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Physiology Exam 3 > The Autonomic Nervous System > Flashcards

The Autonomic Nervous System Flashcards

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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
What does the adrenal medulla secrete when stimulated by the sympathetic NS?
Epinephrine (Epi) and Norepinephrine (NE)
26
Where do parasympathetic preganglionic fibers originate?
In midbrain, medulla, pons, and in the 2-4 sacral levels of the spinal column
27
Where do parasympathetic preganglionic fibers synapse?
In terminal ganglia located next to or within organs innervated
28
T or F: Both sympathetic and parasympathetic fibers innervate blood vessels, sweat glands, and arrector pili muscles.
False; Parasympathetic fibers do NOT innervate blood vessels, sweat glands, and arrector pili muscles -Most parasympathetic fibers do not travel within spinal nerves
29
How many of the cranial nerves contain preganglionic parasympathetic fibers?
4 of the 12 pairs (III, VII, X, XI)
30
Where do cranial nerves III, VII, XI synapse?
In ganglia located in the head
31
Where does the vagus nerve (X) synapse?
In terminal ganglia located in widespread regions of the body (outside the head)
32
What does the vagus nerve (X) innervate?
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
What is the "fight or flight" response?
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
What are the effects of the parasympathetic NS?
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
What is the NT for all preganglionic fibers of both sympathetic and parasympathetic NS?
ACh | -Transmission at these synapses is termed "cholinergic"
36
What is the NT released by most postganglionic parasympathetic fibers at synapse with effector?
ACh
37
T or F: Axons of postganglionic neurons have numerous varicosities along the axon that contain NT.
True
38
What is the NT released by most postganglionic sympathetic nerve fibers?
NE | -Transmission at these synapses is termed "adrenergic"
39
What are the catecholamines?
Epi and NE; both are synthesized from the same precursor (Tyrosine -> DOPA -> Dopamine -> NE/Epi) -Epi is released by the adrenal medulla
40
How do beta adrenergic receptors produce their effects?
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
What does the alpha subunit of the G protein involved in beta adrenergic stimulation activate?
Adenylate cyclase, producing cAMP | -cAMP activates protein kinase, opening ion channels
42
Alpha1 adrenergic receptors produce their effects by the production of ____.
Ca2+ - Epi binds to receptor - Ca2+ binds to calmodulin - Calmodulin activates protein kinase, modifying enzyme action
43
What do alpha2 adrenergic receptors located on presynaptic terminal do?
Decrease release of NE | -Negative feedback control
44
What do alpha2 adrenergic receptors located on postsynaptic terminal do?
Produces vasoconstriction
45
Alpha1 adrenergic receptors are _______, while alpha2 adrenergic receptors are ________.
Stimulatory; inhibitory
46
Does adrenergic stimulation have an excitatory or inhibitory effect?
Both; responses due to different membrane receptor proteins
47
What is the response of adrenergic stimulation of alpha1 receptor protein?
Constricts visceral smooth muscles
48
What is the response of adrenergic stimulation of alpha2 receptor protein?
Contraction of smooth muscle (vasoconstriction) | -Minor role
49
What is the response of adrenergic stimulation of beta1 receptor protein?
Increases HR and force of contraction
50
What is the response of adrenergic stimulation of beta2 receptor protein?
Relaxes bronchial smooth muscles
51
What is the response of adrenergic stimulation of beta3 receptor protein?
In adipose tissue, function unknown
52
All somatic motor neurons, all preganglionic and most postganglionic parasympathetic neurons are ______.
Cholinergic (release ACh as NT)
53
Somatic neurons and all preganglionic autonomic neurons are excitatory or inhibitory?
Excitatory
54
Postganglionic axons are excitatory or inhibitory?
Can be either
55
What binds to muscarinic receptors? What do these receptors require?
Ach binds to receptor; requires mediation of G-proteins | -beta,gamma-complex affects opening or closing a K+ channel, or activating enzymes
56
Are muscarinic receptors excitatory or inhibitory?
Can be either - Excitatory if depolarization occurs (K+ channels closed) - Inhibitory if hyperpolarization occurs (K+ channels opened)
57
Where do muscarinic ACh receptors produce effects?
Produces parasympathetic nerve effects in the heart, smooth muscles, and glands
58
What binds to nicotinic receptors? What does the binding cause?
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
Are nicotinic receptors excitatory or inhibitory?
Always excitatory
60
Where are nicotinic ACh receptors?
Postsynaptic membrane of all autonomic ganglia, all neuromuscular junctions, and some CNS pathways
61
Certain nonadrenergeric, noncholinergic postganglionic autonomic axons produce their effects through other NTS such as?
ATP, VIP, and NO | -All have excitatory roles
62
Most visceral organs receive innervation by parasympathetic or sympathetic fibers?
Dual innervation (by both)
63
What are antagonistic effects of dual innervation?
Sympathetic and parasympathetic fibers innervate the same cells -> actions counteract each other -Heart rate
64
What are complementary effects of dual innervation?
Sympathetic and parasympathetic stimulation produces similar effects (each hormone stimulates a different STEP in the process of the same effect) -Salivary gland secretion
65
What are cooperative effects of dual innervation?
Sympathetic and parasympathetic stimulation produce different effects that work together to produce desired effect -Micturition
66
Which organs achieve regulation without dual innervation?
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
How is the ANS controlled by higher brain centers?
Sensory input transmitted to brain centers that integrate information -> can modify activity of preganglionic autonomic neurons - Medulla - Hypothalamus - Cerebral cortex and limbic system
68
What brain center most directly controls the activity of the ANS?
Medulla | -Location of centers for control of cardiovascular, pulmonary, urinary, reproductive and digestive systems
69
What regulates the medulla?
Hypothalamus
70
What is the cerebral cortex and limbic system responsible for?
Visceral responses that are characteristic of emotional states

Physiology Exam 3 (4 decks)

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