Lecture 8 - Cerebellum

Question 1

What is the reticular formation composed of?

Answer 1

Composed of clusters of gray matter scattered throughout midbrain, pons and medulla

Question 2

What is the reticular formation involved in?

Answer 2

Habituation

Question 3

What is habituation?

Answer 3

a process in which the brain learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others

Question 4

What is the reticular formation inhibited by?

Answer 4

by sleep centres located in the hypothalamus & other brain regions

Question 5

What is the reticular formation depressed by?

Answer 5

depressed by alcohol, sleep-inducing drugs & tranquilisers

Question 6

What does brainstem injury of reticular formation cause?

Answer 6

permanent unconsciousness
(irreversible coma)

Question 7

What does the reticular formation govern?

Answer 7

The arousal of the brain via thalamus

Question 8

Where is the cerebellum located?

Answer 8

posterior cranial fossa

Question 9

What is the cerebellum posterior to?

Answer 9

Superior and inferior medullary velum
Brainstem
4th Ventricle
Cerebellar peduncles

Question 10

What does the cerebellum consist of?

Answer 10

cortex, white matter and deep nuclei

Question 11

What is the cerebellum primarily concerned with?

Answer 11

synchronised, precisely timed movement across multiple joints = synergistic multi-joint limb movement

Question 12

What does the cerebellum recieve?

Answer 12

receives vast amount of sensory information, but does not give rise to conscious sensory perceptions

Question 13

What % of neurons in the brain does the cerebellum contain?

Answer 13

50%

Question 14

What does the cerebellum have more of, afferent or efferent?

Answer 14

40x more afferents than efferents

Question 15

What informs the cerebellum of intent to start voluntary muscle contractions?

Answer 15

Frontal motor association areas (eg. premotor cortex) via the corticopontine-cerebellar tract

Question 16

What does the cerebellum recieve information for?

Answer 16

Proprioceptors throughout body
Visual input
Vestibular (balance) input

Question 17

What does the proprioceptive information to cerebellum include?

Answer 17

Tension in muscles and tendons and the position of joints

Question 18

What does proprioceptive information allow the cerebellum to do?

Answer 18

Allows the cerebellum to evaluate body position and momentum = where the body is and where it intends to go

Question 19

What is the role of the cerebellar cortex and deep cerebellar nuclei?

Answer 19

The cerebellar cortex and the deep cerebellar nuclei calculate the best way to coordinate the force of each muscle contraction to prevent overshoot, maintain posture & ensure smooth coordinated movement.

Question 20

What does the cerebellum dispatch to the motor cerebral cortex?

Answer 20

Blueprint for coordinating movement

Question 21

What does the primary motor cortex influence?

Answer 21

The primary motor cortex then influences motor neurons in the spinal cord to produce movement

Question 22

What is the effect of cerebellar lesion?

Answer 22

A patient with a cerebellar lesion is usually capable of carrying out general outlines of movement, but each movement is executed with suboptimal coordination and precision.

Question 23

What does the cerebellum need to be connected to to achieve function?

Answer 23

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.

Question 24

What are the right and left hemispheres of cerebellum connected by?

Answer 24

Vermis

Question 25

What are folia?

Answer 25

Parallel surface folds of cerebellum made of grey matter

Question 26

What is the regional anatomy of the cerebellum?

Answer 26

Grey matter (cortex) White matter (arbor vitae) - tree of life Deep nuclei

Question 27

What are the two main inputs of the cerebellar circuits?

Answer 27

mossy fibers/axons climbing fibers/axons

Question 28

Where are the climbing fibers/axons from?

Answer 28

mainly from inf. olivary nucleus = proprioceptive input. One ION neuron to 1 PC

Question 29

Where are the mossy fibers/axons from?

Answer 29

from spinal cord or brainstem neurons

Question 30

What do the mossy fibers/axons convey?

Answer 30

conveying motor or sensory input

Question 31

What do the climbing fibers/axons convey?

Answer 31

Proprioceptive input

Question 32

What do the climbing axons form?

Answer 32

Climbing axons form excitatory synapses directly with the Purkinje neurons/cells (PC) in the cerebellar cortex

Question 33

What do the mossy axons form?

Answer 33

Mossy axons form excitatory synapses with granule neurons in the cerebellar cortex.

Question 34

What does the granule neurons send their axon as?

Answer 34

The granule neurons send their axon as a "parallel fibre" to form excitatory synapses with the Purkinje neurons

Question 35

What is the sole output neuron of the cerebellar cortex?

Answer 35

Purkinje neuron

Question 36

What type of neuron is the Purkinje neuron in the cerebellar circuit?

