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Physiology Exam 3 > The Autonomic Nervous System > Flashcards

The Autonomic Nervous System Flashcards

1
Q

What does the ANS innervate?

A

Organs whose functions are not usually under voluntary control

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2
Q

What does the ANS effect?

A

Effectors include cardiac and smooth muscles and glands (part of visceral organs and blood vessels)
-In contrast, somatic motor system effectors are skeletal muscles (voluntary)

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3
Q

How many autonomic neurons are in the efferent pathway?

A

2 (preganglionic neuron and postganglionic neuron)
-Different from somatic motor neurons that have their cell bodies within the CNS and conduct impulses along a single axon from spinal cord to neuromuscular junction

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4
Q

Where is the preganglionic neuron’s cell body?

A

In gray matter of brain or spinal cord

-In contrast, somatic motor system does not have ganglia (somatic neurons have cell bodies within the CNS)

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5
Q

What does the preganglionic neuron synapse with?

A

2nd neuron within an autonomic ganglion (postganglionic neuron)
-Autonomic ganglion has axon which extends to synapse with target tissue

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6
Q

Where do preganglionic autonomic fibers originate?

A

In midbrain, hindbrain, and upper thoracic to 4th sacral levels of the spinal cord
-Origin of the presynaptic ganglia determine sympathetic vs. parasympathetic

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7
Q

Where are autonomic ganglia located?

A

In the head, neck, and abdomen

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8
Q

In terms of axon sheath, what is the difference between presynaptic and postsynaptic neuron?

A

Presynaptic is myelinated (which means that it is faster); postsynaptic is unmyelinated (slower neural response)

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9
Q

T or F: Autonomic nerves release NT that may be stimulatory or inhibitory

A

True

-In contrast, somatic motor system is only excitatory

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10
Q

What happens to smooth muscles in the absence of nerve stimulation?

A

They maintain resting tone

  • Involuntary effectors are somewhat independent of their innervation
  • In contrast, denervation of somatic motor neuron results in flaccid paralysis and atrophy
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11
Q

What is denervation hypersensitivity?

A

Damage to autonomic nerve makes its target tissue more sensitive than normal to stimulating agents

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12
Q

T or F: Cardiac and many smooth muscles can contract rhythmically in absence of nerve stimulation

A

True
-Automaticity is the cardiac cell’s ability to spontaneously generate an electrical impulse (depolarize). Cells that are dedicated to the purpose of generating an impulse to maintain a heart rate commensurate with the body’s need are called pacemaker cells.

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13
Q

What are the divisions of the ANS?

A

Sympathetic NS and Parasympathetic NS

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14
Q

What is true of both sympathetic and parasympathetic NS?

A
  • Both have preganglionic neurons that originate in CNS

- Both have postganglionic neurons that originate outside of the CNS in ganglia

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15
Q

What does Cranial Nerve X innervate?

A

Innervates the heart

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16
Q

Where do sympathetic myelinated preganglionic fibers exit the spinal cord?

A

In ventral roots from T1 to L2 levels

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17
Q

Where do sympathetic preganglionic nerve fibers separate and synapse with?

A

Separate from somatic motor fibers and synapse with postganglionic neurons within paravertebral ganglia

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18
Q

Paravertebral ganglia within each row are _________.

A

Interconnected

-Forming a chain of ganglia that parallels spinal cord to synapse with postganglionic neurons

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19
Q

What is divergence?

A

Preganglionic fibers branch to synapse with # of postganglionic neurons
-Good for bifurcation

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20
Q

What is convergence?

A

Postganglionic neuron receives synaptic input from large # of preganglion fibers
-Ex: many parts of brain interacting with respiration

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21
Q

What is mass activation?

A

Divergence and convergence cause the SNS to be activated as a unit

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22
Q

What is the sympathoadrenal system?

A

The stimulation of adrenal glands by mass activation of the sympathetic nervous system

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23
Q

What is the adrenal medulla innervated by?

