Neuro Anatomy Flashcards
What are the three types of neurone?
Bipolar
Pseudo-unipolar
Multipolar
What are the anatomical subdivisions of the CNS?
Cerebrum - forebrain
Brainstem - midbrain, pons, medulla oblongata
Cerebellum
Spinal Cord
What do the cerebral hemispheres develop from?
Prosencephalon to telencephalon to cerebral hemispheres
What does the diencephalon develop from?
Prosencephalon
What does the mid brain develop from?
Mesencephalon
What do the pons and cerebellum develop from?
Rhombencephalon to mesencephalon to pons and cerebellum
What does the medulla oblongata develop from?
Rhombencephalon to myelencephalon to medulla oblongata
What is the diencephalon?
Innerbrain - thalamus, epithalamus(including pineal gland), sub thalamus and hypothalamus
What is white matter?
Bundles of axons - transmits information from one area to another
What is the corpus callosum and where is it located?
Between the cerebral hemispheres, white matter
What is grey matter?
Nerve cell bodies
What is lissencephaly?
Smooth brain - lacks gyri and sulci
- gene linked brain malformation - learning difficulties
What are the four lobes of the cerebral hemispheres and describe their anatomical location?
Frontal - separated from parietal by central sulcus, contains the pre central gyrus
Parietal - contains the post central gyrus separated from the occipital lobe by the parietooccipital sulcus
Occipital - posterior brain
Temporal - separated from the frontal and parietal lobes by the lateral fissure, lateral brain
What are the functions of the thalamus and hypothalamus?
Thalamus - relay station between brainstem, spinal cord and cerebral cortex
Hypothalamus - controls the autonomic nervous system
How many subdivisions of the CNS are there?
7
cerebral hemispheres, diencephalon, mid brain, medulla, pons, cerebellum and spinal cord
How many bones form the skull, how are they connected and what is the one exception?
22 Bones
Fibrous sutures connect the bones together except from the temporomandibular joint which is a synovial joint
What are the three sinuses?
Frontal, ethmoid and maxillary
What is the Pterion?
What is the clinical significance?
Junction of parietal, frontal, sphenoid and temporal bones of the skull
- Fracture of this area can cause significant bleeding - extradural haematoma/haemorrhage
Describe the three meningeal layers surrounding the CNS
Dura mater - most superficial, very fibrous and tough - periostea and meningeal layers
Arachnoid Mater - Thin layer
Pia mater - very thin follows the gyri and sulci
What are the three dural folds?
Falx cerebri - sickle shaped superior
Tentorium cerebelli - transverse plane
Falx cerebelli - separates two cerebellar hemispheres
Where is CSF produced?
Ventricles by specialised areas of ventricular lining choroid plexus
Describe the ventricular system of the brain
4 ventricles - 2 lateral ventricles, 3rd ventricle between thalami and 4th ventricle between pons and cerebellum
- Contains the choroid plexus
- Median aperture (foramen of magendie)
- Lateral apertures (foramina of luschka)
Why is the lumbar cistern a favoured site for CNS sampling?
Spinal cord ends before the site therefore less likely to damage spinal cord during the procedure
Describe the vertebral artery
Branch of subclavian, ascend in the neck through the transverse foramen of the cervical vertebrae and enter skull via foramen magnum,
Fuse at the base of the brainstem to form the basilar artery
What arteries make up the circle of willis and its branches?
Anterior communicating Anterior cerebral Middle cerebral Internal carotid Posterior communicating Posterior cerebral Basilar
What does the anterior cerebral artery supply?
- Superior and medial areas of frontal and parietal lobes
- corpus callosum
What does the middle cerebral artery supply?
- Lateral areas of frontal, temporal and parietal lobes
What does the posterior cerebral artery supply?
- Occipital lobe
- Inferior and medial surface of temporal lobe
What do the striate arteries supply?
- Deep nuclei
- Deep grey matter
- Internal capsule
- Major descending motor pathway
Where do superficial and deep veins drain in the brain?
