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Medical Studies 2A > 3.2 Autonomic Nervous System > Flashcards

3.2 Autonomic Nervous System Flashcards

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USMLE® Step 1 flashcards
1
Q
A
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2
Q

What is the advantage of the two-neuron chain in the autonomic nervous system (rather than the single neuron from CNS to effector in somatic)?

A

More junctions are possible; greater connectivity

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3
Q

Sympathetic pathways consist of a pre- and post-ganglionic neuron. What is the exception to this?

A

When the preganglionic neuron synapses with the adrenal medulla

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4
Q

Describe the length of the pre/post ganglionic fibres in para vs sympathetic

A

Para: Long pre, short post
Sympa: Short pre, long post

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5
Q

What neurotransmitters are released by para/sympathetic neurons?

A

Para: Ach in both
Sympa: Ach, then noradrenaline

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6
Q

Which neurotransmitter do somatic neurons release at their synapse with effector organs?

A

ACh

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7
Q

Which arm of the autonomic nervous system innervates more structures?

A

Sympathetic

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8
Q

How can the sympathetic nervous system cause dilation AND constriction in different structures, despite a single neurotransmitter (e.g. blood vessels vs bronchioles)

A

Different expression of receptors

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9
Q

Describe the responses of the different kinds of alpha and beta receptors to stimulation

A

Alpha 1/2: smooth muscle contraction

B1: Cardiac muscle contraction

B2/B2: Smooth muscle relaxation

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10
Q

Which is the only case where the sympathetic nervous system does NOT use NA? What receptor is involved, and where?

A
  • Sweat glands
  • ACh
  • Muscarinic receptors

(no sympa. innervation)

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11
Q

What receptors does ACh from the para. nervous system bind to?

A

Muscarinic (M1-M5)

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12
Q

Within what vertebral levels are the cell bodies of sympathetic nerves found?

A

T1-L2 (sympa = together)

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13
Q

What are the two kinds of sympathetic ganglia?

A
  • Paravertebral
  • Prevertebral
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14
Q

All sympa. preganglionic fibres synapse within a paravertebral ganglion in the sympathetic chain, except…

A

Those that innervate the adrenal glands or the abdomen

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15
Q

Describe a sympathetic nerve pathway from pre/post ganglionic through the sympathetic trunk

A
  • Preganglionic fibre arises from lateral horn, and travels out through spinal nerve
  • Exits spinal nerve, ad enters sympathetic trunk
  • Can travel up, down, or stay at same level
  • Synapses on post-synaptic in a ganglion, and heads out to effector through spinal nerve
  • OR: Becomes splanchnic nerve -> Purely atonomic nerves that head into abdominal viscera
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16
Q

True or false: splanchnic nerves contain autonomic and somatic fibres

A
  • False
  • Only autonomic, unlike spinal nerves
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17
Q

What can happen to sympathetic fibres after they leave the sympathetic chain?

A
  • Rejoin spinal nerves to innervates sweat glands, erector pili, blood vessels
  • Or: become splanchnic nerves, and supply viscera
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18
Q

What are the four prevertebral sympathetic ganglia?

A
  • Coeliac
  • Aorticorenal
  • Superior mesenteric
  • Inferior mesenteric
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19
Q

How do preganglionic sympathetic fibres reach the prevertebral ganglia?

A

Through the abdominopelvic splanchnic nerves

20
Q

Which cells within the adrenals do sympathetic fibres innervate?

A

Chromaffin cells

21
Q

Where does the parasympathetic nervous system arise?

A
  • Brainstem (CNs)
  • Sacral, from S2-S4
22
Q

What does the parasympathetic nervous system supply?

A

Organs of Head, neck, trunk, and external genitalia

23
Q

Do parasympathetic fibres synapse near/far from effectors?

A

Near (long pre, short post)

24
Q

The filum terminale is an extension of which meningeal layer?

A

Pia mater

25
Q

Which brain area is considered the “boss” of the autonomic nervous system?

A

The hypothalamus

26
Q

What is the role of the spinal cord in controlling the autonomic nervous system?

