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Block 2; Week 3 > Mutafova Neural Reflexes > Flashcards

Mutafova Neural Reflexes Flashcards

1
Q

What are the physical & physiological factors that affect arterial blood pressure? What does a change in physical factors alter? Physiological factors?

A

Physical: changes pulse pressure (difference b/w systolic & diastolic changes)
Arterial Blood Volume
Arterial Compliance
Physiological: changes mean arterial pressure
Cardiac Output: Stroke Volume, HR
Peripheral Resistance (b.v. diameter)

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2
Q

What are the 6 components of the baroreceptor reflex/neural control system pathway? How would this relate to an increase in mean arterial pressure?

A

Signal (increase in mean arterial pressure)
Detector (baroreceptors)
Afferent Pathways (sensory)
Coordinating Center (brain–>medulla & cardiovascular control center)
Efferent Pathways (autonomic)
Effectors (heart & blood vessels–>here: lower HR & contractility & dilate blood vessels)
Overall Effect: vasodilation, bradycardia

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3
Q

Where are the 2 main locations for high pressure baroreceptors?

A

The aortic arch

At the carotid sinus near the bifurcation of the common carotid arteries.

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4
Q

What actually are baroreceptors? Where are their cell bodies found?

A

Branched & coiled bare ends of myelinated sensory nerve fibers.
Cell bodies found in ganglia near the brainstem.

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5
Q

What do baroreceptors sense?

A

They sense stretch from either changes in BP or in vascular wall tension.

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6
Q

How does a sudden increase in BP alter baroreceptor firing?

A

A sudden increase in BP will increase baroreceptor firing.

A sudden decrease in BP will decrease baroreceptor firing.

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7
Q

T/F Baroreceptors are vital in the regulation of chronic high BP.

A

False. They play a very small role in regulation of chronic BP…they are really great for acute changes in BP. They use a very fast mechanism.

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8
Q

What are the ranges of BP over which aortic & carotid high pressure baroreceptors can monitor?

A

Aortic: 100–>200
Carotid: 50–>200

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9
Q

Where are the cardiopulmonary baroreceptors found? What do they monitor? What is the result of their reflex?

A

At low pressure sites.
Like the atria…& the veins leading into the atria. Even the ventricles.
They monitor venous volume.
They control blood volume through a reflex of release of ADH.

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10
Q

What do cardiopulmonary baroreceptors sense?

A

Stretch.
Changes in left ventricle end diastolic pressure.
Changes in Blood Volume
Changes in Venous Return to the Heart

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11
Q

Where is the coordinating center? What composes it?

A

Medulla Oblongata
Cardioinhibitory center.
Vasoconstrictor
Vasodilator

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12
Q

Which areas of the brain can override the homeostatic function of the medulla/cardiovascular center?

A

Hypothalamus
Limbic System
Cerebral Cortex

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13
Q

What is the approximate set point for mean arterial pressure?

A

About 100 mmHg

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14
Q

If the baroceptor message is firing with higher frequency…what just happened? What is about to happen?

A

Firing more b/c there was a sudden increase in mean arterial pressure (more stretch) that was sensed.
This increase in frequency of firing will increase parasympathetic activity & decrease sympathetic activity.
For obvious reasons–>this will decrease mean arterial pressure.

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15
Q

What happens if you massage both carotid arteries at one time?

A

The person will pass out.

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16
Q

How can massaging one carotid artery be helpful in treating paroxysmal atrial tachicardia?

A

Well, you want the tachycardia to stop. So it’d be nice to slow down the firing of the SA node.
This is a parasympathetic activity.
If you massage the carotid artery…the carotid baroreceptors will sense that there is an increase in mean arterial pressure–>there firing will increase in frequency…thus increasing parasympathetic activity & decreasing sympathetic activity…this will decrease the HR.
This will terminate the episode.

17
Q

What would happen to BP if the aortic & carotid baroreceptors were cut?

A

It wouldn’t be able to buffer the acute changes anymore. So…you would have a larger range of acceptable blood pressures.

18
Q

What would happen to BP if the high & low pressure baroreceptors were cut?

A

You would have a real problem with your long term regulation of BP. It would have a higher set point.

