Neuroanatomy Flashcards
What are the 4 parts of the brain?
1) Cerebrum
2) Diencephalon
3) Cerebellum
4) Brain stem
How many pairs of spinal nerves are there?
31
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
What are the 3 components of the brainstem?
Superior to inferior:
1) Midbrain
2) Pons
3) Medulla
In the spinal cord, (grey/white) matter is central, while (grey/white) matter is peripheral.
Central: grey
Peripheral : white
What are CNS nuclei?
Aggregations of neuronal cell bodies
In the brain, (grey/white) matter is central, while (grey/white) matter is peripheral.
Central: white
Peripheral: grey (cerebral cortex)
What are the components of central grey matter in the brain?
Deep cortical grey matter:
eg. thalamus, hypothalamus
What are nodes of ranvier?
Gaps in myelin sheath in myelinated neurons
What are 5 neuroglial cells?
CNS:
1) Oligodendrocytes
- myelination
2) Astrocytes
- form BBB
3) Microglia
- immune cells
PNS:
4) Schwann cells
- myelination
5) Satellite cells
- structural and nutritional support
How does the mode of conduction differ between myelinated and non-myelinated neurons?
Myelinated: Saltatory conduction (activation in nodes of ranvier)
Non-myelinated: continuous conduction (activation across entire length of axon)
At which spinal level does the spinal cord end?
L1/2
What are the components of a spinal reflex arc?
1) Receptor
2) Afferent sensory neuron
3) CNS integration of information (mono/polysynaptic)
4) Efferent motor neuron carries impulse
5) Effector
Which spinal segments correspond to T10/11 vertebra?
Lumbar nerves
Which spinal segments correspond to T12-L1 vertebra
Sacral nerves
What are the 2 enlargements of the spinal cord?
1) Cervical → Brachial plexus
2) Lower enlargement → Lumbosacral plexus
What are the components of a spinal nerve?
1) Dorsal rootlets/root
2) Ventral rootlets/root
How many cranial nerves at the level of the brainstem?
10
What is the anatomical space between the pons and medulla?
Pontomedullary junction
What is located in the diamond-shaped space between the brainstem and cerebellum?
4th ventricle
What are 2 descending (motor) pathways?
1) Corticospinal (Pyramidal) tract
2) Extrapyramidal (postural) pathways
Which part of the brain integrates sensory information?
Post-central gyrus (in parietal lobe)
How is an upper motor neuron lesion differentiated from a lower motor neuron lesion?
Lower:
- hypotonia → flaccid paralysis
- muscular atrophy
- areflexia
- muscular fasciculations
Upper:
- hypertonia → spasticity, rigid paralysis
- hyperreflexia
- Pathologic reflexes (eg. clasp-knife, Babinski’s sign)
What are the similarities and differences between the neurotransmitters in the sympathetic and parasympathetic system?
Similarity:
- both use ACh @ pre-ganglionic synpase
Difference:
- Postganglionic
S: Noradrenaline (except eccrine sweat glands) - adrenergic nerves
PS: ACh - cholinergic nerves
Which structure separates the frontal and parietal lobe?
Central sulcus
Which structure separates the parietal and temporal lobe?
Lateral sulcus
What structure is located just anterior to the central sulcus?
Pre-central gyrus: motor function
What structure is located just posterior to the central sulcus?
Post-central gyrus: sensory function
What structure is located just inferior to the lateral fissure?
Primary auditory cortex
What are commissural fibers?
Commissural fibers connect an area in one hemisphere with an area in the opposite hemisphere
What is the corpus callosum?
Largest set of commissural fibers in the brain and is a pathway of crucial importance to speech-language functions
Which lobe is the calcarine sulcus located?
Occipital
- primary visual cortex
What 2 cortices are located anterior to the central gyrus?
primary and secondary motor cortex
Which cortex is located anterior to the motor cortices??
Prefrontal cortex
Which cortex is located posteroinferior to the prefrontal cortex and superior to the lateral fissure?
Motor speech cortex
Which 2 cortices are located posterior to the central sulcus?
Primary and secondary sensory cortices
Where is the auditory cortex?
Temporal lobe
Where is the sensory speech cortex?
Mainly temporal lobe but overlaps into parietal
What is the receptor for deep pressure and fast vibrations and where is it found?
Pacinian corpuscle in subcutaneous fat
What is the receptor for sustained pressure and where is it found?
Ruffini nerve endings in dermis layer
What is the receptor for changes in texture and slow vibrations?
Meissner’s corpuscle in upper dermis layer
What is the receptor for sustained touch and pressure and where is it found?
Merkel’s disc in upper dermis
What are 4 somatosensory systems?
1) Spinothalamic
- pain, temp, crude touch, pressure
2) Dorsal column medial lemniscus
- vibration, discriminative touch, conscious proprioception
3) Spinocerebellar
4) Trigeminothalamic
Minor:
5) Spino-reticular
6) Spino-olivary
7) Spino-tectal
What are the sensory modalities that are transmitted via the spinothalamic pathway?
1) Pain
2) Temperature
3) Crude touch
4) Pressure
What are the sensory modalities that are transmitted via the dorsal-column medial lemniscus pathway?
1) Discriminative touch
2) Vibration
3) Concious proprioception
Does sensory information transmitted in the Spinocerebellar tract reach consciousness?
No.
What type of neuron is associated with motor function?
Multipolar (M&M)
What type of neuron is associated with sensory function?
Pseudounipolar (pseudo sensory → SS)
What type of neuron is associated with specialised/special sensory function?
Bipolar (bipolar → special)
What cells are present in the central nervous system?
1) Ependymal cells → CSF
2) Oligodendrocytes → Myelin
3) Astrocytes → Structural support
4) Microglia → Macrophage
What cells are present in the peripheral nervous system?
