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Imperial > 22. Cranial Nerves 🧠 > Flashcards

22. Cranial Nerves 🧠 Flashcards

1
Q

Which limb of the autonomic nervous system has more of an effect on the Liver?

A

Sympathetic – causes hepatic gluconeogenesis and glycogenolysis

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2
Q

Which limb of the autonomic nervous system dominates the lungs and the eyes at rest?

A

Parasympathetic Lungs – causes partial bronchoconstriction Eyes – allows near vision

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3
Q

Describe the relationship between baroreceptor firing and parasympathetic discharge.

A

Baroreceptors are stimulatory to the parasympathetic nerves i.e. an increase in baroreceptor firing stimulates an increase in parasympathetic firing

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4
Q

Describe the differences between sympathetic responses and parasympathetic responses.

A

Sympathetic – coordinated and divergent Parasympathetic – discrete and localised

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5
Q

What type of receptor are nicotinic receptors?

A

Type 1 – ionotropic receptors They are VERY fast

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6
Q

What type of receptor are muscarinic receptors?

A

Type 2 – G-protein coupled receptors Slower than Type 1 receptors

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7
Q

Describe the difference in the transmission through nicotinic and muscarinic receptors.

A

Nicotinic is much faster

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8
Q

What effect does parasympathetic dominance at rest have on the: lungs, gut, bladder and eyes?

A

Lungs – partial bronchoconstriction Gut – increased gut motility Bladder – increased urinary frequency Eyes – short-sightedness

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9
Q

Why would giving a ganglion blocker at rest cause constipation?

A

At rest the parasympathetic nervous system is dominant, which increases gastric motility. This means that a ganglion blocker will knock out this effect and cause constipation.

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10
Q

Where are the three types of muscarinic receptor found?

A

M1 – neural tissue M2 – heart M3 – exocrine and smooth muscle

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11
Q

Which adrenergic receptors are responsible for the sympathetic control of vasculature?

A

Alpha 1 – constriction Beta 2 – dilation

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12
Q

What type of receptor are all adrenergic receptors?

A

G-protein coupled

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13
Q

Describe the synthesis of acetylcholine.

A

It is formed from acetyl CoA and choline by choline acetyltransferase It is broken down by acetyl cholinesterase

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14
Q

Describe the synthesis of Noradrenaline.

A

Tyrosine -> DOPA (enzyme: tyrosine hydroxylase) DOPA -> dopamine (enzyme: DOPA decarboxylase) Dopamine -> Noradrenaline (enzyme: dopamine beta-hydroxylase) This last step takes place in a vesicle

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15
Q

What are the two uptake and breakdown mechanisms of noradrenaline?

A

Uptake 1 – neuronal tissue – mainly Monoamine Oxidase breakdown (MAO) Uptake 2 – extraneuronal tissue – mainly Catechol-O-Methyl Transferase (COMT)

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16
Q

Describe how the sympathetic nervous system exerts control over the trachea and bronchi.

A

The trachea and bronchi have no sympathetic nerve fibres. They are affected by the release of catecholamines from the adrenal medulla.

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17
Q

Describe the response of blood vessels to skeletal muscle during a period of increased sympathetic discharge. What causes this response?

A

Blood vessels supplying the skeletal muscle dilate. This is caused by circulating catecholamines.

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18
Q

Describe the role of the adrenal medulla in the sympathetic nervous system.

A

Adrenal medulla is innervated by sympathetic pre-ganglionic nerve fibres, which release acetyl choline that binds to the nicotinic acetyl choline receptors and causes release of catecholamines from the chromaffine cells.

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19
Q

What is special about the sympathetic innervation of the sweat glands?

A

The sympathetic nerves to the sweat glands release acetylcholine instead of noradrenaline.

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20
Q

What are the two outflows of the parasympathetic nervous system?

A

Craniosacral

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21
Q

State the four cranial nerves that form part of the parasympathetic nervous system.

A

Oculomotor - 3 Facial - 7 Glossopharyngeal - 9 Vagus – 10

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22
Q

Which parasympathetic nerves come out of the sacral region?

A

Pelvic spanchnic nerves

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23
Q

Describe the outflow of the sympathetic nervous system. State the vertebral levels that define the limits of this outflow.