Superficial - dural sinuses
Deep - great cerebral vein
Describe the pathway of venous drainage of deep veins
Internal cerebral veins Great vein of Galen Straight sinus Confluence sinuses Transverse sinus Sigmoid sinus Internal Jugular vein I gave some cheese to Sarahs interns
Describe what arteries cause epidural, subdural and subarachnoid haemorrhages
Epidural - torn meningeal artery
Subdural - torn bridging veins
Subarachnoid - torn cerebral arteries
Describe the tectum, tegmentum and basal area of the brainstem
Tectum - posterior to ventricular system
Tegmentum - anterior to ventricular system
Basal area - most ventral part
Describe the pyramids and olives as part of the medulla
Pyramids - medial raised areas containing descending bodies of motor fibres
Olives - lateral to pyramids
Describe the connections of the cerebellar peduncles
Superior - connects midbrain to cerebellum and forms roof of 4th ventricle
Middle - connects pons to cerebellum
Inferior - connects medulla to cerebellum
Damage to what area of the brain induces a coma?
Ascending reticular activating system
What is the function of the cerebellum?
Coordination, movement, maintenance or balance and posture
What is the foramina and function of cranial nerve I?
Olfactory Nerves
- Cribriform plate
- Special sensory - smell (olfaction)
What is the foramina and function of cranial nerve II?
Optic Nerves
- Optic canals
- Special sensory - vision
What is the foramina and function of cranial nerve III?
Oculomotor Nerve
- Superior orbital fissure
- Somatic motor to 4 extra ocular muscles and levator palpebral superioris
- Visceral motor to cillary muscle and sphincter pupillae
What is the foramina and function of cranial nerve IV?
Trochlear Nerve
- Superior orbital fissure
- Somatic motor to superior oblique
What is the foramina and function of cranial nerve VI?
Abducens Nerve
- Superior orbital fissure
- Somatic lateral rectus
What is the foramina and function of cranial nerve V?
Trigeminal V1 - Ophthalmic division - Superior orbital fissure - Somatic sensation from upper face V2 - Maxillary Division - Foramen Rotundum - Somatic sensation from middle face V3 - Mandibular Division - Foramen ovale - Somatic sensation from lower face mandible and anterior 2/3 tongue - Branchial motor to muscles of mastication, anterior belly of digastric, tensor tympani
What is the foramina and function of cranial nerve VII and the five main branches?
Facial Nerve
- Internal acoustic meatus (Enter), stylomastoid foramen (Exit)
- Branchial motor to muscles of facial expression, stapedius muscle, posterior belly of digastric
- Special sensory as taste to anterior 2/3 of tongue
- Somatic sensory to skin of ear
- Visceral Motor to all glands except parotid
Temporal, zygomatic, buccal, mandibular and cervical
What is the foramina and function of cranial nerve VIII?
Vestibulocochlear Nerve
- Internal acoustic meatus
- Special sensory, hearing and balance
What is the foramina and function of cranial nerve IX
Glossopharyngeal
- Jugular Foramen
- Branchial motor for swallowing
- Visceral motor to parotid
- Special sensory for taste to posterior 1/3 tongue
- Somatic sensory to middle ear, pharynx, posterior 1/3 tongue
- Visceral sensation from carotid body and carotid sinus
What is the foramina and function of cranial nerve X?
Vagus Nerve
- Jugular Foramen
- Branchial motor to muscles of pharynx and larynx, muscles of soft palate
- Visceral motor to thoracic and GI tract
- Visceral and special sensory, taste from epiglottis and palate
- Somatic sensation from epiglottis, skin of external ear and larynx
What is the foramina and function of cranial nerve XI?
Accessory Nerve
- Jugular Foramen
- Somatic motor to sternocleidomastoid and trapezius
What is the foramina and function of cranial nerve XII?
Hypoglossal Nerve
- Hypoglossal canal
- Somatic motor to muscles of tongue
What does injury of the hypoglossal nerve present as?
Deviation of the tongue to the paralysed side
What muscle and nerve controls closing of the eyelids?
Orbicularis oculi
CNVII
What muscles and nerves control the opening of eyelids?
Superior tarsal muscle - sympathetic (keep eye open)
Levator palperbrae superioris - CNIII (open eye)
What muscle and nerve controls dilation of the pupil?
Dilators of iris - sympathetic
What muscles and nerves control constriction of pupil and sense change?
Constriction - sphincter pupillae - CNIII parasympathetic
Change Lens - Cillary muscle - CNIII parasympathetic
Describe the corpus striatum
Internal structures of grey matter of each cerebral hemisphere
- Globus pallidus
- Putamen
- Caudate nucleus
What are the hemispheric limbic structures?
