Chapters 15 16 Single

Cerebellum Little brain „ Midline vermis „ Paravermis „ 2 hemispheres „

Cerebellum „

Tonsils … Part

lobe

of the posterior

Cerebellar Peduncles „

3 pairs of peduncles … Superior „

Midbrain

… Middle „

Pons

… Inferior „

Medulla

Cerebellum - Structure Gray matter „ White matter „ Tree of life „

… Folia

or leaves „

Gyri

Deep Cerebellar Nuclei Dentate „ Emboliform „ Globose „ Fastigial „

„

‘Don’t Eat Greasy Food’

Cerebellar Lobes 2 fissures: anterior & posterolateral „ 3 lobes: anterior, posterior, flocculonodular „

Cerebellar Lobes „

2 fissures … Anterior … Posterolateral

„

3 lobes … Anterior … Posterior … Flocculonodular

Longitudinal Divisions „

Vermis … Fastigial

„

nucleus

Paravermis … Emboliform … Globose

„

Hemisphere … Dentate

Functional Divisions „

Vestibulocerebellum … Flocculonodular „ „

„

Vestibular and reticular nuclei Body equilibrium and eye movements

Spinocerebellum … Anterior „ „

„

lobe

lobe

Spinal cord Axial and limb movements: walking, swimming

Cerebrocerebellum … Posterior „ „ „

lobe

Cerebral cortex Planning and initiation of movements Regulate discrete limb movements

Somatotopic Map „

Anterior lobe … Body

„

inverted

Posterior lobe … Right-side

up … Dual representation across midline … Trunk @ midline … Extremities – lateral

Microscopic Structure „

Cerebellar Cortex …3

layers

„

Outer molecular Basket cells … Stellate cells …

„

Middle Purkinje cell layer …

„

Purkinje cells ƒ Projection neurons.

Innermost granule cell layer Granule cells … Golgi cells …

Cerebellar Cortex Neuronal Types

„

Purkinje cell …

Large dendritic tree … 1 axon „ „

Deep cerebellar nuclei Lateral vestibular nucleus

Cerebellar Cortex Neuronal Types

„

Basket cell – next to Purkinje cells. … Synapses:

„

dendrites, soma, axons of Purkinje

Stellate … Synapses:

dendrites of Purkinje

Cerebellar Cortex Neuronal Types

„

Granule cell …

Axons ascend to molecular layer „ „ „

Bifurcate [T] Form parallel fiber system Contacts dendrites of …

Purkinje, Golgi, Stellate and Basket cells

Cerebellar Cortex Neuronal Types

„

Golgi (Type II) Cell … Axon „

forms part of the glomerulus

Axonal arborization

Cerebellar Glomerulus „

Mossy Fiber … Incoming

cerebellar

input

Dendrites of granule cells „ Axons of Golgi cells „ Dendrites of Golgi cells „

Cerebellar Input „

3 major inputs … Spinal

cord … Vestibular system … Cortex „

Over half the neurons in the brain are in the cerebellum … So

they’re also smaller than cortical neurons

Spinal Input „

Spinocerebellar tract … Dorsal

„

and ventral

Position & condition of muscles, tendons, and joints

Vestibular Input Vestibular nerve „ Vestibular nuclei „ Body equilibrium „

Cortical Input „

Cortex to … Pons … Inferior

Olive

Then to Cerebellum „ Planning & initiation of movement „

Climbing Fiber System Olivocerebellar tract „ Synapse on dendrites of Purkinje cells and intrinsic cells (Golgi, basket, stellate) „ Climbs dendrites of 1 Purkinje cell „ Powerful excitatory effect on *one* Purkinje cell „ Less powerful on intrinsic neurons „

Mossy Fiber System „

Branch out into terminal ‘rosettes’ … Center

of each glomerulus … Contacts 20 different granule cells … Diffuse and complex

Climbing vs Mossy Input

Climbing vs Mossy Fiber Input

Intrinsic Cerebellar Circuitry Output: deep cerebellar nuclei „ Combination of „

… Excitatory

mossy & climbing fiber input „

Collateral projections

… Inhibitory

input from Purkinje cells

Deep Cerebellar Nuclei Output … Major „

Vestibular & reticular nuclei …

„

Nucleus fastigius

Red nucleus & inferior olive …

„

output

Interposed nuclei

Thalamus Dentate … Interposed nuclei …

„

Hypothalamus …

all

Dentate Nucleus „

Inputs … Lateral

cerebellar Purkinje cells … Climbing fibers … Mossy fibers „

Outputs … Ventrolateral

nucleus of the thalamus

Interposed Nuclei „ „

Emboliform & Globose Inputs … Paravermal

Purkinje

cells … Climbing fibers … Mossy Fibers „

Outputs … Red

nucleus … Ventrolateral nucleus of the thalamus … Inferior olive

Fastigial Nucleus „

Inputs … Vermal

Purkinje

cells … Climbing fibers … Mossy fibers „

Outputs … Vestibular

nuclei … Reticular nuclei

Output by Peduncle „

Superior … Thalamus … Red

nucleus … Inferior Olive „

Inferior … Vestibular

nuclei … Reticular nuclei

Cerebellar Functions „

Motor functions … Control

and integration of motor activity … Motor learning & memory … Signs Asthenia – gets tired easily „ Ataxia – trouble walking „ Atonia – poor muscle tone/coordination „ Problems in speed, range, force, or timing of movement „

Motor signs (cont). … Asynergia

– lack of coordination … Dysarthria – slow, slurred speech … Adiadochokinesis – delay in initiating each movement of a sequence … Dysmetria – delay in termination of movement „ „

Hypermetria – overshooting target Hypometria – undershooting target

… Gait

ataxia - staggering gait … Unsteady standing … Nystagmus

Cerebellar vs Basal Ganglia Motor Functions

Cerebellar Non-motor Functions „

Visceral … Cardiovascular,

endocrine, altered respiration, intestinal motility, bladder tone

„

Affective … Reduced

„

aggressiveness, mood changes

Through connections to reticular formation