1) Schwann cells → Myelin
2) Satellite cells → Structural support
How many pairs of cranial nerves are there?
12 pairs
How many pair of spinal nerves are there?
31 pairs
All cervical nerves exit the spinal column ___ each associated vertebral segment except _____ which goes ____.
above
C8
Under C7 vertebra
Each spinal nerve that arises from each associated ______ will exit via the _________ of its corresponding _____ and its adjacent
Spinal segment
Intervertebral foramen
Vertebral segment
At which depth would a lumbar puncture need to be?
@ L2-3
Subarachnoid space
What and where are the 2 spinal cord enlargements?
Brachial plexus (C5-T1)
Lumbosacral plexus (L2-S2)
Where does the spinal cord terminate?
L1/2
Where do all 1st order sensory neurons synapse?
Dorsal root ganglia
Describe the path an action potential takes in the Spinothalamic (Antero-lateral) system
1) Crude touch and pressure → Anterior
Pain and temp (both very pain → L) → Lateral
2) 1st order synapse @ DRG
3) Decussate and spinal segment and go up respective pathway/Spinal tract
4) 2nd order synapse @ Thalamus
5) 3rd order send signal to sensory cortex
Where do the neurons in the Spinothalamic/Antero-lateral tract decussate?
In the spinal cord
What are the sensory modalities transmitted in the Antero-lateral system?
1) Crude touch and pressure → AST
2) Pain and temperature → LST
Describe the path an action potential takes in the Dorsal-Column Medial Lemniscal (DCML) System.
1) Fine touch, vibration, conscious proprioception
2) 1st order synapse @ DRG
3) 2nd order goes up through the nucleus gracilis and cuneatus
4) 2nd order synapse @ Medulla oblongata of brainstem
5) 3rd order send signal to sensory cortex
Where do the neurons in the DCML tract decussate?
At the level of the Medulla Oblongata
What are the sensory modalities transmitted in the DCML system?
1) Fine touch and vibration
2) Conscious proprioception
Describe the path an action potential takes in Spinocerebellar system.
1) Subconscious proprioception
2) 1st order synapse @ DRG
3) 2nd order goes up dorsal or decussates to ventral ST
4) 2nd goes to cerebellum
(not cortex → unconscious)
Where do the neurons in the Spinocerebellar tract decussate?
If they do, it will be in the spinal cord
What are the sensory modalities transmitted in the Spinocerebellar system?
Unconscious proprioception
Where do descending neurons in the Pyramidal system decussate?
If they do (90%), it will be at the level of the medulla
Where do descending neurons in the Pyramidal system synapse?
Ventral horn
Sympathetic fibres have (short/long) preganglionic and (short/long) postganglionic neurons
Short pre, long post
(need immediate effect)
Parasympathetic fibres have (short/long) preganglionic and (short/long) postganglionic neurons
Long pre, short post
( need precise control)
Describe the path an action potential takes in the trigeminothalamic tract.
1) 1° in trigeminal ganglia
2) Synapse at sensory nucleus (brainstem)
3) Decussate @ brainstem
4) 2° transmit to thalamus
5) Synapse at thalamus
6) 3° transmit to sensory cortex
What sensory modalities are transmitted via the trigemino-thalamic system?
1) Crude touch
2) Fine touch
3) Pain
4) Temperature
5) Vibration
6) Pressure
7) Conscious proprioception
Which of the cranial nerves have sensory function?
Purely sensory:
CNI: Olfactory
CNII: Optic
CNVIII: Vestibulo-cochlear
Mixed:
CNV: Trigeminal
CNVII: Facial
CNIX: Glossopharyngeal
CNX: Vagus
Which of the cranial nerves have motor function?
Somatic:
CNIV: Trochlear
CNVI: Abducent
CNXII: Hypoglossal
Visceral:
CNVII: Facial
CNX: Vagus
Mixed:
CNIII: Ocular motor
CNV: Trigeminal
CNIX: Accessory
Where are the nuclei of the cranial nerves located?
Within brainstem
What is the dermatome of the trigeminal nerve?
Anything anterior to the line drawn from the (i) vertex, (ii) ear (iii) chin.
What are the 3 divisions of the trigeminal nerve?
1) Ophthalmic (V1)
2) Maxillary (V2)
3) Mandibular (V3)
Which level does the trigeminal nerve exits the brainstem?
Mid pons
What are the 3 components of the trigeminal sensory nuclei complex?
1) Principal (Chief) sensory nucleus
- fine touch and pressure
- pons
2) Spinal nucleus
- pain and temperature
- in medulla and upper cervical spinal cord
3) Mesencephalic nucleus
- conscious proprioception
- midbrain
What is the most unique property of the mesencephalic nucleus of the trigemino-thalamic tract?
1° sensory neurons are not in trigeminal sensory ganglion
(stays within CNS)
What are the relations of the thalamus?
Inferior: hypothalamus
Anterior: Interventricular septum
The thalamus is part of the ______________, between the ______________.
Thalamus
- part of diencephalon
- between midbrain and cerebral hemisphere
How are the left and right thalamus separated?
Interthalamic adhesion (mass intermedia)
The thalamus is divided into the _________________ by the ___________________.
Divided by internal medullary lamina into:
1) Anterior
2) Medial
3) Lateral (ventral & dorsal)
What are the sensory modalities of CNVII: Facial nerve and where are their 1° and 2° neurons?
1) Pain, temp, crude touch from ear
1°: geniculate ganglion
→ 2°: Spinal trigeminal nucleus
2) Taste from anterior 2/3 of tongue
1°: Geniculate ganglion → 2°: NTS
What are the sensory modalities of CNIX: Glossopharyngeal nerve and where are their 1° and 2° neurons?
