Cerebellum, Cerebrum, Limbic system 1 Flashcards
Three functions of the cerebellum
- equilibrium
- posture
- intended movement
Equilibrium from the cerebellum
- control upright stance with vision and vestibular sense
- vestibular apparatus sends signals to cerebellum so know where head and posture are in space
Posture from the cerebellum
- reinforces axial muscle tone
- allows distal (limb) muscles to be ready for motion
intended movement from the cerebellum
- works with cerebral cortex to generate program for planning and execution of intentional movements
Cerebellum anatomy
- two lobes, R & L hemispheres
- midline is the vermis
- attaches to 4th ventricle
- extending into cerebellum from 4th ventricle is the arbor vitae of white matter (looks like a tree)
what is the “roof” of the fourth ventricle
velum
- anterior to the cerebellum
Cerebellum: three portions on a transverse plane
- outer cortex
- inner fibers
- four deep nuclei on each side
What connects the cerebellum to the midbrain?
inferior, middle, superior peduncles
What does the inferior peduncle (cerebellar) contain?
- tracts projecting TO the cerebellum
- ex. spinocerebellar tract containing proprioceptive information
What does the middle peduncle (cerebellar) contain?
- contains fibers from the pontine nuclei
- ex. fibers from corticospinal tract
- largest of the peduncles
What does the superior peduncle (cerebellar) contain?
output from the cerebellum
Deep cerebellar nuclei
- input into from where?
- projections where?
- input to cerebellum from several places including spinal cord, vestibular apparatus, cortex, pons
- project to the cortex
Where does the cerebellum NOT project to directly?
the body
- all output from the cerebellum goes to the cortex
What are the names of the tiny folds of the arbor vitae?
- folia
- analogous to gyri in the cerebrum
- if stretch out go to the moon (aka they are long)
- gray matter
in the cerebrum and cerebellum what is the arrangement of white and gray matter?
- white is on the inside
- gray on the outside
- opposite the SC
Three layers of the cerebellar cortex
- Internal granular layer (interneurons)
- outer molecular layer
- Purkinje cell layer in the middle
Purkinje cells describe
- physically large
- flat
- single axon
- huge dendritic field
- project to deep cerebellar nuclei
Describe the output of a purkinje cell action potential
huge: able to cross action potential threshold of postsynaptic neuron
List the three main types of input fiber to the cerebellum
- Climbing fibers
- Mossy fibers
- Parallel fibers
Climbing fibers
- what layer of cerebrum
- from where
- describe how they synapse
- specific or general input
- molecular layer
- from inferior olive
- synapse many times on one Purkinje fiber
- one action potential will cause purkinje fiber to fire due to temporal summation
- specific input
Mossy fibers
- what layer of cerebrum
- from where
- describe how they synapse
- specific or general input
- granular layer
- all pre-cerebellar nuclei except the inferior olive, pons is the largest source
- synapse only one time on a given purkinje fiber but synapse on multiple purkinje fibers
- requires a lot of input to cause AP of purkinje fiber
- general input compared to climbing fibers
Parallel fibers
interneurons with parallel fibers that run along the plane of the folia connecting many purkinje fibers
Are mossy fibers, climbing fibers, and parallel fibers excitatory or inhibitory?
excitatory!!
Is the output of purkinje fibers excitatory or inhibitory?
inhibitory (of the deep cerebellar nuclei)
= output of the cerebellum is inhibitory!!
what does inhibition from the cerebellum produce? lack of inhibition?
inhibition = fluid movement lack = tremor
How are purkinje cells arranged in the cerebellum?
- cells with similar function are lined up next to each other
- no homunculus like cerebrum, more general in the cerebellum
What type of information do cerebellar inputs have?
place specific (not time influenced yet, the cerebellum does that)
what type of information does cerebellar output carry?
- timed bursts of inhibition
- changes place to time
- manifests as disturbances in the timing of muscle movements.
What is not initiated in the cerebellum
movement, it is just modified
List four cerebellar dysfunctions
- intention tremor
- Past pointing
- dysdiadochokinesis
- nystagmus
past pointing
when touch finger to own nose and someone else’s fingers, can’t keep up with moving fingers
Dysdiadochokinesis
inability to perform rapid movement (the timing is messed up)
What is the single largest input to the cerebellum?
from the opposite cerebrum through the basilar pontine nuclei
If there is a lesion in the cerebellum, where will the deficit be?
contralateral to the lesion
How is cortical grey matter arranged?
