the cerebrum/ telencephalon Flashcards
what is the telencephalon
- most rostral, highly differentiated and functionally complex portion of the CNS
- lesions generally create contralateral sensory and motor signs - can include blindness, depression, seizures
- involved in higher functions: perception, learning, short and long term voluntary control of movement, sensory discrimination, thinking and planning
cerebral cortex
consists of lobes - frontal, parietal, temporal, occipital, and primiform
white matter
region of underlying white matter consisting of corona radiata that carry axons from individual gyri into and out of the internal capsules, which is the major fiber bundle attaching the telencephalon to the brainstem
commisures
- white matter commisures that connect the two cerebral hemispheres
- biggest is the corpus calosum
- commisures of the fornix (hippocampal commisure)
- rostral (anterior) connecting the two temporal lobes of the cerebral hemispheres across the midline
- caudal (posterior) commisures interconnects the pretectal nuclei, mediating the consensual pupillary light reflex
ventricles
lateral ventricles of the ventricular system
basal ganglia
participate in complex locomotor behavior and emotions
basal forebrain
important in memory
neocortex: frontal, parietal, occipital, and temporal lobes
- most modern, largest and most developed part of the cortex
- only in mammals, 6 layers
archiocortex: hippocampus
- involved in declarative memory function
- spatial memory, cognitive map of space
- mood, reward
paleocortex: olfactory cortex or piriform lobe
separated from neocortex by the rhinal fissure
what do each of the 6 layers of the neocortex do
- layer 4 - input layer
- local circuits - local connectivity between layers
- layer 2 and 3 - to other cortical areas: local circuit, short association, long association
- layer 5 - to subcortical areas (spinal cord, brainstem, basal ganglia)
- layer 6 - feedback to thalamus
what is brodmann’s 52 cytoarchitectonic regions of neocortex
differences in
- cell shapes
- cell sizes
- packing densities
somatosensory primary receiving areas (SI and SII) in neocortex - all topographically organized:
- mapping sensory sheet (retina, skin, etc) onto primary receiving areas (for sensory systems)
- somatotopic motor map in M1 matches map in S1
origin of the corticospinal tract (UMN)
- initiation of complex voluntary movemenbt
- activity in M1 neurons occurs before and during a voluntary movement
- activity encodes force and direction of movement
effect of corticospinal tract lesions
- difficulty moving distal limbs
- loss of ability to make independent finger movements - does not recover
what is area 6 - supplementary motor area, SMA - premotor area, PMA involved in?
motor planning
lateral pathways
- voluntary movement of distal musculature
- unde direct cortical control
- innervate distal musculature
ventromedial pathways
- control of posture, locomotion, orienting and balance
- under brainstem control
- innervate axial and proximal musculature
what are the two tracts of the lateral spinal pathways
- corticospinal tract: limbs
- rubrospinal tract: distal limb muscles
corticobulbar tract
- travels with CST and provides UMN innervation to LMNs in cranial nerve motor nuclei
- face, jaw, tongue, and throat
corticopontine
to pontine nuclei
balance tract
vestibulospinal tract
orienting reflexes
- tectospinal tract: head
- tecobulbar: eyes
what tracts are for posture and locomotion
- pontine reticulospinal tract
- medullary reticulospinal tract
what are clinical signs of UMN lesions
- increased tone (spasticity)
- hyperactive reflexes
- pathological reflexes
what are the clinical signs of LMN lesions
- decreased tone
- hypactive reflexes
- weakness
- atrophy
- fasciculations
what do the basal ganglia and cerebellum act on
cerebral cortex through relay nuclei in the thalamus
what are the 3 sections of the basal ganglia
- caudate
- globus pallidus
- putamen
striatum is ____ station for basal ganglia
globus pallidus is ____ of basal ganglia
input; output
globus pallidus tonically ____ VL thalamus
inhibits
anything that increases GP output leads to:
hypokinesis (parkinson’s) degeneration of dopaminergic cells in substantia nigra
decreased GP output leads to:
hyperkinesis (hemiballisum) - loss of tonic inhibitory output to thalamus, cell loss in subthalamus
basal ganglia damage produces two basic disturbances related to motor activity in humans:
- disturbances of muscle tone (hypotonia or hypertonia)
- dyskinesias (abnormal involuntary movements)
- athetosis
- chorea
- ballismus
- resting tremor
in animals with basal ganglia lesions the most typical disturbance of motor activity is one of excessive locomotion - constant pacing or ____
hyperkinesia