1) Pain, temp crude touch from posterior 1/3 of tongue, ear, pharynx
1°: Glossopharyngeal ganglion (superior) → 2°: NTS
2) Taste from posterior 1/3 of tongue
1°: Glossopharyngeal ganglion (inferior) → 2°: NTS
3) Baroreception from carotid sinus
1°: Glossopharyngeal ganglion (inferior) → 2°: NTS
What are the sensory modalities of CNX: Vagus nerve and where are their 1° and 2° neurons?
1) Pain, temp, crude touch from external ear, larynx
1°: Vagal ganglion (Superior)→ 2°: Spinal trigeminal nucleus
2) Taste from pharynx
1°: Vagal ganglion (Inferior) → 2°: NTS
3) Baroreception from aortic body and sinus and other viscera (eg. lungs, GIT)
1°: Vagal ganglion (Inferior) → 2°:NTS
Where are the cell bodies of UMNs located?
Pyramidal: cerebral cortex
Extra-pyramidal: Brainstem
Where are the cell bodies of LMNs located?
Spinal nerves: Ventral horns
Cranial nerves: Brainstem
What are the descending motor pathways?
Pyramidal:
1) Corticospinal
2) Corticobulbar
Extrapyramidal:
3) Vestibulospinal
4) Reticulospinal
5) Rubrospinal
6) Tectospinal
The corticospinal tract transmits impulses for _______________.
Voluntary movement
Where do the pyramidal pathways arise from?
Cerebral cortex
What are the extra-pyramidal pathways and where do they arise from?
All from brainstem:
1) Rubrospinal ← red nucleus
2) Vestibulospinal ← vestibular nucleus
3) Tectospinal ← superior colliculus (tectum)
4) Reticulospinal ← reticular formation
What is the function of the rubrospinal tract and where does it arise from?
Rubrospinal tract:
- stimulate flexor, inhibit extensor + fine motor control
- red nucleus
What is the function of the reticulospinal tract and where does it arise from?
Reticulospinal tract:
- reflexes, muscle tone, voluntary movement
- reticular formation
What is the function of the tectospinal tract and where does it arise from?
Tectospinal tract:
- reflex head and neck movements to visual/auditory stimuli
- Superior colliculus (tectum)
What is the function of the vestibulospinal tract and where does it arise from?
Vestibulospinal tract:
- balance and postural stability by extensor muscles
- Vestibular nucleus
Describe the path of a upper motor neuron in the corticospinal tract.
Cerebral cortex
→ corona radiata
→ internal capsule
→ crus cerebri (midbrain)
→ pyramids (medulla)
→ ±decussate (most decussate)
- if decussate → lateral CST
- if no decussate → ventral CST
How do the lower motor neurons in the corticobulbar and corticospinal tract differ?
Corticospinal: contralaterally influenced
Corticobulbar: Bilaterally influences (except CNXII and part of CNVII that innervate lower facial muscles)
The trigeminal motor nucleus is located in the _________ and receives corticobulbar fibers (ipsi/contra/bi)laterally to innervate _________________.
Trigeminal motor nucleus (CNV):
- pons
- bilateral
- supplies:
i) Muscles of mastication (temporalis, medial and lateral pterygoid muscles, masseter)
ii) Mylohyoid and anterior belly of digastric
iii) Tensors (tympani and palatini)
The glossopharyngeal nerve’s nucleus is known as ___________ which is located in the _____________ and receives corticobulbar fibers (ipsi/contra/bi)laterally to innervate _________________.
CNIX: Glossopharyngeal
- Nucleus ambiguus in medulla oblongata
- bilateral
- supplies: stylopharyngeus
The Vagus nerve’s nucleus is known as ___________ which is located in the _____________ and receives corticobulbar fibers (ipsi/contra/bi)laterally to innervate _________________.
CNX: Vagus
- Nucleus ambiguus in medulla oblongata
- bilateral
- supplies:
i) All intrinsic muscles of soft palate (except Tensor Veli Palatini)
ii) Pharynx (except Stylopharyngeus)
iii) Larynx
The spinal accessory nucleus is located in the _________ and receives corticobulbar fibers (ipsi/contra/bi)laterally to innervate _________________.
Spinal accessory nucleus (CNXI):
- cervical spinal cord
- bilateral
- supplies:
i) SCM
ii) Trapezius
The Hypoglossal nucleus is located in the _________ and receives corticobulbar fibers (ipsi/contra/bi)laterally to innervate _________________.
Hypoglossal nucleus (CNXII):
- medulla oblongata
- bilateral
- supplies:
all muscles of tongue (except palatoglossal)
The Facial motor nucleus is located in the _________ and receives corticobulbar fibers (ipsi/contra/bi)laterally to innervate _________________.
Facial motor nucleus (CNVII):
- lower part of pons
- bilateral (except part that supplies lower part of face is contralateral)
- supplies:
i) Muscles of facial expression
ii) Stapedius
iii) Posterior belly of digastric
iv) Stylohyoid
Which of the cranial nerves have autonomic function?
CNIII: Oculomotor
CNVII: Facial
CNIX: Glossopharyngeal
CNX: Vagus
In a stroke, why would a px present with drooping on 1 side of the face?