- Hippocampus
- Fornix - contains main efferent fibres of the hippocampus, follows a C shape over the thalamus
- Amygdala
What are the three classes of fibres in the white matter of cerebral hemispheres?
Association fibres - interconnect areas within a hemisphere and adjacent gyri
Commissural fibres - interconnect areas between hemispheres
Projection Fibres - Interconnect cerebrum with rest of CNS, corona radiata
Describe the internal capsule
- Passes between head of caudate and lentiform nuclei
- Connects to crus cerebri anterior part of pons and medulla pyramids
What are the medial sulci and gyri?
- Cingulate sulcus and gyrus
- Pareto-occipital sulcus
- Calcirine sulcus
- Collateral sulcus
- Parahippocampal gyrus
- Uncus
Describe uncal herniation
Herniates under tentorium cerebelli and compresses the midbrain
- Tonsil of cerebellum herniate through foramen magnum and compress the medulla oblongata
Describe the primary projection areas
Sensory - General sensation - post central gyrus Visual - either side of calcimine sulcus and occipital pole Auditory - heschl's gyrus Olfactory - uncus Gustatory - Inferior post central gyrus Motor - primary motor cortex - pre central gyrus
Describe the association secondary areas
Sensory -
General sensation - superior parietal lobe
Visual - pre striate area
Auditory - lateral fissure/superior temporal gyri
Motor -
Premotor area - anterior to pre central sulcus on lateral surface
Supplementary motor area - anterior to pre central sulcus on medial surface
Frontal eye field - anterior to premotor
What does the primary motor cortex control?
Voluntary contraction of specific muscles
- Somatotopically organised
What is cerebral dominance ?
Two language areas are located within dominant hemispheres
What is motor/non-fluent aphasia?
Inability to correctly articulate speech
Broca’s area
What is sensory/fluent aphasia and the area of the brain associated?
Inability to understand language
Wernicke’s area
What is conduction aphasia?
Impaired repetition, comprehension and fluency intact
How many of each vertebrae are in each segment of the vertebral column?
7 cervical 12 thoracic 5 Lumbar 5 Sacral (fused to form he sacrum) 3-4 fused to form the coccyx
What does the spinal cord terminate as?
Conus medullaris + filum terminale extends and attaches to the coccyx - made up of arachnoid and dura mater
Describe the spinal nerve and vertebral levels relationship
- Cervical segment all nerves emerge above the corresponding vertebrae except C8 which emerges above T1
- Thoracic segment all nerves emerge below their corresponding vertebrae
Describe the marginal zone nucleus, its cord level, lamina and function
Cord - all
Lamina - 1
Function - spinothalamic tract cells
Describe the substantia gelatinosa nucleus, its cord level, lamina and function
Cord - all
Lamina - 2
Function - pain and temperature
Describe the proprius nucleus, its cord level, lamina and function
Cord - all
Lamina - 3-4
Function - general sensory
Describe the intermedia lateral nucleus, its cord level, lamina and function
Cord - T1-3 and S2-4
Lamina - 7
Function - sympathetic neurones and parasympathetic neurones
Describe the Clarkes nucleus, its cord level, lamina and function
Cord - C8-L3
Lamina - 7
Function - dorsal spin-cerebella tract cells
Describe the motor nuclei, its cord level, lamina and function
Cord - all
Lamina - 9
Function - motor neurones
Describe the phrenic nucleus, its cord level, lamina and function
Cord - C3-5
Lamina - 9
Function - motor diaphragm
Describe the accessory nucleus, its cord level, lamina and function
Cord - medulla - C5
Lamina - 9
Function - motor SCM and trapezius
Describe the C1-C2 atypical vertebrae
C1 articulates with occiput - allows nodding of head up and down
C1-C2 - articulate with each other and form a pivot joint - allows head to turn from side to side
Describe hangman’s fractures
C2 fracture - can be caused by hyperextension of the head
- Bilateral fracture of the pars interarticularis
- Body of C2 can be displaced anteriorly
- Likely injury to brainstem or spinal cord
Describe upper motor neurones
- Originate in the cerebrum and subcortical structures
- Influence LMN activity
- modify local reflex activity
- Superimpose more complex patterns of movement
Describe lower motor neurones
- Originate from the brainstem and spinal cord - ventral grey horn
- peripheral nerves to motor end plates/neuromuscular junctions
What are the 3 main descending motor pathway ?
