Year 4 Recap Flashcards
What are the exits and entrances to the skull compartment?
-Foramina (Foramen Magnum- spinal cord to brainstem)
-Fossa
=Anterior cranial
=Posterior cranial (cerebellum and brainstem)
=Middle cranial (temporal lobes)
Lobe functions
- Executive function: frontal
- Memory: temporal
- Visuo-spatial: parietal
- Language: fronto-temporal
- Vision: occipital
- Coordination: cerebellum
- Pre-central gyrus= MOTOR
- Post-central gyrus=SENSORY
Areas of deep grey matter
- Basal ganglia
- Thalamus
Location of spinal cord tracts
- Left and right dorsal/ posterior columns (ascending proprioception)
- Antero-lateral aspect: ascending spinothalamic axons (temperature and pain)
- Lateral descending upper motor neurone axons
Describe arterial circulation to the brain
-Anterior =L and R carotid -Circle of Willis anastomosis (DRAW) -Posterior =R+L vertebral= basilar= cerebellum and brainstem -Prone to embolism
What arteries supply the deep grey structures?
- Lenticulo-striate arteries= basal ganglia and internal capsule
- Prone to thrombosis due to hypertension or diabetes
Describe the venous circulation of the brain
- Cerebral veins drain into venous sinuses (superior sagittal, inferior sagittal)
- Then drained into internal jugular vein
- Thrombotic events= raised ICP
Describe the ventricle system and CSF
- Lateral connected to third= Foramen of Munro
- Third to Fourth= Cerebral Aqueduct
- All into central spinal canal
- 15-20ml CSF in ventricles, volume increases with age
- Choroid plexus produces CSF in ventricles
- Absorbed in subarachnoid space into venous sinuses
Describe the location of LMN to head/neck muscle
- Cell bodies= brain stem nuclei
- Axons= cranial nerves
Describe the location of LMN supplying the limb and trunk muscles
- Cell bodies in cord anterior horns
- Axons= roots= peripheral nerves
Describe the location of UMN
- Cell bodies= brain (for classical UMN system in pre-central gyrus)
- Axons= cortico-bulbar (through internal capsule to brain stem LMN)/ cortico-spinal (spinal cord LMN, crossing in lower medulla so control contralaterally)
Why is the corticobulbar UMN different to corticospinal UMN?
- A need for bilateral UMN control
- Reflex arcs typically involve different cranial nerves
Facial nerve examples of facial movements
-Upper face =Eye closure =Eyebrow elevation =Frowning -Lower face =Lip closure =Mouth elevation =Pouting
Describe UMN control of the facial nerve
- R UMN controls L lower face and all upper face (vice versa with L UMN)
- A unilateral UMN lesion causes weakness of lower half of other side of face (as upper face has bilateral innervation)
What other examples of different innervation of the head/neck muscles are there?
- Ipsilateral UMN control of Sternomastoid
- Bilateral UMN control of jaw movements
- Eye movements: looking left or right
What are the components of the extrapyramidal system?
-Basal ganglia =caudate nucleus =putamen =globus pallidus =subthalamic nucleus =substantia nigra -Certain brain stem nuclei =red nucleus =reticular formation =vestibular nuclei =olive =superior colliculus (eye movements) -Connections to cerebral cortex, cerebellum and LMN
What is the most important EPS loop?
-Striatum-Substantia nigra- Striatum loop
=Degenerates in Parkinson’s disease
What are the roles of the basal ganglia?
- To facilitate movements that are required and appropriate in particular contexts
- To inhibit movements that are unwanted and inappropriate in particular contexts
- To organise individual movements into complex, sequenced actions
Symptoms of basal ganglia disease
-Abnormal motor control
=Bradykinesia/ Akinesia (can be action-specific)
-Alterations in muscle tone (rigidity)
-Abnormal involuntary movements (tremor, chorea)
Examples of sensory modalities and how they ascend to the brain
- Simple and discriminative touch
- Pain and temperature (cross at point of entry and ascends in antero-lateral spinothalamic tracts)
- Proprioception/ joint position sense (DORSAL COLUMN= ascends same side and crosses to other side at top of brain)
- Vibration
Describe the somatosensory pathway from limbs and trunk
- Receptor
- Sensory axon runs into peripheral nerve-root to cell body in dorsal root ganglion
- DRG to spinal cord in white matter tracts to brain
How might hemi-cord lesions present differently to a transverse cord lesion?
-Right hemi-cord lesion
=Impaired simple touch and proprioception on right
=Impaired spinothalamic on left
-Transverse
=All sensory modalities impaired at site of lesion
What are the aspects of vision?
