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Head, neck and introduction to neuroanatomy > Session 4 > Flashcards

Session 4 Flashcards

1
Q

What are the components of the CNS?

A
  • Brain
  • Spinal cord
  • Cerebellum
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2
Q

What information do cranial nerves carry?

A
  • Sensory and motor information
  • Not all cranial nerves are mixed
  • Carry special senses e.g. taste, vision, smell
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3
Q

What is the forebrain?

A
  • Part of CNS that sits on top of the brainstem
  • Cerebrum and diencephalon
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4
Q

Describe the structure of the cerebrum

A
  • Largest portion of forebrain
  • Can be split into 2 symmetrical hemispheres
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5
Q

Describe the structure of the diencephalon

A
  • Hypothalamus sits in centre
  • Thalamus x2 sit on either side and act as relay stations for information coming up towards the brain
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6
Q

Describe the structure of the brainstem

A
  • Top = midbrain
  • Middle = pons (bulbous structure)
  • Bottom = medulla
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7
Q

What happens once the medulla passes through the foramen magnum?

A
  • It becomes the spinal cord
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8
Q

Which components of the brain make up grey matter?

A
  • Cortex
  • Sulci and gyri
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9
Q

Why is grey matter grey?

A
  • Due to high density of nerve cell bodies
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10
Q

What is the function of the grey matter of the brain?

A
  • Necessary for conscious awareness
  • All sensory menalities arise from grey matter and need to reach grey matter in order to be perceived
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11
Q

Describe the cortex of the brain

A
  • Grey matter
  • Outer surface of cerebrum
  • A few mm thick
  • Highest level at which motor system is represented
  • Conscious decisions to move body originate here
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12
Q

What is the function of the sulci and gyri?

A
  • Allows increase in surface area and the number of neurones that can be packed inside the brain
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13
Q

What are fissures?

A
  • Deep furrows into surface of cortex
  • Longitudinal fissure (falx cerebri found here)
  • Lateral fissures x2
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14
Q

Why is white matter white?

A
  • Colour is due to myelinated axons
  • White matter is densely packed with axons that arise from cell bodies in grey matter
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15
Q

What are the 4 key lobes of the hemisphere?

A
  • Frontal
  • Parietal
  • Temporal
  • Occipital
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16
Q

Which sulci/fissures delineate the different lobes of the hemisphere?

A
  • Central sulcus delineates frontal lobe from parietal lobe
  • Lateral fissure delineates temporal lobe from frontal and parietal lobes
  • Parieto-occipital sulcus delineates parietal lobe from occipital lobe
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17
Q

What is the corpus callosum?

A
  • White matter connecting the 2 hemispheres of the brain
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18
Q

What is the ventricle of the brain?

A
  • Cavity full of CSF
  • Normally covered by septum pellucidum
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19
Q

What terms do we use when describing the orientation of the brain?

A
  • Dorsal (superior surface of the brain)
  • Caudal (posterior surface of brain)
  • Ventral (inferior surface of brain)
  • Rostral (anterior surface of brain)
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19
Q

What terms do we use when describing the orientation of the brain?

A
  • Dorsal (superior surface of the brain)
  • Caudal (posterior surface of brain)
  • Ventral (inferior surface of brain)
  • Rostral (anterior surface of brain)
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20
Q

What are the components of the brainstem?

A
  • Midbrain
  • Pons
  • Medulla
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21
Q

What are the major functions of the midbrain?

A
  • Many centres and cranial nerve nuclei important for coordinating eye movement found here
  • Also important for coordinating reflexes of pupils
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22
Q

What are the major functions of the pons?

A
  • Important role in feeding trigeminal nerve involved in mastication
  • Contains centres for controlling sleep
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23
Q

What are the major functions of the medulla?

A
  • Contains important centres for CVS and the respiratory centre
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24
Q

Why do pathologies involving the brainstem impact a significant number of functions?

A
  • Brainstem contains lots of nervous tissue in a relatively small area
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25
Q

How do nerve signals enter the brainstem?

A
  • Signals travel from forebrain to cranial or spinal nerves via the brainstem
  • Sensory information passes to forebrain via the brainstem to be conciously perceived
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26
Q

What behaviours are controlled by the frontal lobe?

A
  • Voluntary motor control
  • Speech production
  • Social behaviour
  • Impulse control
  • Higher cognition (planning, thinking)
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27
Q

What behaviours are controlled by the temporal lobe?

A
  • Language
  • Emotion
  • Long-term memory
  • Sense of smell
  • Hearing
  • Taste
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28
Q

What behaviours are controlled by the parietal lobe?

A
  • Somatosensory perception
  • Spatial awareness
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29
Q

What behaviours are controlled by the occipital lobe?

A
  • Visual perception
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30
Q

What behaviours are controlled by the cerebellum?

A
  • Co-ordination and motor learning
31
Q

What is the clinical significance of the uncus?