Stroke → lesion in UMN of corticobulbar tract
→ all other facial muscles receive bilateral influence so can compensate
EXCEPT lower part of face only contralateral → flaccid paralysis
CNIII: Oculomotor
a) Supplies:
b) Pre-ganglionic nucleus:
c) Post-ganglionic ganglion:
CNIII: Oculomotor
a) Intrinsic muscles of eyeball
b) Edinger-Westphal nucleus
c) Ciliary ganglion
CNVII: Facial
a) Supplies:
b) Pre-ganglionic nuclei:
c) Post-ganglionic ganglion:
CNVII: Facial
a) Supplies:
i) Submandibular and sublingual glands
ib) Salivatory
ic) Submandibular
ii) Lacrimal gland
iib) Lacrimal
iic) Pteryogopalatine
CNXI: Glossopharyngeal
a) Supplies:
b) Pre-ganglionic nuclei:
c) Post-ganglionic ganglion:
CNXI: Glossopharyngeal
a) Supplies:
- Parotid gland
b) Pre-ganglionic nuclei:
- Salivatory
c) Post-ganglionic ganglion:
- Otic
CNX: Vagus
a) Supplies:
b) Pre-ganglionic nuclei:
c) Post-ganglionic ganglion:
CNX: Vagus
a) Supplies:
- CVS, Respi, GIT systems
b) Pre-ganglionic nuclei:
- Dorsal motor nuclei of vagus
c) Post-ganglionic ganglion:
- respective ganglia near/within target organs
How are the 2 cerebral hemispheres separated?
Longitudinal fissure
What is the cerebral cortex?
Covering of cerebral hemisphere composed of grey matter
What are the histological layers of the cerebral cortex?
Superficial to deep:
1) Mainly axon and dendrites
2) Small neurons + intracortical connections
3) Medium neurons + associated & commissural fibers
4) Thalamic fibers termination
5) Giant betz cells (pyramidal tract projection fibres)
6) Association and projection fibres
Which layer of the cerebral cortex do thalamic fibres termination?
Layer 4
Which layer of the cerebral cortex do pyramidal tract fibres project from?
Layer 5
Which layer of the cerebral cortex are commissural fibers found?
Layer 3 (medium neurons)
What are 3 types of white matter fibers in the brain and how are they different?
1) Association fibers
- within hemispheres
- layer 3
2) Commissural fibers
- between 2 hemispheres (eg. corpus callosum)
- layer 3
3) Projection fibers
- link cerebrum to other parts
- layer 5
Which layers of the somatic sensory and primary motor cortex white matter are enlarged and why?
Somatic sensory:
- layer 4 (needs to receive more info from thalamic fibers)
Primary motor:
- layer 5 (needs to project more via pyramidal tract)
What are 5 functional areas of the frontal lobe?
1) 1° motor cortex
- precentral gyrus
- somatotropically arranged
2) 2°Motor areas:
i) Premotor cortex (PMC)
ii) Supplementary motor area (SMA)
- between motor cortex and frontal gyri
- controls 1° motor cortex (skilled movements)
3) Motor/Broca’s speech area
- inferior frontal gyrus
4) Prefrontal cortex
- anterior to pre-motor area
- behaviour, plan, foresight (higher mental faculties)
5) Frontal eye field (FEF)
- conjugate eye movement
Which area of the frontal lobe controls higher mental faculties?
Prefrontal cortex
Which area of the frontal lobe controls skilled movements?
2° Motor area
Where is the secondary motor cortices?
Both: anterior to 1° motor cortex (area 6)
Premotor cortex: lateral side of hemisphere
Supplementary motor area: medial side of hemisphere
What are 2 difference between the secondary motor cortices?
1) Input
PMC: (i) frontal lobe for motor intentions (ii) sensory input from parietal lobe for tactile and visuospatial signals
SMA: internal cues for motor planning (pre-programmed movements)
2) Location
PMC: lateral side of hemisphere
SMA: medial side of hemisphere
What does a Broca’s area lesion cause?
Expressive aphasia
- difficulty in speaking/writing
Where is the Broca’s motor speech area?
Posterior part of inferior frontal gyrus in dominant hemisphere
Where is the frontal eye field?
Anterior to SMA/PMC
What do frontal eye field lesions cause?
Ipsilateral conjugate deviation of eyes
How does the cerebral cortex control eye movements?
Indirectly through gaze centers in reticular formation in brainstem
Which part of the brain would be affected if the following functions were impaired:
- inappropriate social behavior
- difficulty in adaptation and loss of initiative
- sucking, groping, grasping reflexes?
Prefrontal cortex
The pre-frontal cortex has two-way connections with all parts of the cerebral cortex except ____________________.
Primary motor and sensory areas
What are the components of the limbic system?
1) Hippocampus
2) Amygdala
3) Anterior thalamic nuclei
4) Limbic cortex
Where are the amygdalae?
Deep and medially within temporal lobes of brain
What is the function of the amygdala?
1) Memory
2) Decision making
3) Emotional reactions
4) Aggressive behavior
The parietal lobe receives input from _______________.
Ventral posterior nucleus of thalamus
Which brain area enables stereognosis?
Somesthetic association area
The somesthetic association area receives input from ________ and respond to ____________ stimuli.
Primary somatosensory cortex
Multimodal
- cutaneous and proprioceptive stimuli
What is the inferior parietal lobe for?
“Body schema”
- awareness of exisistence and spatial relationships of body
The inferior parietal lobule receives information from ______________________.
1) Supplementary visual
2) Somesthetic cortices
What does a inferior parietal lobule lesion cause?
Contralateral hemineglect
- failure to be aware of items to one side of space
What are 3 components of the parietal lobe?
1) 1° somatosensory cortex
2) Somesthetic association area
- stereognosis
3) Inferior parietal lobule
- body schema
What are 2 components of the temporal lobe?
1) 1° auditory cortex
2) Wernicke’s/sensory speech area
Where is the primary auditory cortex?
Upper surface of superior temporal gyrus
What are the fibers that connect Broca’s motor and Wernicke’s speech area?
Arcuate fasciculus
What does a Wernicke’s area lesion cause?
Receptive aphasia
- difficulty in understanding spoken word
What is the difference between a Broca’s and Wernicke’s area lesion?
Broca’s: Expressive aphasia
- difficulty in speaking/writing
Wernicke’s: Receptive aphasia
- difficulty in understanding spoken word
What are 2 components of the occipital lobe?
1) 1° visual cortex
2) Visual association area
Where is the primary visual cortex?