in layers of neuron cell bodies
Three types of cortical neuron arrangement
- archicortex
- paleocortex
- neocortex
Archicortex
- associated with the limbic system
- three layers
Paleocortex
- olfactory system
- 3-5 layers
Neocortex
- 90% of the cerebral cortex
- 6 layers
- layer thickness varies with histologically district areas (Brodmann’s map)`
Area 312 name
Somatosensory area
Area 4 name
primary motor area
Area 6 name
Premotor, supplementary motor areas
Area 8
- name
- describe
- Frontal eye fields
- responsible for saccade (flicking of eyes when look places and keeps L and R eye together when eyes move)
Areas 5 and 7
- name
- describe
- Somatosensory association area
- interpret sensation in parietal lobe
Area 17
- name
primary visual area
Area 18 and 19
- name
visual association area
Areas 23 and 24
- name
- describe
- cingulate area
- where sensory input from the env. enters the limbic system
Areas 41 and 42
- name
- Auditory area
- Transverse gyrus of Heschel in the temporal lobe
Area 22
- name
- describe
- Wernicke’s area
- temporal lobe
- related to speech
Areas 44 and 45
- name
- describe
- Broca’s area
- frontal lobe
- in front of the primary motor strip
- related to speech
Afferent fibers to the cortex (3) list
- cortical association
- callosal
- thalamocortical
Thalamocorticol afferents to the cortex
from thalamus to cortex for excitation
Corticoassociation afferents to the cortex
- fibers that travel within the cortex
- from one hemisphere to the other, one gyrus to another, one lobe to another…
- don’t leave the corte
Callosal afferent to the cortex
- type of association fiber
- cross midline of the brain
- corpus callosum (99%) and the small anterior and posterior projections (1%)
List three cortical efferent fibers leaving the cortex
- association and callosal
- corticothalamic
- corticofugal
What does fugal mean
- projects outside the cerebral cortex
Corticofugal tract
Corticospinal tract
Corticobulbuar tract to the nuclei of the brainstem
List the four neurotransmitters pathways that are prominent in the brain
- dopaminergic
- noradrenergic
- serotonergic
- cholinergic
Dopaminergic pathways in the brain
- common example
- heavy concentration in what path
- too much =
- too little =
- substantia nigra to the caudate
- Tons of dopaminergic projections from brainstem up to the cortex
- Too little = Parkinson’s
- Too much = Schizophrenia
Noradrenergic pathways in the brain
- two locations found
- important nucleus
- important for what
- cortex and brainstem
- locus coeruleus in the pons
- learning and brain “plasticity”
locus coeruleus
- when go to sleep, locus coeruleus stops producing action potentials
- just before wake up, locus starts firing again, increasing noradrenergic input to cortex
Serotonergic pathways in the brain
- role in what functions
- too little =
- sleep/wake cycle and mood
- too little = depression (SSRI to tx)
Cholinergic pathways in the brain
- important for what
- involved in what pathology
- learning and memory
- loss = dementia
- one treatment for dementia is cholinergic medications
How are cortical structures arranged in the cortex?
columns of cells (through the 6 layers) with similar connections
What kind of scan helps ID functions of diff parts of the brain?
PET scan
- picks up high metabolic activity
On a PET scan, what parts of the brain would light up during the following tasks:
- passively viewing words
- listening to words
- visual association in occipital lobes
- auditory area (transverse gyrus of Heschle) and Wernicke’s area
On a PET scan, what parts of the brain would light up during the following tasks:
- speaking words
- generating verbs
- Primary motor strip at area of vocal muscles (larynx is at bottom of pre-central gyrus), drives the actual motor movement to create sound
- Brocas’ area: think about what your going to say, drives the motor area
What is the brain
- property of the nervous system that gets things done like walking and eating
- like lower animals
What is the mind
part of the brain that makes us human: thought, contemplation, intuition
What makes is different from “lower” animals
- sense of self
- projecting self and others into the future
- perspective on the last which gives them context
- abstract thinking like math
- dexterity
- ability to teach and learn
- spirituality
- alturism
How does primary sensory cortical concentration change as move through phylogenic tree?
- area taken up by primary sensory and motor function decreases as ascend tree
- increases the proportion of higher order association areas (as ascend)
- humans have sacrificed primary sensation/motor for thinking
How does frontal association concentration change as move through phylogenic tree?
dramatic increase as ascend the tree
What fossa is the:
- frontal pole in
- temporal pole in
- occipital pole
- anterior cranial fossa
- middle cranial fossa
- occipital sits on tentorium, NOT posterior cranial fossa
two main fissures
- longitudinal and lateral
How many lobes are in the brain?
5
- temporal
- frontal
- parietal
- occipital
- Insula
What are lobes divided into? what divides them?
divided into areas/lobules by sulci
What separates the frontal and parietal lobes
central sulcus
what separates the frontal and temporal lobes
lateral fissure
what separates the parietal and occipital lobes
- parietooccipital sulcus
what is above the corpus callosum?
cingulate gyrus
where is the angular gyrus
posterior end of the temporal lobe
describe the cingulate gyrus
- where limbic system originates
- continues around into the temporal lobe as the parahippocampus
- terminates in the uncut
Where is the insula
medial to the lateral fissure
List the five lobes and their basic function(s)
- frontal: motor and behavior
- Parietal: memories and sensation
- Occipital: vision
- Temporal: hearing, smell, behavior
- Insula: behavior
Short vs. long association fibers in the cortex
- short: from one gyrus to the next
- long: from one lobe to the next
What are commissural fibers
- run between cortices (corpus callosum, anterior and posterior commissures)
What are projection fibers of the cortex?
leave the cortex and descend to basal ganglia, brainstem, or spinal cord
What are the three parts of the corpus callosum?
- genu (knee, at the bend)
- body (long)
- splenium (most posterior, little nubbin)
