Cerebral Cortex I and II Flashcards
What is the function of the cerebral cortex?
Analyzes, plans and initiates response.
Sensory pathways- brings IN information
Reticular system- adjust its level of responsiveness/turns it off or on.
What is the role of pyramidal cells?
- Most of the projection cells out of the brain
- Usually in layer 5
- Long apical dendrite and a basal dendrite
- Use glutamate (excitatory)
- dendritic spines, selectively modified by learning
- 80% of cells in the brain
- found more in agranular layers
What are the neocortical layers?
6 layers that include most of the cortex:
-Agranular with large pyramidal cells and granular areas with small neurons
-
86 billion nerve cells 19% in the cerebral cortex
(most in cerebellum)
What is the role of non-pyramidal cells?
- interneurons of the CC
- 20% of cels in the brain.
- various shapes and appearances
- axons don’t leave the cortex
- use GABA = inhibitory
What are important broadmann areas?
Pre-central: 4
Post-central: 312
Commissural bundles?
l
Association bundles?
= fasciculi
- corticocortical fiber tract connections in the same hemisphere
- Way in which the front communicates with the back
- None are discrete points to point and fibers travel/enter/leave in both directions
- cigulum, sup occipitofrontal fasciculus, sup long fasciulus (arcurate), inf occipitofrontal
arcurate is how brocas and wernkikes areas communicate
What are the neocortical area functions?
- Layer 5: most pyramidal
- Thalamus input usually ends in layers 2, 3, 4
Primary association cortex?
“direct link to the world”
In: thalamic nuclei
out: brainstem and Spinal
primary motor (4) primary somatosensory (312) primary visual (17) primary auditory (41) primary gustatory (ant insula) primary vestibular (p. insula)
Unimodal association cortex?
more complex response function
Loc: adj to 1 areas
Injury could cause agnosia
premotor (6)- larger groups of muscles in an activity
supp motor (6)- posture or using muscles on both sides of the body
somatosensory (5, 7)
visual (18,19 +..)
info is analyzed more deeply, but still having to do with one function.
greater amount of cortex involved
Mulitimodal association cortex?
High level of intellectual fxn
Association areas send convering inputs, may respond to multiple stimuli or under particular circumstances.
Most of the cortex is associated with multimodal associations.
Injury: apraxia (motor) or neglect (sensory)
What is a disconnection syndrome?
White matter damage that interferes with the connection between both hemispheres using the corpus collosum.
ex) alexia without agraphia: cannot read but they can write.
(both sides of the brain can communicate)
What splits the occipital lobe?
The calcarine fissure.
Above the calcarine fissure it processes vision from the lower visual field in the opposite side of the body.
Below, processes visual field from the upper field in the opposite side.
What types of cortex are found in the cerebral cortex?
Neocortex
Archicortex- hippocampus 3 layers
Paleocortex- telencephalon base, olfactory (3-5 layers)
Where would you find more granular cells?
- Post-central cortex
- more non-pyramidal cells than pyramidal.
What is the role of the anterior commissure?
Interconnects temporal lobe and components of the olfactory system.
*temporal lobe
What are the parts of the corpus callosum and what is its function?
Connects mirror images of cortical areas. Genu in frontal lobe anterior body in frontal posterior in parietal splenium in occipital and temporal
note: the brain is not necessary symmetric between the cerebral hemispheres, such that some functions are predominantly on one side or in a different area of the other.
What are the cortical areas taht don’t receive CC commissural fibers?
- Hand area of somatosensory and motor cortex
- Area 17, not including areas adjacent to vertical midline
- temporal lobe connections which travel through the anterior commissure
Where on the cerebral cortex is language mostly found?
Left
Problems:
aphasia: inability to undersand language, written or spoken
How are broca’s and wernikes areas connected?
Through arcuate/superior longitudinal fascicules.
What are some of the multimodal association areas?
Parieto-occipital-temporal region:
- injury to right inf parietal lobe can cause contralateral neglect
- injury to left parietal area can cause an apraxia
Prefrontal area:
working memory & decision
dorsolateral
ventromedial
Where is language localized?
Left hemisphere, around sylvian fissure, temporal, parietal and frontal lobes
Reticular formation:
Network of neurons within the brainstem that have a special architecutre that allow it to “coordinate” connections between sensory and motor systems:
Converges somatosen info
diverges efferent outputs
Role in: sleeping and wakefulness, pattern generator, centers for respirator/cardiovascular, nociception.
