The Autonomic Nervous System Flashcards Preview

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Flashcards in The Autonomic Nervous System Deck (92)
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1
Q

Regulates the function of smooth muscle and cardiac muscle and also controls some aspects of metabolism

-involuntary

A

Autonomic Nervous System (ANS)

2
Q

The ANS is centrally regulated by nuclei in the

A

Medulla, Pons, Hypothalamus, and Spinal cord

3
Q

Some examples of tissues that are modulated by the ANS include

A

Cardiovascular, renal, GI, and Endocrine

4
Q

Afferent tracts that affect the ANS are classified as

A
  1. ) Visceral afferents
  2. ) Somatic Afferents
  3. ) Central chemo afferents
  4. ) Cognitive components of CNS
5
Q

Information regarding anger, arousal, stress, etc

A

Cognitive components of the CNS

6
Q

Designed for coping with acute challenges such as elevations in heart rate and blood pressure

A

Sympathetic nervous system (SNS)

7
Q

Very active during resting conditions and chronically regulates metabolism and cardiovascular function

A

Parasympathetic nervous system (PSNS)

8
Q

Upregulated to help counteract elevated SNS activity

-more localized in its action than the SNS

A

PSNS

9
Q

The sympathetic chain is a series of ganglia located on either side of the vertebral column. What type of neurons are preganglionic SNS neurons?

A

Cholinergic fibers (i.e. ACh is their primary neurotransmitter)

10
Q

Dendrites and cell bodies of the post-ganglionic SNS fibers express ACh receptors, and these post-ganglionic cholinergic nreceptors can also bind

A

Nicotine

11
Q

Dendrites and Cell bodies of Post ganglionic SNS fibers have receptors that are thus identified as

A

Cholinergic-nicotinic (N2) receptors

12
Q

When choinergic-nicotinic receptors are bound to ACh or nicotine, they are activated and allow

A

Inward Na+ or Ca2+ current

13
Q

Branching of the axons of pre- and post-ganglionic fibers explains, in part, the diffuse action of the

A

SNS

14
Q

Post-ganglionic SNS fibers are considered to be

A

Noradrenergic (use norepinephrine as primary neurotransmitter)

15
Q

Cell plasma membranes of effector tissues that are innervated by the SNS fibers express

A

Adrenergic receptors

16
Q

Adrenergic receptors (adrenoceptors) are grossly classified as type α and β. These receptor families are subclassified as type

A

α1, α2, β1, β2, and β3

17
Q

The specific complement of receptor isoforms determines specificity of the response to

A

Adrenergic stimulation

18
Q

Adrenoreceptors belong to the family of

A

G-protein coupled receptors

19
Q

Can mobilize phospholipase C, and in turn ligand-gated Ca2+ channels can be activated

A

α1 adrenoreceptors

20
Q

Binding of adrenergics to α1 receptors in smooth muscle results in what 5 things?

A
  1. ) activation of Gi proteins
  2. ) Decrease in cGMP and cAMP production
  3. ) Opening of membrane Ca2+ channels
  4. ) Increase in sarcoplasmic [Ca2+]
  5. ) Vasoconstriction
21
Q

Often associated with inhibitory effects on GI smooth
muscle contractility, inhibition of some glandular secretions, and inhibition of neurotransmitter
secretion

A

Activation of α2 adrenoreceptors

22
Q

Located on the prejunctional membrane of some post-ganglionic SNS fibers (e.g., cardiovascular)

A

α2 receptors

23
Q

When activated by adrenergics, these α2 receptors are involved in

A

Down regulating neurotransmitter release (negative feedback)

24
Q

Closely associated with stimulating Gs protein/cAMP signaling

A

β1 and β2 adrenoreceptors

25
Q

Predominant in the heart

A

β1 receptors

26
Q

Also expressed within the heart and couple to both stimulatory (Gs) and inhibitory (Gi) signaling motifs

-also found in many smooth muscle beds

A

β2 receptors

27
Q

In the heart, the activation of β1 and β2 receptors results in increased

A

Heart rate (chronotropy) and cardiac contractility (inotropy)

28
Q

Also couple to Gi protein-mediated pathways which induce negative inotropy

A

Cardiac β2 receptors

29
Q

Associated with the relaxation of smooth muscle, hepatic glycogen metabolism, and glycogenolysis in skeletal muscle

A

β2 receptors

30
Q

In the kidney, activation of β1 receptors stimulates

A

Renin secretion from JG cells

31
Q

Synthesized in the axon termini of SNS post ganglionic neurons

A

Norepinephrine

32
Q

What are the steps of norepinephrine synthesis?