A

Preganglionic sympathetic fibers

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24
Q

Why is the adrenal medulla considered a modified sympathetic ganglion?

A

Its cells are derived from the same embryonic tissue that forms postganglionic sympathetic neurons

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25
Q

What does the adrenal medulla secrete when stimulated by the sympathetic NS?

A

Epinephrine (Epi) and Norepinephrine (NE)

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26
Q

Where do parasympathetic preganglionic fibers originate?

A

In midbrain, medulla, pons, and in the 2-4 sacral levels of the spinal column

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27
Q

Where do parasympathetic preganglionic fibers synapse?

A

In terminal ganglia located next to or within organs innervated

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28
Q

T or F: Both sympathetic and parasympathetic fibers innervate blood vessels, sweat glands, and arrector pili muscles.

A

False; Parasympathetic fibers do NOT innervate blood vessels, sweat glands, and arrector pili muscles
-Most parasympathetic fibers do not travel within spinal nerves

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29
Q

How many of the cranial nerves contain preganglionic parasympathetic fibers?

A

4 of the 12 pairs (III, VII, X, XI)

30
Q

Where do cranial nerves III, VII, XI synapse?

A

In ganglia located in the head

31
Q

Where does the vagus nerve (X) synapse?

A

In terminal ganglia located in widespread regions of the body (outside the head)

32
Q

What does the vagus nerve (X) innervate?

A

Heart, lungs, esophagus, stomach, pancreas, liver, small intestine and upper half of large intestine
-Preganglionic fibers from the sacral level innervate the lower half of large intestine, the rectum, urinary and reproductive systems

33
Q

What is the “fight or flight” response?

A

A sympathetic effect that involves the release of NE from postganglionic fibers and Epi from the adrenal medulla

  • Mass activation prepares for intense activity
  • HR increases, bronchioles dilate, blood [glucose] increases
34
Q

What are the effects of the parasympathetic NS?

A

Release ACh as NT -> relaxing effects with smooth muscle, contraction effects with skeletal muscle

  • HR decreases, visceral blood vessels dilate, digestive activity increases
  • normally not activated as a whole (stimulation of separate parasympathetic nerves)
35
Q

What is the NT for all preganglionic fibers of both sympathetic and parasympathetic NS?

A

ACh

-Transmission at these synapses is termed “cholinergic”

36
Q

What is the NT released by most postganglionic parasympathetic fibers at synapse with effector?

A

ACh

37
Q

T or F: Axons of postganglionic neurons have numerous varicosities along the axon that contain NT.

A

True

38
Q

What is the NT released by most postganglionic sympathetic nerve fibers?

A

NE

-Transmission at these synapses is termed “adrenergic”

39
Q

What are the catecholamines?

A

Epi and NE; both are synthesized from the same precursor (Tyrosine -> DOPA -> Dopamine -> NE/Epi)
-Epi is released by the adrenal medulla

40
Q

How do beta adrenergic receptors produce their effects?

A

By stimulating production of cAMP

  • NE binds to receptor
  • G protein dissociates into alpha subunit or beta,gamma-complex
  • Depending upon tissue, either alpha subunit or beta,gamma-complex produces the effects
41
Q

What does the alpha subunit of the G protein involved in beta adrenergic stimulation activate?

A

Adenylate cyclase, producing cAMP

-cAMP activates protein kinase, opening ion channels

42
Q

Alpha1 adrenergic receptors produce their effects by the production of ____.

A

Ca2+

  • Epi binds to receptor
  • Ca2+ binds to calmodulin
  • Calmodulin activates protein kinase, modifying enzyme action
43
Q

What do alpha2 adrenergic receptors located on presynaptic terminal do?

A

Decrease release of NE

-Negative feedback control

44
Q

What do alpha2 adrenergic receptors located on postsynaptic terminal do?

A

Produces vasoconstriction

45
Q

Alpha1 adrenergic receptors are _______, while alpha2 adrenergic receptors are ________.

