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1 - PBS2 > 21 - Autonomic Nervous System > Flashcards

21 - Autonomic Nervous System Flashcards

1
Q

Tissues innervated by autonomic nervous system

A

All tissues except skeletal muscle fibres (careful: ANS innervates blood vessels within skeletal muscle)

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2
Q

What does the ANS need in order to maintain homeostasis?
1
2

A

• Signalling from the periphery, i.e. specialised sensors,
visceral sensory nerves
• CNS circuits to
– ‘interpret’ the signals
– decide on the most suitable outcome
– activate the appropriate sympathetic or parasympathetic
nerves

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3
Q

Anatomical distinction between sympathetic and parasympathetic nervous systems

A

Sympathetic fibres emerge from thoraco-lumbar part of spinal cord.

Parasympathetic fibres emerge from the cranio-sacral parts of the spinal cord.

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4
Q

Parts of spinal cord where no autonomic pathways originate

A

Cervical spine or lumbar enlargements.

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5
Q

Location of sympathetic pre-ganglionic neuron cell bodies

A

Intermediolateral cell column (T1 to L3)

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6
Q

Connections of sympathetic preganglionic neurons

A

Sympathetic postganglionic neurons lie in two types of ganglia:

1) Paravertebral ganglia (sympathetic chain)
2) Prevertebral ganglia

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7
Q

Function of sympathetic paravertebral ganglia

A

Primary source of vasoconstrictor muscles

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8
Q

Function of sympathetic prevertebral ganglia

A

Primary source of neurons innervating non-vascular smooth muscle

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9
Q

Sympathoadrenal system

A

Sympathetic preganglionic neurons innervate adrenal medulla (release of adrenaline)

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10
Q

Parasympathetic brainstem nuclei
1
2
3

A

Edinger-Westphal nucleus

Salivatory nuclei

Dorsal motor nucleus of vagus
and nucleus ambiguus

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11
Q

Edinger-Westphal nucleus role

A

To ciliary ganglion to control

sphincter pupillae, ciliary muscle

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12
Q

Salivatory nuclei role

A

To submandibular, sphenopalatine and otic ganglia to
control lacrimal, salivary, sublingual, nasal and palatine
glands

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13
Q

Dorsal motor nucleus of vagus and nucleus ambiguus role

A

To microganglia near and on outer surface of thoracic and abdominal organs: numerous functions

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14
Q

Sacral spinal parasympathetic preganglionic location

A

Intermediolateral cell column (S1 to S5)

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15
Q

Where do sacral postganglionic parasympathetic neurons connect?

A

Postganglionic neurons lie in pelvic plexus (inferior hypogastric plexus).

Form microganglia on target organs.

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16
Q

Pelvic ganglia

A

Pelvic ganglia contain many sympathetic and parasympathetic neurons:
i.e., these are mixed ganglia =
very unusual

17
Q

Where do the sympathetic neurons which deliver sensory information to ANS travel?

A

In the same nerve bundles as motor ANS neurons.

18
Q

How do ANS neurons connect with target organs?

A

Complex networks of unmyelinated axons within organs

More than one site of transmitter release per axon (axon varicosities)

19
Q

Major CNS integrative centre of autonomic function

A

Nucleus tractus solitarius (nucleus of the solitary tract)

20
Q

Type of neurons in the nucleus tractus solitarius

A

Second-order sensory neurons, which receive input from visceral afferents.

21
Q

Functions of the nucleus tractus solitarius
1
2

A

Information received from the periphery is distributed to either:
1. Provide feedback to reflexes that control organ/tissue function

  1. Provide information to higher centres to drive more complex responses (coordinated behaviour: visceral, somatic, endocrine; emotion)
22
Q

Central coordinator of autonomic output

A

Hypothalamus

23
Q

Examples of AND reflexes that don’t require the CNS

A

Enteric nervous system function.

24
Q

What often accompanies sympathetic NS activation?

A

Adrenal medulla activation (sympathoadrenal system).

25
Q

Why is sympathetic NS able to stimulate a large number of targets quickly?
1
2

A

• Catecholamine hormones spread through the
bloodstream
• Each preganglionic neuron activates many
postganglionic neurons

26
Q

Situations where sympathetic mass activation is necessary

A

Extreme, ‘fight or flight’ situations

27
Q

Situations where subtle sympathetic control are necessary

A

Adjustments of blood pressure (postural), small temperature changes, reproductive, voiding

28
Q 
Examples of parasympathetic functions
1
2
3
4
A
  • Decreased heart rate
  • Decreased contractile force of heart
  • Increased gut motility
  • Constriction of airways
29
Q

Why is the ability of the parasympathetic NS to ‘mass activate’ limited, compared to the sympathetic?
1
2
3

A
  • Much lower ratio of pre:postganglionic neurons
  • No equivalent of adrenal gland, ie no circulating Ach to
    affect all organs at once.
  • Therefore coordination has to occur by brain
    mechanisms
30
Q

Are the sympathetic and parasympathetic NSs often antagonistic?
1
2
3

A

• There are very few cases where the two systems are
genuinely antagonistic at the cellular level.
• More commonly, actions are on different tissues to
cause different type of actions (synergistic but not
necessarily opposite).
• Some tissues only have one type of innervation.

31
Q

Examples where sympathetic and parasympathetic NSs are genuinely antagonistic at the cellular level
1
2

A

1) Heart rate (S increases heart rate, P decreases, acting on SA node)
2) Airways (S relaxes, P constricts)

32
Q

Examples of functional antagonism between S and P
1
2

A

Sympathetic
contract pupil dilator muscle
contract base of bladder (continence)

Parasympathetic
contract pupil sphincter muscle
contract body of bladder (voiding)

33
Q

Examples of different but not opposite actions of S and P
1
2
3

A

Sympathetic
serous salivary secretion - only S innervation
constriction of abdominal vasculature - only S innervation
lipolysis
—

Parasympathetic
mucous salivary secretion
--
--
Tear secretion (lacrimal glands) - only P innervation
34
Q

Electroceuticals

A

Implanting an electrical device in the body which modulates nervous function

1 - PBS2 (96 decks)

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