Reticular formation and Cerebellum

Question 1

Reticular formation

Answer 1

It is composed of grey matter scattered throughout the midbrain, pons and medulla.

Question 2

What is the role of reticular formation?

Answer 2

it covers the arousal of the brain via the thalamus.

it is involved in habituation - a process in which the brain learns to ignore repetitive, unimportant stimuli.

Question 3

What inhibits the reticular formation?

Answer 3

it is inhibited by sleep centers in the hypothalamus and other brain regions.
it is depressed by alcohol, sleep-inducing drugs and tranquilisers

Question 4

Where is the cerebellum located?

Answer 4

posterior to the cranial fossa, and underneath the tentorium cerebelli. it is also posterior to the superior and inferior medullary velum, brainstem, 4th ventricle, vela and cerebellar peduncles.

Question 5

What does the cerebellum consist of?

Answer 5

cortex, white matter and deep nuclei.

Question 6

Synergistic multijoint movement

Answer 6

frontal motor association areas via the corticopontine-cerebellar tract inform the cerebellum of intent to start voluntary muscle contraction.
at the same time, the cerebellum receives information from proprioceptors throughout the body, as well as visual and vestibular input. this information allows the cerebellum to evaluate body position and momentum.
the cerebellar cortex and deep cerebellar nuclei then evaluate the best way to coordinate the force of each muscle contraction to ensure successful movement.
this decision is sent back to the motor cortex for execution.

Question 7

What happens to a patient with cerebellar lesions?

Answer 7

movement is executed with suboptimal coordination and precision

Question 8

posterior cerebellar incisure

Answer 8

contains the falx cerebelli

Question 9

vermis

Answer 9

connects the right and left cerebellar hemispheres

Question 10

folia

Answer 10

parallel surface folds of grey matter

Question 11

what are the two main inputs of cerebellar circuits?

Answer 11

climbing fibers and mossy fibers

Question 12

climbing fibers

Answer 12

innervate Purkinje cells directly. there are mainly from the inferior olivary nucleus and detect proprioceptive input. they are very precise, as there is one ION neuron innervating one Purkinje cell

Question 13

Mossy fibers

Answer 13

firstly innervate granulate cells, and then the granulate cells have parallel fibers (axons) which innervate the purkinje cells

Question 14

Purkinje neurons

Answer 14

are the sole output of the cerebellar cortex. they are inhibitory. they work with input axons to regulate the firing frequency and amplitude of the neurons in the deep cerebellar nuclei and produce the blueprint which is sent to the motor cortex.
Purkinje cells have an oval-shaped cell body and an elaborate flattened, fan-like dendrite tree

Question 15

primary fissure

Answer 15

divides the cerebellum into the inferior and posterior lobes

Question 16

flocculonodular lobe

Answer 16

lies deep to the vermis, in the inferior surface. it communicates with the vestibular system.

Question 17

What is the structure of the flocculonodular lobe?

Answer 17

it is made up of the flocculus and the modulus. inferiorly, lie the tonsils.

Question 18

how does increased intracranial pressure affect the tonsils?

Answer 18

it can push the tonsils down, transferring the pressure onto the tonsils which then put pressure onto the medulla. This can cause the medulla nerves to get damaged and may cause death.

Question 19

zones of the cerebellum

Answer 19

each zone projects to a specific deep cerebellum nucleus which corresponds to a distinctive functional subdivision in the sagittal plane

Question 20

the median zone (vermis)

Answer 20

projects to the fastigial nucleus

Question 21

the intermediate zone

Answer 21

projects to the interposed/interpositus nucleus

Question 22

the lateral zone

Answer 22

projects to the dentate nucleus

Question 23

the cerebrocerebellar circuits (function)

Answer 23

control multi-joint movement in the limbs.

Question 24

the cerebrocerebellar circuits (pathway)

Answer 24

first, the cerebral cortex communicates with the cerebellum that it would like to initiate a movement. that information travels through the cerebropontine cerebellar tract from the premotor cortex. the information proceeds to the lateral zone. sensory information is sent via the spine-olivary tract, crosses over to the olive, and crosses over back again to the lateral zone. neurons in the cerebellum integrate the information and send it to the deep cerebellar nucleus (dentate nucleus), which relays the motion blueprint back to the motor cortex. if the blueprint is approved, information is sent down to the muscles via the lateral corticospinal tract.

Question 25

the spinocerebellar intermediate zone circuit (function)

Answer 25

controls accuracy of movement of the limbs

Question 26

the spinocerebellar medial/median/vermal zone circuits (function)

Answer 26

controls posture via influencing axial muscles in the trunk (throat and abdomen)

Question 27

the vestibulocerebellar circuit (function)

Answer 27

maintain balance via axial and limb muscles

Question 28

inferior cerebellar peduncle

Answer 28

conveys sensory information to the cerebellum from muscle proprioceptors throughout the body and from the vestibular nuclei of the brainstem. it contains both motor and sensory information

Question 29

middle cerebellar peduncle

Answer 29

contains only afferent axons (crossed axons from the contralateral pontine nuclei)

Question 30

superior cerebellar peduncle

Answer 30

connects the cerebellum to the midbrain. it is formed by axons by arise from deep cerebellar nuclei. fiber decussate at various levels.
crossed fibers ascend - they either terminate in the red nucleus or continue rostrally to end with the thalamus

Question 31

Do cerebellar hemisphere influence the body ipsilaterally or contralaterally?

Answer 31

ispilaterally.

decussate at the superior cerebellar peduncle (going to the cortex) and at the corticospinal tract (efferent signals).

Question 32

Cerebellar dysfunction

Answer 32

leads to loss of coordination of muscle activity

Question 33

ataxia

Answer 33

inaccuracy in the speed force and distance of movement

Question 34

tremor

Answer 34

involuntary oscillation of the limbs or the trunk

Question 35

nystagmus

Answer 35

rhythmic involuntary oscillations of the eye

Question 36

headache and vomiting

Answer 36

often the 1st symptom of cerebellar tumour. it occurs due to blockage of CSF drainage from the 4th ventricle