L7 Flashcards
what is the reticular formation composed of
Composed of clusters of gray matter scattered throughout
midbrain, pons and medulla
what is the role of the reticular formation
Its role is for arousal and it does this by the thalamus. (it sends its neurons to the thalamus)
what is the reticular formation involved in
habituation
what is habituation
a process in which the brain
learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others
what is the reticular formation inhibited by
inhibited by sleep centres located in the hypothalamus & other brain regions
this is because when you are asleep you don’t want to be woken
what is the reticular formation depressed by
depressed by alcohol, sleep-inducing drugs &
tranquilisers
what would happen if you were to damage the brainstem
permanent unconsciousness
(irreversible coma) because this is where the reticular formation is therefore if that is damaged then you would be unable to be woken
what % of neurons are in the cerebellum
50%
what is the important functions of the cerebellum
balance and coordination
where is the cerebellum located
in the posterior cranial fossa
what is the dame of the 3 sections that the base of the skull is divided into
The base of the skull is divided into the anterior, middle and posterior cranial fissure
what structures is the cerebellum posterior to
the superior medullary velum ( the roof of the 4th ventricle)
and
the inferior medullary velum (chloride plexus)
what are the main structures of the cerebellum
cortex, white matter and deep nuclei
what are the primary roles of the cerebellum
synchronised, precisely timed movement across
multiple joints = synergistic multijoint limb movement
Eg. throwing a ball, finger-to-nose test
control of muscle tone (posture)
maintenance of balance
does the cerebellum give rise to conscious sensory perceptions
no
it receives vast amount of sensory information, but does not give rise to conscious sensory perceptions
is the cerebellums role for afferent or efferent information
it has 40x more afferents than efferents. this is because of the vast amount of sensory information coming in
how is synergetic multi joint movement achieved
Frontal motor association areas (eg. premotor cortex)
via the corticopontine-cerebellar tract, inform cerebellum of intent to start voluntary muscle contractions
At the same time, the cerebellum receives information from proprioceptors throughout the body, as well as visual and vestibular (balance) input
The proprioceptive information includes tension in muscles and tendons and the position of joints.
This information allows the cerebellum to evaluate body
position and momentum = where the body is and where it intends to go.
The cerebellar cortex and the deep cerebellar nuclei then calculate the best way to coordinate the force of each muscle contraction to prevent overshoot, maintain posture & ensure smooth coordinated movement.
Then, the cerebellum dispatches to the motor cerebral cortex its “blueprint” for coordinating movement. The primary motor cortex then influences motor neurons in the spinal cord to produce movement.
what structure do the neurons from the premotor cortex go through to inform the cerebellum that you want to start a movement
corticopontine-cerebellar tract
which structures calculate the best way to ensure smooth coordinated movement
the cerebellar cortex and deep cerebellar nuclei
what would be expected if an individual had a cerebellar lesion
they are usually capable of
carrying out general outlines of movement, but each movement is executed with suboptimal coordination and precision.
they will be clumsy
what anatomy is needed to achieve synergistic multijoint movement
Cerebellum needs to be connected to the motor input from cerebral cortex, the various sensory inputs and needs to send its output or blueprint back to the cerebral cortex.
it also needs the cerebellar penuckle’s to connect one region of the brain to the other
what are the names of the 3 cerebellar peduncles and where are they located
the superior cerebellar peduncle is located in the midbrain
the middle cerebellar peduncle is located in the pons
the inferior cerebellar peduncle is located in the medullar
from what view would you see the cerebellar peduncles
an dorsolateral view of the brainstem
or
the anterior view of the cerebellum
what structures is the cerebellum posterior to
Brainstem, 4th Ventricle, Vela, Cerebellar Peduncles
when looking at the anterior view of the cerebellum what do the peduncles look like
they are white because they are white matter tracts
the superior on is the thin skinny bit
the middle and the inferior are the circular bit.
the middle is the circle bit closes to the superior cerebellar peduncle
what is a insisure
it is the equivalent of a sulcus in the cerebellum
how can you identify the anterior and posterior cerebellar incisures
anterior is the bit of the cerebellum that dips in where the brainstem is
posterior is the bit that dips in at the middle back of the cerebellum
what do the anterior and posterior cerebellar incisures contain
the flux cerebelli
what are the right and left hemispheres of the cerebellum connected by
the vermis
what are the parallel surface folds of the cerebellum called
folia (leaves)
what do folia consist of
gray matter
what is the white matter in the cerebellum called
arbor vitae
tree of life
where do the deep nuclei sit in the cerebellum
in the white matter
what are the main cells in the cerebellum
purkinje cell
granule cell (has parallel fibers)
mossy fibers
climbing fibers
what plain do the dendrites of the purkinje cells sit in
caronal
what are two main inputs of the cerebellar circuits
mossy fibers and climbing fibers
what is the role of mossy fibers
mossy fibers/axons come from spinal cord or brainstem neurons and convey motor or sensory input to the cerebellum
Mossy axons form excitatory synapses with granule
neurons in the cerebellar cortex.
what is the role of climbing fibers
mainly from inferior olivary nucleus therefore they bring proprioceptive input.
