Term
| Muscle spindle structure and function |
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Definition
- Muscle spindles are in parallel with extrafusal fibres and attached to muscle connective tissue - signal length and rate of change of length of the muscle
- Encapsulated spindle shaped structure
- Two morphological types - nuclear chain fibres (variable number per spindle) and nuclear bag fibres (2-3 per spindle)
- 1α afferents record centre of all fibres and report on dynamic and static information
- Type II afferents only from static bag and all chain fibres - information on spindle length
- Efferent γ fibres - seperate supply to static and dynamic intrafusal fibres
- 1α afferents synapse with α motor neuron to contract muscle when weight added (stretch reflex), while acting via inhibitory interneurons to relax antagonist
- γ static activity for the control of predictable movement, γ dynamic for rapid, unpredictable movement
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Term
| Golgi tendon organ structure and function |
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Definition
- Golgi tendon organs are in series with extrafusal fibres and signal the tension in the tendon
- 1β fibres interwoven with collagen fibres at muscle-tendon junction
- Stretch compresses and stimulates afferent
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Term
| Spinal interneurons in muscle stretch reflex |
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Definition
- Descending inpuit on Renshaw inhibitory interneurons to inhibit firing muscle to prevent fatigue
- Ia inhibitory interneuron to inhibit antagonist muscle in stretch reflex
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Term
Primary motor cortex function anatomy and connections |
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Definition
- Motor cortex - Toes in longitudinal fissure, knee at vertex, them hip, trunk, shoulder, arm, elbow, wright, hand, fingers, thumb, neck, brow, eye, face, lip, jaw tongue, swallowing
- Inputs from supplementary motor area, premotor, somatosensory cortex, ventral anterior and ventral leteral thalamus (cerebellum and basal ganglion)
- Outputs to corticospinal ract, corticostriate tract, corticobulbar tract (pons, cranial nerve nuclei, colliculus, reticular formation, red nucleus)
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Term
| Direct and indirect basal ganglia pathways |
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Definition
- Direct - striatal output inhibits SNr/GPi and reduces GPi inhibition on thalamus, facilitating movement - D1 mediated by facilitating pathway
- Indirect - striatal output inhibits GPe and reduces DPe inhibition of STN. Increased STN activity increases GPi inhibition of thalamus, inhibiting movement - D2 inhibits this pathway, and thus disinhibiton
- Altogether, dopamine facilitates chosen movement
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Term
| Inhibitory and excitatory pathways in the cortico-thalamic-basal ganglia loop |
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Definition
- Cortex excites both striatal direct and indirect pathways
- Striatum inhibits both SNr/GPi and GPe
- SNr/GPi inhibits feedback loops and thalamus
- GPe inhibits STN, which reciprocally activates GPe
- STN activates SNr/GPi
- SNc activates direct pathway and inhibits indirect pathway
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Term
| Functional division of cerebellum |
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Definition
- Vestibulocerebellum - flocculonodular lobe
- Spinocerebellum - vermis
- Pontocerebellum - hemispheres
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Term
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Definition
- Pontocerebellar nucleus cell projects mossy fibre (spinocerebellar pathway, brainstem reticular formation, pontine nucleus) to granule cells and, the arborisations of which innervate many Purkinje cells as parellel fibres (+)
- Inferior olivary nucleus cell projects one axon to wind around Purkinje cell (+)
- Basket and stellate cell dendrites interact with parellel fibres (+) and Purkinje cells (-)
- Mossy fibres and climbing fibres project also do deep cerebellar nuclei cells
- Frequency of mossy fibre firing is modulated by sensory and motor inputs
- Climbing fibres depress parellel fibre inputs that were recently active - prediction error
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Term
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Definition
- Vestibular - movement of the eye through the vestibuloocular reflex
- Pursuit - frontal pursuit area of cortex induces smooth movement tracking an object (as well as superior colliculus)
- Saccadic - jerky movements controlled by frontal eye fields of superior colliculus as mechanism for fixation and rapid eye movement
- Vergence - to move fovea of both eyes on a object - rotation of each eye in opposite directions
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Term
| Pupillar light reflex neural pathway |
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Definition
- Ipsilateral afferent limb from CN2 to pretectal nucleus
- Edinger-Westphal nucleus of CNIII innvervated by both contralateral (consensual) and ipsilateral (direct) fibres
- CNIII innervates ciliary sphincter the ciliary ganglion
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Term
| Pupillary light reflex diagnosis |
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Definition
- Optic nerve damage - Left optic nerve damage before chiasm
- Ipsilateral direct and contralateral consensual reflex lost (no constriction of either pupil) when left eye stimulated because no information passes through left optic nerve
- Contralateral direct and ipsilateral consensual reflex is intact as right optic nerve and both oculomotor nerves are in tact
- Oculomotor nerve damage - left efferent limb damage
- Ipsilateral direct and ipsilateral consensual reflexes are lost as no efferent information to left pupil, while contralateral consensual and contralateral direct reflexes are intact
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