A

Thoracolumbar (T1 - L2)

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24
Q

Describe the relative lengths of sympathetic and parasympathetic pre-ganglionic fibres.

A

Sympathetic nerves have a short preganglionic and a long post ganglionic Parasympathetic has a long preganglionic and a short post ganglionic

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25
Q

Describe the effect of the SNS on the heart.

A

The SNS has an inotropic (increase force of contraction) and chronotropic (increase heart rate) effect

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26
Q

Describe the effect of increased sympathetic firing on the blood vessels.

A

Increased sympathetic firing causes constriction of most blood vessels (except those supplying the skeletal muscle, which dilate)

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27
Q

How does the SNS affect arterial blood pressure?

A

SNS increase cardiac output via the chronotropic and inotropic effects and it increases TPR by causing vasoconstriction so it increases blood pressure

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28
Q

What can cause vasodilation in various tissues?

A

Vasodilation can be caused by local mediators such as nitric oxide and histamines Vasodilation in the penis is caused by increased parasympathetic stimulation Vasodilation in the blood vessels supplying skeletal muscle is due to increased sympathetic activity (by circulating catecholamines)

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29
Q

Describe how the SNS affects the GI tract.

A

SNS decreases gut motility and tone SNS stimulates contraction of sphincter SNS generally inhibits secretory activity

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30
Q

Describe the effects of increased sympathetic activity on the lungs and airways.

A

Increased sympathetic activity dilates the airways

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31
Q

Describe the effects of sympathetic and parasympathetic activity on the eye muscles.

A

Sympathetic - causes dilation of the pupil (contraction of radial muscles) Parasympathetic - constriction of the pupil and ciliary muscle contracts (lens bulges allowing near vision)

32
Q

Describe the nervous control of the bladder.

A

The parasympathetic nervous system controls the muscles of the bladder wall The sympathetic nervous system controls the internal sphincter There is somatic motor control of the external sphincter

33
Q

What is the capacity of the bladder?

A

450-500 mL

34
Q

State the three nerves involved in micturition.

A

Pelvic - sensory input from the stretch receptors in the wall of the bladder Hypogastric - sympathetic input to the internal sphincter Pudendal - voluntary control of the external sphincter

35
Q

What is acetyl choline made from?

A

Acetyl CoA and Choline

36
Q

What are catecholamines derived from?

A

Tyrosine

37
Q

What structure is common to all catecholamines?

A

Hydroxylated phenyl ring

38
Q

If you block acetylcholine action in autonomic ganglia, how would it affect heart rate?

A

The effect on heart rate would be dependent on which branch of the autonomic nervous system was more dominant at the time. Because all autonomic ganglia have acetyl choline so blocking it would affect both sympathetic and parasympathetic pathways.

39
Q

What are the differences between nicotinic and muscarinic receptors?

A

Nicotinic receptors are ion channel linked receptors so they allow fast transmission Muscarinic receptors are G protein linked receptors so their transmission is slower

40
Q

Describe the synthesis and breakdown of acetyl choline.

A

Acetyl choline is synthesised from Acetyl CoA and choline via the action of choline acetyl transferase. It is broken down in the synaptic cleft by acetyl cholinesterase

41
Q

What would happen if you inhibit acetylcholinesterase?

A

Inhibiting acetylcholinesterase would result in a build up of acetylcholine in the synaptic cleft and a decrease in the responsiveness of the post synaptic neurone receptors to acetylcholine and you will become paralysed. This how botulinum toxin works.

42
Q

Describe the synthesis of noradrenaline.

A

Tyrosine β€”> DOPA (tyrosine hydroxylase) DOPA β€”> Dopamine (dopamine decarboxylase) Dopamine β€”> Noradrenaline (Dopamine  hydroxylase)

43
Q

What can happen to the noradrenaline after it has had its effect?

A

It is taken up into pre-synaptic neurones and into extraneuronal tissue In the pre-synaptic neurones it is broken down by MAO (monoamine oxidase). In extraneuronal tissue it is broken down by COMT (Catechol-o-methyl transferase)

44
Q

Which cells in the adrenal medulla produce catecholamines?

A

Chromaffine cells

45
Q

What extra step and enzyme is involved in the synthesis of adrenaline?

A

Noradrenaline leaves the vesicle and is converted to adrenaline (via PNMT - phenylethanolamine N-methyl transferase) and repackaged into vesicles.

