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NEUR532 > Cerebrum > Flashcards

Cerebrum Flashcards

1
Q

what are the types of cortex based on phylogeny in mammals?

A

-archicortex –> 3 layers – hippocampal formation

-paleocortex –> various layers but up to 5 –> olfactory and parts of limbic system

-neocortex –> 6 layers.

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2
Q

describe the topography of the cerebral hemispheres

A

-folding of surface of cortex increases surface area –> approx. 1m^2

-gyri –> convolutions
-sulci –> groove
-fissure –> cleft

-Two-thirds of the cortex forms the walls of the sulci
-Some gyri, sulci and fissures are common features of the cerebral surface
-These are used as common landmarks in studying human neuroanatomy

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3
Q

What are the boundaries for the cortical lobes?

A

The lateral, parieto-occipital and central sulci

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4
Q

describe the precentral sulcus in frontal lobe

A

–Runs parallel to central sulcus and outlines the precentral gyrus
–Landmark for the primary motor area

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5
Q

what is the frontal lobe divided into?

A

superior, middle, inferior gyri by the superior and inferior sulci, and precentral gyrus

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6
Q

describe the inferior frontal gryi

A

-divided into Opercular, triangular, and orbital (from back of brain to front)
–Left hemisphere the opercular and triangular areas consist of Brocas expressive speech area

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7
Q

describe the postcentral sulcus in parietal lobe

A

-Runs parallel to central sulcus and outlines the postcentral gyrus
–Landmark for the somatosensory area

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8
Q

What is the parietal lobe divided into?

A

superior, inferior parietal lobules by intraparietal sulcus and the postcentral gyrus

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9
Q

describe the inferior parietal lobule

A

-Supramarginal and angular gyrus
–Left hemisphere these gyri are involved in perception and interpretation of spoken and written

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10
Q

describe the insular lobe

A

-Concealed by the frontal, parietal, and temporal opercula

-Outlined by the circular sulcus and divided into two regions by the central sulcus
– Short gyri anterior to the central sulcus
– Long gyri posterior to the central sulcus

-Involved in visceral sensations of taste and smell and controlling involuntary visceral activity via the autonomic nervous system

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11
Q

Describe the major gyri and sulci of lateral surface of temporal lobes

A

-Superior and inferior sulcus
– Divide the lateral surface into superior, middle, and inferior gyri

-The superior temporal gyrus forms the floor of the lateral sulcus

-The anterior part is the transverse temporal gyri
– Location of the primary auditory cortex

-The posterior part is the planum temporale
– Part of the receptive language area

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12
Q

describe the major gyri and sulci of lateral surface of occipital lobe

A

-The lateral surface of the occipital lobe only has minor sulci and gyri that have little anatomical significance
-Some minor features are the calcarine sulcus and the lunate sulcus that is curved around the end of the calcarine sulcus
-The primary visual cortex occupies and surrounds the calcarine sulcus

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13
Q

Describe the major gyri and sulci of the cingulate sulcus and gyrus

A

-cingulate sulcus separates the cingulate gyrus and the medial frontal gyrus
-The cingulate sulcus gives off a paracentral sulcus
-Divides into marginal and subparietal sulci in the parietal lobe
-The region between the paracentral, marginal and central sulci is the paracentral lobule
-Above the subparietal sulcus is the precuneus
-The paraoccipital and calcarine sulci bound the cuneus of the
occipital lobe

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14
Q

what is the collateral sulcus?

A

medial surface –>Defines the lateral margin of the lingual and parahippocampal gyri

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15
Q

rhinal sulcus defines…

A

the entorhinal area

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16
Q

describe the occipitotemporal sulcus

A

-divides the medial and lateral occipitotemporal gyri

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17
Q

describe the olfactory sulcus

A

-divides the gyrus rectus and orbital gyri

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18
Q

describe the limbic lobe

A

-Cingulate and parahippocampal gyri:
– Connected by a narrow isthmus (retrosplenial cortex)
– They form the limbic lobe

-Part of the limbic system:
–Hippocampus
–Amygdala
–Hypothalamus
-septum
-thalamus

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19
Q

how many cortical neurons are there and what are they?

