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Year 1 - Organisation of the Body > 6.2.2 Autonomic Nervous System (ANS) > Flashcards

6.2.2 Autonomic Nervous System (ANS) Flashcards

1
Q

What are the divisions of the autonomic nervous system?

A

Sympathetic, parasympathetic and enteric

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2
Q

What is the saying associated with the sympathetic nervous system?

A

Flight or flight

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3
Q

What is the saying for the parasympathetic nervous system?

A

Rest and digest

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4
Q

What is the function of the autonomic nervous system?

A

Acts as the efferent system for involuntary/visceral control of bodily functions.

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5
Q

What are the features of the sympathetic division of the autonomic nervous system?

A

Segmental chain ganglia (run in parallel to spinal cord)
Mainly thoracic spinal cord pre-ganglionic output
Visceral (internal organ) specific ganglia
Short pre-ganglionic and long post-ganglionic nerves
No outflow from brain or cervical spinal cord

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6
Q

What are the features of the parasympathetic division of the autonomic nervous system?

A

Output in cranial nerves and sacral spinal cord
No segmental organisation (still cover entirety of body)
Ganglia close to targets
Long pre-ganglionic and short post-ganglionic nerves

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7
Q

Are the features of the parasympathetic and sympathetic divisions of the autonomic nervous system similar?

A

No, they’re almost mirror opposites

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8
Q

What are the differences in length between pre- and post-ganglionic nerves in the parasympathetic and sympathetic nervous systems?

A

Sympathetic: short pre-ganglionic, long post-
Parasympathetic: long pre-ganglionic, short post-

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9
Q

What is the enteric nervous system?

A

The intrinsic nerves/nervous system in the gut wall

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10
Q

What are the two plexi of the enteric nervous system?

A

Submucosal and myenteric

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11
Q

Where is the submucosal plexus located?

A

Just below the epithelial layer

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12
Q

Where is the myenteric plexus located?

A

Deep in the smooth muscle of the gut wall

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13
Q

What is also considered to be part of the autonomic nervous system?

A

Important afferent sensory nerves that run with the autonomic motor nerves

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14
Q

What is the function of the afferent sensory nerves that run with the efferent autonomic motor nerves?

A

To relay information from stretch- and chemoreceptors to the CNS -> deliver information in the opposite direction to efferent autonomic nerves

Examples include stretch receptors in the aorta and chemoreceptors in the carotid bodies

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15
Q

What is the autonomic nervous system derived from?

A

Derived from the neural crest, instructed to differentiate by the interface between the ectoderm and the neuroectoderm.

If initial crest is removed, ectoderm will instead differentiate to form neural crest

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16
Q

How can migration of neural crest cells be observed?

A

Through tagging them with fluorescent proteins

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17
Q

What dictates the fate of neural crest cells?

A

Release dictates what they become, and the crest cells are released in ‘waves’, so all differentiate fully.

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18
Q

Why are the sympathetic chain ganglia arranged segmentally?

A

The neural crest migrates through the rostral half of each so the and forms the sympathetic neural chain ganglia.

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19
Q
  • What prevents neural cell migration in the caudal half of somites?
A

The caudal halves contain inhibitory molecules like Ephrin B1, so prevents growth toward this region.

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20
Q

How is the formation of sympathetic ganglia from a bipotent precursor cell determined?

A

Through the effect of local factors (i.e. FGF2) which also promote cell survival.
Presence of FGF2 results in the formation of a NGF competent cell, which inhibits action of glucocorticoids (which would instead result in the formation of chromaffin/adrenomedullary cell), so a sympathetic neuron is formed

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21
Q

From where does the enteric crest arise?

A

ONLY from cervical levels

Neural crest cells will invade gut and the pass down the hindgut

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22
Q
  • What can occur if not enough stem cells invade the gut during development?
A

Issues with gut function as the enteric plexi aren’t fully formed.

For example, Hirschprung’s disease: congenital megacolon
Failure to enter or survive of neural crest cells in gut wall cause a loss of nerve plexi and ‘megacolon’ (severely distended gut) - the gut is aganglionic and becomes huge.
Failure of crest colonisation could be due to mutations in GDNF (glial cell-line derived neurotrophic factor, promotes neural cell survival) or in genes for its receptor, c-ret

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23
Q

What do the superior cervical ganglion of the sympathetic nervous system supply?

A

The head and neck

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24
Q

What do the middle cervical and stellate ganglia in the sympathetic nervous system supply?

A

The heart and lungs

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25
Q

What do the thoracic chain ganglia in the sympathetic nervous system supply?

A

Skin, blood vessels and adipose tissue

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26
Q

What do the pre-vertebral ganglia in the sympathetic nervous system supply?

A

The abdominal and pelvic organs

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27
Q

What are the main pre-vertebral ganglia that supply the enteric nervous system innervated by?

A

The greater, lesser and least Splanchnic nerves

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28
Q

What ganglion supplies the foregut region of the enteric system?

A

The Coeliac ganglion

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29
Q

What ganglion supplies the midgut region of the enteric system?

A

The superior mesenteric ganglion

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30
Q

What ganglion supplies the hindgut region/pelvic organs of the enteric system?