- Colour vision
- Visual acuity
- Visual field
Describe colour vision defects
- Congenital/ acquired
- Acquired= optic neuritis (inflammation of optic nerve)
What is visual acuity?
- Measure of the clarity of vision
- Spatial resolution
- Refractive errors common, neurologists interested in non-correct visual acuity
What is visual field?
-Actual extent of vision in space
Describe the visual pathway
- Conjunctiva, cornea, aqueous humour, lens, vitreous humour
- Retina
- Optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, optic radiation, visual cortex
What are the features of the retina?
- Rods= dim, black and white
- Cones= bright, colour
- Photosensitive ganglion cells= reflex)
- Macula= 6mm diameter, yellow oval spot near centre specialised for high acuity vision, 13 degree of central field
- Fovea= 1.5mm pit in macula centre so area of greatest VA and colour vision, 3 degrees of central field
How does visual space affect optic nerve information?
- Visual information from right visual space hits temporal retina of left eye and nasal retina of right eye
- Nasal retina= temporal field and vice versa
- Nasal retina so temporal field information crosses to other side in optic chiasm
How are major optic defects classed?
- Pre-chiasmal: lost all data from one eye (uni-ocular visual loss)
- Chiasm: lost half the data cross (bitemporal hemianopia, pituitary tumours)
- Post-chiasm: loose all left visual space data on right post chiasmal area and vice versa (homonymous hemianopia)
What are the components of the human ear?
-Outer =Pinna =Auditory canal =Tympanic membrane -Middle (small air-filled chamber) =x3 ossicles -Inner ear =hearing and vestibular receptors in membranous labyrinth within bony labyrinth in temporal bone
What are the components of the inner ear?
- Cochlea (hearing)
- Utricle and saccule (vestibular)
- Horizontal, anterior and posterior canal (vestibular)
What nerves innervate the inner ear?
-Cochlear nerve
-Vestibular nerve
=Vestibulo-cochlear nerve (8th cranial) to medulla-pons junction
What is the vestibular function?
- Perception of position and motion
- Static gravitational orientation
- Motion in space
What components reflect rotations and linear translations and how?
-The semi-circular canals (rotation= vertical, sagittal plane and frontal plane axis) =Motion causes flow of fluid within them =Fluid flow stimulates hair cells =Hair cells generate electrical impulses -Otoliths (utricle, saccule)= linear translations =otoliths sit on hairs of hair cells =Motion causes otolith to move =Movement bends hairs =Hair cells generate electrical impulses
What are the clinical aspects of hearing and vestibular damage?
- Tinnitus and hearing loss
- Vertigo and imbalance/ unsteadiness
What are the functions of the cerebellum?
-Motor control
=Input of motor and sensory information
=Outputs motor control- constant adjustments to actions
-Cognitive functions
What are the areas of cerebellar control?
- Hemisphere: unilateral limb (ipsilateral so not crossed)
- Midline: trunk, posture, gait
Describe ataxic syndrome
- Ataxia of upper limbs
- Ataxia of lower limbs
- Truncal ataxia
- Gait ataxia
- Dysarthria (incoordination of tongue)
- Nystagmus (eyes)
- SENSORY/ MOTOR/ CEREBELLAR/ BRAINSTEM problem
What are the dimensions of consciousness?
- Wakefulness (arousal)= the capacity for consciousness
- Awareness= the content of consciousness
What does consciousness depend on?
-Intact and interacting…
=Brainstem Reticular Activating system (arousal)
==activate thalamus and cerebral cortex
=Cerebral hemispheres (awareness)
What causes loss of arousal?
-Brainstem problems =Structural damage to brainstem =Secondary impairment to brainstem (coning) =Drugs =Widespread brain damage
What causes loss of awareness?
-Cortical damage
=widespread cortical malfunction
=relatively intact brain stem
What are the cognitive domains?
- Consciousness
- Attention, concentration and orientation
- Language
- Memory
- Visuo-spatial function
- Executive function
What are the main areas of wakefulness?
-Ascending RF of pons and midbrain
-Certain thalamic nuclei
-Posterior hypothalamus
-Basal forebrain
=reduced cortical activation in NREM sleep (REM sleep very localised in contrast)
What is the glymphatic system?
-Functional waste clearance pathway in the vertebrate CNS
=reflects on glial cells
=similar to lymphatic system
Describe the glymphatic system
- Para-arterial route allows CSF to enter the brain parenchyma
- ISF (interstitial fluid) removed from the interstitial compartments of the brain/cord
- Exchange of solutes between CSF and ISF driven by arterial pulsation
- System regulated, during sleep, by the expansion and contraction of brain extracellular space
- ISF removal: soluble proteins, waste products, excess extracellular fluid
- Best in slow wave sleep