A

-between 2.6x10^9 - 1.6x10^10
-they are principle cells and interneurons

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20
Q

describe principle cells

A

-pyramidal and fusiform cells
-The principle cells (neurons with long axons) are the pyramidal neurons (10-50 µm)
-Around two-thirds of all cortical neurons
-All excitatory

-Giant pyramidal cells are know as Betz cells 100µm –> Found only in the primary motor area

-dendrites conspicuous apical and basal or lateral with branches covered in spines

-axon emerges from the base of the pyramid or a large dendrite –> Many collaterals

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21
Q

describe fusiform cells

A

-Atypical principle cells with irregularly elliptical cells bodies
-Located in deep layers of the cortex
-Many local intracortical connections

-Axons connect with other neurons in three ways:
-Projection neurons
-Association neurons
-Commissural neurons

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22
Q

what are the interneurons

A

around 30 types recognised based on dendritic cytoarchitecture
They are divided into:
-stellate cells
-basket cells
-retzius-cajal cells
-cells of martinotti

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23
Q

describe stellate cells

A

-interneurons
-excitatory
-found in layer IV

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24
Q

Describe basket cells

A

-interneurons
-inhibitory
-lateral branching axons embracing pyramidal cells

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25
Q

describe ratzius cajal cells

A

-interneurons
-superficial layers

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26
Q

describe cells of martinotti

A

-interneurons
-deep layers with axons that project toward the top layer

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27
Q

describe the cortical layers

A

-Thickness of neocortex varies from 4.5mm (primary motor area) to 1.5mm (primary visual area)

-Differ in density, size, shape and constituent of neurons

-6 layers (based on Brodmann):
1. Molecular layer
2. External granular layer
3. External pyramidal layer
4. Internal granular layer
5. Internal pyramidal layer
6. Multiform layer

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28
Q

describe the molecular layer of the cortex

A

-Synaptic field of the cortex
-Superficial layer consists of terminal branches of dendrites and axons
-Most dendritic branches come from the pyramidal cells
-Axons originate from ipsilateral and contralateral cortex and thalamus and cells of Martinotti
-Horizontal cells of Retzius-Cajal

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29
Q

describe the external granular cortex layer

A

-many small pyramidal cells and interneurons

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30
Q

describe the cortical external pyramidal layer

A

-typical pyramidal cells
-form association and commissural fibres

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31
Q

describe the cortical internal granular layer

A

-layer IV
-stellate cells
-small number of other interneurons and pyramidal cells

32
Q

describe the cortical internal pyramidal layer

A

-layer V
-large pyramidal cells
-projections fibres

33
Q

describe cortical multiform layer

A

-fusiform cells
-small number of interneurons
-pyramidal cells –> project to thalamus and claustrum

34
Q

what are the exceptions of the 6 layer structure of the neocortex

A

-Exceptions are the primary visual, auditory, and somatosensory areas
-Layers 2-5 merge into a single layer of numerous small interneurons

35
Q

describe the layers in the primary and premotor areas

A

-Numerous pyramidal neurons and less interneurons
-Layers 2-6 appear as a single zone consisting of pyramidal cells of different sizes

36
Q

describe intracortical circuits

A

-Axons of other cortical cells excite apical dendrite of pyramidal cells

-Thalamic afferents excite basal dendrites of pyramidal cells and stellate cells

-Stellate cells excite pyramidal cells

-Thalamic afferents and pyramidal cells excite basket cells

-Basket cells inhibit surrounding pyramidal cells

37
Q

describe the primary somatic sensation area

A

-Postcentral gyrus (lateral) paracentral lobule (medial)
-Areas 3,2 & 1
-Afferent fibres from the ventral posterior nucleus of the thalamus
-The size of the cortical area for a particular part of the body is determined by the functional importance (homunculus)