Pyramidal corticospinal
Corticobulbar/corticonuclear
Extrapyramidal
Describe the corticospinal and corticonuclear pathways
Cerebral cortex Precentral gyrus Internal capsule Basal ganglia Basal pons Pyramids Pyramidal decussation - 85% of fibres Brainstem/spinal cord - some will exit spinal cord at level of innervation to provide bilateral innervation
More anterior corticospinal pathway - less decussation
Describe the internal capsule lesion
- Vulnerable to vascular damage
- Small end arteries at risk in hypertension
- Main important sensory and motor fibres in small area
Describe the reticulospinal pathway
- Reticular formation - pons and medulla to spinal cord
- Controls voluntary movement/breathing/consciousness
Describe the vestibulospinal pathway
Vestibular nuclei - pons and rostral medulla to spinal cord - anterior horn
- Controls posture
Describe rubrospinal pathway
Red nucleus - midbrain to spinal cord
- controls muscle tone
Describe the 3 neurones chain
1st neurone - pseudo unipolar - cell body in sensory ganglion DRG or CN ganglion
2nd neurone - axon crosses midline ascends to ventral posterior thalamus - travels up contralateral side to thalamus
3rd neurone - axon projects to post central gyrus - parietal lobe - relay to primary sensory cortex
What are the 3 trigeminal nuclei and their function?
Mesencephalic - proprioception
Pontine - discriminative touch
Spinal - simple touch, pressure, pain and temperature
Describe the pathway for pain and temperature
- Primary cell bodies in trigeminal ganglion
- secondary axon crosses and ascends in trigeminothalamic tract to thalamus
Describe the pathway of crude touch and pressure
- Primary cell bodies in trigeminal ganglion
- Some fibres descend in spinal tract of trigeminal nerve
- Some fibres synapse with secondary neurones more rostrally in spinal nucleus
- axons cross and ascend in trigeminothalamic tract to thalamus
Describe the pathway for discriminatory touch
- Primary neurone cell bodies in trigeminal ganglion
- Synapses with secondary in pontine chief nucleus
- Axon crosses and ascends in trigeminothalamic tract to thalamus
Describe the proprioception pathway
- Primary neurone cell bodies in mesencephalic nucleus
- Primary axons travel in the mandibular division of trigeminal to thalamus
- Secondary axon crosses and ascends to thalamus in trigeminothalamic tract
Describe the spinal reflex as a basis for motor control
- Sensory receptor fires action potential upon stimulus
- Sensory neurone carries action potential to spinal cord
- Integration centre - relay sensory to motor
- can be monosynaptic or polysynaptic - Motor Neurone
- Effector organ
Describe the myotatic stretch reflex with regard to the patellar tap reflex
- Tap quadriceps tendon and stretch of quadriceps muscle
- Activation of the muscle spindle and increased firing of a 1a afferent
- Afferent terminals synapse directly with and excite the alpha motor neurone
- Increased alpha motor neurone efferent axon activity
- Contraction of the agonist homonymous muscle - ie muscle from which afferent arose
Describe the inverse myotactic stretch reflex (Golgi reflex)
Controls the tension of an active muscle in response to muscle contraction to avoid tendon damage
- Tension feedback and overload protection
1. Golgi tendon organ excitation
2. Increasing firing in 1b afferent
3. Indirect inhibition via an inhibitory interneuron of the alpha motor neurone
4. Decreased alpha motor neurone activity to homonymous muscle
5. Relaxation/inhibition of the homonymous muscle
Describe the crossed extensor/flexor withdrawal reflex
Noxious (Harmful/unpleasant) cutaneous stimulation causes flexion withdrawal from the offending stimulus. Simultaneous extension of contralateral limb may occur for weight bearing
- Damage limitation of avoidance, maintained balance on limb withdrawal
1. Increased activity in A-delta & C afferents
2. Polysynaptic activation of ipsilateral flexors
3. Polysynaptic inhibition of ipsilateral extensors
4. Polysynaptic inhibition of contralateral flexors
5. Polysynaptic excitation of contralateral extensors
Enables automatic maintenance of balance during reflex
What are the layers of the skin?
Epidermis - keratin producing squamous epithelium
Dermis - papillary dermis and reticular dermis
Subcutis - adipose tissue
What are the 5 layers of thick skin?
Basal layer - stratum basal Prickle cell layer - stratum spinosum Granular layer - stratum granulosum Stratum lucidum - skin of the sole Keratin layer - stratum corneum
What are the cells found in the epidermis?