A

The inferior mesenteric ganglion

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31
Q

How are ganglia inner are? (Three reasons)

A

Some pre-ganglionic nerves terminate in the ganglia
Some pass along the chain before terminating
Some pass to pre-vertebral/midline ganglia via splanchnic nerves

32
Q

Is the white or grey ramus seen in a nerve root myelinated?

A

The white is, the grey isn’t

33
Q

Draw out the structure of a nerve root

A

Do it!

34
Q

What is innervated by the parasympathetic III oculumotor nerve?

A

The eye and iris - mainly controls the size of the pupil.
Controls 4 out of 6 eye muscles (the smooth muscles), there is one nerve for every muscle fibre which results in very high precision.

35
Q

What is innervated by the parasympathetic VII facial nerve?

A

Tear and salivary glands
Innervation of the Pterygopalatine ganglion results in secretions of the lacrimal gland and nasal mucosa (why nose runs if you cry).
Innervation of the submandibular ganglion for salivary glands.

36
Q

What is innervated by the autonomic IX glossopharyngeal nerve?

A

Parotid (sides of mouth, just in front of ears)salivary gland
Otic ganglion got parotid gland, controls salivary secretions

37
Q

What is innervated by the parasympathetic X vagus nerve?

A

The heart, lungs and other viscera

Vagus means ‘wandering’, major supply to organs of thorax and abdomen

38
Q

What does the parasympathetic ganglionic supply for oculomotor, facial, glossopharyngeal and vagus nerves (amongst others) emerge with?

A

Cranial nerves

39
Q

What other nervous system can the vagus nerve stimulate?

A

The enteric nervous system

40
Q

What is the function of the submucosal plexus?

A

Regulates local blood flow, shape of luminal surface, controls glandular secretions and modulates electrolyte and water concentrations.

41
Q

What is the function of the myenteric plexus?

A

Sets up waves of contraction along smooth muscles know as peristalsis

42
Q

How is peristalsis stimulated?

A

Food in gut causes mechanical release of serotonin, which stimulates cells of the submucosal plexus (and secretion of digestive enzymes) which then in turn stimulates the myenteric plexus.

43
Q
  • How can the necessity for Ca^2+ in smooth muscle contraction be measured?
A

Through the use of calretinin. This is a molecule able to store Ca^2+, and will release the stored ions once it has been exposed to bright light (optogenetic stimulation). Electrical activity within colonic nerves can be measured after the molecule is exposed to light

44
Q

What are the terminals of autonomic nerves called?

A

Varicosities (NOT synapses)

45
Q

What are varicosities?

A

These are enlargements apparent along the autonomic nerves where junctions occur - this is where the neurotransmitters are released (all varicosities are packed full of neurotransmitter-carrying vesicles, as can be seen in cross-sections)

46
Q

What type of neurotransmitter and receptor are seen in ganglions of the ANS?

A

Neurotransmitter: acetylcholine
Receptor: nicotinic

47
Q

What type of neurotransmitter and receptor are seen at the terminals of the sympathetic ANS?

A

USUALLY
Neurotransmitter: norepinephrine (NE)
Receptor: alpha or beta-adrenergic receptors

OCCASIONALLY
Neurotransmitter: acetylcholine (ACh)
Receptor: muscarinic

48
Q

What type of neurotransmitter and receptor are seen at the terminals of the parasympathetic ANS?

A

Neurotransmitter: acetylcholine (ACh)
Receptor: muscarinic

49
Q

What is an example of a muscarinic sympathetic nerve?

A

Some of those innervating sweat glands - late phenotypic switch during development results in this change. The target cells instruct the receptor/nerve what to become.
I.e. thoracic sebaceous glands in hair follicles are an adrenergic target, whereas sweat glands in foot pad tissue are cholinergic

50
Q

What are neuromodulators?

A

These are molecules that modulate/control the action of primary transmitters

51
Q
  • What are some neuromodulators for the sympathetic ANS?
A

ATP (adenosine triphosphate)
NA (noradrenaline)
NPY (Neuropeptide Y)

52
Q
  • What are some neuromodulators for the parasympathetic ANS?
A

ACh (acetylcholine)
VIP (vasoactive intestinal polypeptide)
ATP (adenosine triphosphate)
NO (nitrous oxide)

53
Q
  • What are some neuromodulators for the sensory and motor nervous systems?
A

CRGP (calcitonin gene-related peptide)
SP (substance P)
ATP (adenosine triphosphate)

54
Q
  • What are some neuromodulators for the enteric ANS?
A

NANC inhibitory (non-adrenergic, non-cholinergic):
ATP (adenosine triphosphate)
NO (nitrous oxide)
VIP (vasoactive intestinal polypeptide)

Excitatory:
ACh (acetylcholine)
SP (substance P)

55
Q

What happens when the sympathetic nervous system is stimulated in the fight or flight response?

A

Impulse originates at hypothalamus
Goes to head ganglion of autonomic nervous system
Innervates greater splanchnic nerve which in turn stimulates the adrenal medulla
This secretes neurotransmitters (i.e. noradrenaline) into general circulation

56
Q

What are some effects of sympathetic nervous system?