Ascending Reticular Activating System (ARAS):
Role of reticular formation in activation of the cerebral cortex; impt for our level of alertness, sleep-wake rhythms and alerting rxns.
afferent info: cerebral cortex to modulate ARAS
Partners:
Cholinergic neurons (locus)
Orexin (hypothal)
Basal nuc of Meynert (basal forebrain)
What is consciousness:
A state of self-awareness in which it is possible to direct attention and manipulate abstract ideas.
Modulated by different projections to the cortex and thalamus
Maintained by the subcortical modulating system: Raphe nuclei (SER) Locus (NE) Midbrain RF (ach) Tubermamaillary nuc (hist) L. hypothalamus (Orexin) Basal nuc of Meynert (ach)
Sleep:
Some functions of sleep:
- Consolidation of memory and daily experiences.
- Brain growth and development
- Restoration and recovery
- tissue repair…
Neurons can change your sleep rapidly; sleep/awake states abruptly change
Certain changes in EEG are visible: alpha waves –> slower waves
REM:
- Low amplitude, fast freq, desynchronized
- almost no muscle tone
- highest arousal level
- detailed, visual and emotional dreams
- increased sympathetic irregular pulse and respiration
Preoptic area active
Non-Rem sleep:
- large amplitude, slow frequency, synchronized
- decreased muscle tone
- progressively higher arousal level
- vague dreams
- increased parasympathetic, slow, regular pulse and respiration
Pre-optic area active, as you move into awake, orexin increases
suprachiasmatic nucleus
Clock within your nervous system, helps produce slep and certain types of sleep
“pacemaker” of the mammalian circadian system.
preoptic area
Most active during times of non-REM slep; falls during “awake” cycle
midbrain reticular formaiton
ACH to the thalamus
How do the columns in the neocortex layers work?
radial glial cells are like the scaffold then neurons then “crawl” up and stop at different layers
Broca lesion:
- motor lesion
- Non-fluent, telegraphic
- Poor repetition
- good comprehension
- poor naming
Wernicke lesion:
- sensory lesion
- fluent
- poor repetition
- poor comprehension
- poor naming
Lesion at arcurate fasciculus/ superior longitudinal:
- fluent
- poor repetition
- good comprehension
- poor naming
What are the afferents of reticular formation?
Primarily project to gigantocelluaris, caudal and oral pontine nuclei (paramedial group):
- spinoreticular:
- cerebelloreticular: fastigial nucleus
- CNs project to L. parvocellular area
What are the nuclei of the reticular formation?
Aminergic neurons (midline) Paramedian Zone (effector) Lateral zone (sensory)
- extend from thalamus to medulla
- diffused, arranged in three big columns (raphe, paramedian and lateral)
What are the efferents of reticular formation?
Arise from the gigantocellularis, caudal and oral pontine nuclei- medial group.
Spinal Cord:
- pontine and medullar reticulospinal tracts.
- descend bilaterally
- terminate in intermediate gray
- effect axial muscles of posture and locomotion
Brain Stem:
- reticulobulbar, central tegmental tract
- indirect to CN, direct to dorsal column and parasympathetic nuclei
Raphe:
- located in midline
- use SEROTONIN as NT
- largest territorial distribution of any CNS neurons
Midbrain –> cortex
Pons –> brainstem, cerebellum
Medulla –> spinal cord
(other serotonergic projects show similar pattern)
What are the function of serotonergic and adrenergy systems?
- sleep arousal mxn
- integrative behavior and neuroendocrine fxns
- modulate actions of other neurotransmitters
- brain growth and development
- pain suppression
Ventral tegmental nucleus
- Dopamine
- projects to frontal lobe
- addictions and arousal
Locus ceruleus
- Midline structure
- Norepinhephrine
- role in sleep
Magnus Raphe
- role in pain suppression
- Serotonin
Orexin
Loc: lateral hypothalamus
One of the primary NT that helps stabilize wake states and helps ensure rem cycle is turned OFF.
Major role in stabilizing wake states
keeps REM from occurring
What are some sleeping disorders?
Narcolepsy: difficulty staying awake.
- fall into REM quickly when falling asleep.
most also show…
Cataplexy:
- people are awake but their bodies go into “sleep” mode
What inputs into the cortex control your awake/sleep state?
- Basal forebrain
-Hypothalamus
orexin, histamine, GABA..
-Thalamus
Reticular nucleus GABA
-Brainstem
Raphe (seratonin)
Locus Cer (Ne)
Ach