38
Q

describe the somaesthetic association cortex

A

-Superior parietal lobule (lateral) precuneus (medial)
-Areas 5 & 7
-Afferent fibres from primary somesthetic area and lateral posterior thalamus and pulvinar
-Allows for example to be able to recognise the characteristics of an object held in the hand without visual aid

39
Q

describe the primary auditory area

A

-Located on the ventral wall of the lateral sulcus
-Posteriomedial region of the anterior transverse temporal gyri (Herschl’s convolutions)
-Areas 41 & 42
-Afferent fibres from medial geniculate body of the thalamus by way of the auditory radiations
-Spatial representation with low frequencies (anteriolateral) and high frequencies (posteriomedial)

40
Q

describe the taste area

A

-Inferior end of the postcentral gyrus extending into the insula and frontal operculum
-Area 43
-Afferent fibres from the medial division of the ventral posterior nucleus of the thalamus

41
Q

describe the olfactory area

A

-Limen insulae and the uncus
-Area 34
-Afferent fibres directly from the olfactory tubercle as well as the medial dorsal nucleus of the thalamus
-Olfactory tubercle also innervated the amygdaloid body and entorhinal cortex (limbic system)
-Odour discrimination, emotion, motivation and memory

42
Q

describe vestibular representations in the brain

A

-No cortical area is known that is activated exclusively by the vestibular system
- Intraparietal sulcus in the somatosensory cortex and the posterior part of the insula
-Integration of vestibular input with proprioceptive signals from the muscles of the head
-These projections contribute to motor regulation and awareness of spatial orientation
-Presumably also contribute to vertigo and motion sickness

43
Q

describe the primary motor area

A

-Located in the precentral gyrus, including the anterior wall of the central sulcus and the anterior part of the paracentral lobule
-Area 4
-Contain the giant Betz pyramidal cells
-Afferent fibres from other areas of the motor cortex, somesthetic cortex and the posterior division of the ventral lateral thalamus which receives the cerebellar input
-Electrical stimulation elicits contraction of muscles on the opposite side of the body

44
Q

describe the supplementary and cingulate motor area

A

-Located medial part of area 6 and anterior half of the cingulate sulcus
-Area 6
-Afferent fibres from many cortical areas and ventral lateral thalamus
-Electrical stimulation elicits conscious urge to make a movement and the anticipation of motor tasks
-People with lesions have no motivation to move or speak

45
Q

describe the premotor area

A

-Located lateral part of area 6 anterior to the primary motor area
-Afferent fibres from many cortical areas and the ventral anterior and ventral lateral thalamus which receive the pallidal input
-Generate programs for motor routines necessary for skilled voluntary action

46
Q

describe the prefrontal cortex

A

-Part of the frontal lobe that does not elicit motor action when stimulated
-Areas 9,10,11, & 12
-Has extensive connections through association fasciculi with the parietal, temporal and occipital lobes
-Thus the PFC gains access to contemporary sensory experience as well as to the repository of data derived from past experience
-Monitors behaviour, exercises control based on higher mental faculties such as judgement and foresight

47
Q

describe the language areas

A

-Receptive language area
-Left posterior part of the superior temporal gyrus (Wernicke’s area)
-Comprehension of spoken and written language

-Expressive speech area
-Left opercular and triangular parts of the inferior frontal gyrus (Broca’s area) areas 44 & 45
-Motor speech area

48
Q

what is the cerebral white matter categories?

