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FNS 7: Cerebrum
Neuro Lecture 7: Cerebral Cortex 1a
| Question | Answer |
|---|---|
| By ____ of embryonic development, all 5 major brain subdivisions are identifiable. | 5th week |
| Name the 5 major subdivisions of the brain | telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon |
| Which subdivision of the brain contains the cerebral hemispheres and basal ganglia? | telencephalon |
| The cerebral cortex accounts for about ___ of the volume of the adult brain | 45% |
| Which cerebral hemisphere is larger than the other? | right |
| How much is the overall loss of cortical volume by age 75? | ~4% |
| How much is the loss of frontal cortical volume by age 75? | ~12% |
| Do all cortical areas decrease in size the same amount? | no different areas are differentially affected |
| Does each person’s cerebral cortex decrease the same amount? | no- there is substantial individual variability |
| How big is the total flattened area of the cerebral cortex? | ~200 cm2 |
| How much of the cerebrum is visible on the external surface? | 1/3 |
| How thick is the cortex? | ~1.5 - 4.5 mm |
| What’s the thickest part of the cortex? | primary motor cortex |
| What’s the thinnest part of the cortex? | primary visual cortex |
| How many neurons are contained in the mature cerebrum? | about 20 billion |
| How many glial cells are contained in the mature cerebrum (compared to neurons)? | 2-10x more |
| What are the 2 major groups of cortical neurons? | spiny neurons and aspiny (spine-sparse) neurons |
| What percentage of cortical neurons are spiny neurons? | about 75% |
| Are spiny neurons excitatory or inhibitory? | excitatory |
| Which NT do spiny neurons use? | glutamate |
| Which specific neurons are included in the group “spiny neurons”? | pyramidal neurons and stellate neurons |
| Which type of neurons make up the majority of spiny neurons? | pyramidal neurons |
| Which type of neuron is the major “output” neuron of the cortex? | pyramidal neurons |
| What are the single long projections of the pyramidal neurons called? | apical dendrites |
| What are the many smaller projections of the pyramidal neurons called? | basilar dendrites |
| Due to the large density of spines on the spiny neurons, how many other neurons can contribute input to a single neuron? | thousands |
| What types of conditions have shown reduction in cortical pyramidal spine density? | dementias, chronic alcoholism, schizophrenia, and trisomy 21 |
| Do aspiny neurons have spines? | few, if any |
| What percentage of cortical neurons are aspiny neurons? | about 25% |
| Are aspiny neurons excitatory or inhibitory? | inhibitory |
| Which NT do aspiny neurons use? | GABA- gamma aminobutyric acid |
| Are aspiny neurons presynaptic, postsynaptic, or interneurons? (not actually a technically sound question) | interneurons |
| As interneurons, what is the (very general) function of aspiny neurons? | make synaptic connections with nearby pyramidal cells- conductors/ traffic cops |
| Loss of which type of neurons have been reported in epileptic patients? | chandelier cells (aspiny neurons) |
| What is the term for “superficial-to-deep” variations in histological features in the cerebral cortex? | laminar organization |
| What is the term for “superficial-to-deep” commonalities in functional properties in the cerebral cortex? | columnar organization |
| About 95% of the cortical area is termed _______, which has __ layers and is also known as _______ | isocortex (“same cortex”), 6, neocortex |
| The other 5% of the cortical area is termed ______, which has __ layers and is also known as _______ or _______. | allocortex, 3-5, archicortex or paleocortex |
| Name the 6 layers of the isocortex? | 1. Molecular, 2. External Granular, 3. External Pyramidal, 4. Internal Granular, 5. Internal Pyramidal, 6. Multiform |
| What is the description of the first isocortex layer? | rich in fibers, but few neurons |
| What is the description of the second isocortex layer? | densely-packed small cells |
| What is the description of the third isocortex layer? | medium-sized pyramidal cells |
| What is the description of the fourth isocortex layer? | small pyramidal & stellate cells |
| What is the description of the fifth isocortex layer? | many large pyramidal cells |
| What is the description of the sixth isocortex layer? | mixture of pyramidal cells and irregularly-shaped cells |
| What are possible differences in cytoarchitecture between cortical layers? | overall thickness, relative thickness/density of different layers, size/shape of neurons |
| (Brodmann’s map)- electrical stimulation studies have shown high correlation between ______ boundaries and ________ boundaries | cytoarchitectonic and functional |
| Which cortical layer(s) are the origin of commissural and association fibers that connect different cortical regions? | 2 and 3 |
| Which types of cortical regions do commissural fibers connect? | homologous regions between hemispheres (eg primary motor cortex) |
| Where do commissural fibers run? | corpus callosum and anterior commissure |
| Which types of cortical regions do association fibers connect? | heterologous regions within the same hemisphere |
| Where do association fibers run? | in large fiber bundles (like superior longitudinal fasciculus) |
| Which cortical layer receives most afferent input from the thalamus? | 4 |
| Which cortical layer is best developed in primary sensory cortices? | 4 |
| Which cortical layer is the origin of projection fibers to subcortical regions (striatum, thalamus, SC)? | 5, 6 |
| Which cortical layer is particularly well-developed in the primary motor cortex? | 5 |
| What is the main cortical region receiving dopamine input? | frontal cortex |
| Which cortical layers receive input from the basal forebrain/brainstem neuromodulatory systems? | all 6 |
| How wide are the columns of columnar organization in the cortex? | 200-500 micrometers |
| Who discovered columnar organiztion? How? | Mountcastle (1950s) inserted electrodes vertically and obliquely |
| All regions of cortex may be placed into one of 3 categories | primary sensory areas (primary receptive cortex), primary motor areas (primary projection cortex), association areas |
| Which cortex has the lowest threshold for eliciting movement by electrical stimulation? | primary motor cortex |
| Which cortex(ices) are the first regions to receive modality-specific information? | primary sensory cortices |
| What is Brodmann’s area 3,1,2? | primary somatosensory cortex |
| What is Brodmann’s area 4? | primary motor cortex |
| What is Brodmann’s area 41? | primary auditory cortex |
| What is Brodmann’s area 17? | primary visual cortex |
| What are the 2 categories of association cortices? | sensory association areas and motor association areas |
| Which cortex areas are areas of parietal, occipital, and temporal cortex that receive input from primary sensory areas? | sensory association areas |
| Which cortex areas integrate information from different modalities? | sensory association areas |
| Where are motor association areas located? | frontal lobe |
| Which cortex areas project to the primary motor cortex? | motor association areas |
| Which cortex areas provide dense input to subcortical regions involved with movement generation (eg basal ganglia)? | motor association areas |
| What is cerebral lateralization? | Many complex brain functions are more dependent on one hemisphere than the other |
| Which hemisphere controls language skills for a large majority of people (of either handedness)? | left hemisphere (95% of righties & 75% of lefties) |
| What are some examples of cerebral lateralization? | language, musical ability, attention, math |
| What is aphasia? | without speech |
| What is affected (more specifically) with aphasia? | loss of language expression and/or comprehension |
| What is agnosia? | without knowledge |
| What is affected (more specifically) with agnosia? | difficulty recognizing the meaning or sensory stimuli, while primary sensory function is intact |
| What is apraxia? | without capability |
| What is affected (specifically) with apraxia? | inability to carry out skilled or purposeful movement- no frank paralysis |
Created by:
mbyess
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