Neuroanatomy Flashcards
Motor system pathway
Efferent pathway:
Motor cortex - precentral gyrus of frontal lobe (Brodmann area 4) and premotor cortex (Brodmann area 6) anterior to it
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Descends via corticospinal tract
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Centrum semiovale and corona radiata
- fibres gethered into small bundles -> more extensive symptoms, more areas affected
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Internal capsule anterior portion of posterior limb (basal ganglia)
Corticobulbar fibres (facial fibres) travel in internal capsule genu
- very tightly packed fibres
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Brainstem - both sides lie close together, CN3 also here
* Weber syndrome -> ipsilatereal CN3 palsy + contralateral hemiparesis
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(lesion before this point is contralateral)
Pyramids in lower ventral medulla - fibre decussation
(lesion beyond this point is ipsilateral)
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Spinal cord and termination at anterior horn cell
(junction between UMN and LMN)
- Mostly as lateral corticospinal tract; some in ventral corticospinal tract
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Peripheral nerves into muscles
Sensory system pathway
Afferent system:
Peripheral nerves from skin and end organs
- Myelinated: fast conducting (proprioception)
- Unmyelinated: slow conducting (pain fibres)
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Spinal cord (dorsal column)
- Same side: touch, vibration, proprioception
- Decussate: spinothalamic (pain, temperature)
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Brainstem - > medial lemniscus
- Dorsal column fibres decussate (touch, vibration, proprioception)
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Thalamus - fibres tightly packed
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Primary sensory cortex - postcentral gyrus of frontal lobe
Visual system pathway
Retina - detects light and convert to electrical impulses
> Temporary blindness: amaurosis fugax
> Permanent blindness: CRAO
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Optic nerve
> Blindness of single ipsilateral eye
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Optic chiasm - optic nerve partially cross over
> Central lesion (pituitary): bitemporal hemianopia
> Whole chiasm: complete blindness
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Optic tract - carries information from one visual field
> Lesion affects same field in BOTH eyes (homonymous hemianopia)
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Optic radiation - from lateral geniculate nucleus to cortex
> Quadrantanopia
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Visual cortex in occipital cortex
> Homonymous hemianopia
(Other motor tracts)
What is the reticulospinal tract?
Origin: pre-central gyrus
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Synapse in reticular formation of brainstem
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Descends into spinal cord
Function: inhibitory effect on alpha and gamma motor neurons
(Other motor tracts)
What is the vestibulospinal tract?
Efferent from lateral vestibular nucleus
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Descends spinal cord
Resides lateral to spinothalamic tract
Function: coordinates motor and vestibular performance
(Other motor tracts)
What is the medial longitudinal fasciculus (MLF)?
Efferent of lateral vestibular nucleus
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Ascends to CN3, CN4 and CN6 nuclei
Interneurons origin from paramedian pontine reticular formation (PPRF)
What is the function of frontal lobe?
- Voluntary eye movement
- Somatic motor control
- Planning and sequencing of movements
- Emotion and personality
Also lies Broca’s area (area 44) - motor control of speech (expressive)
What is the function of temporal lobe?
- Auditory and visual perception
- Learning and memory integration
- Emotion
- Olfaction
Wernicke’s area (area 22) in dominant lobe - comprehension of speech (receptive)
Non-dominant lobe - mediates prosody and spatial relationships
What is the function of parietal lobe?
- Cortical sensation
- Motor control
- Visual perception
Dominant lobe: ideomotor praxis
Non-dominant lobe: visual-spatial orientation
What is the function of occipital lobe?
- Visual perception
- Involuntary smooth pursuit eye movement
How is language processed?
Receptive: Wernicke’s area in dominant temporal lobe
Expressive: Broca’s area in frontal lobe
Where is the lesion that causes achromatopsia (inability to match colours and hues)?
Dominant occipital lobe (area 18)
Syndrome with alexia without agraphia
Describe the anatomical divisions of cerebellum.
What is the main function of cerebellum?
Divided into 2 hemispheres, midline vermis and flucculonodulus
Function: coordinate and stabilise movement, balancing
What are the functions of each cerebellar lobe?
What is the clinical significance of cerebellar infarct and oedema?
Hemispheres: appendicular control
(Atrophic in alcoholics)
Input: motor and sensory cortex - > hemispheres - > dentate nucleus - > output: thalamus VL to premotor cortex
Vermis: axial control
Input: muscle spindles, Golgi tendon organs -> spinocerebellar tracts - > paravermis -> interposed nuclei -> output: red nucleus
Flocculonodular: vestibular balance
Input: vestibular system - > flocculonodular -> fastigial and vestibular nuclei -> output: vestibular system
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Cerebellar tonsils lie lateral to medulla
In cerebellar infarct and oedema, middle lobe of cerebellar may compress onto medulla causing tonsillar herniation
Deep nuclei of the cerebellar
(lateral to medial)
Dentate nucleus: receives input from lateral hemispheres, outputs via superior cerebellar peduncle
Globose nuclei and endoliform nucleus (interposed nuclei) : receive input from paravermian regions, outputs via superior cerebellar peduncle
Fastigial nucleus: input from vermis and flocculonodular lobe, outputs via juxtarestiform body of inferior cerebellar peduncle
Cerebellar peduncles and inputs to cerebellum
Cerebellar peduncle and outputs from cerebellum
Outputs from cerebellum comes from deep nuclei
What are the components of basal ganglia?
What structure is the lateral border of the caudate?
Group of nuclei situated in the deep part of cerebrum and upper part of brainstem
Nuclei:
1. Corpus striatum - caudate, putamen, nucleus accumbens (ventral stiatum)
2. Pallidum - globus pallidus (internal and external), subthalamic nucleus
3. Substantia nigra - pars compacta, pars reticulata
(Lentiform nucleus: putamen + globus pallidus)
Functions: initiation and modulation of movement, regulate posture
Diseased state:
1. Movement paucity (hypokinetic)
2. Abnormal movement (hyperkinetic)
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Anterior limb of the internal capsule is the lateral border of the caudate
