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630: Medical Physiology > Autonomic Nervous System > Flashcards

Autonomic Nervous System Flashcards

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USMLE® Step 1 flashcards
1
Q

The _____ nervous system is under conscious control and innervates skeletal muscle

A

somatic

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2
Q

The _____ nervous system is under involuntary control and innervates visceral organs

A

autonomic

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3
Q

Each pathway in the autonomic nervous system consists of what 2 neurons?

A

preganglionic and postganglionic neurons

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4
Q

Where does the cell body of each preganglionic neuron reside?

A

In the CNS

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5
Q

Where do the axons of preganglionic neurons synapse with the bodies of postganglionic neurons?

A

In the autonomic ganglia located outside the CNS

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6
Q

All preganglionic neurons of the ANS release what NT?

A

ACh

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7
Q

All postganglionic neurons of the ANS release one of what 2 NTs?

A

ACh or norepinephrine

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8
Q

What are the 3 divisions of the ANS?

A
  • Sympathetic
  • Parasympathetic
  • Enteric
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9
Q

What NT do adrenergic receptors release?

A

norepinephrine

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10
Q

What are receptors for norepinephrine on the effector organs called?

A

Adrenoreceptors

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11
Q

What NT do cholinergic receptors release?

A

ACh

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12
Q

What are receptors for ACh on the effector organs called?

A

Cholinoreceptors

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13
Q

What type of receptors describes some postganglionic parasympathetic neurons of the GI tract that release peptides or other substances as their NT rather than ACh?

A

Non-adrenergic, non-cholinergic receptors

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14
Q

Because all preganglionic neurons release ACh they are called what?

A

cholinergic

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15
Q

Most postganglionic parasympathetic neurons release ACh therefore they are called what?

A

cholinergic

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16
Q

Postganglionic sympathetic neurons release ACh and norepinephrine therefore they are called what?

A

cholinergic OR adrenergic

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17
Q

What is the junction between postganglionic neurons and their effector organs called?

A

the neuroeffector junction

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18
Q

Describe neuroeffector junctions

A

They are diffuse, branching networks in which the receptors are not concentrated in one region

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19
Q

What is the overall function of the sympathetic nervous system?

A

mobilize the body for activity

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20
Q

Where do the preganglionic neurons of the sympathetic division arise from?

A

In spinal cord segments T1 - L3 (thoracolumbar)

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21
Q

Where are the ganglia of the sympathetic nervous system found?

A

Near the spinal cord, either in the paravertebral ganglia (sympathetic chain) or in the prevertebral ganglia

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22
Q

Because sympathetic ganglia are located near the spinal cord, the preganglionic nerve axons are ____ and the postganglionic nerve axons are _____.

A

short

long

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23
Q

Preganglionic neurons of the sympathetic division are always _____ because they release ACh

A

cholinergic

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24
Q

Postganglionic neurons of the sympathetic division are _____ in all of the effector organs, except for the thermoregulatory sweat glands.

A

adrenergic

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25
Q

thermoregulatory sweat glands of the sympathetic division are innervated by what?

A

sympathetic cholinergic neurons, and therefore have muscarinic cholinorecpetors

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26
Q

What are the 4 types of adrenoreceptors of the sympathetic division?

A
  • alpha1
  • alpha2
  • beta1
  • beta2
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27
Q

Sympathetic adrenergic varicosities contain both the classic neurotransmitter and non-classic transmitters. What are they?

A

Classic: norepinephrine

Non-classic: ATP and neuropeptide Y

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28
Q

Describe the roles of norepinephrine, ATP, and neuropeptide Y play in contraction via the sympathetic nervous system

A

1) ATP binds to purinergic receptors on the target tissue causing contraction of the vascular smooth tissue
2) Norepinephrine binds to its receptors on vascular smooth muscle and causes a second, more prolonged contraction
3) With more intense stimulation, the large dense-core vesicles release neuropeptide Y which binds to its receptors on the target tissue causing a third, slower phase of contraction

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29
Q

What is considered a specialized sympathetic ganglion whose preganglionic neurons originate in the thoracic spinal cord (T5-T9), pass through the sympathetic chain and the celiac ganglion without synapsing, and travel in the greater splanchnic nerve to the adrenal gland?

A

the adrenal medulla

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30
Q

Once the axons from the adrenal medulla reach the adrenal gland what do they do?

A

They synapse on chromaffin cells and release ACh, which activates nicotinic receptors

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31
Q

When activated the chromaffin cells of the adrenal medulla secrete __% epinephrine and __% norepinephrine

A

80

20

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32
Q

Why does the adrenal medulla secrete both epinephrine and norepinephrine?

A

Because of the presence of phenylethanolamine-N-methyltransferase (PNMT) which catalyzes the conversion of norepinephrine to epinephrine

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33
Q

What is a pheochromocytoma?

A

a tumor of the adrenal medulla

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34
Q

A pheochromocytoma releases what primarily?

