Functions of Cerebellum & Brainstem Flashcards
what are the 3 functions of the brainstem
- conduction: all information relayed from the body to the cerebrum and cerebellum and vice versa must transverse the brainstem
- cranial nerves function: cranial nerves III-XII emerge from brainstem
- integrative functions: involved in cardiovascular system control, respiratory control, alertness, awareness, and consciousness
what is the cradiovascular centre in the brainstem
found in the medulla oblongata
- regulation of heart rate
- change of blood pH and CO2 –> chemoreceptors
- change of blood pressure –> baroreceptors in aortic and carotid bodies
how does the cardiovascular centre regulate the heart rate
acts by sending nerve impulse to pacemaker via autonomic fibres
what is the cushing reflex
hypertension & bradycardia
- raised ICP (intracranial pressure)
- reduced CPP (cerebral perfusion pressure
- reduced CBF (cerebral blood flow)
- raised PaCO2 –> causes raised ICP
- raised PaCO2 detected by chemoreceptors
- sympathetic stimulation
- arterial hypertension
- baroreceptors
- vagal stimulation (brainstem)
- bradycardia
- raised ICP
what are the respiratory centres
found in medulla oblongata and pons
what is the function of respiratory centres
control the rate and depth of resp movements
injury may lead to resp failure
what do the chemoreceptors in the respiratory centres detect
change of blood pH and CO2
what is the Cheyne-Stokes respiration
periods of respiration during which the tidal volume starts shallow and gets progressively deeper and then gets progressively shallower
followed by periods of significant apnea
what is Biot’s respiration
periods of “clusters” of rapid respiration of near equal depth followed by regular periods of apnea
what are the abnormal breathing patterns seen with brainstem lesions
- Cheyne-Stokes respiration
- Biot’s respiration
- Apneustic respiration
- Ataxic respiration
what is apneustic respiration
prolonged inspiratory phase followed by a prolonged expiratory phase commonly believed to be apneic phase
what is ataxic respiration
completely irregular breathing pattern with irregular pauses and increasing episodes of apnea
what is the ascending reticular activating system (ARAS)
reticular formation: collection of neuronal cell bodies that form a ill-defined meshwork in the central core of the brainstem
from the caudal diencephalon to the medulla oblongata
responsible for awake state, level of consciousness and sleep
what is the mental status grading
- occasional periods of alertness and responsive to environment
- depression or delirium, responds but response may be innappropriate
- semicomatose, response to visual stimuli
- semicomatose, response to auditory stimuli
- stupor, respond only to noxious stimuli
- coma, unresponsive even to noxious stimuli
how can brainstem dysfunction be detected using neurological exam
- mentation: obtunded
- gait: ataxia, unable to walk
- cranial nerves: head tilt to left, positional strabismus of left eye, vertical nystagmus, reduce facial sensation on left side and tongue hypotonia
- proprioception: proprioceptive deficits on left thoracic and pelvic limb
- spinal reflexes, muscle mass and tone: normal
no pain on spinal palpation
what are the mentation signs of brainstem dysfunction (6)
- normal, obtunded, stupor or coma
- head tilt and wide base stance can be seen
- cranial nerves III-XIII can show deficits
- ipsilateral proprioceptive deficits
- abnormal heart rate
- abnormal breathing pattern
what are the functions of the cerebellum
- smooth and coordinate motor function for posture and movement
- acts as regulator, not a primary initiator, of motor activity
- modulates the activity of the upper motor neuron (UMN) affecting agonist and antagonist muscles
what do cerebellar afferents convey
- proprioceptive information from limbs, body and head (ipsilateral)
- information relevant to the planning and execution of motor activity
what proprioceptive information do cerebellar afferents convey
from limbs body and head (ipsilateral) –> spinocerebellar, vestibulocerebellar and tectocerebellar pathways: proprioceptive inputs
what is the corticopontocerebellar pathway
corticopontocerebellar pathway: input about planned motor activity, pyramidal (contralateral)
via olivary nucleus: input from extrapyramidal system (contralateral)
what are the efferent fibers from the cerebellar cortex
purkinje cells –> inhibitory
most of them synapse in deep cerebellar nuclei
vestibulocerebellum bypasses the deep cerebellar nuclei and synapse directly onto the vestibular nuclei
what are the deep cerebellar nuclei neurons
are all excitatory to nuclei of pyramidal and extrapyramidal systems
they can be excitatory or silent but never inhibitory
what are the afferent and efferent pathways from the rostral cerebellar peduncle
afferent: from ventral spino-cerebellar
efferent: to thalamus, to midbrain
what are the afferent and efferent pathways from the middle cerebellar peduncle
afferent: from cortico-ponto-cerebellar pathway
efferent: NO
what are the afferent and efferent pathways from the caudal cerebellar peduncle
afferent: from dorsal spino-cerebellar, reticular formation, olivary nucleus, cuneo-cerebellar, vestibular nuclei
efferent: to reticular formation and vestibular nuclei
what are the 3 functional subdivisions of the cerebellum
- vestibulocerebellum (or archicerebellum): flocculo-nodular lobe –> paradoxical vestibular
- spinocerebellum (or paleocerebellum): vermis and paravermis –> hypermetria and spasticity
- cerebrocerebellum: cerebellar hemispheres –> dysmetria and tremors
what are other cerebellar functions
- menace response
- senory systems, cognition, language and emotions
12y old irish setter with change in gait
what is the neurolocalization
- mentation: normal
- gait: hypermetria, intention tremors, wide base stance
- cranial nerves: bilateral absent menace response
- proprioception: hypermetric hopping, otherwise normal
- spinal reflexes, muscle mass and tone: normal
no pain on spinal palpation
neurolocalization: cerebellum
cerebellar mass
9y old beagle with inability to stand
- mentation normal
- gait: ataxia, unable to walk
- cranial nerves: absent menace response on the right and head tilt to left
- proprioception: reduce on the right thoracic and pelvic limb
- spinal reflexes, muscle mass and tone: normal
no pain on spinal palpation
neurolocalization: right cerebellum, paradoxical vestibular
right cerebellar infarct
what are the histological layers of the grey matter in the cerebeullum
- molecular cell layer
- purkinje cell layer
- granule cell layer
what are these structures
cerebellum
what are these structures
cerebellum
how are cells organized inside the cerebellum
white matter brings info into the cerebral cortex through 2 types of fibres –> 1. mossy fibre (synapse in the granule cell layer and activate purkinje cells) 2. climbing fibres (from olivary nucleus) (synapse directly with purkinje cells)
all info leaves thru axons of the purkinje to deep cerebellar nuclei
what are the cerebellar nuclei
deep inside the white matter
- fastigial nucleus
- interpositus nucleus
- dentate nucelus
- facial nucleus
what are the pathways of the pontine mossy fibres, climbing fibres from olivary nucleus, mossy fibres
pontine: middle cerebellar peduncle
mossy: bringing proprioceptive info from the spinocerebellar tract
climbing: go through the caudal cerebellar peduncle
what occurs when the cerebellum makes a decision
goes through thecerebellar nuclei and through the rostral cerebellar peduncle
what are the neurological signs of cerebellar dysfunction
- mentation: normal
- hypermetria, dysmetria (ipsilateral): cerebellar ataxia
- intention tremors
- head tilt (contralateral) in some cases and nystagmus –> paradoxical vestibular: lesions in the foculonodular lobe. Side of lesion has increase activity due to lack of inhibition