On both sides of the calcarine sulcus
What is the function of the visual association cortex?
Feature extraction (eg. motion, colour, shape)
What are the 2 pathways of the visual association cortex?
1) Ventral visual pathway
- form and colour (WHAT)
- underside of temporal lobe
2) Dorsal visual pathway
- spatial relationships and motor information (WHERE)
- into posterior parietal lobe
Which arteries provide anterior circulation to the brain?
i) Internal carotid →
ii) Middle cerebral
iii) Anterior cerebral
Which arteries provide posterior circulation to the brain?
i) Vertebral arteries →
ii) Basilar
iii) Posterior cerebral
The internal carotid artery enters the skull through the _____________ and divides into the _________________.
Enter through carotid canal
Divide into:
i) Anterior cerebral
ii) Middle cerebral
iii) Posterior communicating → posterior circulation anastomoses
The vertebral arteries enter the skull through the _______________ and merge at the __________ to form ________________ where it ascends to the _________ and divides into the _____________.
Enter skull through foramen magnum
Merge at pontomedullary junction → basilar artery
Ascend to pons
Divide into 2 posterior cerebral arteries
Which parts of the brain are supplied by the anterior cerebral artery?
Medial surface of frontal and parietal lobes
(motor and sensory cortices of lower limbs)
Which parts of the brain are supplied by the middle cerebral artery?
1) Lateral surface of frontal, parietal, temporal lobes (motor, sensory, auditory cortices)
2) Insula
What the branches of the middle cerebral artery?
Cortical branches:
1) Superior division
2) Inferior division
Deep branches:
3) Lenticulostriate arteries
What do the lenticulostriate arteries supply?
1) Posterior limb of internal capsule
2) Part of basal nuclei
What are the components of the vertebral-basilar system?
1) Basilar artery
2) Spinal arteries
3) Posterior inferior cerebellar artery
What does the basilar artery supply?
1) Cerebellum (anterior inferior cerebellar arteries)
2) Inner ear (Labyrinthine arteries)
3) Pons (Pontine arteries)
4) Cerebellum (Superior cerebellar arteries)
Posterior cerebral arteries:
5) Occipital lobe/visual cortex
6) Temporal lobe (inferio-medial)
What are the branches of the basilar artery?
1) Posterior cerebral
2) Superior cerebral
3) Pontine
4) Labyrinthine
5) Anterior inferior cerebellar
What are the branches of the internal carotid artery?
1) Anterior cerebral
2) Middle cerebral
3) Ophthalmic
4) Hypophyseal
5) Anterior choroidal arteries
6) posterior communicating
Which of the cerebral arteries is most likely occluded in an ischemic stroke?
Middle cerebral artery
What is the effect of a superior division middle cerebral artery occlusion?
1) Contralateral hemiparesis
- face, hand, arm but SPARES leg
2) Contralateral hemisensory
- in same distribution except vision (no homonymous hemianopia)
What is the effect of a inferior division (less common in isolation) middle cerebral artery occlusion?
1) Contralateral homonymous hemianopia
2) Marked impairment of cortical sensory function
3) Disorders in spatial thought (eg. dressing apraxia, unaware deficit exists, contralateral hemineglect)
What is the blood supply to Broca’s area?
Superior division of middle cerebral artery
What is the blood supply to Wernicke’s area?
Inferior division of middle cerebral artery
What is the effect of a deep branch middle cerebral artery occlusion?
1) Contralateral hemiplegia
2) Sensory loss
- face, hand, arm and leg
What is the effect of a posterior division middle cerebral artery occlusion?
1) Homonymous hemianopia affecting contralateral visual field (macular vision can be spared by dual supply from posterior cerebral artery)
2) Difficulty naming objects and read (if in dominant hemisphere)
3) Ocular anomalies eg. disturbances in gaze and oculomotor nerve palsy (if near origin of posterior cerebral artery at level of midbrain)
What are 3 arteries that supply the spinal cord?
1) Anterior spinal
2) Posterior spinal
3) Segmental/radicular
What are the components of the blood brain barrier?
1) Capillary endothelium
- continuous w tight junctions
- only some are fenestrated (eg. pineal gland, area postrema, median eminence)
2) Basement membrane
3) Perivascular foot plates of astrocytes
What are the types of brain in the vein?
1) Superficial
2) Dural venous sinuses
3) Deep
What is Bell’s palsy?
CNVII: Facial nerve palsy
→ abrupt ipsilateral paralysis of facial muscles
Where does the trigeminal nerve (CNV) exit the brainstem?
Mid pons
Where does the Facial nerve (CNVII) exit the brainstem?
Pontomedullary junction
Which cranial nerves lie within the posterior cranial fossa after exiting the brain stem and how do they leave the fossa?
CN5:
- middle cranial fossa
CN7, 8
- internal acoustic meatus
CN9, 10, 11
- jugular foramen
Describe the path of the trigeminal nerve as it exits the brainstem?
Exit @ mid pons
→ posterior cranial fossa
→ middle cranial fossa (Trigeminal sensory ganglion)
→ cavernous sinus
i) V1 → superior orbital fissure
ii) V2 → foramen rotundum
iii) V3 → foramen ovale
What are the components of the cavernous sinus in the middle cranial fossa?
1) CN3
2) CN4
3) CN5 (V1, 2)
4) CN6
5) Internal carotid artery
What is the most important relation of the cavernous sinus?
Pituitary gland
Where do the trigeminal branches exit the cranial cavity?
V1 - Ophthalmic - superior orbital fissure
V2 - Maxillary - foramen rotundum
V3 - Mandibular - foramen ovale
Where does the hypoglossal nerve exit the cranial cavity?
Hypoglossal canal
Describe the course of the glossopharyngeal nerve.
