Chapter 6 - Cerebellum Flashcards
Where is the cerebellum located?
- hind brain
- at the posterior cranial fossa
- inferior to the tentorium cerebelli (the cerebellum is covered superiorly by the tentorium cerebelli)
Enumerate the neighbors of the cerebellum
1) superiorly: tentorium cerebelli
2) anteriorly: fourth ventricle, pons, and medulla oblongata
The ovoid cerebellum is divided into (1) by a narrow median constriction called (2)
(1) right and left cerebellar hemisphere
(2) vermis
The cerebellum is connected to the posterior part of the brainstem by 3 symmetrical bundles of nerve fibers namely:
1) superior cerebellar peduncle
2) middle cerebellar peduncle
3) inferior cerebellar peduncle
Lobes of the cerebellum
1) anterior lobe
2) middle/ posterior lobe
3) flocculonodular lobe
lobes are separated by the following fissures:
* primary fissure
* uvulonodular fissure
The anterior lobe of the cerebellum that may be seen superiorly is separated from the middle lobe by a wide V-shaped fissure called
Primary Fissure
The largest part of the cerebellum
Middle lobe or Posterior lobe
situated between the primary and uvulonodular fissures
Cerebellum
Separates the middle lobe and the flocculonodular lobe
Uvulonodular fissure
Lobes of the Cerebellum
Memorize
Lobes of the Cerebellum
Memorize
Deep fissure separating the superior from the inferior surfaces of the cerebellum
Has no morphologic or functional significance
Horizontal fissure
Cortical arrangement of the cerebellum
- outer cortex - gray matter
- inner white matter
- embbeded gray matter in the inner white matter (intracerebellar nuclei)
The cut surface branched appearance when a section made through the cerebellum parallel with the median plane that divides the folia at right angles is called
Arbor vitae
means “Tree of life”
3 layers of the cerebellar gray cortex
(from outer to inner)
1) molecular layer
2) purkinje layer
3) granular layer
MPG
Two types of neurons found in the cerebellar molecular layer
1) outer stellate cells
2) inner basket celld
Neuroglial cells are found between neurons
Large glogi type 1 neurons that are flask shaped and are arranged in a single layer
Purkinje cells
found at the purkinje layer of the cerbellum gray cortex
What are the functional areas of the cerebellum
vertically divided
1) vermis
2) intermediate zones
3) lateral zones
Part of the cerebellum that influences the movements of the long axis of the body namely the neck, thorax, abdomen, and hips
Vermis
Area of the cerebellum that controls the muscle of the distal body parts such as the limbs and especially the hands and feet
Intermediate zone
Function of the cerebral hemisphere’s lateral zone
Part of the cerebral hemisphere that is concerned with the planning of sequential movements of the entire body and is involved with the conscious assesment of movement errors
Enumerate the four masses of gray matter embedded in the white matter of the cerebellum on each side
From lateral to medial:
1) dentate nuclei
2) emboliform nuclei
3) globose nuclei
4) fastigial nuclei
DEG F
Largest of the cerebellar nuclei
Dentate
Largest of the cerebellar nuclei that is shaped of a crumpled bag with the opening facing medially
its white fibers form part of the superior cerebellar peduncle
Dentate Nuclei
Intracerebellar nuclei
ovoid and situated medial to the dentate nucleus
Emboliform nucleus
Intracerebellar nuclei
consists of one or more rounded cell groups that lie medial to the emboliform nucleus
Globose nucleus
Intracerebellar nuclei
lies near the midline in the vermis and close to the roof of the fourth ventricle - larger than the globose nucleus
Fastigial nucleus
(True/False)
There is a large amount fo white matter at the vermis while only a small amount of white matter in each cerebellar hemisphere
False
There is a small amount of white matter in the vermis - resembers a tree trunk with branches (arbor vitae)
There is a large amount of white matter in each cerebellar hemisphere
Three groups of fibers in the cerebellar white matter
1) intrinsic fibers
2) afferent fibers
3) efferent fibers
Function of cerebellar white matter intrinsic fibers
connects different regions of the cerebellum specifically:
* folia of the cerebellar cortex and vermis at the same side
* right and left cerebellar hemispheres
Fibers from the dentate, emboliform, and globose nuclei leave the cerebellum through ()
superior cerebellar peduncle
Fibers from the fastigial nucleus leave through ()
Inferior cerebellar peduncle
Two main lines of input to the cerebellar cortex
Excitatory to the Purkinje cells
1) climbing fibers
2) mossy fibers
Climbing fibers definition
terminal fibers of the olivocerebellar tracts
