Lecture 5: Brainstem and Cranial Nerves (I) Flashcards

1
Q

Brainstem consists of the

A

Consists of the

midbrain, pons and medulla

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2
Q

Brainstem is positioned between

A

Positioned between

the forebrain and spinal cord, and connected to the cerebellum dorsally

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3
Q

Brainstem provides a pathway for

A

Provides a pathway for axonal tracts running between the forebrain, cerebellum and spinal cord

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4
Q

Brainstem is associated with

A

Associated with 10 pairs of cranial nerves

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5
Q

Ventral =

A

anterior

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6
Q

Dorsal =

A

posterior

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7
Q

Cranial nerves - PNS or CNS?

A

Considered a part of the PNS rather than the CNS as they are considered peripheral nerves

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8
Q

Cerebral peduncles translation

A

little feet of the cerebrum

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9
Q

Cerebral peduncles other name

A

crus cerebri

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10
Q

What are the cerebral peduncles?

A

Collection of axonal tracts that connects one major brain region to another

white matter that connects brainstem to the cerebrum

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11
Q

What do the cerebral peduncles include?

A

includes axons that descend from the cerebral cortex to the brainstem and spinal cord
(passing longitudinally on the ventral surface of the midbrain)

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12
Q

What does the cerebral peduncle help to do?

A

help to anchor the cerebrum to the brainstem

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13
Q

III cranial nerve and cerebral peduncles

A

anterior

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14
Q

IV cranial nerve and cerebral peduncles

A

posterior

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15
Q

Colliculus define

A

any of a number of small swellings in the roof of the midbrain, involved in vision and hearing.

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16
Q

Superior cerebellar peduncle associated with

A

midbrain

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17
Q

Middle cerebellar peduncle associated with

A

pons

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18
Q

Inferior cerebellar peduncle associated with

A

medulla

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19
Q

How many mounds make up the mid brain

A

4 colliculi

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20
Q

What should you find in order to visualise the superior colliculus and the inferior colliculus?

A

Find the cerebral aqueduct

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21
Q

Superior colliculi =

A

visual relay & reflex centres

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22
Q

Functions of the superior colliculi

A

• receive inputs from the retina (anteriorly)/visual cortex (posteriorly going forward) &
project to vision-related areas in cortex
• concerned with the detection of movement of
objects in the visual field - track objects with eyes and to do so need to move eyes therefore muscles of the eye are innervated
• relay vision information to neurons innervating
the muscles that control eye movement

part of the visual pathway therefore relay information and also involved in reflexes

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23
Q

Inferior colliculi =

A

auditory relay and reflex nuclei

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24
Q

Functions of the inferior colliculi

A
  • relaying auditory information from hearing receptors of the ear to the sensory cortex - in particular on the primary auditory cortex which is the transverse temporal gyrus
  • act in reflexive responses to sound (e.g., startle reflex)
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25
Q

Substantia nigra location

A

located deep to the cerebral peduncle

internal structure in the midbrain

consists of two parts

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26
Q

Substantia nigra contains

A

contains melanin pigment which is the precursor of dopamine and gives the dark colouring

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27
Q

Function and damage to the substantia nigra

A

functionally linked to the basal nuclei/ganglia**

dopamine neuron degeneration-Parkinson’s disease - part of the substantial nigra contains dopamine neurons and these die in Parkinson’s disease

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28
Q

Two parts of substantia nigra

A

pars compacta (SNpc) and pars reticulata (SNpr)

SNpr is ventral/anterior to SNpc

SNpc dopamine neurons are located here

SNpr is between the cerebral peduncle and compacted

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29
Q

SNpr

A

pars reticulata

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30
Q

SNpc

A

pars compacta

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31
Q

SNpr has connections similar to ….

A

SNpr has connections similar to the internal division of the globus pallidus (GPi) = inhibitory input to the thalamus

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32
Q

Red nucleus in relation to substantia nigra

A

deep to substantia nigra

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33
Q

Why is the red nucleus red?