One ION neuron innovates 1 PC therefore this is a very precise system
Climbing axons form excitatory synapses directly with the purkinje neurons/cells in the cerebellar cortex.
mossy fibers synapse with granule neurons. what happens from here
The granule neurons send their axon as a parallel fibre (because it is parallel to the surface) to form excitatory synapses with the Purkinje neurons.
what is the role of the purkinje cell
Purkinje neuron is sole output neuron of the cerebellar cortex. Is inhibitory. Works with input axons to regulate the firing frequency and amplitude of the neurons in the deep cerebellar nuclei = “blueprint” sent to motor cortex.
what is the role of the neurons in the deep cerebellar nuclei
they integrate synaptic output
what are they layers of the cerebral cortex
outer most to inner most
molecular layer
purkinje cells
granule cell layer
white matter
describe what a purkinje cell looks like
it has an oval shaped cell body in the granule cell layer
elaborate flattened, fanlike dendrite tree (sagittal section)
what divides the cerebellum into the anterior and posterior lobe
the primary fissure
what is the name of the 3rd lobe in the cerebellum
flocculonodular lobe
what is the function of the lobes in the cerebellum
anterior and posterior lobes = coordination of movement
flocculonodular lobe = balance
where is the flocculonodular lobe located
the inferior surface, deep to the vermis
what structures make up the flocculonodular lobe
the 2 flocculus and the nodulus
what is hydrocephalus effect on the tonsils
If you have increased intracranial pressure (hydrocephalus) then it will push the tonsils down which puts pressure on the medulla which is where the neurons for the heart and lungs are which means that if they are damaged then you will die
what are the sagittal functional subdivisions of the superior surface of the cerebellum
the lateral zone (the lost lateral part)
the intermediate zone (middle)
the median zone (vermis)
what are the 4 deep cerebellar nuclei
Fastigial
Globose
Emboliform
Dentate
which of the 4 deep cerebellar nuclei from the Interposed/Interpositus Nucleus
Globose and Emboliform
which deep cerebellar nuclei does the vermis project to
the Fastigial nucleus
which deep cerebellar nuclei does the intermediate zone project to
the interposed/interpositus nucleus
which deep cerebellar nuclei does the lateral zone project to
the dentate nucleus
the Flocculonodular lobe can also be called the…..
= Vestibulocerebellum
what are the Cerebrocerebellar circuits responsible for
controls multijointed movements of limbs to create fluid and coordinated movement
what are the Spinocerebellar intermediate zone
circuits responsible for
controls accuracy of movement of the limbs.
eg. precision at a joint
what are the Spinocerebellar medial/median/vermal
zone circuit responsible for
Controls posture via influencing axial muscles in trunk
what are the Vestibulocerebellar circuits responsible for
maintain balance via axial and limb muscles
describe the pathway of the cerebrocerebellar circuits
the first thing that happens is the cerebral cortex tell the cerebellum what to do via the CPCT
This is from the premotor cortex neurons inform the cerebellum what you want to do
The neurons in the cerebrum to the pontine nuclei and then into the lateral zone of the cerebellum
The spino-olivary tract comes up form the spine, crosses in the olive and then crosses to the lateral zone. This is proprioceptive information
The PC cells then go to the deep cerebellar nuclei (dentate nucleus) which then send the blueprint back up to the motor cortex
From there the movement gets sent down
describe the pathway of the spinocerebellar intermediate zone circuits
This time the CPCT goes to the intermediate zone no the lateral zone
Even though this is called spine there is still CPCT input
Sensory information comes up from the inferior olivary nucleus to the intermediate zone
The PC innovate the interpositus neurons which create the blueprint
This then gets sent through the red nucleus to the thalamus to motor cortex and leaves through the lateral corticospinal tract
describe the pathway of the spinocerebellar vermal zone circuit
Integrating information from the spinocerebellar tracts and the inferior olivary nucleus
These go the the median zone of the deep cerebellar nuclei the PC cells innovate the visidual nucleus (the most medial). This goes to the thalamus and then to the PMC. It leave through the ventral corticospinal tract
describe the pathway of the vestibulocerebellar circuits
Input from the inferior olivary nucleus
These are climbing and mossy fibers
The mossy fibers are coming from the vestibular labyrinth (semi-circular canals)
Both climbing and mossy fibers go via the inferior cerebellar peduncle to the pocculondualar lobe. From there the PC go directly with the vestibular nuclei to the vestibular spinal tract.
what is the role of the inferior cerebellar peduncle
conveys sensory information to the cerebellum from muscle proprioceptors throughout the body
AND from the vestibular nuclei of the brainstem
(equilibrium & balance)
contains both afferent (chiefly) & efferent axons
what is the role of the middle cerebellar peduncle
contains only afferent axons (crossed axons from contralateral pontine nuclei). Eg CPCT
what are the characteristics of the superior cerebellar peduncle
formed by axons that arise from deep cerebellar nuclei (main efferent pathway)
fibers decussate at various levels
crossed fibers ascend - either terminate in the red
nucleus or continue rostrally to end within the
thalamus (then to cerebral motor cortex)
what does ipsilateral haf mean
same side
where does each cerebellar hemisphere excert its influence in the body
Each cerebellar hemisphere exerts its influence primarily on the ipsilateral half of the body
this is because they are doubly crossed
what is ataxia
inaccuracy in the speed, force and distance of
movement (staggering gait, dysmetria, slurred speech)
what is a tremor
involuntary oscillation of the limbs or trunk
what is nystagmus
rhythmic involuntary oscillation of the eyes
what could be the cause of a headache and vomiting in relation to the cerebellum
this is often 1st symptoms of cerebellar tumour
Tumor which blocks the CSF drainages from the 4th ventricle which increases the pressure causing a headache. The vomiting if from pressure on the medulla
