Neuro anatomy Flashcards
Medulla oblongata
Viewed from dorsal surface of brainstem - gracile (medial) and cuneate (lateral) tubercles, round swellings on either side of midline - contain dorsal column nuclei, ascending sensory tract pathways
Sensory
Dorsal column:
- fasciculus gracilis - T7 down
- fasciculus cuneatus - T6 up
- ipsilateral
- fine touch, vibration, proprioception
Spinocerebellar:
- proprioception
- to cerebellum
Spinothalamic tract (= anteroateral):
- contralateral
- to thalamus
- crude touch, pain, temperature
Three order neurones - 1st is DRG to medulla, 2nd is medulla to thalamus, 3rd is thalamus to post central gyrus
Fourth ventricle
Diamond shaped rhomboid fossa forms floor
Limits:
- lateral - middle cerebellar peduncle
- anterior - superior cerebellar peduncle
- posterior - gracile + cuneate tubercles
- inferior - obex
Tectum
Superior part of midbrain, above aqueduct
4 small swellings of grey matter, colliculi:
- superior colliculus for vision
- inferior colliculus for audio
- reflex movement towards sight/sound
Third ventricle
In diencephalon
- walls by thalamus and hypothalamus
+ epithalamus (containing pineal body) and subthalamus (both too small to see)
Thalamus
Symmetrical, two halves joined at interthalamic adhesion, flattened disc on medial surface
On either side of third ventricle
Each half is divided into anterior, medial, lateral parts by sheets of white matter
Contain nuclei for info to and from cerebral cortex
- specific nuclei to restricted cortical areas
- non-specific nuclei diffuse across cortex
Thalamic nuclei
Anterior nuclear group - from mamillary bodies to cingulate cortex (limbic system circuit of Papez)
Central posterior group - sensory information
Pineal body
In epithalamus
Endocrine gland
Synthesises melatonin
For circadian rhythm
Inhibitory effect on gonads
Often calcifies with age
Internal capsule
Contains cerebral cortical projection fibres
To and from frontal lobes - most anterior
Parietal fibres in between
To and from temporal/occipital lobes - posterior
Retrolenticular capsule: auditory to temporal (front), optic to occipital cortex (back)
Wraps around:
- caudate nucleus (head and tail)
- lentiform nucleus (inc globus pallidus and putamen)
- thalamus
- anterior and posterior horns of lateral ventricle
Somatosensory cortex
Primary - SI, Brodmann’s 1,2,3
- postcentral gyrus
- somatotopic representation of body
Secondary - SII
- extends posteriorly behind primary cortex down to lateral sulcus
Somatosensory association cortex - Brodmann’s 5
- posterior to primary cortex in superior part of parietal lobe
Brain cancer
15/100,000 new cases per year, prevalence increasing
50-70yo most common, but gliomas at any age
PRIMARY - 130 types, glioma most common
SECONDARY - 10x more common
- Skin Lung Kidney Breast Gastrointestinal
some love killing brain glioma
40% live to one year
Symptoms
- raised ICP - headache, papilloedema, nausea and vomiting
- focal neurological deficit - cranial nerve palsy, weakness
- seizure
Locations of brain tumours and their effects
FRONTAL - personality change, difficulty planning, hemiparesis
TEMPORAL - hallucinations, seizure, word finding difficulty
PARIETAL - aphasia, sensory loss, agnosia
CEREBELLAR - ataxia, poor coordination, vertigo, diplopia
OCCIPITAL - visual loss
PITUITARY - bitemporal visual loss, endocrine changes
Sensory peripheral neuropathy
Glove and stocking distribution
Affecting touch, pain, temperature
Motor cortex
Includes:
- primary motor cortex - Brodmann’s 4 - precentral gyrus and area immediately in front
- premotor cortex - Brodmann’s 6 - immediately in front and to lateral surface of motor cortex, close connections with it
- supplementary motor area - superior and medial surfaces of hemisphere above PMC
-> for voluntary movements of opposite side of body
upper/medial part - lower limb, perineum
lower/lateral part - trunk, upper limb, neck, head
Ventral pons and medulla
PONS
Groove (containing basilar artery) runs through
Middle cerebellar peduncles are striations out
MEDULLA
Partially divided by anterior median fissure
Pyramids immediately lateral to fissure on each side, mark position of underlying corticospinal/pyramidal tract fibres
80% corticospinal fibres decussate here
Olive to side of each pyramid - swellings containing inferior olivary nucleus, which are connected to contralateral cerebellar circuits to influence movement
Motor
Corticospinal tract (pyramidial):
- voluntary movement below neck (corticobulbar for above neck)
- in lateral tract, contralateral (90%)
- in anterior tract, ipsilateral (10%)
Rubrospinal tract:
- from red nucleus
- unimportant in humans, upper limb flexion?