A

rich blood supply and contains iron pigment therefore red due to lots of erythrocytes and the presence of iron pigment

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34
Q

Red nucleus function

A

relay nucleus in some descending motor pathways therefore part of the movement pathway

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35
Q

Cerebral peduncle and red nucleus and substantia nigra named most anterior to most posterior

A

cerebral peduncle is most anterior then substantia nigra and then the red nucleus

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36
Q

Parts of the midbrain

A
• Cerebral peduncles 
• Colliculi (superior colliculi and inferior colliculi)
• Substantia nigra
 • Red nucleus
• Cranial nerves
- oculomotor (III) - trochlear (IV)
  • Cerebral aqueduct
  • Superior cerebellar peduncle • Mammillary bodies
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37
Q

Pons - cranial nerves associated

A
5-8 
5 = trigeminal 
6 = abducens 
7= facial
8=vestibulocochlear
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38
Q

Other structures that the pons is associated with

A

4th ventricle and middle cerebellar peduncle

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39
Q

Mamillary body is associated with

A

the hippocampus

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40
Q

What are mammillary bodies in the brain?

A

The mammillary bodies are a pair of small round bodies, located on the undersurface of the brain that, as part of the diencephalon, form part of the limbic system. They are located at the ends of the anterior arches of the fornix.

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41
Q

Pons composed of

A

Composed of conduction tracts - both ascending sensory & descending motor tracts
Composed of pontine nuclei e.g. pneumotaxic centre - not only composed of tracts also have specific clusters of neuronal cell bodies called nuclei (pontine nuclei)

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42
Q

Pons (bridge)

A

fibres forming a bridge from the pons into the cerebellum but also it is a bridge between the cerebrum and going down to the medulla and spinal cord

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43
Q

Pneumotaxic centre (respiratory centre)

A

Part of the pons, example of pontine nuclei

helps to maintain normal rhythm of breathing
(together with medullary centre ) - groups of neurons controlling breathing in the pons AND the medulla

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44
Q

4th ventricle and pons relationship

A

4th ventricle is posterior to the pons, 4th ventricle is associated with the pons

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45
Q

Components of the medulla

A

• Pyramids
• Olives
(these two sit in the medulla)

• Cranial nerves

  • glossopharyngeal (IX)
  • vagus (X)
  • accessory (XI)
  • hypoglossal (XII)

• 4th ventricle
• Inferior cerebellar peduncle
(these two are associated with the medulla)

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46
Q

Cranial nerves associated with the medulla

A
9-12 
9= glossopharyngeal 
10 = vagus 
11 = accessory 
12 = hypoglossal
47
Q

Pyramid location and origin

A

Located in the midline of the medulla, one on each side and inferior to each pyramid is the pyramidal decussation

neurons of origin of these axons are the pyramidal neurons in the cerebral cortex (which look like pyramids)

48
Q

Pyramid decussation

A

axons of pyramidal tracts cross over to the opposite side at the level just above the medulla- spinal junction (at the level of the foramen magnum) - cross over happens at the level of the first spinal nerve therefore at the junction of the medulla and the spinal cord

cross over of axons in the pyramid in the medulla

49
Q

Pyramid and olive location relative to each other

A

pyramid more at midline, olive protrudes out and is more lateral to the pyramid

50
Q

pyramids formed by

A

formed by the large

pyramidal (corticospinal) tracts descending from the (primary) motor cortex

51
Q

Olives

A

containing inferior olivary nuclei, which relay sensory information to the cerebellum

52
Q

medulla and 4th ventricle

A

4th ventricle is associated with the medulla (floor)

53
Q

Dorsal column composure

A

two tracts actually form large part of spinal cord called the dorsal column. This is fasiculus cunneatus and fasiculus gracilis