A

Stimulatory; inhibitory

46
Q

Does adrenergic stimulation have an excitatory or inhibitory effect?

A

Both; responses due to different membrane receptor proteins

47
Q

What is the response of adrenergic stimulation of alpha1 receptor protein?

A

Constricts visceral smooth muscles

48
Q

What is the response of adrenergic stimulation of alpha2 receptor protein?

A

Contraction of smooth muscle (vasoconstriction)

-Minor role

49
Q

What is the response of adrenergic stimulation of beta1 receptor protein?

A

Increases HR and force of contraction

50
Q

What is the response of adrenergic stimulation of beta2 receptor protein?

A

Relaxes bronchial smooth muscles

51
Q

What is the response of adrenergic stimulation of beta3 receptor protein?

A

In adipose tissue, function unknown

52
Q

All somatic motor neurons, all preganglionic and most postganglionic parasympathetic neurons are ______.

A

Cholinergic (release ACh as NT)

53
Q

Somatic neurons and all preganglionic autonomic neurons are excitatory or inhibitory?

A

Excitatory

54
Q

Postganglionic axons are excitatory or inhibitory?

A

Can be either

55
Q

What binds to muscarinic receptors? What do these receptors require?

A

Ach binds to receptor; requires mediation of G-proteins

-beta,gamma-complex affects opening or closing a K+ channel, or activating enzymes

56
Q

Are muscarinic receptors excitatory or inhibitory?

A

Can be either

  • Excitatory if depolarization occurs (K+ channels closed)
  • Inhibitory if hyperpolarization occurs (K+ channels opened)
57
Q

Where do muscarinic ACh receptors produce effects?

A

Produces parasympathetic nerve effects in the heart, smooth muscles, and glands

58
Q

What binds to nicotinic receptors? What does the binding cause?

A

ACh binds to 2 nicotinic receptor binding sites (ligand-gated channels b/c ion channels are part of receptor)
-Causes ion channel to open within the receptor protein -> opens a Na+ channel

59
Q

Are nicotinic receptors excitatory or inhibitory?

A

Always excitatory

60
Q

Where are nicotinic ACh receptors?

A

Postsynaptic membrane of all autonomic ganglia, all neuromuscular junctions, and some CNS pathways

61
Q

Certain nonadrenergeric, noncholinergic postganglionic autonomic axons produce their effects through other NTS such as?

A

ATP, VIP, and NO

-All have excitatory roles

62
Q

Most visceral organs receive innervation by parasympathetic or sympathetic fibers?

A

Dual innervation (by both)

63
Q

What are antagonistic effects of dual innervation?

A

Sympathetic and parasympathetic fibers innervate the same cells -> actions counteract each other
-Heart rate

64
Q

What are complementary effects of dual innervation?

A

Sympathetic and parasympathetic stimulation produces similar effects (each hormone stimulates a different STEP in the process of the same effect)
-Salivary gland secretion

65
Q

What are cooperative effects of dual innervation?

A

Sympathetic and parasympathetic stimulation produce different effects that work together to produce desired effect
-Micturition

66
Q

Which organs achieve regulation without dual innervation?

A

Adrenal medulla, arrector pili muscle, sweat glands, and most blood vessels receive only sympathetic innervation

  • Nonshivering thermogenesis
  • Regulation achieved by increasing/decreasing firing rate
67
Q

How is the ANS controlled by higher brain centers?

A

Sensory input transmitted to brain centers that integrate information -> can modify activity of preganglionic autonomic neurons

  • Medulla
  • Hypothalamus
  • Cerebral cortex and limbic system
68
Q

What brain center most directly controls the activity of the ANS?

A

Medulla

-Location of centers for control of cardiovascular, pulmonary, urinary, reproductive and digestive systems

69
Q

What regulates the medulla?

A

Hypothalamus

70
Q

What is the cerebral cortex and limbic system responsible for?

A

Visceral responses that are characteristic of emotional states

Physiology Exam 3 (4 decks)

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