A

norepinephrine

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35
Q

The fight or flight system of the sympathetic nervous system includes what?

A
  • Increases in HR, CO, BP, ventilation, and blood glucose
  • Redistribution of blood flow away from the skin and splanchnic regions toward the skeletal muscle
  • Decreases in GI motility and secretions
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36
Q

What is the overall function of the parasympathetic nervous system?

A

Restorative, to conserve energy

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37
Q

Where do the preganglionic neurons of the parasympathetic division arise from?

A

nuclei of cranial nerves III, VII, IX and X or from sacral spinal cord segments S2-S4 (craniosacral)

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38
Q

Where are the ganglia of the parasympathetic nervous system found?

A

near, on, or in the effector organs

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39
Q

Because parasympathetic ganglia are located near or in the effector organs, the preganglionic nerve axons are ____ and the postganglionic nerve axons are _____.

A

long

short

40
Q

Preganglionic neurons of the parasympathetic division are always _____ because they release ACh

A

cholinergic

41
Q

Most of the postganglionic neurons of the parasympathetic division are _____.

A

cholinergic

42
Q

ACh released from preganglionic neurons of the parasympathetic division activates _____ receptors, whereas ACh released from postganglionic neurons of the parasympathetic division activates _____.

A

nicotinic

muscarinic

43
Q

Parasympathetic cholinergic varicosities contain both the classic neurotransmitter and non-classic transmitters. What are they?

A

Classic: ACh

Non-classic: Vasoactive intestinal peptide (VIP) and nitric oxide (NO)

44
Q

Describe the roles of ACh, VIP, and neuropeptide NO play in contraction via the parasympathetic nervous system

A

1) ACh is released from the varicosities and binds to muscarinic receptors on the target tissue which direct its physiological action
2) With intense stimulation the large dense-core vesicles release VIP or NO which binds to receptors on the target tissues and augments the actions of ACh

45
Q

Because most organs have both sympathetic and parasympathetic innervation they are said to work ____ to produce coordinated movement

A

reciprocally or synergistically

46
Q

An increase in sympathetic activity and a decrease in parasympathetic activity ____ heart rate via beta1 and muscarinic receptors of the SA and AV nodes

A

decreases

47
Q

When the urinary bladder is filling _____ control predominates which produces a relaxation of the detrusor muscle, via ___ receptors and contraction of the internal sphincter via ____ receptors

A

sympathetic

beta2

alpha1

48
Q

During micturition (emptying of the bladder) _____ control predominates which produces a contraction of the detrusor muscle and relaxation of the internal sphincter, both via ____ receptors

A

parasympathetic

muscarinic

49
Q

What are the 2 muscles of the iris?

A
  • pupillary dilator (radial) muscles

- pupillary constrictor (circular) muscles

50
Q

The pupillary dilator (radial) muscles are controlled by ______ innervation through ___ receptors

A

sympathetic

alpha1

51
Q

Activation of alpha1 receptors causes constriction of the radial muscles which causes ____ of the pupil

A

dilation

52
Q

The pupillary constrictor (circular) muscles are controlled by ______ innervation through ___ receptors

A

parasympathetic

muscarinic

53
Q

Activation of muscarinic receptors causes constriction of the circular muscles which causes ____ of the pupil

A

constriction

54
Q

What are the 6 organs that have only sympathetic innervation?

A
  • sweat glands
  • vascular smooth muscle
  • pilomotor muscles of the skin
  • liver
  • adipose tissue
  • kidney
55
Q

In the parasympathetic division, effector organs have what type of receptor?

A

muscarinic receptors only

56
Q

In the sympathetic division, effector organs have what type of receptor?

A
  • 4 adrenoreceptors (alpha1, alpha2, beta1, and beta2)

- muscarinic receptors

57
Q

Because there is more than one receptor type in the sympathetic division, what does the receptor type depend on?

A

function

58
Q

What do alpha1 and alpha2 receptors cause?

A

contraction of smooth muscle such as vascular smooth muscle, GI and bladder sphincters, pilomotor muscles, and the radial muscles of the iris

59
Q

What are beta1 receptors involved in?

A

metabolic functions such as glucogenesis, lipolysis, renin secretion, and all functions in the heart

60
Q

What doe beta2 receptors cause?

A

relaxation of smooth muscle in bronchioles, wall of the bladder and wall of the GI tract

61
Q

What center of the hypothalamus is responsible for temperature regulation, thirst, food intake, and micturition?

A

the midbrain

62
Q

What center of the hypothalamus is considered the pneumotaxic center?

A

the pons

63
Q

What center of the hypothalamus is responsible for breathing, cardiovascular function, swallowing, coughing, and vomiting?