19
Q

How does chronic high BP relate to baroreceptors?

A

Baroreceptors have a higher set point in people with chronic HTN.
Note: they still only respond to acute changes.
They don’t regulate long-term or chronic HTN BP.

20
Q

Where are the peripheral chemoreceptors located?

A

Same places roughly as the high pressure baroreceptors.

Carotid sinus & aortic arch.

21
Q

What do arterial chemoreceptors sense?

A

Acute changes…Respond to:
Hypoxia
Hypercapnia
Acidosis

22
Q

What usu prompts an increase in the action & reflexes of chemoreceptors? What is their effect?

A

Ischemia or Hemorrhagic Hypotension
pO2<80 mmHg
*can cause hyperventilation
*can cause vasoconstriction, increase in TPR & BP after going to the vasomotor control center.

23
Q

What is the arterial chemoreflex in response to asphyxia?

A

Low pO2, High pCO2, Low pH
Arterial Chemoreceptors sense
Nucleus Tractus Solitarii & Hypothalamus sense the message.
Increase Vagus nerve activity–>decrease HR
Increase Sympathetic activity–>RAAS activated, veno & vasoconstriction…increase in lung tidal volume.

24
Q

Where are the central chemoreceptors located?
What do they respond to?
What is the result?

A

They are located in the medulla.
They respond to high pCO2 or low pH.
If these things are high…they cause hyperventilation.
If they are low…they cause hypoventilation.

25
Q

It’s complicated…but with only peripheral chemoreceptors responding to changes in O2 or CO2 or pH or whatever…what is the end result?
How is this different than the integrated response of the peripheral & central chemoreceptors?

A

Only Peripheral:
Bradycardia & increased TPR.

Both Peripheral & Central:
Tachycardia & increased TPR
*only explanation is sorta that hyperventilation overwhelms the initial response to lower HR.

26
Q

What is the CNS ischemic response?

A 
Ischemia--low O2 & high CO2
Vasomotor center stimulated
Increased Symp activity:
Increased HR, SV, & TPR.
But also increased Parasymp activity:
Decreased HR.
Overall effect:
Decreased HR
Increased BP
*Note: the Cushing reflex integrates this ischemic response.
27
Q

What is another name for ADH?
Remember…this is a part of RAAS.
What prompts the release of ADH?
What does it do?

A 
Vasopressin.
Activation of low pressure baroreceptors.
Vasoconstriction -->V1 receptors.
Water Reabsorption-->V2 receptors.
Increased in Blood Volume & BP.
28
Q

So…here’s a story. You have low BP b/c you have low blood volume. You recruit extracellular fluid to be reabsorbed in order to increase your blood volume. Is this ECF edema?

A

No, it’s not edema.

But this is a true story–another mechanism for increasing blood volume & BP.

29
Q

An increase in CO causes an increase in BP for 2 reasons. What are they?

A
  1. BP=CO X TPR. Clearly, CO goes up, BP goes up.
  2. CO increase also increases TPR b/c it will cause an increased stretch in the blood vessels. Their response will be to constrict.
30
Q

Review: Where are natriuretic peptides released from? What do they do?

A

They are released from the atria when they sense over-stretching.
They cause vasorelaxation (TPR decreases)
They inhibit renin release (prevent that increase in BP)
They increase sodium excretion & water excretion @ the kidney (lower blood volume).

31
Q

Which reflexes for maintenance of BP are the fastest acting? Which are intermediate? Slowest acting?

A

Baroreceptors & chemoreceptors are the fastest acting. & Baro are more important & stronger.
Then ischemic brain reflexes & RAAS.
Slowest: renal fluid retention & aldosterone.

32
Q

Which reflexes act to restore good BP at the lowest blood pressures?

A

Ischemic Brain Reflex–>the last effort to save cerebral blood flow. A very strong reflex.

33
Q

T/F The baroreceptors operate over a range of blood pressures that we encounter in our daily life.

A

True. Their set point is usu about 100 mmHg.

34
Q

T/F The chemoreceptors operate over a range of BP that is slightly higher than the baroreceptors.

A

False. They work over a range that is slightly lower than the baroreceptors.

Block 2; Week 3 (11 decks)

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