Exit from medullar oblongata
→ posterior cranial fossa
→ exit @ jugular foramen
→ between Internal carotid artery and internal jugular vein
i) supply posterior 2/3 of tongue
ii) supply pharynx
Describe the course of the vagus nerve?
Exit from medullar oblongata
→ posterior cranial fossa
→ exit @ jugular foramen
→ between Internal carotid artery and internal jugular vein
i) Thorax (root of lungs)
ii) Esophagus
iii) Diaphragm
Describe the course of the accessory nerve.
Spinal portion:
Exit from upper cervical ventral horns
Cranial portion:
Exit from medulla oblongata
Both:
enter posterior cranial fossa
→ jugular foramen
→ posterior triangle of neck
Describe the course of the hypoglossal nerve.
Exit from medullary oblongata
→ hypoglossal canal
→ external carotid artery
→ submandibular
Describe the visceral reflex arch for the homeostasis of blood pressure.
Sensory afferent nerve:
CNIX → inferior glossopharyngeal ganglion
CNX → inferior vagal ganglion
both synapse to NTS
Motor efferent nerve:
CNX:
Preganglionic: Dorsal vagal nucleus
Postganglionic: Cardiac ganglia
What are the components of the eye (superficial to deep)?
Outer: (fibrous)
1) Sclera
2) Cornea
Intermediate: (vascular and pigmented)
3) Choroid
4) Ciliary body
5) Lens (suspensory ligaments)
Innermost: (nervous)
6) Retina
What is the function of the ciliary body?
Near-far accommodation
- ciliary muscle constrict → suspensory ligaments relax → lens thicker and rounder → near vision
- vice versa
What are the intraocular muscles and what are their functions?
1) Ciliary muscle
- contract → near vision
2) Dilator pupillae
- dilate pupil
3) Sphincter pupillae
- constrict pupil
Which cranial nerve supplies the intraocular muscles?
CNIII: Oculomotor nerve
What are the layers of the retina?
1) Pigment
2) Photoreceptor
3) Outer nuclear
4) Outer plexiform
5) Inner nuclear
6) Inner plexiform
7) Ganglion cell
8) Nerve fiber
Describe the structure of the nervous layer of the retina.
1) Photoreceptors
- transduce light stimuli
2) Bipolar cells
- transmit APs to ganglia
3) Ganglion cells
- project to thalamus → CNII: Optic nerve
What are 3 differences between rod and cone cells?
Rods:
1) Sensitive to dim light
2) Colour transmission
3) Not in fovea
Cones:
1) Work in bright light → acute detail
2) Black and white vision
3) Most numerous in fovea
Where in the eye does the optic nerve exit?
Optic disk
What is the most sensitive part of the eye?
Fovea centrale
Which form of photoreceptors are found at the optic disk?
Neither, it is a blind spot.
Visual images that travel through the retina are __________________ by the lens.
Inverted and reversed
The central 2/3 of the visual field are _______________ while the outer 1/6s on each side are __________________.
Central 2/3: Binocular
Lateral 1/6: Monocular
How is the visual field related to the retinal field?
Visual field
→ inverted and reversed
→ retinal field
(eg. UL → LR)
Which part of the optic nerve of each eye would decussate at the optic chiasm?
Nasal hemiretina (temporal is I/L)
Where do the optic nerves synapse?
Lateral geniculate nucleus of thalamus
→ optic radiation → 1° visual cortex
What are the nuclei in the midbrain that are responsible for visual reflexes?
1) Super colliculus → extraocular muscles (corneal reflex)
2) Pretectal nucleus → intraocular (accommodation and pupillary reflex)
The lateral geniculate body receives signals from the (ipsi/contra)lateral nasal hemiretina and (ipsi/contra)lateral hemiretina?
C/L nasal
I/L temporal
What are the optic radiations?
Axons from relay neurons in lateral geniculate nucleus of thalamus
- carries visual information to the visual cortex
Which part of the visual field does the Meyer’s loop transmit?
Superior quadrants
The primary visuals cortex is located on both sides of the ______________. While the visual association areas are located adjacent to _____________.
1° visual cortex adjacent to Calcarine sulcus
Visual association areas adjacent to 1° visual cortex
What happens to visual signals after reaching the 1° visual cortex?
1) Ventral visual pathway
- form and colour
- under side of temporal love
2) Dorsal visual pathway
- motion and spatial relationships
- posterior parietal lobe
How would a px with a optic chiasm lesion present?
Bitemporal hemianopia
- loss of lateral visual field
How would a px with a single optic nerve lesion present?
Ipsilateral monocular blindness
How would a px with a bilateral optic chiasm compression present?
Binasal hemianopia
- loss of medial visual field
How would a px with a single optic tract lesion present?
Contralateral homonymous hemianopia
How would a px with a 1° visual cortex stroke present?
Homonymous hemianopia with macular sparing
- macular sparing by collateral circulation of middle cerebral and posterior cerebral
How would a px with a partial meyer’s loop lesion present?
Contralateral superior quadrantanopia
What is the difference between seeing and looking?
Looking → attention → align thing into fovea (foveation)
What is the difference between looking and watching?
Looking: static
What are the extraocular muscles and their innervation?
Recti:
1) SR3
2) IR3
3) MR3
4) LR6
Oblique:
5) SO4
6) IO3
What are the movements of the eye mediated by the extraocular muscles?
1/2) Ad/Abduction (lateral → abduct)
3/4) In/external rotation (round lateral → external)
5/6) Elevation/depression
Which part of the brain does the oculomotor nerve exit?
Cerebral peduncle of brainstem
CNIV: Trochlear nerve is the only cranial nerve that exits __________________________.
Posteriorly before running anteriorly
Which part of the brain does the Abducens nerve exit?
Pontomedullary junction of the brainstem
Describe the course of Oculomotor, Trochlear and Abducens nerve.