A

the medulla

64
Q

Describe the difference between beta1 receptors in the SA node and ventricular muscle

A

The beta1 receptor in the SA node is coupled to mechanisms that increase the spontaneous rate of depolarization and increase heart rate
- binding of an agonist such as norepinephrine to this B1 receptor increases the heart rate
The beta1 receptor in ventricular muscle is coupled to mechanisms that increase intracellular Ca2+ concentration and contractility
- binding of an agonist such as norepinephrine to this B1 receptor increases contractility, but does has no direct effect on the HR

65
Q

Drugs that are B1 agonists are expected to cause _____ HR and contractility

A

increased

66
Q

Drugs that are B1 antagonists are expected to cause _____ HR and contractility

A

decreased

67
Q

Agonists _____ their receptors and antagonists _____ their receptors

A

activate

block

68
Q

What are G-protein-linked receptors?

A

Autonomic receptors that are coupled to GTP-binding proteins (G proteins)

69
Q

Describe the structure G-protein-linked receptors

A

They are composed of a single polypeptide chain that winds back and forth across the cell membrane 7 times.

70
Q

What do the 2 ends of the

A

The ligand binds to the extracellular domain of its G-protein linked receptor. The intracellular domain of the receptor binds to a G protein

71
Q

G proteins are heterotrimeric , meaning that have 3 different subunits, what are these subunits?

A
  • α
  • β
  • γ
72
Q

What does the α subunit of a G protein bind to?

A

Either guanosine diphosphate (GDP) or guanosine triphosphate (GTP)

73
Q

What a G protein is bound to guanosine triphosphate (GTP) it is in its _____ state. When it is bound to guanosine diphosphate (GDP) it is in its ______ state.

A

active

inactive

74
Q

Activated G proteins activate enzymes (e.g. adenylyl cyclase, phospholipase C) that produce what?

A

A second messenger (e.g. cyclic adenosine monophosphate [cAMP] or inositol triphosphate [IP3]) that amplifies the message and executes the final physiological action

75
Q

In some cases can a G protein directly alter the function of an ion channel without the mediation of a second messenger?

A

Yes

76
Q

Where are adrenoreceptors found?

A

In target tissue of the sympathetic nervous system

77
Q

What 2 hormones activate adrenoreceptors?

A

norepinephrine and epinephrine

78
Q

What are the 2 types of adrenoreceptors and the 4 subtypes?

A

α and β

 - α1 
 - α2
 - β1
 - β2
79
Q

Where are α1 receptors found?

A

In vascular smooth muscle of the skin, skeletal muscle, and the splanchnic region, in the sphincters of the GI tract and bladder, and in the radial muscle of the iris

80
Q

Activation of α1 receptors leads to what?

A

The contraction of the tissues in which it is found

81
Q

Describe the mechanism of action of α1 adrenoreceptors

A

IP3 is catalyzed and causes a release of Ca2+ from intracellular stores in the endoplasmic reticulum

82
Q

Where are α2 receptors found?

A

On presynaptic adrenergic and cholinergic nerve terminals and in the GI tract

83
Q

Describe the mechanism of action of α2 adrenoreceptors

A

They inhibit adenylyl cyclase which results in cAMP levels decreasing

84
Q

Where are β1 receptors found?

A

In the heart, salivary glands, adipose tissue, and in the kidneys

85
Q

When β1 are activated in the SA node what happens?

A

heart rate increase

86
Q

When β1 are activated in ventricular muscle what happens?

A

contractility increases

87
Q

When β1 are activated in the salivary gland what happens?

A

secretion increases

88
Q

When β1 are activated in in the kidney what happens?

A

renin is secreted

89
Q

Where are β2 receptors found?

A

In the vascular smooth muscle of skeletal muscle, in the walls of the GI tract and bladder, and in the bronchioles

90
Q

Activation of β2 receptors leads to what?

A

Relaxation or dilation of the tissues in which they are found

91
Q

Describe the mechanism of action of β1 and β2 adrenoreceptors

A

They activate the stimulation of adenylyl cyclase which results in the increase of cAMP levels

92
Q

_______ is the primary catecholamine released from postganglionic sympathetic adrenergic nerve fibers

A

Norepinephrine

93
Q

_______ is the primary catecholamine released from the adrenal medulla

A

Epinephrine

94
Q

Where are nicotinic receptors found?

A
  • on the motor end plate of skeletal muscle
  • on all postganglionic neurons of both sympathetic and parasympathetic nervous systems
  • on the chromaffin cells of the adrenal medulla
95
Q

Describe the mechanism of action of nicotinic receptors

A

When rhw nicotinic receptor is activated by ACh, then channel opens and both Na+ and K+ flow through the channel leading to depolarization

96
Q

Where are muscarinic receptors found?

A
  • In all effector organs of the parasympathetic nervous system heart, GI tract, bronchioles, bladder, and male sex organs)
  • In the sweat glands of the sympathetic nervous system
97
Q

Describe the mechanism of action of muscarinic receptors

A

IP3 is generated which causes a release of Ca2+ from intracellular stores

630: Medical Physiology (24 decks)

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