Control of Circulation Flashcards

1
Q

What is the basal arterial tone?

A

It is a theoretical reference point, and is the amount of vascular contraction found under resting conditions without neural or hormonal (extrinsic) influences.

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2
Q

What is the resting sympathetic tone?

A

It is the amount of vascular constriction found under resting conditions as a result of tonic sympathetic nerve activity. The resistance is higher than the basal arterial tone due to the presence of tonically- released norepinephrine.

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3
Q

How do active mechanisms affect the vascular resistance?

A

They induce a change in the resistance AWAY from the basal tone.

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4
Q

How do passive mechanisms affect the vascular resistance?

A

They induce a change in the resistance TOWARDS the basal tone.

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5
Q

What is passive vasoconstriction?

A

Increase in pressure towards the basal tone

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6
Q

What is passive vasodilation?

A

Decrease in pressure towards the basal tone

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7
Q

What is active vasoconstriction?

A

Increase in pressure away from the basal tone

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8
Q

What is active vasodilation?

A

Decrease in pressure away from the basal tone

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9
Q

How do α-receptors mediate vascular tone?

A

They are located on vascular smooth muscle and cause vasoconstriction.

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10
Q

How do β-1 receptors mediate vascular tone?

A

They are the primary adrenergic receptor on cardiac muscle and they stimulate heart rate and contractility.

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11
Q

How do β-2 receptors mediate vascular tone?

A

They are in vascular smooth muscle and stimulate vasodilation.

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12
Q

Describe the arterial baroreceptor reflex.

A

It is a negative feedback loop in order to control arterial pressure and works by making short term adjustments.

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13
Q

Where are baroreceptors found?

A

They are located in the walls of the carotid sinus and the aortic arch.

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14
Q

How do the baroreceptors respond to a decrease in arterial pressure (hemorrhage/standing up in the morning)?

A

Stimulates the sympathetics and inhibits the parasympathetics.

  • Increased vasoconstriction
  • Increased HR
  • Increased contractility

Opposite occurs for increased arterial pressure.

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15
Q

How does the baroreceptor firing frequency change with increased arterial pressure and decreased arterial pressure?

A

It increases with increased arterial pressure and decreases with decreased arterial pressure.

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16
Q

What kinds of pressures are baroreceptors more responsive to?

A

Pulsatile rather than static

17
Q

What are peripheral chemoreceptors?

A

They are small vascular bodies located in the aortic arch that are activated mainly by low arterial PO2 and also low pH

18
Q

What is the function of chemoreceptors?

A

Involved in regulation of respiration and mainly only affect eh cardiovascular system during severe hypoxia. It affects the respiratory system much more.

19
Q

Where is chemoreceptor nerve activity from the carotid carried?

A

CN IX

20
Q

Where is chemoreceptor nerve activity from the aorta carried?

A

CN X

21
Q

What do the chemoreceptors stimulate?

A

Sympathetic - Vasoconstriction

Parasympathetic - Bradycardia

22
Q

In real life though, what does hypoxia actually cause?

A

Tachycardia because increase in ventilation by the respiratory system will serve to increase the heart rate.

23
Q

How does the amount of CO2 affect the response of chemoreceptors?

A

It increases their sensitivity to O2

24
Q

When the PO2 decreases or PCO2 increases or pH decreases, what will be activated?

A

Peripheral chemoreceptors

25
Q

What effect do the peripheral chemoreceptors have on the cardiovascular center of the brainstem?

A

It will stimulate both the sympathetics and parasympathetics

26
Q

How is the parasympathetic activation of the chemoreceptors inhibited?

A

Increase in rate and depth of respiration will stimulate the mechanoreceptors in the lungs that will inhibit the parasympathetic activity and increase HR.

27
Q

What is the main mechanism for long term regulation of blood pressure?

A

Renin-Angiotensin-Aldosterone

28
Q

Describe the Renin-Angiotensin-Aldosterone control.

A

When arterial pressure is low ->
Sympathetic stimulation ->
Renin release from kidney ->
Renin coverts angiotensinogen to angiotensin I ->
ACE is released from endothelial cells and it changes angiotensin I into angiotensin II ->
Angiotension II causes vasoconstriction and stimulates thirst and release of ADH ->
Aldosterone release from adrenal cortex which increases Na resorption

29
Q

What do ACE inhibitors do?

A

They lower blood pressure by inhibiting the activity of angiotensin converting enzyme (ACE)