All → exit from brainstem
→ posterior cranial fossa → middle cranial fossa (within cavernous sinus)
Enters orbit via superior orbital fissure
Which extraocular muscle is innervated by the Abducens nerve?
Lateral rectus
How would a px with an Abducens nerve lesion present?
Paralysis of lateral rectus muscle:
1) Diplopia on lateral gaze of side of affected eye ← disconjugated movement
2) Affected eye cannot abduct (medial deviation of eye)
Which extraocular muscle is innervated by the Trochlear nerve?
Superior oblique muscle
How would a px with an Trochlear nerve lesion present?
Paralysis of superior oblique muscle:
- elevation of affected eye during forward gaze
- exacerbated/relieved with adduction/abduction (test with head tilting)
How would a px with an Edinger Westphal nucleus/ciliary ganglion lesion present?
Failure of near-far accommodation → mydriasis
How would a px with a Oculomotor nerve lesion present?
1) Ptosis (paralysed levator palpebrae superioris)
2) Passive lateral deviation (check by lifting affected eyelid) (unopposed action of lateral rectus by CN6)
3) Diplopia (Except in lateral gaze: monocular)
4) Mydriasis
What is the difference between saccades and smooth pursuit?
Saccades:
- quick, darting, conjugate movement
Smooth pursuit:
- slower conjugate movement
What is conjugate movement of the eyes?
Two eyes rotates at same time, in same direction and by same amount
Con/Divergence involves ________________ in the eye, to allowing near-far accommodation.
Directing 2 foveae at same object
Describe the pupillary light reflex pathway.
Bright light → retina → pretectal nucleus:
1) I/L Edinger-Westphal nucleus → Ciliary ganglion → contraction of sphincter pupillae (direct reflex)
2) Posterior commissure → C/L Edinger-Westphal nucleus → Ciliary ganglion → contraction of sphincter pupillae (consensual reflex)
Describe the pathway for near vision accommodation.
Near vision → visual cortex → visual association area → superior colliculus (brainstem):
1) CN3, 4, 6 nuclei → extraocular muscles → ocular convergence
2) Edinger-Westphal nucleus → ciliary ganglion →
(i) sphincter papillae muscle → pupillary constriction
(ii) ciliary muscles → lens thickening
Describe the pathway for pain-mediated pupillary dilation.
1) Hippocampal formation + Ventroposterior nucleus + Dorsomedial nucleus → hypothalamus
2) Limbic system → reticular formation
→ Intermediolateral nucleus
→ Superior cervical ganglion
→ Internal carotid plexus
→ Dilator pupillae
Which parts of the brain control motor skills?
1) Cerebral cortex
- control execution of movements
2) Cerebellum
- monitors muscles during movement
3) Basal ganglia
- control position and voluntary movements
How are the motor cortex, cerebellum and basal ganglia related?
1) Cerebral cortex → cerebellum (via pons)
→ excitatory → motor cortex (via thalamus)
2) Cerebral cortex → BG
→ inhibitory → motor cortex (via thalamus)
3/4) Via LMNs (corticospinal)
i) → cerebellum (via spinocerebellar) → cortex (via thalamus)
ii) → BG → cortex (via thalamus)
What are the neuronal inputs to the cerebellum?
1) Muscle (Spinocerebellar tract)
2) Cerebral cortex (via pons)
What separates the occipital lobe from the cerebellum?
Tentorium cerebellum (dural fold)
What are the arteries supplying the cerebellum?
Vertebral-basilar system
1) Anterior inferior cerebellar artery (AICA)
2) Posterior inferior cerebellar artery (PICA)
3) Superior cerebellar artery (SCA)
How is the cerebellum connected to the brainstem?
Cerebellar peduncles:
1) Superior (cerebellum → cortex)
2) Middle (cortex → cerebellum)
3) Inferior (spinal cord → cerebellum)
What are the lobes of the cerebellum?
1/2) Anterior and posterior (separated by 1° fissure)
3) Flocculonodular lobe (from central nodule)
(vs 3 zones: medial to lateral/saggital)
How are the cerebellar hemispheres separated and connected?
Connected by vermis
Separated by vallecula
What are the deep nuclei of the cerebellum?
1) Dentate nuclei
2) Interposed nuclei (globose + emboliform)
3) Fastigial
What are the layers of the cerebellar cortex?
1) Molecular layer
2) Granule cell layer
What are the 5 main cellular components of the cerebellum?
1) Purkinje cells (between molecular and granular cell layer)
2) Granule cells
3) Parallel fibers (axons of granule cells)
4/5) Mossy and climbing fibers (enter cerebellum → deep cerebellar nuclei)
What is the main function of deep cerebellar nuclei?
Efferent pathways from cerebellum
What are the 3 zones of the cerebellum?
Medial to lateral
1) Vermis (midsagittal)
2) Paravermal (intermediate)
3) Lateral hemispheres
(not lobes: 3, coronally)
What are the functional divisions of the cerebellum?
1) Vestibulo-cerebellum
- flocculonodular lobe
- vestibular reflex + postural maintenance
2) Spino-cerebellum
- Vermis + paravermal
- sensori-motor integration → adaptive motor coordination
3) Cerebro(Neo)-cerebellum
- Lateral hemisphere
- planning and timing of movements + cognitive functions
What is the (i) function (ii) location and (iii) pathway of the vestibulo-cerebellum tract?
i) Vestibular reflexes (eye) + postural maintenance
ii) Flocculonodular lobe
iii) Vestibular nuclei →
a) spinal cord → axial musculature
b) CNIII, IV, VI → Eye movements (vestibulo-ocular reflex)
What is the (i) function (ii) location and (iii) pathway of the spino-cerebellum tract?
i) Intergration of sensory input with motor command + adaptive motor coordination
ii) Vermis + Paravermis
iii) Spinocerebellar → vestibular (+ red) nuclei → spinal cord
What is the (i) function (ii) location and (iii) pathway of the cerebro-cerebellum tract?
i) planning and timing of movements + cognitive functions
ii) lateral hemispheres
iii) cerebral cortex (cortico-pontine → cortico-cerebellar) → thalamus → cortex
The cerebellum is responsible for the (ipsi/contra)lateral control of the (i)____________ (ii) _________________ (iii)__________________.