A

Tyrosine —> L-dopa —>Dopamine —> Norepinephrine

33
Q

Dopamine is converted to norepinephrine by

A

Dopamine β-hydroxylase

34
Q

Norepinephrine can be converted to epinephrine by

A

Phenolethaolamine N-methyltransferase

35
Q

A catcholamine that acts through two receptor isoforms

A

Dopamine

36
Q

Expressed within the vascular smooth muscle beds of the cerebral, renal, coronary and mesenteric circulations

A

Type 1 dopamine receptor (DA1)

37
Q

DA1 induces

A

Vasodilation

38
Q

Expressed within presynaptic SNS fibers and SNS ganglia

A

Type 2 dopamine receptor (DA2)

39
Q

Inhibits the secretion of norepinephrine as well as SNS ganglionic transmission

A

DA2

40
Q

After diffusing across the synapse, adrenergics bind to adrenoceptors on the

A

Post-synaptic membrane of the effector tissue

41
Q

Adrenergics can be degraded by

A

Catechol-O-methyl transferase (COMT) and/or monoamine oxidase (MAO)

42
Q

Secrets epinephrine and to a much lesser degree, norepinephrine

A

The adrenal medulla

43
Q

Preganglionic SNS fibers terminate within the adrenal medulla and synapse with modified post-ganglionic SNS neural cells called

A

Chromaffin cells

44
Q

Chromaffin cells synthesize

A

Epinephrine and norepinephrine

45
Q

Chromaffin cells are stimulated by

A

ACh

46
Q

Adrenal-derived epi supports the action of the norepi that is locally secreted from

A

Post-ganglionic SNS fibers

47
Q

Has a high binding affinity for both α and β adrenoreceptors

-dose-dependent

A

Epinephrine

48
Q

At all doses, Epinephrine is a potent

A

β1 agonist

49
Q

At a low dose, epinephrine tends to bind B2 receptors and induce

A

Vasodilation

50
Q

At a high dose, epinephrine binds α1 adrenoreceptors and thus induces

A

Vasoconstriction

51
Q

A potent α1 and β1 agonist and thus augments both systolic (β1) and diastolic (α1) blood pressure

A

Norepinephrine

52
Q

At lower doses, norepinephrine does not have as much of an effect on cardiac function, but instead exerts more of a

A

Presser effect (α1 mediated vasoconstriction)

53
Q

Norepinephrine has a lower affinity for

A

β2 adrenoreceptors

54
Q

So called beta blockers (e.g., atenolol and metoprolol) are type β1 adrenoceptor antagonists; these agents are used to

A

Lower heart rate and contractility

55
Q

Commonly used beta blockers with a high degree of specificity against β1 adrenoceptors

A

Atenolol and metoprolol

56
Q

The SNS stimulates increased arterial BP through

A

Increased cardiac output (B1) and vasoconstriction (a1)

57
Q

What is responsible for the increased blood flow to contracting skeletal muscle seen in SNS response?

A

B2

58
Q

What is responsible for the concurrent decreased blood flow to non-contracting skeletal muscle and the GI tract?

A

a1

59
Q

SNS response of increased glycolysis in the liver and skeltal muscle is due to

A

B2 activation

60
Q

What mediates the following SNS responses?

  1. ) Decreased insulin secretion
  2. ) Upregulated glycogenolysis resulting in increased plasma glucose level
A
  1. ) a2 and pancreatic B cells

2. ) B2 activation, hepatocytes, and skeletal muscle

61
Q

What mediates the following SNS responses?

