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Physiology Part 1 > Lec 5 Adrenergic > Flashcards

Lec 5 Adrenergic Flashcards

1
Q

What are two non-selective adrenergic agonists?

A
  • epinephrine

- norepinephrine

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2
Q

What is one B-receptor agonist?

A

isoproterenol

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3
Q

What is one B2-selective agonist?

A

albuterol

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4
Q

What is one B-receptor blocker?

A

propanolol

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5
Q

What is one B1-selective blocker?

A

metoprolol

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6
Q

What is one a-receptor agonist?

A

phenylephrine

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7
Q

What is one a-receptor blocker?

A

phentolamine

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8
Q

Definition of an agonist

A

substance that binds protein receptor and causes response

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9
Q

Definition of antagonist

A

substance binds receptor and produces no effect but prevents binding of agonist to receptor – prevents agonist producing its effect

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10
Q

Kd of an agonist [equation]

A

Kd = [A][R]/[AR] where AR = concentration of agonist-receptor complex

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11
Q

What are the primary organs controlled by sympathetic [2 primary, 3 secondary]

A

primary: heart and vasculature
secondary: eye, lung, GI

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12
Q

What do adrenergic agonists do? What different mech?

A

act at end organ innervated by sympathetic neurons

    • direct: mimic effect of norepinephrine or epinephrine by directly activating adrenergic receptors in organ
    • indirect:
  • —- cause release normal physiologic agonist from sympathetic nerve terminal
  • —- inhibit termination of transmitter so prolong response
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13
Q

What are 4 receptor types found at cells of end organs innervated by sympathetic?

A
  • alpha adrenergic receptors [a-receptors]
  • beta adrenergic receptors [b-receptors]
  • dopamine receptors [in renal + mesenteric vasculature]
  • muscarinic ACh receptors [only in sweat glands]
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14
Q

What are two exceptions to the fact that most sympathetic postganglionic neurons release NE?

A
  • in renal and mesenteric vasculature release dopamine

- in eccrine sweat glands release cholinergic

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15
Q

What is the only organ that secretes epinephrine?

A

adrenal gland

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16
Q

What are 2 names for the drugs that mimic NE/Epi?

A
  • adrenergic

- sympathomimetic

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17
Q

What do you call drugs that interfere with adrenergic signal?

A

sympatholytic

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18
Q

Where are a1 receptors notably absent [2 places]?

A
  • bronchioles

- heart

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19
Q

a1 receptors [what type of G protein do they activate, pathway, what function do they mediate]

A
  • activate Gq which is couple to phospholipase C
  • phospholipase C hydrolyzes PIP2 to DAG and IP3
  • DAG activates protein kinase C [PKC]
  • IP3 causes release of stored Ca
  • mediated contraction of smooth muscle [splanchnic/cutaneous arterioles, apocrine sweat]
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20
Q

a2 receptors [pre or post synaptic, what type of G protein] * he said these are not very important for these lectures

A

presynaptic

coupled to Gi/o

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21
Q

What are two main subtypes of B receptors in ANS

A

B1 and B2

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22
Q

Mech of action of B receptors?

A
  • coupled to Gs
  • increase cAMP
  • causes contraction of cardiac muscle and relaxation of smooth muscle
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23
Q

Which type of B receptor predominate in heart?

A

B1

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24
Q

Which type of B receptor predominate in vasculature of skeletal muscle?

A

B2

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25
Q

Which type of B receptor predominate in bronchioles?

A

B2

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26
Q

What tissues does a1 act in [2 types] and what action?

A
  • most vascular smooth muscle –> contraction

- pupillary dilator muscle –> dilates pupil

27
Q

What tissue does B1 act in and what action?

A

heart – increases force and contraction rate

28
Q

What tissue does B2 act in and what action?

A

bronchioles and subset of blood vessels in skeletal muscle –> promotes smooth muscle relaxation

29
Q

Effect of epinephrine [type of action/receptors, where is it released from, action on arterioles, BP, heart, bronchioles]

A
  • non-selective adrenergic agonist
  • direct acting
  • acts on a1, B1, B2
  • released as hormone from adrenal medulla

Functions

  • increases systolic BP by interacting with B1 receptors on heart
  • – get more contractile force [inotropic]
  • – get higher HR/rate of contraction [chronotropic]
  • vasoconstriction in most arterioles [via alpha] but dilation in skeletal vessels [via B2]
  • dilates bronchioles
30
Q

Where is epinephrine released from ?

A

adrenal medulla

31
Q

Function of Epi on heart [via what receptor type?]?

A

Increases systolic BP by interacting with B1 receptors on heart

  • – get more contractile force [inotropic]
  • – get higher HR/rate of contraction [chronotropic]
32
Q

Function of Epi on blood vessels [via what receptor types?]?

A
  • vasoconstriction in most arterioles [via alpha]

- dilation in skeletal vessels [via B2] to get more blood to skeletal muscle for fight or flight

33
Q

On what receptors does epi act?