46
Q

Describe the effect of cortisol on adrenaline secretion.

A

Cortisol increases adrenaline secretion by upregulating PNMT.

47
Q

What are the break down products of noradrenaline and adrenaline by COMT and MAO-A? What do measurements of these values in the urine give an indication of?

A

COMT - VMA MAO-A - MOPEG Levels of MOPEG in the urine given an indication of sympathetic activity in the brain VMA give an idea of peripheral production of noradrenaline

48
Q

What are the main effects of the sympathetic nervous system on the CO = MABP/TPR equation?

A

Sympathetic has an inotropic and chronotropic effect thus SV and HR are increased so CO is increased. Sympathetic firing also causes generalised vasoconstriction so TPR increases.

49
Q

Describe the response to a decrease in blood pressure.

A

Decrease in blood pressure causes a decrease in baroreceptor firing so there is a decrease in the inhibition of the SNS. The SNS activity increases so you get an increase in CO and TPR.

50
Q

Describe the changes that take place when you stand up.

A

Gravity pushes a column of blood towards your toes so the blood pools in the distensible veins. This means that there is less venous return to the heart and so a lower force of contraction (Starling’s Law). This means that there is a drop in blood pressure when you stand up.

51
Q

What causes postural hypotension?

A

Impaired sympathetic nervous system response to transient hypotension

52
Q

Describe the effects of the sympathetic and parasympathetic nervous system on the eye muscles.

A

Sympathetic - contracts radial muscles and dilates the pupil Parasympathetic - contracts circular muscle and contracts ciliary muscles so you get pupil constriction and lens thickening to allow near vision

53
Q

State two drugs that affect the eye muscles and how they work.

A

Pilocarpine - acetyl choline drug - causes MIOSIS (constriction) Atropine - blocks the parasympathetic nervous system - causes MYDRIASIS (dilation)

54
Q

Describe the pupillary light reflex.

A

Afferent information goes via the optic nerve to the pretectal nucleus. From here, the impulses travel to the Edinger-Westphal nucleus where there parasympathetic neurons begin. The preganglionic parasympathetic neuron goes to synapse in the ciliary ganglion. There is a short postganglionic neuron that goes to the iris.

55
Q

What is the consensual reflex and what causes it?

A

When you shine a light in one eye, both eyes constrict. This is caused by the afferent information converging on the pretectal nucleus.

56
Q

If you achieve a direct response in the right eye with no consensual response in the left eye, where does the problem lie?

A

There is a problem with the parasympathetic nerves in the left eye.

57
Q

What are the main effects of the sympathetic nervous system on the CO = MABP/TPR equation?

A

Sympathetic has an inotropic and chronotropic effect thus SV and HR are increased so CO is increased. Sympathetic firing also causes generalised vasoconstriction so TPR increases.

58
Q

Describe the response to a decrease in blood pressure.

A

Decrease in blood pressure causes a decrease in baroreceptor firing so there is a decrease in the inhibition of the SNS. The SNS activity increases so you get an increase in CO and TPR.

59
Q

Describe the changes that take place when you stand up.

A

Gravity pushes a column of blood towards your toes so the blood pools in the distensible veins. This means that there is less venous return to the heart and so a lower force of contraction (Starling’s Law). This means that there is a drop in blood pressure when you stand up.

60
Q

What causes postural hypotension?

A

Impaired sympathetic nervous system response to transient hypotension

61
Q

Describe the effects of the sympathetic and parasympathetic nervous system on the eye muscles.

A

Sympathetic - contracts radial muscles and dilates the pupil Parasympathetic - contracts circular muscle and contracts ciliary muscles so you get pupil constriction and lens thickening to allow near vision

62
Q

State two drugs that affect the eye muscles and how they work.

A

Pilocarpine - acetyl choline drug - causes MIOSIS (constriction) Atropine - blocks the parasympathetic nervous system - causes MYDRIASIS (dilation)

63
Q

Describe the pupillary light reflex.

A

Afferent information goes via the optic nerve to the pretectal nucleus. From here, the impulses travel to the Edinger-Westphal nucleus where there parasympathetic neurons begin. The preganglionic parasympathetic neuron goes to synapse in the ciliary ganglion. There is a short postganglionic neuron that goes to the iris.