54
Q

Fasciculus gracilis

A

medial, part of dorsal column

Sensory information from the LOWER limb

55
Q

Fasiculus cunneatus

A

lateral, part of dorsal column

sensory information from the upper limb

56
Q

Medulla plays a role in

A

maintaining body homeostasis

cardiovascular centre, respiratory centres, other reflex centres

57
Q

Medulla - Cardiovascular centre

A

Cardiac centre adjusts rate and force of heart beat to meet the body’s needs
Vasomotor centre adjusts blood vessel diameter to regulate blood pressure

Cluster of neurons specifically associated with cardiovascular function

58
Q

Medulla - respiratory centres

A

control rate and depth of breathing (together with centre in pons)

along with pontine centre for respiration

controls lungs etc

59
Q

Medulla - other reflex centres

A

controls activities such as coughing, sneezing, gagging, swallowing, vomiting, sweating

60
Q

Pons AND medulla stroke

A

death due to inability to control breathing

61
Q

Medulla has a functional association with the

A

hypothalamus - the medulla does not work by itself

62
Q

Medulla and hypothalamus

A

The hypothalamus is an important autonomic (rather than conscious, parasympathetic and sympathetic) control centre. It sends its instructions to the medullary reticular centres (network of neurons), which carry them out by synapsing with the target structure(s) - to carry out the effect such as fibres to the heart, GI tract etc

63
Q

Cross sectional anatomy of medulla

A

structure internally is different to the spinal cord

  • Segmental arrangement of spinal cord ceases - each level of the spinal cord has a spinal nerve associated with it which is called a segmental arrangement, this is present in the spinal cord but ceases at the medulla
  • Reorganisation of white and grey matter - medulla has little clusters of grey matter and white matter everywhere else
  • Columns of white matter become distinct tracts- spinal cord has anterior columns which consist of a number of tracts, for medulla there is one major tract which is the corticospinal/pyramidal tract
  • Grey matter arranged into distinct nuclei
64
Q

How many pair of cranial nerves are there?

A

12 pairs

65
Q

How many cranial nerve pairs are associated with brainstem?

A

10 pairs

66
Q

How many cranial nerve pairs are attached to the forebrain?

A

2 pairs

67
Q

Cranial nerves - function

A

sensory and/or motor nerves - some are mixed and some are pure

68
Q

Sensory functions of cranial nerves

A
  • touch, pain for face e.g. pain in teeth
  • hearing, vision, smell (special senses)
  • visceral organs e.g. GI tract
69
Q

Motor functions of cranial nerves

A
  • eye movement
  • jaw & tongue muscles, facial expression
  • visceral organ activity
70
Q

