Limbic System, Cerebral Cortex, Neuroembryology Flashcards
reticular formation
- contrains the principal discharge pathways for the olfactory/limbic systems and the hypothalamus
- plays an important role as a mediator of somatic and visceral motor components of autonomic, emotional, and behavioral responses
components of emotional expression:
- hippocampus: memory recall
- amygdala
- neocortex: modify rxn
- hypothalamus: effector of emotional behavior
brainstem ascending reticular activating system
- glasgow coma scale
- level of consciousness
- drugs
-sends info to intralaminar reticular nuclei–>cortex (EEG and cognition) and prefrontal cortex (Broca’s, Prefrontal Lobe Syndrome)
septal areas
- addiction
- behavior/misbehavior
- pleasure (+), punishing (-)
- drugs
olfactory input
goes straight to septal areas and amygdala
hypothalamic circuitry
- most of ascending input into the hypothalamus is from reticular formation
- most of descending influences are mediated by reticular formation
lesions of hypothalamus
S/S:
- obesity
- personality changes
- diabetes insipidus
- temp maintenance problems
- hormonal problems
Korsakoff’s Syndrome
- bilateral destruction of mammillary bodies and dorsal medial nucleus of thalamus
- may result from long term alcoholism or pituitary tumors
- if pituitary tumor, may cause bitemporal hemianopsia
- primary deficit is impairment of recent memory
- pts report confabulation to fill the gaps in their memory
Paper Circuit
cortex–>entorhinal cortex of uncus–>hippocampus–>fornix–>mammillary body–>anterior nucleus of dorsal thalamus–>cingulate gyrus–>parahippocampus
olfactory input–>amygdala and hippocampus and septal area
-hippocampus and amygdala goes thru the stria terminalis to the septal area–>hypothalamus–>midbrain tegmentum
medial forebrain bundle
-interconnects septal area, hypothalamus, and midbrain tegmentum
primary olfactory cortex or pyriform lobe
- lateral olfactory gyrus
- amygdaloid nucleus and pariamygdaloid area
- entorhinal cortex: uncus and parahippocampus
- connects sensory info going over the cerebral cortex and puts it into memory
entorhinal cortex
- chief input into the hippocampus
- acts as a critical integrator and mediator of info to hippocampus
- cortical electrical impulses cascade over the surface in a spiral like pattern that converges on the entorhinal cortex
- important link in Paper memory circuit
- neocortical representation of external sensory world and a person’s memory seem to merge in entorhinal cortex
amygdala
- fibers from olfactory tract and pyriform cortex terminate here
- convey emotional and motivational component of odors–pheromones
- pivotal processing center for olfactory, somatosensory, viscerosensory, and emotional expressions
- relays info to the hypothalamus, dorsomedial thalamic nucleus, septal areas, or midbrain tegmentum
amnesia
- refers to any defect in memory but most assoc with cases of severe and relatively isolated memory deficits like in Korsakoff’s
- anterograde–unable to learn new material
- retrograde–is an inability to recall events from recent past
hippocampal amnesia
- bilateral lesions of hippocampus
- pts IQ and formal reasoning were normal but unable to master new facts, recognize new acquaintances, or adjust to new surroundings
- pyramidal cells of CA1 region of hippocampus are vulnerable to hypoxic or ischemic injury
- axons form the fimbria-fornix pathway and send recurrent collaterals to entorhinal cortex
olfactory hallucinations
- an imaginary, disagreeable odor, movements of lips and tongue, and dream state of consciousness
- sensations may be mildly pleasant or curious
- odors (hallucinations) may disturb the individual, and disrupt activities especially sleep
uncal herniation
- any unilateral lesion that inc the hemispheric volume is likely to cause herniation of uncus thru IPSILATERAL central notch
- deficits:
- compresses oculomotor N: pupillary dilation, external strabismus, and complete ptosis
- compresses abducens N: gaze is down and in
- compression of cerebral peduncle: pushes contralateral cerebral peduncle against shape edge of tentorium cerebella and spastic hemiplegia occurs on same side of ipsilateral lesion
- compression of PCA: contralateral incongruous homonymous hemianopsia with macular sparing