A single purkinje neuron makes a synaptic connection with only one climbing fiber while one climbing fiber makes contact with 1 to 10 purkinje neurons
Mossy fibers definition
Terminal fibers of all cerebellar afferent tracts except for the olivocerebellar tract
Diffuse excitatory effect
A single mossy fiber may stimulate thousands of Purkinje cells through the granule cell
Function of stellate, basket and golgi cells of the cerebellar cortex
inhibitory interneurons
limits the area of cortex excited and influences the degree of Purkinje cell excitation produced by climbing and mossy fiber input
Forms the center of a functional unit of the cerebellar cortex
Purkinje cells
- Once excited or inhibited, the Purkinje cells will send inhibitory impulses to the intracerebellar nuclei
- the intracerebellar nuclei will modify muscular activity through motor control areas of the brainstem and cerebral cortex
Neurotransmitters used by excitatory climbing and mossy afferent fibers
Glutamate
as the excitatory transmitter on the dendrites of the purkinje cells
other neurotransmitters used are norepinephrine and serotonin
Connects the cerebellum and the midbrain
superior cerebellar peduncle
Connects the cerebellum and the pons
middle cerebellar peduncle
Connects the cerebellum and the medula oblongata
inferior cerebellar peduncle
Cerebellar Afferent Pathways
Cerebellar Efferent Pathways
Cerebral functions control which side of the body?
Ipsilateral side
What is ataxia?
Ataxia is a neurological condition that affects a person’s ability to control their voluntary movements. It can result in problems with coordination, balance, speech, and eye movements. Ataxia may be caused by various factors including genetic disorders, head injury, stroke, or certain medications. There are different types of ataxia, including hereditary ataxia, acquired ataxia, and sporadic ataxia. Treatment options for ataxia may include medications, physical therapy, and occupational therapy.
What is dysmetria?
Dysmetria is a neurological condition that affects a person’s ability to accurately measure distances and control the range and direction of their movements. It is a type of ataxia and is often seen in people with cerebellar disorders. Dysmetria can cause movements to be too short or too long, resulting in clumsiness, difficulty with fine motor skills, and problems with coordination and balance. Dysmetria may be caused by a variety of factors, including genetic disorders, head injury, stroke, or certain medications. Treatment options for dysmetria may include physical therapy and occupational therapy to help improve motor skills and coordination.
Cerebellar Signs
Cerebellar signs refer to a group of neurological signs that reflect dysfunction of the cerebellum, which is the part of the brain responsible for motor coordination, balance, and muscle tone. Some of the common cerebellar signs include:
1) Ataxia: Impaired coordination of voluntary movements, resulting in unsteady gait, poor balance, and difficulty with fine motor skills
2) Dysmetria: Difficulty with judging the distance and range of movements, causing over or undershooting of targets.
3) Dysdiadochokinesia: Difficulty with rapid alternating movements, such as pronation-supination or tapping movements.
4) Intention tremors: Involuntary shaking of limbs that occurs during voluntary movements.
5) Hypotonia: Reduced muscle tone, resulting in a floppy appearance of limbs.
6) Rebound phenomenon: Inability to halt movements and maintain a steady posture when resistance is suddenly removed.
7) Nystagmus: Involuntary rhythmic oscillation of the eyes.
These cerebellar signs can be caused by a variety of conditions, including genetic disorders, stroke, brain injury, and degenerative diseases. The presence of these signs can help doctors diagnose and localize the underlying neurological problem.
What is cerebellar infarct?
Cerebellar infarct is a type of stroke that occurs when there is a blockage of the blood vessels supplying blood to the cerebellum, a part of the brain responsible for motor coordination, balance, and muscle tone. Cerebellar infarcts can be caused by a variety of factors, including atherosclerosis, blood clots, or emboli, and can result in symptoms such as vertigo, nausea, vomiting, dizziness, difficulty with speech, and difficulty with coordination and balance. Cerebellar infarcts can be diagnosed with imaging studies, such as CT or MRI scans, and treated with medications to dissolve blood clots or surgery to remove the blockage. Rehabilitation may also be necessary to help patients regain motor coordination and balance.