A

Controlling sympathetic visceral reflexes and parasympathetic visceral reflexes (depending on area of spinal cord)

27
Q

What are some autonomic processes that the hypothalamus mediates?

A
  • Temperature
  • Sex drive
  • Hunger
  • Circadian rhythms
28
Q

Autonomic nervous system maintains physiological parameters within an optimal range by means of…

A

Feedback loops

29
Q

Where does the solitary nucleus receive input from?

A
  • All chemo/baroreceptors
  • Visceral sensory input from thorax and adbomen (by CN X, VII, IX)
30
Q

Where does the solitary nucleus send output to (up and down)?

A

Within brainstem: Para. preganglionic neurons, sympa. control centres, resp. neurons.

Up: Hypothalamus, amygdala, thalamus

31
Q

What are the functions of autonomic brainstem nuclei?

A
  • Mediate autonomic reflexes
  • Control specific autonomic functions
  • Modulate global autonomic tone
32
Q

Where does the hypothalamus receive input from in terms of autonomic regulation?

A
  • Spinal cord/brainstem nuclei
  • Limbic system
33
Q

The hypothalamus doesn’t just maintain a stable internal environment by modulating our autonomic tone. It also alters our…

A

Behaviour

34
Q

Is the autonomic nervous system purely driven by REACTIVE feedback loops?

A
  • No; it can also be proactive (e.g. increased ventilation before exercise)
  • This is in response to higher order thinking
35
Q

What are the two muscles of the iris; which is controlled by which arm of the ANS, and which does what?

A
  • Pupillary sphincter (para., inner, constricts pupil)
  • Pupillary dilator (sympa., outer, dilates pupil)
36
Q

Which arm of the ANS is involved in near/far vision, and what are the corresponding lens changes

A
  • Near: lens bulges, para.
  • Far: lens tightened, sympa.
37
Q

Which muscle/ligament attaches to the lenses of the eye and controls near/far vision? What is the relationship between muscle contraction and ligament tension?

A
  • Ciliary muscle
  • Suspensory ligament
  • When the muscle contracts, the ligament is loosened (myopia)
38
Q

Which muscle receives sympathetic innervation that keeps the eyelid open when contracted? What larger muscle is it a part of?

A

Superior TAsal muscle. TAgs along as part of levator palpebrae superioris.

39
Q

What causes Horner’s Syndrome? From this, derive the three signs

A

Caused by lost sympathetic nerve supply to the eye:

  1. Drooping eyelid (partial ptosis)
  2. Constricted pupil (miosis)
  3. Bilateral anhidrosis
40
Q

Describe parasympathetic innervation of the pupil (fully)

A
  • Occulomotor nucleus in brainstem
  • Synapses in ciliary ganglion
  • Heads out to muscarinic receptors in pupillary sphincter
41
Q

Describe sympathetic innervation of the pupil (fully)

A
  • First order neuron runs from hypothalamus to upper thoracic region (T1-T6)
  • Second order neuron runs up sympa. chain to superior cervical ganglion, and synapses
  • Third order neuron travels with internal carotid artery before entering superior orbital fissure
42
Q

In terms of autonomic innervation, which receptors can be found in the bladder, and where?

A
  • Detrusor: muscarinic (P), and B2 (S)
  • Internal urethral sphincter: alpha 1 (S)
43
Q

True or false: the internal urethral sphincter has parasympathetic innervation

A
  • False
  • We simply mediate the amount of sympathetic input (like regenerative braking)
44
Q

Why doesn’t everyone piss themselves all the time?

A

Because we have top-down cortical inhibition of the pontine micturition center, which prevents contraction of the destrusor muscle via local, spinal reflexes.

45
Q

How is a suprapontine lesion likely to influence micturition (assuming it does in some way)?

A

Hyperreflexia -> loss of top down inhibition

46
Q

How is a suprasacral spinal lesion likely to influence micturition (assuming it does in some way)?

A

Detrustor-sphincter dyssynergia; detrusor overactivity

47
Q

How is a sacral spinal lesion likely to influence micturition (assuming it does in some way)?

A

Hypocontractile/acrontractile detrusor (failure of fundamental reflex pathway)

Medical Studies 2A (110 decks)

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