64
Q

What is the consensual reflex and what causes it?

A

When you shine a light in one eye, both eyes constrict. This is caused by the afferent information converging on the pretectal nucleus.

65
Q

If you achieve a direct response in the right eye with no consensual response in the left eye, where does the problem lie?

A

There is a problem with the parasympathetic nerves in the left eye.

66
Q

Cranial Nerve #1

A

Olfactory Sensory Fxn: smell Location: receptors are in olfactory part of nasal mucosa in the roof of nasal cavity (along medial wall of superior nasal concha). The olfactory fibers pass through foramina in cribriform plate and enter olfactory bulb in anterior cranial fossa. The nerve fibers synapse with mitral cells in the olfactory bulb and the axon of these cells form the olfactory tract which conveys the impulses to the brain. Cranial Exit: cribriform plate

67
Q

Cranial Nerve #2

A

Optic Sensory Fxn: vision Location: From retina the nerve exits the optic canal to enter middle cranial fossa where it forms the optic chiasma. This is where fibers from the medial half of each retina decussate in the chiasma and join uncrossed fibers from the lateral half of the retina to form the optic tract, this allows for binocular vision (depth perception) . So fibers from the right halves of both retinas form the right optic tract and fibers from the left halves form the left optic tract. Cranial Exit: optic canal

68
Q

Cranial Nerve #3

A

Oculomotor Motor Fxn: powers superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris muscles. Cranial Exit: superior orbital fissure

69
Q

Cranial Nerve #4

A

Trochlear Motor Fxn: motor to superior oblique muscle of the eye Location: Travels from midbrain and then along the lateral wall of the cavernous sinus and then passes into the superior orbital fissure into the orbit. Cranial Exit: superior orbital fissure

70
Q

Cranial Nerve #5

A

Trigeminal (3 branches) Ophthalmic: sensory, passes through superior orbital fissure. Supplies orbital structures, nasal cavity, skin of forehead, upper eyelid, eyebrows and superior nasal cavity. Maxillary: sensory, exits through foramen rotundum. Supplies lower eyelid, superior lip, gums and teeth, anterior cheek, lateral part of nose, posterior nasal cavity and maxillary sinus. Mandibular: mixed, exits through foramen oval. Supplies sensory innervation to anterior 2/3 of tongue, floor of mouth, mandibular teeth, lower lip, buccal, parotid and temporal regions of face, and external ear. Supplies motor innervation to muscles of mastication (masseter, temporalis, pterygoid muscles).

71
Q

Cranial Nerve #6

A

Abducens Motor Fxn: motor to lateral rectus to turn eye laterally (abduct) Cranial Exit: Superior orbital fissure

72
Q

Cranial Nerve #7

A

Facial (5 branches) - Temporal, zygomatic, buccal, mandibular, cervical Sensory and motor Fxn: facial expression, salivation, lacrimation, and taste Cranial exits: internal acoustic meatus to facial canal, exits at stylomastoid foramen.

73
Q

Cranial Nerve #8

A

Vestibulocochlear Sensory Fxn: hearing and equilibrium Exit: into internal acoustic meatus

74
Q

Cranial Nerve #9

A

Glossopharyngeal Sensory and Motor Fxn: swallowing, salivation and taste Sensory: posterior 1/3 of tongue, posterior pharynx, receptors for blood pressure, pH, oxygen and carbon dioxide concentrations (carotid body and sinus) Motor: pharyngeal muscles and parotid salivary gland Exit: jugular foramen

75
Q

Cranial Nerve #10

A

Vagus Sensory and motor Sensory: input from the mouth, thorax, heart and abdomen Motor: to soft palate, larynx, visceral organs of the thoraco, abdominal, and pelvic cavities. Exit: jugular foramen

76
Q

Cranial Nerve #11

A

Spinal Accessory (2 branches - cranial and spinal) Motor Fxn: Spinal - powers the sternocleiodomastoid and trapezius Cranial - helps to power the soft palate, pharynx and joins up with the Vagus nerve Exits: Enters the foramen magnum and exits the jugular foramen

77
Q

Cranial Nerve #12

A

Hypoglossal Motor Fxn: powers the intrinsic and extrinsic muscles of the tongue Exit: hypoglossal canal

Imperial (23 decks)

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