A
  • Can be pushed through tentorial notch when intracranial pressure rises - uncal herniation
  • Uncus is located proximal to cranial nerve III
  • When uncus herniates, it pushes against this nerve, causing dysfucntion
32
Q

What is the clinical significance of the uncus?

A
  • Can be pushed through tentorial notch when intracranial pressure rises - uncal herniation
  • Uncus is located proximal to cranial nerve III
  • When uncus herniates, it pushes against this nerve, causing dysfunction
33
Q

What is the uncus?

A
  • Where we receive olfactory information
34
Q

What is meant by a topographical representation of the brain?

A
  • Specific parts of the body are mapped onto specific regions of the cortex
  • Certain parts of the body have greater representation in the cortex than others e.g. fingertips, tongue, lips
  • Mapping helps localise where lesions might be in the brain because lesions will cause very specific neurological dysfunction
35
Q

Outline the route taken by motor pathways in the brain

A
  • Primary motor cortex is responsible for motor control in contralateral side of the body
  • Pathways decussate (cross) to opposite side at level of lower medulla
  • I.e. motor control of the left arm is initiated in the right side of the brain
36
Q

Outline the pathway taken by sensory pathways in the brain

A
  • Sensory information comes into the primary somatosensory cortex
  • This pathway also crosses
  • I.e. sensory information felt in right arm reaches and is perceived by left somatosensory complex
37
Q

What do we mean by the statement that spinal nerves are mixed?

A
  • Spinal nerves contain some axons of motor neurones and some axons of sensory neurones
38
Q

What is meant by the statement that cranial nerves have dual cortical control?

A
  • Pathways connecting primary motor cortex with cranial nerves controlling the muscles of neck/face decussate to the opposite side
  • Crossing over occurs at level of nuclei onto which they synapse
  • Cortical control of muscles is contralateral
  • But most cranial nerves also have a back-up from the ipsilateral cortex
39
Q

Give brief overview of the cranial nerves

A
  • Supply tissues and structures if head and neck region including special sense organs
  • Part of peripheral nervous system (except CNS I and II)
  • Arise as pairs
  • Most are associated with the brainstem due to their nuclei location
40
Q

What kinds of fibres are carried in the cranial nerves?

A
  • Some are mixed with motor and sensory fibres
  • Some can be purely motor or sensory
  • 4 cranial nerves carry parasympathetic fibres
  • Nio sympathetic fibres
41
Q

What can neurological signs of cranial nerve dysfunction arise due to?

A
  • An injury or lesion involving
    1. The cranial nerve during its route outside of the CNS
    2. The brainstem where CN nuclei are located
    3. The neurones within the forebrain/brainstem which connect other parts of the brain to cranial nerves
42
Q

What is meant by 2 2 4 4?

A
  • 2 cranial nerves arise from the forebrain
  • 2 cranial nerves arise from the midbrain
  • 4 cranial nerves arise from the pons
  • 4 cranial nerves arise from the medulla
43
Q

List the names and numbers of all the cranial nerves

A
  • I = olfactory nerve
  • II = optic nerve
  • III = oculomotor nerve
  • IV = trochlear nerve
  • V = trigeminal nerve
  • VI = abducens nerve
  • VII = facial nerve
  • VIII = vestibulocochlear nerve
  • IX = glossopharyngeal nerve
  • X = vagus nerve
  • XI = accessory nerve
  • XII = hypoglossal nerve
44
Q

What is special about CN I and CN II?

A
  • They arise as extensions of the forebrain
45
Q

What can cause olfactory nerve lesions?

A
  • Head/facial injury - shears olfactory neurones during passage through cribriform foramina
  • Anterior cranial fossa tumours - compresses olfactory bulb/olfactory tract
  • Parkinson’s, Alzheimer’s
  • Commonest cause for anosmia is a common cold
46
Q

How do we test for olfactory nerve lesions?

A
  • Absence or reduced sense of smell (anosmia/hyposmia)
  • Test one nostril at a time
  • Not routinely tested
47
Q

Outline the passage of the olfactory nerve

A
  • Olfactory receptors within olfactory mucosa
  • Olfactory nerves travel up through base of skull through cribriform foramina
  • Travel to right or left olfactory bulb
48
Q

Why is the optic nerve affected by raised intracranial pressure?

A
  • It carries an extension of the meninges
49
Q

How is the optic nerve tested?

A

Pupillary size and response to light - CNII forms sensory/afferent limb of the pupillary light reflex
- Visual acuity (Snellen chart) and visual fields
- Ophthalmoscopy - can directly visualise part of optic nerve

50
Q

What will a patient with an optic nerve lesion report?

A
  • Blurred vision or complete absence of vision in the eye supplied by the affected optic nerve
  • On clinical examination, patient will have poor visual acuity, abnormalities in pupil size and response to light, evidence of pathology on ophthalmoscopy
51
Q

Which diseases can cause optic nerve lesions?

A
  • Optic neuritis
  • Anterior ischaemic optic neuropathy
52
Q

What changes might you see on opthalmoscopy of a patient with an optic nerve lesion?