Keratinocytes
Melanocytes
Langerhans cells
Describe the 4 skin receptors
Meissner Corpuscles - touch and vibration
Merkel cells - slow adopting touch and pressure
Pacinian corpuscles - fast acting vibration
Ruffini endings - vibration and pressure
Describe the autonomic nervous system
Largely involuntary
Monitors conditions in the internal environment to maintain homeostasis
Influenced Rostrally by the hypothalamus
Describe the autonomic motor and sensory fibres of the PNS autonomic division
Motor: efferent fibres to smooth muscles, cardiac muscles or glands
Sensory: afferent fibres from sensory receptors in an internal organ - responsible for referred pain
Only carried within segmental spinal nerves T1-L2 and S2-S4
Describe the parasympathetic division of the autonomic nervous system
Cranio-sacral origin - brainstem and S2-S4- lateral cord of sacral grey horn
Acetylcholine
Localised effects
What 4 cranial nerves do parasympathetic fibres run?
III - to constrict pupil
VII - to salivary glands and lacrimal glands
IX - to salivary glands
X - to cardiac pulmonary and digestive systems
Describe the sympathetic division of the ANS
- Thoracic-lumbar origin T1-L2 spinal segments
Pre: acetylcholine
Post: noradrenaline except sweat glands
Widespread Effects - neuronal divergence and adrenal medulla
What level do all preganglionic fibres leave cord in segment spinal nerves ?
T1-L2 only
Describe the role of the hypothalamus in the ANS
- Controlling influence upon the activity of the ANS
- Central role in neuroendocrine function via connections with pituitary
- Important connections with the limbic systems
Describe the spinal reflex path
- Sensory receptor - fires action potential upon stimulus
- Sensory neurone - carries action potential to spinal cord
- Integration centre - relay sensory to motor
Can be monosynaptic or polysynaptic - Motor neurone
- Effector organ
Describe the myotatic stretch reflex and run through the sequence of events in relation to the quadriceps muscle
Muscle contraction, in response to stretching within the muscle
- Tap quadriceps tendon and stretch quadriceps muscle
- Activation of the muscle spindle and increased firing of a 1a afferent
- Afferent terminals synapse directly with and excite the alpha motor neurone
- Increased alpha motor neurone efferent axon activity
- Contraction of the agonist homonymous muscle
Describe the antagonist response of the myotatic stretch reflex
direct excitation of motor neurones and indirect inhibition via the 1a inhibitor interneuron of motor neurones innervating antagonist
Describe the inverse myotatic stretch reflex (Golgi tendon reflex)
Control the tension of an active muscle in response to muscle contraction to avoid tendon damage
- The Golgi tendon organ excitation
- Increased firing in 1b afferent
- Indirect inhibition via inhibitory interneuron of the alpha motor neurone
- Decreased alpha motor neurone activity to homonymous muscle
- Relaxation/inhibition of the homonymous muscle
Describe the crossed extensor/flexor withdrawal reflex
Noxious cutaneous stimulation causes flexion withdrawal from the offending stimulus
- Simultaneous extension of contralateral limb may occur for right bearing
Damage limitation of avoidance
Maintained balance on limb withdrawal
1. Increased activity in A-delta and C afferents
2. Polysynaptic activation of ipsilateral flexors
3. Polysynaptic inhibition of ipsilateral extensors
4. Polysynaptic inhibition of contralateral flexors
5. Polysynaptic excitation of contralateral extensors
Enables automatic maintenance of balance during the reflex
What are the functions of the cerebellum?
