ambiguus baroreceptors?

A

The parasympathetic neurons in the vagus nerve (CNX) decelerate the heart rate

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9
Q

What is the role of the sympathetic baroreceptor pathway?

A

Preganglionic and postganglionic neurons go to blood vessels

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10
Q

Baroreception is what kind of system?

A

A negative feedback system

A homeostatic system

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11
Q

What affect does an increased MAP have?

A
  • Stimulation of the CVLM neurons, reducing tonic sympathetic activity in the RVLM
  • Reduction of HR and MAP
  • Stimulation of the parasympathetic neurons in nucleus ambiguus, decreasing HR
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12
Q

What is the set operating point?

What determines the set point?

A
  • Where the baroreflex is the most sensitive and produces the max response for a shift in BP
  • Determined by sensitivity of RVLM neurons to baroreceptive input
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13
Q

How is RVLM sensitivity to BP altered?

A
  • Top down: cerebral input

- Bottom up: sensory input via brain stem centers

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14
Q

What are the characteristics of the negative feedback system of baroreceptors?

A
  • Only works when BP has already changed; occurs as a response
  • Time delay between disturbance and homeostatic restoration; produces changes in vascular function
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15
Q

What are the characteristics of the feedforward control system of baroreceptors?

A
  • Signal associated with disturbance sent to RVLM to anticipate a change in BP; creates a pre-emptive compensatory response to BP
  • Reduces changes in the vascular system by stabilizing responses
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16
Q

What are the characteristics of CNS baroreflex regulation?

A
  • Long term BP is tightly regulated

- CNS generates a vascular tone (baseline) of BP for specific behavioral or emotional contexts

17
Q

How does the RVLM maintain BP with pacemaker-like cells?

A
  • Continuous activity projected to preganglionic sympathetic neurons
  • Bottom up regulation (baroreceptors adjust RVLM to stabilize BP)
  • Top down regulation (cerebral cortex and limbic system activity)
18
Q

What do the cerebral cortex and the limbic system affect? What are they responsible for?

A
  • Anticipatory, emotional or cognitive responses to environmental stress/threats (project into the hypothalamus; paraventricular nucleus)
  • Responsible for behavior- related adjustments to sympathetic tone (feedforward control of baroreflexes)
19
Q

What does the paraventricular nucleus do?

A

Regulates ANS control of BP and baroreflex sensitivity

20
Q

What do paraventricular and supraoptic nuclei do?
What does their destruction cause?
Where does the paraventricular nucleus project into?

A
  • Regulate water balance; produce ADH and oxytocin
  • Destruction causes diabetes insipidus
  • PVN projects into autonomic nuclei of brainstem and spinal cord
21
Q

What does the anterior nucleus do?

What does its destruction result in?

A
  • Thermal regulation via heat dissipation; stimulates PNS

- Destruction causes hypothermia

22
Q

What does the preoptic area contain?

What does it do?

A
  • Contains sexually dimorphic nucleus.

- Regulates release of gonadotrophic hormones

23
Q

What does the suprachiasmatic nucleus do?

A

Receives input from retina, controls circadian rhythms

24
Q

What does the dorsomedial nucleus stimulation result in?

A

Obesity and savage behavior

25
Q

What does the posterior nucleus do?

What does its destruction result in?

A
  • Thermal regulation; stimulation of SNS

- Destruction results in inability to thermoregulate

26
Q

What does the stimulation of the lateral nucleus do?

What about its destruction?

A
  • Stimulation induces eating

- Destruction induces starving

27
Q

What does the mammillary body do?

A
  • Recieves input from the hippocampal formation
  • Projects to anterior nucleus of thalamus
  • Contains hemorrhagic lesions in Wernicke’s encephalopathy
28
Q

What is the ventromedial nucleus?

What does its destruction do?

A
  • Satiety center

- Destruction results in obesity and savage behavior

29
Q

What does the Arcuate nucleus do?

What does it contain?

A
  • Produces hypothalamic releasing factors

- Contains DOPA-ergic neurons that inhibit prolactin release

30
Q

How does the PVN nucleus regulate RVLM and baroreflex sensitivity?

A
  • Specific pathways from PVN to RVLM and spinal cord preganglionics
  • Subgroup regulates heart, vascular system, and kidney to estabilsh BP and HR baselines of behavioral contexts
31
Q

What is the internal control of the PVN?

What is the result of hypertension in the PVN?

A
  • GABA and NO inhibit RVLM pathways

- Decreased inhibition by GABA and NO permit higher sympathetic activity and BP

32
Q

How does the CNS reset the baroreflex to maintain different levels of BP?
What is the affect of changing baroreceptor sensitivity to higher BP levels?

A
  • PVN temporarily enhances sympathetic vasoconstriction or desensitizes baroreceptors to changes in BP
  • Rightward shift in equilibrium point of baroreception
33
Q

How does exercise increase BP?

A
  • Decreases baroreflex sensitivity

- Anticipatory limbic and PVN during exercise resets the baroreflex equilibrium to the right

34
Q

What is transient orthostatic hypotension?

A

Sudden downward flow of blood via gravity; causes momentary lightheadedness; ANS responds with a baroreceptor reflex

35
Q

How does aging affect baroreflex capacity?

A
  • Carotid artery stiffness decreases baroreflex sensitivity (reduces response magnitude)
  • Delayed peak cardiovascular responses to acute carotid baroreceptor loading
36
Q

What does high frequency in power spectral analysis correspond to?

A

respiratory activity

  • increased pulmonary circulation during O2 intake, decreased circulation during CO2 release
  • primarily a result of parasympathetic activity
37
Q

What does low frequency in power spectral analysis correspond to?

A

(Meyer Waves)

  • Both HR and BP variability
  • Related to feedback changes of baroreflexes
38
Q

What is sinus arrhythmia?

A
  • HR increases with inspiration, decreases with expiration

Organ Systems (20 decks)

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