Answer 36

Inhibitory

Question 37

What does the Purkinje neuron work with/do?

Answer 37

Works with input axons to regulate the firing frequency and amplitude of the neurons in the deep cerebellar nuclei = "blueprint" sent to motor cortex

Question 38

What do neurons in cerebellar deep nuclei integrate?

Answer 38

Synaptic input

Question 39

What is the structure of Purkinje cells?

Answer 39

Oval-shaped cell body Elaborate flattened, fanlike dendrite tree (sagittal section)

Question 40

Where does the Flocculonodular lobe lie deep to?

Answer 40

Vermis

Question 41

What surface is the Flocculonodular lobe on?

Answer 41

Inferior surface of cerebellum

Question 42

What do the anterior and posterior lobes of cerebellum do?

Answer 42

Co-ordinate movement

Question 43

What is the FNL?

Answer 43

Flocculonodular lobe

Question 44

What is the role of the Flocculonodular lobe?

Answer 44

Balance

Question 45

What is on the superior surface of the cerebellum?

Answer 45

Anterior lobe vermis Posterior lobe folia FNL

Question 46

What are the zones on the superior surface of the cerebellum? and what do they correspond with?

Answer 46

Lateral to medial Lateral zone Intermediate zone Vermis (median zone) Corresponding to sagittal functional subdivisions

Question 47

What is the deep cerebellar nuclei composed of?

Answer 47

Fastigial Interposed/interpositus nucleus: - Globose - Emboliform Dentate

Question 48

What does the Vermis (median zone) project to?

Answer 48

Vermis (median zone) projects to the fastigial nucleus

Question 49

What does the Intermediate zone in deep cerebellar nuclei project to?

Answer 49

Intermediate zone projects to the interposed/interpositus nucleus

Question 50

What does the Lateral zone in deep cerebellar nuclei project to?

Answer 50

Lateral zone projects to the dentate nucleus

Question 51

What are the functional divisions of the cerebellum?

Answer 51

three sagittal functional regions, with the flocculonodular lobe being a 4th non-sagittal functional region

Question 52

What are the spinocerebellum divisions?

Answer 52

Vermis Intermediate zone

Question 53

What is the cerebrocerebellum division?

Answer 53

Lateral zones

Question 54

What is the vestibulocerebellum division?

Answer 54

Flocculonodular lobe

Question 55

What is the overall function of the cerebrocerebellar circuits?

Answer 55

controls multijointed movements of limbs

Question 56

What is the function of the spinocerebellar intermediate zone circuits?

Answer 56

controls accuracy of movement of the limbs. eg. precision at a joint

Question 57

What is the function of the spinocerebellar medial/median/vermal zone circuit?

Answer 57

Controls posture via influencing axial muscles in trunk

Question 58

What is the function of the vestibulocerebellar circuits?

Answer 58

maintain balance via axial and limb muscles

Question 59

What does the inferior cerebellar peduncle convey?

Answer 59

Sensory information to the cerebellum From muscle proprioceptors throughout the body From the vestibular nuclei of the brainstem (equilibrium & balance)

Question 60

What axons does the inferior cerebellar peduncle contain?

Answer 60

Contains both afferent (chiefly) & efferent axons

Question 61

What axons does the middle cerebellar peduncle contain?

Answer 61

Contains only afferent axons (crossed axons from contralateral pontine nuclei). Eg CPCT

Question 62

What does the superior cerebellar peduncle connect?

Answer 62

The cerebellum to the midbrain

Question 63

What is the superior cerebellar peduncle formed by?

Answer 63

Formed by axons that arise from deep cerebellar nuclei (main efferent pathway)

Question 64

Describe the fibres of the superior cerebellar peduncle

Answer 64

Fibres decussate at various levels Crossed fibres ascend - either terminate in the red nucleus or continue rostrally to end within the thalamus (then to cerebral motor cortex)

Question 65

What does each cerebellar hemisphere primarily exert its influence on?

Answer 65

Each cerebellar hemisphere exerts its influence primarily on the ipsilateral half of the body

Question 66

What happens when there is cerebellar dysfunction?

Answer 66

Loss of co-ordination of muscle activity

Question 67

What is ataxia?

Answer 67

Inaccuracy in the speed, force and distance of movement (staggering gait, dysmetria, slurred speech)

Question 68

What is tremor?

Answer 68

Involuntary oscillation of the limbs or trunk

Question 69

What is nystagmus?

Answer 69

rhythmic involuntary oscillation of the eyes

Question 70

What is often the 1st symptom of cerebellar tumour?

Answer 70

Headaches and vomiting Due to blockage of CSF drainage from 4th ventricle