Ipsilateral
i) Equilibrium
ii) Muscle tone
iii) Coordination voluntary muscle activity
How does a px with flocculonodular lobe lesion present?
1) Loss of balance
2) Wide stance
3) Altered gait
How does a px with a cerebellar lateral zone lesion present?
Problems with skilled voluntary/planned movements:
1) Dysarthria
2) Dysmetria
3) Dysdiadochokinesia
4) Tremors
5) Hypotonia
6) Impaired check reflex/rebound phenomenon
How does a lesion from the vermis of the cerebellum differ from that of the paravermis?
Vermis/midline: whole-body movements
Paravermis/more lateral: fine movements of hands/limbs
What is the typical presentation of dysequilibrium?
1) Unsteady and swaying while standing
2) Staggering and falling when walking
What is dystonia?
Loss in resistance normally offered by muscles to passive manipulation
What is dyssnergia?
Loss of coordinated muscle movement/inability to arrest muscular movement at desired point (eg. past pointing in finger-nose test)
The inner ear consist of cavities known as _______________, filled with __________________. This, in turn, encases the _______________ which contains _______________.
Bony labyrinth
- perilymph (high Na+, low K+)
Membranous labyrinth
- endolymph (high K+)
What are the components of the cochlear canal?
1) Scala media (Cochlear duct)
- endolymph (high K+)
- separates bony canals:
2) Scala vestibuli
3) Scala tympani
- bony canals joined at tip of cochlea (helicotrema)
What are the components of the vestibular apparatus?
1) 3 Semicircular canals
2) Vestibule (utricle + saccule)
Which part of the cochlea is reponsible for transducing auditory stimuli for hearing?
Organ of Corti in basilar membrane of Scala media (Cochlear duct)
Describe the path of soundwaves until they are transduced as auditory signals.
1) Soundwaves collected by outer ear → tympanic membrane
2) Transmitted by middle ear ossicles → stapes vibrate oval window
3) Soundwaves converted to perilymphatic pressure in scala vestibuli
4) Transmitted through vestibular membrane → basilar membrane → Organ of Corti (sits on basilar membrane)
5) Perilymphatic pressure further spread onto scala tympani → round window (pressure valve)
What is the tonotopic map of the basilar membrane?
Sensitivity to soundwaves organised geographically by frequency
Describe the path of an auditory stimulus.
Inner ear:
Hair cells (organ of corti) → Cochlear nerve (CNVIII)
→ 1° sensory neuron (spiral/cochlear ganglion)
Brainstem:
→ synapse to 2°(cochlear nucleus)
→ decussate @ brainstem
→ superior olivary nucleus → inferior colliculus
Brain:
→ thalamus (medial geniculate nucleus)
→ auditory radiation
→ 1° auditory cortex (superior temporal/Heschl’s gyrus)
Why is the central auditory pathway not a common cause of hearing loss?
Presence of accessory (superior olivary + inferior colliculus) nuclei → bilateral representation of auditory impulses on each side
What is the function of the superior olivary nucleus and the inferior colliculus?
Superior olivary nucleus
- localisation of sounds in space
Inferior colliculus
- integrates spatial information from SON
- integrates intensity and pitch
What is the function of the tensor tympani and stapedius?
Tensor tympani (CNV)
- dampen sound from our own voice
Stapedius
- dampen sound from external sounds
How does a cochlear implant work?
1) External speech processor captures and converts sounds into digital signals
2) Signals transmitted to internal implant under skin
3) Implant coverts signals to electrical impulses → electrode array in cochlear
4) Electrodes stimulate Cochlear nerve directly
How do the functions and receptors of the vestibule differ from the semicircular canals?
1) Vestibule (saccule + utricle)
- detect linear acceleration (static) → position of head
- by maculae (receptors) in otolithic membrane with otoliths in Otolithic organ
2) 3 Semicircular canals
- detect angular acceleration (rotation) → movements of head
- by cristae ampullaris with cupula in ampulla
Describe the vestibular pathway.
Maculae (vestibule)/Cristae ampullaris (semicircular canals) → Vestibulocochlear nerve (Scarpa’s ganglion)
Brainstem:
→ pontomedullary junction → Vestibular nuclei (complex)
Brain:
a) Cerebellum
- spinocerebellar
b) CNIII, IV, VI nuclei
- vestibulo-ocular reflex via medial longitudinal fasciculus
c) Spinal cord
- vestibulospinal tract → balance
d) Reticular formation
- adjust circulation and breathing to posture
e) Thalamus + cortex
- conscious motor control
Describe the vestibulo-ocular reflex.
Rotational acceleration/deceleration of the head
→ cristae ampullaris in semicircular canals
→ vestibular nuclei
→ ocular motor nuclei (inhibitory and excitatory on each side)
→ extraocular muscles (compensatory movement)
What is nystagmus?
Fast uncontrollable movement of eyes
- horizontal, vertical, rotary
What is vertigo?
Sensation of turning/rotating in space in absence of actual rotation
What is motion sickness?
Activation of reticular formation in pons and medulla → activation of autonomic reflexes
What is vestibular neuronitis?
Inflammation of vestibular labyrinth
- no hearing loss
- but nystagmus, postural imbalance and nausea
What is Meniere’s disease?
Intermittent relapsing vertigo
- ±heading disorders eg. tinnitus and distorted hearing