Cranial nerve I

A

Olfactory

71
Q

Cranial nerve II

A

Optic

72
Q

Cranial nerve III

A

Oculomotor

73
Q

Cranial nerve IV

A

Trochlear

74
Q

Cranial nerve V

A

Trigeminal

75
Q

Cranial nerve VI

A

Abducens

76
Q

Cranial nerve VII

A

Facial

77
Q

Cranial nerve VIII

A

Vestibulocochlear

78
Q

Cranial nerve IX

A

glossopharyngeal

79
Q

Cranial nerve X

A

Vagus

80
Q

Cranial nerve XI

A

Accessory

81
Q

Cranial nerve XII

A

Hypoglossal

82
Q

Most anterior cranial nerve

A

Number 1 - olfactory nerve

83
Q

Most posterior cranial nerve

A

Number 12 - hypoglossal nerve

84
Q

Caudal

A

posterior

85
Q

rostral

A

anterior

86
Q

Sensory and/or Motor? - Olfactory nerve

A

Sensory

87
Q

Sensory and/or Motor? - optic nerve

A

Sensory

88
Q

Sensory and/or Motor? - oculomotor nerve

A

Motor

89
Q

Sensory and/or Motor? - trochlear nerve

A

Motor

90
Q

Sensory and/or Motor? - trigeminal nerve

A

Both

91
Q

Sensory and/or Motor? - abducens nerve

A

Motor

92
Q

Sensory and/or Motor? - facial nerve

A

both

93
Q

Sensory and/or Motor? - vestibulocochlear nerve

A

sensory

94
Q

Sensory and/or Motor? - glossopharyngeal nerve

A

both

95
Q

Sensory and/or Motor? - vagus nerve

A

both

96
Q

Sensory and/or Motor? - accessory nerve

A

motor

97
Q

Sensory and/or Motor? - hypoglossal nerve

A

motor

98
Q

Cranial nerves associated with forebrain

A
olfactory nerve (I)
optic nerve (II) 

2 in total associated

99
Q

Cranial nerves associated with midbrain

A
oculomotor nerve (III) 
Trochlear nerve (IV) 

2 in total associated

100
Q

Cranial nerves associated with pons

A
trigeminal nerve (V) 
abducens nerve (VI) 
Facial nerve (VII) 
Vestibulocochlear nerve (VIII) 

4 in total associated

101
Q

Cranial nerves associated with medulla

A
Glossopharyngeal (IX) 
Vagus nerve (X) 
Accessory nerve (XII) 
Hypoglossal nerve (XII) 

4 in total associated

102
Q

Olfactory nerves

A

cranial nerve I

tiny sensory nerves (filaments or fascicles )

run from the nasal mucosa, pass through cribriform plate
of ethmoid bone to synapse with the olfactory bulb

the olfactory receptor cells sit in the nasal mucosa, they are the olfactory nerves

Provide sense of smell (therefore sensory) - have these fine filaments of nerves sitting and detecting smell whilst they are sitting in your nasal mucosa and then sending the information up to the olfactory bulb which then sends its axons back as the olfactory tract

103
Q

Conduction pathway of smell with olfactory nerves

A

Olfactory receptor cells first which go up to the olfactory bulb with their filaments through the holes, then have the olfactory tract where the information is passed posteriorly and goes to various parts of the cerebrum so firstly it goes to the olfactory cortex in the temporal lobe which is where we become consciously aware of what we are smelling (is it burning, is it nice), then also have a pathway to the hippocampus where we have a memory of smells, also to the amygdala where we can have emotional responses to smells and lastly there is a pathway to the hypothalamus which is going from the hypothalamus back to the medulla particularly to the reticular formation/network which goes on to innervate the gastrointestinal tract where you can have responses by the viscera to the smell such as making enzymes in the digestive tract etc

104
Q

Damage to olfactory nerves

A

damage causes impaired sense of smell known as anosmia

This can happen when you fracture the ethmoid bone through a fracture of the skull as it can damage the fine filaments of the olfactory nerves

105
Q

Cribriform plate

A

holes in the ethmoid bone which fascicles/filaments go up through

106
Q

Optic nerves

A

Cranial nerve II

Axons arising from the retina of the eye to form optic nerve

Each optic nerve passes through its optic foramen of the orbit. Nerves converge to form optic chiasm (axons partially cross over) & continue on as optic tracts

Enables vision (aim of the optic system)

107
Q

Retina processing

A

Local currents are produced in response to light

rods and cones first (most posterior and closest to pigmented layer) then information transferred to bipolar neurons and then the information is passed on to retinal ganglion cells and it is the axons of these cells that form the optic nerve which project to subcortical and cortical visual areas

108
Q

Visual projection pathway

A

retina - optic nerve - optic chiasm - optic tract - superior colliculus and lateral geniculate nucleus - optic radiation - occipital lobe (visual cortex)

Superior colliculus - send information back to visual cortex through optic radiation back to the visual cortex

lateral geniculate nucleus of the thalamus is a thalamic nuclei

109
Q

Nasal retina sees

A

a temporal visual field

110
Q

Temporal retina sees

A

nasal visual field

111
Q

left side of each retina sees

A

the right visual field

112
Q

right side of each retina sees

A

the left visual field

113
Q

which retinas cross

A

nasal retinas