A
  • Papilloedema - swollen optic disc seen in cases of raised intracranial pressure
  • Pale optic disc
53
Q

Outline the route taken by the optic nerve

A
  • Retinal ganglion cell axons converge at optic disc and form optic nerve
  • Optic nerve exits back of orbit via optic canal
  • Fibres from left and right optic nerve merge at optic chiasm (close to pituitary gland)
  • Continue as left and right optic tracts
  • Some fibres communicate from tract into brainstem to give information about light intensity and control pupil size
  • Some continue visual pathway
54
Q

Which pathologies can cause optic nerve lesions?

A
  • Retinal detachment
  • Optic neuritis
  • Pituitary tumour - compress optic chiasm
  • Strokes
55
Q

Why can optic nerve lesions affect either one eye or both eyes?

A
  • Depends on location of lesion along optic nerve
  • Pathology affecting a retina or an optic nerve on one side will cause blurring/visual symptoms in that one eye
  • Lesions involving optic chiasm onwards cause visual disturbances in both eyes
56
Q

What do the oculomotor, trochlea and abducens nerve all have in common?

A
  • Supply muscles in the orbital cavity that move the eyeball
  • Have commonality in route after exiting brainstem at different levels
57
Q

What is the common route taken by the oculomotor, trochlea and abducens nerve?

A
  • Cavernous sinus
  • Superior orbital fissure
  • Orbital cavity
58
Q

How do we clinically test the oculomotor, trochlea and abducens nerve?

A
  • Observe patient’s resting gaze
  • Ask patient to perform a series of eye movements
59
Q

What fibres make up the oculomotor nerve?

A
  • Contains motor and parasympathetic fibres
60
Q

What are the targets of the oculomotor nerve?

A
  1. Somatic efferent fibres are motor
    - Travel to skeletal muscle - all extraocular muscles (except 2)
    - Also supply levator palpebrae superioris (opens eyelid)
  2. Visceral efferent fibres are parasympathetic
    - Supply muscles inside the eyeball: ciliary muscle (controls thickness of lens) and sphincter pupillae
61
Q

Explain how we clinically examine the oculomotor nerve

A
  • Check eyelid position - supplies levator palpabrae superioris that keeps eyelid retracted
  • Eye movements - oculomotor nerve responsible for most muscles that move eyelid
  • Pupils and pupillary light reflex - parasympathetic fibres supply muscles controlling pupillary constriction
62
Q

What suggests an oculomotor nerve lesion?

A
  • Pt reports double vision
  • Ptosis
  • Abnormal position of eye - ‘down and out’
  • Pupil may or may not be dilated
  • Signs arise due to involvement of somatic fibres
63
Q

Where does the oculomotor nerve arise from?

A
  • Midbrain
  • Has close relationship to tentorium cerebelli edge as it travels to cavernous sinus
64
Q

How are parasympathetic fibres arranged in a mixed cranial nerve?

A
  • Around the periphery
65
Q

What are the pupil sparing oculomotor nerve lesions?

A
  • Microvascular ischaemia
  • Risk factors include: age >50 years and diabetes/hypertension
66
Q

What are pupil involving oculomotor nerve lesions?

A
  • Compressive lesions
  • E.g. aneurysmal, head injury, uncal herniation
67
Q

What is the function of the trochlear nerve?

A
  • Supplies superior oblique muscle
68
Q

What fibres make up the trochlear nerve?

A
  • Motor only
69
Q

How do we examine the trochlear nerve?

A
  • Inspect resting gaze - subtle abnormal eye position
  • Test eye movements - pt will have difficulty moving eye downwards when eye is positioned inwards
  • Pt will also report double vision
70
Q

Where does the trochlear nerve arise from?

A
  • Dorsal midbrain
71
Q

How do trochlear nerve lesions arise?

A
  • Congenital or acquired
  • Acquired due to:
  • microvascular ischaemia (risk factors include age >50, diabetes, hypertension)
  • trauma (causes nerve to snap or stretch)
  • intracranial tumour
72
Q

From where does the abducens nerve arise?

A
  • Caudal pons
  • Takes a vertical upwards route to cavernous sinus - this makes it susceptible to stretch e.g. when intracranial pressure rises
73
Q

What can result in abducens nerve lesions?

A
  • Microvascular ischaemia (diabetes, hypertension)
  • Head injury, tumour
  • Raised intracranial pressure - results in false localising sign
74
Q

Out of the oculomotor, trochlea and abducens nerve, which is most likely to be affected by raised ICP?

A
  • Abducens nerve
  • Has upwards vertical route
  • Is fixed at point of brainstem exit and entry to cavernous sinus
75
Q

What would you see on examination of a patient with abducens nerve lesion?

A
  • Pt reports double vision
  • Abnormal eye position at rest (one eye moves inwards when pt tries to look ahead)
  • Difficulty/inability to move affected eye laterally

Head, neck and introduction to neuroanatomy (11 decks)

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