- Production of coordinated movements
- Maintain equilibrium balance and posture
- Coordinates appropriate time force and duration of muscle contraction
- Store instructions for patterns of movements
- Linguistic and cognitive functions
- Cerebellum acts ipsilaterally
Describe the vestibulocerebellum
Comprises flocculonodular lobe and part of vermis
- Coordinates muscles involved in maintaining balance and consistency of visual fields
Describe the spinocerebellum
Comprises most of vermis and adjacent region of hemispheres
- co-ordinates muscles involved in posture and locomotion
Describe cerebrocerebellum
Lateral parts of cerebral hemispheres
- Coordinates movements of distal limbs particularly fine, skilled and targeted movements of hands
Describe the vestibulocerebellum
Regulates balance and eye movements
- Receives ipsilateral information from balances
- Associated with vestibular apparatus and nuclei
- Adjusts muscles and eye movements in response to vestibular stimuli
Describe the spinocerebellum
Receives unconscious proprioception from Golgi organs/muscle spindle
- Adjusts muscle tone and execution of movements
Describe the cerebrocerebellum
Control of fine motor skills and targeted movements of limbs particularly hands
- Receives information on intended movements that are in progress from the cerebral cortex - corticopontine fibres and olivocerebellar fibres
- Ensures a smooth and orderly sequence of muscle contractions with intended precision, force and direction = particularly important for upper limb activity
Describe the cerebellar peduncles and the inputs/outputs
Left Side
SCP - output to motor cortex, reticular nuclei and red nucleus
Ensure intended movement coordinated and controlled
MCP - Input from cortex including motor cortex via nuclei in pons
Knows about intended movements
ICP - input from cortex including motor cortex via inferior olivary nucleus
Knows about intended movements
Rights side
knows what muscles are doing
Proprioception and other sensory information from spinal cord passes into the cerebellum via the ICP
What are the effects of cerebellar damage?
Incoordination or ataxia
Person is still able to move but in disordered manner
A unilateral lesion to cerebellar hemisphere causes symptoms on the ipsilateral side of the body
What is truncal ataxia?
- Inability to stand or sit without falling over
- Midline lesion affecting vestibulocerebellum
- Most commonly due to medulloblastoma
What is gait ataxia?
Where is the most likely lesion to cause this?
- Lower limbs most affected, staggering wide based gait
- Lesion of spinocerebellum
- Most common in chronic alcoholics due to degeneration of cerebellar neurone in paranormal areas
Describe a lesion in the cerebrocerebellum
- Inco-ordination of voluntary movement particularly in the upper limb
- Many possible causes
Tremor of intent
Past pointing or dysmetria
Adiadochokinesia
Dysarthria
What are the functions of the three parts of the ear?
External: receives sound waves transmitted towards tympanic membrane
Middle: sound waves to mechanical waves
Inner: mechanical waves to electrical waves
Describe the middle ear
- Connected to nasopharynx - prone to infection
- Connected to mastoid air cells - infection may spread to middle cranial fossa
- Internal jugular vein lies inferior - risk of thrombosis
- Internal carotid artery lies anterior - link to pulsatile tinnitus
- Transversed by chords tympani and facial canal - infection risk
Describe the inner ear
- Located in petrous part of temporal bone
- Composed of 2 special sense organs
- Vestibular system - balance and equilibrium
- Vestibule and semicircular canals and semicircular ducts
- Cochlea and cochlear ducts
Bony outer labyrinth contained with perilymph and membranous inner labyrinth containing endolymph
Describe the cochlear and cochlear duct and the two chambers of the cochlear
Cochlear duct separates cochlea into two chambers
- Scala vestibuli (SV)
- Scala tympani (ST)
Two chambers are continuous at the apex of the cochlea through a narrow slit - helicotrema
- Fluid (Perilymph) moves around the bony cochlea it deforms the endolymph inside the cochlear duct
Cochlear duct contains spiral organ - tectorial membrane, embedded hair cells
Describe the spiral organ of corti
Stimulated by the deformation of the cochlear duct by the perilymph in the surrounding SV and ST
- Converts fluid pressure into electrical signals via cochlear nerve
Describe the auditory pathway
Cochlea
Cochlear nerve to cochlear nuclei
Superior olivary nuclei (receives bilateral auditory information)
through mid pons, pons-midbrain junction to inferior colliculus (receives lateral reminisces)
To medial geniculate nucleus - auditory cortex
Describe the tonotopic organisation of the cochlea and auditory cortex
Different regions of the basilar membrane respond to sounds of different pitch
Low frequency = anterolateral
High frequency = posteromedial part
Describe Broca’s area and wernicke’s area
Function and blood supply
Brocas: anterior
Motor production of words
Blood supply - upper anterior division of middle cerebral artery
Wernicke’s: posterior
Sensory understanding
Blood Supply - lower posterior division of middle cerebral artery
Describe the areas of the retina
Neural layer
Optic nerve
Optic disk
Macula + fovea
Describe the nerve cell types as part of the retina
Optic nerve = ganglion cells
Bipolar cells - linking photoreceptors to ganglion cells
Cones and rods
Describe rods and cones in the eye
Rods - 20x more common - Sensitive to light - Vision in dim light - High level convergence Cones - many In fovea - Colour vision - High visual acuity - Lower level of convergence - At macula one cone to one ganglion cell
Describe papilloedema
- Swelling of optic disc
- Optic nerve is surrounded by the meninges
- Increases CSF pressure can swell the optic nerve
- Increase in pressure compresses the central retinal vein preventing venous drainage from the eye
Symptoms: head-aches, drowsiness, blurred vision and vomiting
Describe the calcarine sulcus and surrounding area
Calcarine sulcus - primary visual cortex lies above and below
Above - parietoccipital sulcus - visual association
Below - visual association area
Describe the visual pathway
- Left half of visual field goes to right hemisphere
- Right Half of visual field goes to left hemisphere
- Upper visual field goes to lower bank of calcimine sulcus
- Lower visual field goes to upper bank of calcimine sulcus
Centre of visual axis (macula) goes to occipital pole
Describe the retinotopic mapping of the optic chiasm and optic radiations
Temporal fibres = closest to temporal bone
Nasal fibres = fibres closest to nose (inner)
Left half of visual field goes to right hemisphere
Right half of visual field goes to left hemisphere
Superior trajectory - lower visual fibres
Inferior trajectory/meyers loop - upper visual field fibres
What is a scotoma, anopia, homonymous and heteronymous?