A

All adrenergic receptors! its non-selective

34
Q

On what receptors does NE act?

A
  • direct agonist against a1 and B1

- no B2 activity

35
Q

Where is NE released from?

A

adrenergic nerve terminals

36
Q

Difference in EPI vs NE effect on skeletal vascular beds?

A
  • NE not agonist against B2 so no effect

- EPI is agonist against B2 so causes vasodilation

37
Q

Effect of NE on BP/HR

A
  • causes largely increased BP [via B1]
  • positive inotropic effect [increased contractile force]
  • increased BP effect causes strong baroreceptor reflex that overwhelms direct effect of NE on heart [that would have increased HR] so end up with overall decreased HR
38
Q

What receptors does Isoproterenol affect?

A
  • B1 and B2 receptors only

- direct acting

39
Q

Effect of isoproterenol on vasculature/BP/heart?

A
  • dilates skeletal muscle arterioles
  • decreases diastolic BP and mean arterial pressure
  • increases cardiac output
  • increases HR [chronotropic], contractile force [inotropic] via B1
40
Q

Does isoproterenol causes vasoconstriction or vasodilation? Via which receptor?

A

Vasodilation via B2

41
Q

What is pulse pressure? How does isoproterenol change it?

A
  • pulse pressure = systolic - diastolic

- it is increased by isoproterenol

42
Q

Effect of intravenous Epi on BP/HR/peripheral resistance

A
  • decreased peripheral resistance [net vasodilation]
  • increased HR [because want to increase sympathetic to heart]
  • increased avg BP [increased systolic, decreased diastolic]
  • increased pulse pressure [contractility of heart]
43
Q

Effect of intravenous NE on BP/HR/peripheral resistance

A

A1 and B1 receptors

  • increased BP [increased both sys and dia]
  • pulse pressure may have increased
  • decrease in HR [because reflex effect overwhelms direct effect of B1 receptors on heart]
  • increased peripheral resistance [vasoconstriction, alpha mediated]
44
Q

Effect of intravenous isoproterenol on BP/HR/peripheral resistance

A

just B receptors

  • decreased BP [particularly diastolic]
  • increased pulse pressure [difference sys - di]
  • hugely increased HR [from combination reflex action and direct effect B1]
  • decreased peripheral resistance [due to vasodilation in skeletal]
45
Q

What is phenylephrine?

A
  • a non-catecholamine

- non-selective a agonist [a1 and a2]

46
Q

What receptors does phenylephrine act on?

A

a1 and a2

47
Q

What is effect of phenylephrine on BP and vasodilation or constriction?

A
  • interacts with a1 receptor in vascular smooth muscle –> vasoconstriction in custaneous and splanchnic arterioles + increased BP
48
Q

What is effect of phenylephrine on HR?

A

baroreceptor senses increase in BP –> turns of parasympathetic and turns down sympathetic –> decreased HR

49
Q

What is effect of phenylephrine on airway?

A

None – no a1 receptors in the bronchus!

50
Q

What is phentolamine?

A
  • alpha blocker

- competitive antagonist against a1 and a2

51
Q

What receptors does phentolamine act on?

A

a1 and a2

52
Q

How does phentolamine affect peripheral resistance?

A

decreased peripheral resistance by blocking a1

53
Q

How does phentolamine affect diastolic pressure?

A
  • decrease due to blocking of resting a1-mediated tone of vasculature
54
Q

How does phentolamine affect HR

A

may get tachycardia via baroreceptor mediated reflex

55
Q

What is bad negative side effect of phentolamine/a blockers?

A

orthostatic hypotension

56
Q

What is propranolol?

A
  • non-selective B blocker [B1, B2, B3]
  • decrease HR
  • lower BP
57
Q

What is example where phentolamine is used clinically?

A

used in tumor of adrenal gland prior to surgery [pheochromocytoma] because in hypertensive crisis, more valuable in norepinephrine secreting receptor

58
Q

Effect of propranolol on diastolic BP

A
  • acutely get increased BP

- followed by long term decrease BP by other unclear mech

59
Q

Effect of propanolol on vasculature?

A

constrict skeletal muscle vasculature because block B2

60
Q

Effect of propanolol on HR?

A

decrease [because block B1]

61
Q

Effect of propanolol on airway?

A

constrict [because block B2]

62
Q

What is metoprolol?

A
  • B1-selective blocker
  • decreases BP but less likely to exacerbate asthma compared to non-selective [since B2 bronchodilates –> if you block you get bronchoconstriction]
  • but still not specific: can have side effects of bronchospasm, wheezing, etc
63
Q

What is albuterol?

A
  • B2-selective agonist
  • treatment for asthma
  • dilates bronchioles
64
Q

Why can albuterol cause tachycardia?

A
  • because selective not specific –> can get vasodilation of vessels that express B2 [skeletal, atria] –> get tachycardia

Physiology Part 1 (37 decks)

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