Reticulospinal tract:
- from reticular formation
- for visceral functions eg awake, breathing, maintaining muscle tone
Vestibulospinal tract:
- from vestibular nuclei
- for anti-gravity posture, limb extensors
Tectospinal tract:
- from tectum
- for reflex movements of head and neck to visual and auditory stimuli
Basal nuclei
Caudate nucleus (comma shaped mass grey matter)- striatum
Putamen (darker, lateral) - striatum, lentiform nucleus
Globus pallidus (lighter, medial) - lentiform nucleus
Subthalamic nucleus
Substantia nigra - black line between crus cerebri, destroyed in Parksinson’s so no dopamine
Claustrum - immediately deep to insular cortex, separated by extreme capsule
-> for practise, planning movement, intitiating movement. Gatekeeper, to inhibit or allow movement.
Cerebellum
Hindbrain
Two ovoid hemispheres joined in midline by median vermis
Outer cortex - highly folded layer grey matter
Inner core - white matter surrounding deep nuclei
Primary fissure separates anterior and posterior lobes
Tonsils at base of cerebellum - if raised ICP then shift down, coning, into foramen magnum
Flocculo-nodular node (posterior lobe)
- floccules each side, nodule in middle
- vestibular information
Examining cerebellar function
DANISH P
D - dysdiadochokinesis
A - ataxic gait
N - nystagmus (towards side of lesion)
I - intention tremor
S - slurred speech (dysarthia)
H - hypotonia
P - past pointing (dysmetria)
All signs ipsilateral to lesion!
Meningitis
Purpuric (non-blanching) rash - leeching of RBCs from vessels
Pus accumulates at meninges, so raised ICP
Stretching neck is painful, reduced consciousness
Cranial nerves and their roots in the brain
Olfactory - forebrain
Optic - forebrain
Occulomotor - midbrain
Trochlear - midbrain
Trigeminal (opthalmic, maxillary, mandibular) - pons hindbrain
Abducens - pons hindbrain
Facial - medullary-pontine junction hindbrain
Vestibulocochlear - medullary-pontine junction hindbrain
Glossopharyngeal - medulla hindbrain
Vagus - medulla hindbrain
Accessory - medulla hindbrain
Hypoglossal - medulla hindbrain
Olfactory nerve
Through cribiform plate
Special sense of smell - sensory only
Anosmia caused by infection/inflammation, nasal polyps, head trauma + associated fracture, frontal tumour
Optic nerve
Through optic canal
Special sense of sight - sensory nerve only
Clinically assess acuity + colour vision, fundoscopy, light reflex, accomodation, visual fields
Lesions of visual pathways
Total blindness of one eye - ipsilateral optic nerve damage
Bitemporal hemianopsia (can only see middle) - optic chiasm
Ipsilateral nasal hemianopia (lost medial one side) - part of optic nerve cut
Contralateral hemianopsia (one side of both eyes lost) - optic tract
Occulomotor nerve
Through superior orbital fissure
Motor - symp and parasymp to all muscles of eye except LR6SO4
Clinically tested with light reflexes and assessment of eye movements
Palsy -> dilated pupil, unresponsive to light, no accomodation, down and out eye, ptosis
Palsy may be from aneurysm/atherosclerosis in basilar artery
Trochlear nerve
Through superior orbital fissure
Motor to superior oblique
Palsy -> diplopia, esp looking down