encephalization of sensory and motor system
sophisticated sensory and motor systems are dependent on cortical areas which could discriminate, analyze, interpret, and respond to specific stimuli
-upward shifting of fcns to cortex is encephalization
language and the cerebral cortex
- derivative of neocortical evolution
- development of brain for reception, comprehension, and expression
lateralization of cortex
- language underwent lateralization which was allowed by the corpus callous
- specific fcn residing in one hemisphere yet still share its info with other side
layers 1-2 of cerebral cortex
- form the most superficial layers of cortex
- layers play a role in important roles in assoc and higher cognitive fcns such as memory, interpretation of sensory input, and certain discriminative fcns
layers 3-4 of cerebral cortex
- receive most of afferents into cortex
- only 1% of these afferents are thalamocortical fibers
- remaining are corticocortical fibers
layers 5-6 of cerebral cortex
-innermost layers of cortex of cortex are source of efferents from cortex such as assoc fibers, commissural fibers, and projection fibers
superior longitudinal fasciculus (SLF)
- AKA arcuate fasciculus
- interconnects frontal, parietal, and occipital lobes
- critical link for language association areas
- lesions result in conduction aphasia
- fluent with minor word finding pauses and paraphasia, and can’t repeat words or sentences
- comprehension and reading ability intact but writing has errors
cingulum
-interconnects septal area, cingulate, parrahippocampal gyro to entorhinal cortex
uncinate fasciculus
interconnects base of assoc areas of frontal lobe to inferior temporal lobe
genu of internal capsule
- fibers: corticobulbar fibers
- lesion: supra nuclear facial palsy
posterior limb of internal capsule
- fibers: corticospinal fibers
- lesion: contralateral spastic hemiplegia
- fibers: somesthetic fibers
- lesion: contralateral hemianesthesia
retrolenticular of internal capsule
putamen and globus pallidus
- fibers: optic radiations
- lesion: contralateral homonymous hemianopsia
Brock’s Aphasia
- nonfluent speech
- full comprehension
- right sided paralysis
Wernicke’s Syndrome
- fluent and paraphasic speech
- no comprehension
- slight or no right sided paralysis
3 month fetus and growth of SC
-spinal cord extends throughout the entire length of vertebral column
5 month fetus and growth of SC
- vertical column has grown longer than the SC
- conus medullaris is at the level of first sacral vertebra
neonate and growth of SC
-conus medullaris is at the level of 3rd lumbar vertebrae
adult and growth of SC
- conus medullaris at level of LV1-2 interspace
- nerve roots coursing in lumbar cistern below level of conus medullaris are lengthened due to this differential growth and will form caudal equina
rachischisis
- vertebral column defect with exposure of primitive SC or Ns
- failure of neuropore to close
spina bifida occulta
- herniation of meninges or neural tissue
- presents as cystic, midline, hairy mass in lumbar region of vertebral column
- may be due to failure of the roof plate of neural tube to induce the development of overlying spinous processes
spina bifida meningocele
-vertebral column defect with herniation of meninges
spina bifida meningomyelocele
-vertebral column defect with herniation of meninges, SC
hydrocephalus
- congenital stenosis of portion of ventricular system or certain fetal infections
- assoc with meningomyelocele
Arnold Chiari malformation
- common cerebellar anomaly
- almost always with meningomyelocele
- involve an elongation of the cerebellar vermis, which herniates thru foramen magnum
- syringomyelia may also occur
anencephaly
- involve cranial or cervical rachischisis–meroanencephaly
- means absence of brain but pt usually has brainstem
meningoencephalocele
- cranial defect with herniation of meninges and brain tissue
- most infants with with have Arnold Chiari malformation
- also have hydrocephalus
meningocele
cranial defect with herniation of meninges
meningohydroencephalocele
-cranial defect with herniation of meninges, brain, ventricles
cranial rachischisis
- congenital absence of forebrain usually with cranial defect of frontal and parietal bones
- due to failure of neural tube to close
