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Unit 12 (Tommy) > 12.1 The Autonomic Nervous System > Flashcards

12.1 The Autonomic Nervous System Flashcards

1
Q

What does the peripheral nervous system comprise of?

A
  1. Somatic nerves
    • ​​Innervate skeletal muscle & cranial nerves
    • 2 types:
      1. Afferent (sensory)
      2. Efferent (motor)
  2. Autonomic nerves
    • ​​Innervate glands, smooth muscle etc
    • 2 types:
      1. Visceral Afferents (sensory)
      2. Visceral Efferents (sympathetic/parasympathetic)
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2
Q

Where do the efferent neurones in the ANS arise from?

A

Sympathetic

Thorocolumbar T1-L2

Parasympathetic

Craniosacral CN III, VII, IX & X & S2-4

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3
Q

Draw a typical spinal nerve and where autonomic nerves travel through?

A

Autonomic nerves travel through the sympathetic chain

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4
Q

What are the types of motor fibres and and what do they innervate (ANS)?

A
  • A pre-ganglionic fibre which synapses with a post-ganglionic fibre
  • Cell body of pre-ganglionic fibres is in b_rain stem / grey matter of spinal cord_
  • Cell body of post-ganglionic fibres is located outside CNS in autonomic ganglia (different locations for sympathetic /parasympathetic)
  • Motor fibres innervate smooth muscle, cardiac muscle, glandular cells, viscera
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5
Q

What is the role of the autonomic nervous system?

A
  • ANS regulates activity in cardiac muscles, smooth muscles, glands
    • Detects change
    • Interprets change
    • Organises response (e.g. secretion, smooth muscle contraction)
  • 2 divisions – sympathetic & parasympathetic
  • Regulated primarily by the HYPOTHALAMUS - coordinates hormonal & neural outputs to maintain HOMEOSTASIS
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6
Q

What is the difference between the sympathetic and parasympathetic system?

A

Sympathetic “fight or flight”

  • Pupils dilate, ↑ sweating, goosebumps arrector pili, ↓ saliva (dry mouth)
  • Heart rate & BP ↑, peripheral arteries vasoconstrict, coronary arteries dilate,
  • Air ways dilate
  • Stomach, digestive system– ↓ secretion & peristalsis

Parasympathetic‘rest and digest’:

  • Heart rate ↓, force of contraction↓,
  • Vasoconstriction of coronary arteries,
  • Stomach & digestive system: ↑ secretion & peristalsis, ↑ saliva/tears
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7
Q

What is the difference between preganglionic & postganglionic fibres?

A

Preganglionic fibres

  • Arise from only 1 location
    • The lateral horn of the spinal cord grey matter T1—L2

Postganglionic fibres

  • Arise from only 2 possible locations:
    1. Paravertebral ganglia (sympathetic chain)
    2. Prevertebral ganglia (surrounding the abdominal aorta)
    • Coeliac ganglia
    • Superior mesenteric ganglia
    • Aortico-renal ganglia
    • Inferior mesenteric ganglia
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8
Q

How do the preganglionic fibres enter the sympathetic chain?

A
  1. Cell body in lateral horn of grey matter
  2. Leaves via the ventral root
  3. Enters the chain via the white ramus commuicans
  4. THERE ARE 3 POSSIBLE PATHWAYS HEREAFTER
    1. Preganglionic neurons can synapse immediately (or pass through the sympathetic chain & synapse later) within the sympathetic chain at the same vertebral level
    2. Preganglionic neurons can ASCEND before synapsing in the sympathetic chain
    3. Preganglionic neurons can DESCEND before synapsing in the sympathetic chain
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9
Q

How do post-ganglionic sympathetic fibres get to the organs?

A

Post-ganglionic sympathetic fibres to organs follow blood vessels (e.g. splanchnic nerves)

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10
Q

What is the purpose of visceral afferents (ANS) & how they do this?

A
  • Visceral afferents transmit sensations of visceral pain, stretch / fullness back to CNS;
  • Their ganglia are in dorsal root ganglion
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11
Q

What are the different types of splanchnic nerves and where do they travel to?

A
  • The GREATER splanchnic nerve (T5-9/10)
    • _​T_ravels to the celiac ganglion
  • The LESSER splanchnic nerve (T9-10 or T10-11)
    • Travels to the aorticorenal ganglion
  • The LEAST splanchnic nerve when present (T12)
    • Travels to the renal plexus
  • 2-4 LUMBAR splanchnic nerves
    • ​Travel to the superior hypogastric plexus
  • SACRAL splanchnic nerves
    • ​Travel to the inferior hypogastric plexus
  • •
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12
Q

What is special about the suprarenal glands in terms of the autonomic nervous system?