Scotoma - localised patches of blindness
Anopia - refers to the loss of one or more quadrants of the visual field
Hemi - half of the visual field is lost
Quad - quarter of the visual field is lost
Homonymous - visual field losses are similar for both sides
Heteronymous - visual field losses are on different sides
What is the pupillary light reflex?
The ability of both pupils to respond dependent on the level of light the retina receives
- Utilises two cranial nerves oculomotor and optic
What is the accommodation reflex?
Series of changes that occur when the gaze is transferred from a distant to near object
- Accommodation - ciliary muscles contract - lens becomes rounded
- Pupil constricts - sphincter pupilae
- Ocular convergence - medial rectus
What is the primary function of the basal ganglia?
To provide a feedback mechanism to the cerebral cortex for initiation, control and cessation of motor response
- Relays decision to move through thalamus
1. Excite cerebral cortex: facilitate wanted movement
2. Dampen cerebral cortex: inhibition of unwanted movement
What do lesions in the basal ganglia cause?
Dyskinesia - abnormal involuntary movements
What are the functional basal ganglia?
Corpus striatum - Caudate nucleus + putamen Globus pallidus Substantia nigra Subthalamic Nucleus
Describe the afferent connections of the basal ganglia
Input nuclei - striatum
- From the cortex - corticostriatal fibres information about intended movement
- From substantia nigra pars compacta - nigrostriatal fibres release dopamine
Describe the efferent connections of basal ganglia
Output nuclei - GPi + Sir - send efferent fibres to supply the thalamus - pallidothalamic fibres - inhibitory - inhibit the thalamus
Describe the intrinsic connections of basal ganglia
Direct - facilitate a specific movement programme - neurones from the striatum that project to GPi directly
Indirect - inhibit a specific movement programme, allow direct pathways programme - neurones from the striatum that project to GPe, from the GPe neurones project strongly to the subthalamic nucleus which later projects back to GPi
What is the role of the substantial nigra pars compacta?
Release dopamine - has modularity role in the direct and indirect pathways - main function to initiate movement
Disruption of what leads to Parkinson’s disease?
Nigrostriatal input
- Most common disease of basal ganglia
What are the limbic structures?
HOME Hypothalamus - homeostasis Paraolfactory area - olfaction Amygdala - emotions Hippocampus - memory
What is the cingulum?
Receiver of information from pre-frontal, parietal, occipital and temporal gyri - association fibres
Involved in formation of memories and emotions
Describe the amygdala
Almond shaped nuclear complex in the medial temporal lobe - deep to uncus - mainly involved in emotions and behaviour
Describe hippocampal formation and its functions
Nuclear complex in the medial temporal lobe
- deep to parahippocampal gyrus
- Mainly involved in memory - short term
- Formation of new memories and learning
- Damage leads to inability to recall recent events
What are the stria terminals?
Band of fibres that runs along the ventricular surface of the thalamus
Describe the circuit of papez
Reinforcement of emotion, memory and olfaction with each other for survival responses
Hippocampus - fornix - maxillary bodies - anterior thalamic nuclei - cingulate gyrus - hippocampus