A 
Pupils dilate (allow more light in for better vision, optimises light passage to the retina)
Vasoconstriction occurs (blood directed to muscles and areas of necessity, causes person to go pale)
Also later causes blushing but we are unsure as to why or how, seems to be connected to self consciousness in stressful situations - distress signal?
57
Q

How are cardiovascular effects driven and controlled?

A

Through CNS control centres

58
Q

What are the sympathetic cardiovascular effects?

A

Increase of heart rate, incr force of contraction, electrical conduction of heart increases

59
Q

What is the effect of sympathetic stimulation on the respiratory system?

A

Rate and depth of ventilation increases

60
Q
  • What type of nerves are the diaphragm and intercostal nerves innervated by?
A

Somatic, NOT autonomic. This is because we must sometimes control breathing - changes occur in the brain, the diaphragm isn’t smooth muscle.

61
Q

What are some other effects of the sympathetic nervous system?

A

Gastrointestinal tract: decreased motility (beta2), contraction of sphincters (alpha)

Liver: glycogenolysis (beta2 and alpha), gluconeogenesis (beta2 and alpha), lipolysis (beta2 and alpha), renin secretion (beta2), viscous salivary secretions (alpha)

62
Q
  • What is Horner’s syndrome?
A

This is where a lesion occurs on one side of the sympathetic superior cervical ganglion - often caused by a tumour at the apex of the lung.
Results in one pupil constricted (both should be the same), eyelid droops (ptosis, smooth muscle in eyelid), dry flushed facial skin

63
Q
  • What is hyperhidrosis and how can it be treated?
A

Excessive sweating
Old treatment:
Treated by cutting the sympathetic chain to prevent stimulation (burn nerve roots, but you lose all sympathetic responses in the hand/targeted area)
New treatment:
Use botulinum toxin (Botox) to prevent excessive stimulation of sympathetic nervous system, results in decrease in sweating

64
Q

What is the pupil reflex?

A

This is stimulation of the oculomotor parasympathetic nerves which in turn stimulates post-ganglion fibres from the ciliary ganglion that innervate the iris constrictor muscles -> this causes the pupil to constrict

65
Q

What is the micturition reflex?

A

There is a large debate over this process

Stretch receptors in bladder wall send signals to CNS via autonomic nerves (parasympathetic)
Stimulation of smooth muscle (the detrusor muscle) of the bladder wall results in contraction
Voluntary relaxation of sphincter muscles
In babies, bladder filling initiates reflex emptying - control is gained with age but we don’t know how.

66
Q

What is the defecation reflex?

A

Anal sphincter usually closed by voluntary/somatic and sympathetic tonic (slow and graded) stimulation
Detection of full bowel by autonomic afferents
Evacuation of bowel by voluntary opening of sphincters, stimulation of bowel smooth muscle and inhibition of tonic sympathetic control of sphincters

This control is again gained with age

67
Q

What are the male genital reflexes?

A

Afferent inputs by somatic and autonomic nerves
Erection occurs through dilation of helicine arteries
Sympathetic stimulation leads to emission of seminal fluid and closure of bladder sphincter
Somatic control over penile muscles causes ejaculation
NANC autonomic Neurons have a role here (look up more)

68
Q

What nerve roots do sympathetic nerves arise from?

A

Three cervical ganglia (superior cervical ganglion is the largest)
Others arise from T1-L2 -> these go to the viscera

69
Q

Are the sympathetic ganglia interconnected?

A

Yes, they have interconnecting neurones, passing up and down the chain ganglia

70
Q

Are post-ganglionic nerve fibres myelinated or non-myelinated?

A

Non-myelinated, so are slow

71
Q

Are pre-ganglionic fibres mostly myelinated or mostly unmyelinated?

A

Mostly myelinated with slow to medium velocity

72
Q

What is the gland closely associated with the sympathetic nervous system and what innervates it?

A

The adrenal glands

The greater splanchnic nerve

73
Q

What is important to remember about the cranial nerves that innervate the head and face?

A

They provide a mix of motor, sensory and autonomic supply - the cranial nerves emerge in an ordered sequence from I (olfactory) to XII (hypoglossal)

74
Q

What types of tissue are innervated by autonomic post-ganglionic nerves?

A

Smooth and cardiac muscle

Glands

75
Q

What sympathetic ganglia are likely to release noradrenaline?

A

Midline: coeliac, superior and inferior sympathetic ganglion cells - most release NA

76
Q

What are adrenal medullary cells?

A

Modified sympathetic ganglion cells that secrete adrenaline into the blood

77
Q

What is referred pain from viscera?

A

Referred pain is where the pain is felt at an area distant/separate from the origin of the pain.
In viscera, this occurs through a complicated process - visceral afferent nerves (usually nociceptive) run in similar pathways to those of the sympathetic nervous system and are exclusively thinly myelinated A-delta or unmyelinated C nerves. Injury can result in these nerves becoming mechanosensitive and leaking between the visceral and somatic system which can result in pain
Poorly understood

Year 1 - Organisation of the Body (20 decks)

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