A
  • Adrenal medulla is innervated directly the PREGANGLIONIC neurones
    • NO post ganglionic neurone
    • NO parasympathetic innervation
  • Innervation of adrenal glands causes widespread sympathetic response via hormonal release
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13
Q

How do sympathetic nerves reach the head?

A
  1. Sympathetic nerves can travel with spinal nerves* & on the *surface of arteries
  2. They reach into the head via the internal carotid plexus
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14
Q

What is Horner’s syndrome and what are typical symptoms?

A

HORNER’S SYNDROME

Disruption of sympathetics on one side leads to unilateral symptoms

TYPICAL SYMPTOMS

  • Miosis - persistently small pupil
  • Ptosis - drooping of upper eyelid (paralysis of superior tarsal muscle)
  • Enophthalmos - sunken appearance to the eye
  • Anhidrosis - on affected side of face (inability to sweat)
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15
Q

Which muscles OPEN the eyelid?

A
  • Levator Palpebrae Superioris
  • Superior Tarsal Muscle

Both innervated by CN III

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16
Q

Where do preganglionic fibres arise from?

A
  1. Brain stem
    • They leave the brain stem in cranial nerves 3,7, 9 and 10
      • Cranial nerves 3, 7 and 9 synapse in one of 4 cranial nerve ganglia : ciliary*, *pterygopalatine*, *submandibular* , *otic
  2. S2-4 spinal cord segments
    * They synapse leave the spinal cord as pelvic splanchnic nerves S2-4
17
Q

Describe & explain CN X & what its target & function is

A

Vagus n (CN X): contains parasympathetic fibres

  • Preganglionic neurons: medulla (Dorsal vagal motor nucleus)
  • Postganglionic neurons: within walls of viscera E.g. enteric NS
  • Target: Thoracic & abdominal viscera (up to the splenic flexure)
  • Function: Rest & digest
18
Q

Describe & explain CN III & what its target & function is

A

Oculomotor n (CN III): contains parasympathetic fibres

  • Preganglionic neurons: midbrain (Edinger-Westphal nucleus)
  • Postganglionic neurons: Ciliary ganglion
  • Targets: Ciliary muscle & sphincter pupillae
  • Function: Accommodation of the lens, constriction of pupil
19
Q

Describe & explain CN VII & what its target & function is

A

Facial n (CN VII): contains parasympathetic fibres

  • Preganglionic neurons: pons (superior salivatory nucleus)
  • Postganglionic neurons: pterygopalatine & submandibular ganglia
  • Targets: Lacrimal glands, submandibular gland, sublingual gland
  • Function: Increased secretion (tears and/or saliva)
20
Q

Describe & explain CN IVX & what its target & function is?

A

Glossopharyngeal n (CN VIX): contains parasympathetic fibres

  • Preganglionic neurons: pons (inferior salivatory nucleus)
  • Postganglionic neurons: Otic ganglion
  • Target: Parotid gland
  • Function: Increased secretion
21
Q

Explain pelvic splanchnic nerves & what they target & function

A

Pelvic Splanchnic nerves (S2,3,4) contain parasympathetic fibres

  • Preganglionic neurons: S2-S4
  • Postganglionic neurons: within walls of viscera
  • Target: Hindgut & pelvic viscera
  • Function: Peristalsis, glandular secretion, engorgement of erectile bodies, urination
22
Q

Label this diagram

A
23
Q

Explain visceral afferents & their roles

A
  • Bring information about viscera to the CNS –Reflexive or Nociceptive
  • Visceral reflexes do not reach consciousness
    • Update brainstem/ hypothalamus on visceral function
    • Travel with parasympathetic nerves
  • When reached at a conscious level, information from visceral afferents is perceived as poorly localised pain, or felt as cramps that convey hunger, fullness, or nausea
24
Q

Explain pelvic pain

A
  • Pain from viscera ‘above or in contact with inferior layer of peritoneum’
    • Travels via sympathetic splanchnic nerves T10-L1
  • Pain from sub-peritoneal organs is conveyed via parasympathetic nerves S2-4
25
Q

What is referred pain?

A
  • Visceral pain results from excessive stretch, violent contractions, or ischaemia
  • Pain is vague, poorly localised, & is often referred to cutaneous regions
  • When pain spreads to a somatic structure it becomes sharper and more easily identified

Unit 12 (Tommy) (17 decks)

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