  1. ) Bronchial smooth muscle relaxation
  2. ) Increased platelet aggregation
A
  1. ) B2 ativation

2. ) a2 activation

62
Q

Compounds which stimulate adrenoceptor activity (adrenoceptor agonists)

A

Sympathomimetics

63
Q

Endogenous as well as pharmacologic adrenoreceptor agonists

A

Epinephrine and norepinephrine

64
Q

Low concentrations of epinephrine stimulates both B1 and B2 activity whereas high concentrations function as more of an

A

a1 agonist

65
Q

A very effective a1 and B1 agonist but has little B2 effect

A

Norepinephrine

66
Q

Impair SNS activity by blocking adrenoceptor activity

A

Adrenoreceptor antagonists

67
Q

Suppress vascular smooth muscle tone and thus are useful for reducing hypertension

A

Alpha blockers

68
Q

Non-specific alpha blockers have a suppressive effect on presynaptic a2 receptors and will cause

A

Reflex tachycardia

69
Q

Widely used to control angina and hypertension

A

Beta blockers

70
Q

Beta agonists are indicated to control

A

Asthma

71
Q

Beta blockers with a relatively high specificity for the B1 adrenoreceptor

A

Atenolol and Metoprolol

72
Q

An example of a non-specific beta blocker is

A

Propranolol

73
Q

Cell bodies of the preganglionic PSNS neurons originate within the

A

Brainstem and sacral region of the spinal cord

74
Q

Myelinated axons emerging from the brainstem are distributerd within which 4 nerves?

A

Cranial Nerves

  1. ) III (oculomotor)
  2. ) VII (facial)
  3. ) IX (glossopharyngeal)
  4. ) X (vagus)
75
Q

Approximately 75% of the axons of preganglionic PSNS fibers are in the

A

Vagus nerve

76
Q

Myelinated axons of the sacral PSNS neurons are distributed with

A

Pelvic nerves

77
Q

These fibers are choinergic and terminate in ganglia that are seated very near to the effector tissues

A

Preganglionic PSNS neurons

78
Q

Like postganglionic SNS fibers, post-ganglionic PSNS fibers have

A

Cholinergic-nicotinic receptors (and are unmyelinated)

79
Q

All pre-ganglionic ANS neurons are

A

Cholinergic

80
Q

Dendrites and cell bodies of all post-ganglionic ANS neurons express

A

Cholinergic nicotinic receptors

81
Q

Cholinergic nicotinic receptors are functionally classified as

A

Ligand-coupled (or ligand-activated) Na+ channels

82
Q

Effectors that respond to PSNS activity posses which type of receptors?

-G-protein coupled receptors

A

Cholinergic-muscarinic (CM) receptors

83
Q

ACh is synthesized in the PSNS nerve termini via the reaction between

A

Acetyl-CoA and choline

84
Q

ACh synthesis is fairly exclusive to

A

Pre-ganglionic ANS fibers and Post-ganglionic PSNS fibers

85
Q

Can synthesize ACh, but rely upon extracellular choline as the substrate for ACh production

A

α motor neurons

86
Q

Binds to cholinergic receptors (either muscarinic or nicotinic) on the post-synaptic membrane

A

ACh

87
Q

Upon binding, ACh is rapidly degrade by

A

ACh esterase (cholinesterase)

88
Q

A hydrolytic product of cholinesterase activity, can be re-uptaken by the presynaptic terminus and recycled for the re-synthesis of ACh

A

Choline

89
Q

Compounds that can activate PSNS activity

A

Chiolinomimetics

90
Q

Compounds which can impair PSNS activity

A

Muscarine antagonists

91
Q

Muscarine antagonists will block the effects of (post-ganglionic) muscarine, and thus have a wide variety of uses. A common example is

A

Atropine

92
Q

Uses include:

  1. ) Anesthesia: block vagal activity to reduce salivary and bronchial secretions and alleviate the inhibition of heart rate
  2. ) Pupil dilation
  3. ) Prevention of motion sickness
  4. ) Reduction in intestinal spasm
A

Muscarine antagonists such as atropine