A

-association fibres
-commissural fibres
-projections fibres

49
Q

describe association fibres

A

-Confined to one hemisphere
-Short fibres (arcuate) connect adjacent area
-Long fibres connect different lobes

50
Q

describe the commissural fibres

A

-Connect the two hemispheres
-Corpus callosum and anterior cingulate

51
Q

describe the projection fibres

A

-Connection between the cortex and subcortical areas
-Corticopetal (afferent) and corticofugal (efferent)

52
Q

describe the cingulum

A

-Association fasciculus of the limbic lobe
-Interconnect the cingulate gyrus, parahippocampal gyrus and septum

53
Q

describe the superior longitudinal fasciculus (arcuate)

A

-association fasciculi
-Connect the parietal, temporal and occipital lobes with the frontal lobe

54
Q

describe the inferior occipitofrontal and uncinate fasciculus

A

-association fasciculi
-Connection orbital frontal cortex with the temporal lobe

55
Q

describe the superior occipitofrontal fasciculus

A

-association fasciculi
-Connect the anterior and posterior regions of the frontal cortex

56
Q

what are the association fibres?

A

-cingulum
-superior longitudinal fasciculus (arcuate)
-inferior occipitofrontal and uncinate fasciculus
-superior occipitofrontal fasciculus

57
Q

what are the commissure fibres?

A

-corpus callosum
-anterior commissure

58
Q

describe the corpus collosum

A

-Majority of neocortical fibres

-Features:
-Trunk – compact part near the midline
-Splenium – posterior connects the occipital lobe via the forceps occiptalis
-Genu – anterior connects the frontal lobe via the forceps frontalis
-Genu tapers into the rostrum
-Tapetum thin sheet over the temporal horn of the lateral ventricle connect the temporal lobes

59
Q

describe the anterior commissure

A

-Crosses the midline in the lamina terminalis
-Provides additional communication between the temporal lobes
-Middle and inferior temporal gyri
- Olfactory cortex of the temporal lobes
-Olfactory bulbs

60
Q

what are the projection fibres?

A

-internal capsule
-thalamic radiations
-motor projection fibres (corticofugal)

61
Q

describe the internal capsule

A

-Anterior limb – bounded by the lentiform nucleus and the head of the caudate
-Genu – medial to the lentiform nucleus
-Posterior limb – intervenes between the lentiform nucleus and the thalamus
-Retrolentiform part – region behind the lentiform nucleus
-Sublentiform part – pass beneath the posterior part of the lentiform nucleus

62
Q

what are the thalamic radiations broken up into?

A

-anterior
-middle
-posterior
-inferior
-auditory

63
Q

describe the anterior thalamic radiation

A

-anterior limb of the internal capsule
-Connects mediodorsal thalamus with the prefrontal cortex

64
Q

describe the middle thalamic radiation

A

-posterior limb of the internal capsule
-Connects the somatosensory projection from the ventral posterior thalamus nucleus to the somesthetic area in the parietal lobe
-Reciprocal connections between the thalamus and association cortex of the parietal lobe
-Ventral lateral thalamic projections to the primary, pre,
supplementary and cingulate motor areas via the genu

65
Q

Describe the posterior thalamic radiation

A

-sublentiform and retrolentiform parts of the internal capsule
-Connects the lateral geniculate body and the visual cortex via the geniculocalcarine tract
-Reciprocal connections between the pulvinar of the thalamus and association cortex of the occipital lobe

66
Q

describe the inferior thalamic radiation

A

sublentiform parts of the internal capsule

67
Q

describe the auditory thalamic radiation

A

connects the medial geniculate
body and the primary auditory cortex

68
Q

describe the corticobulbar and corticospinal tracts

A

-Pyramidal motor system
-Originate in the primary, pre, supplementary, and cingulate motor areas in the frontal and parietal lobes
-Converge as they traverse the corona radiata and enter the posterior limb of the internal capsule

69
Q

describe the corticopontine fibres

A

-Originate in all four lobes of the cortex and terminate in the pontine nuclei in the pons

70
Q

describe the frontopontine tract

A

Frontopontine tract traverse the anterior limb of the internal capsule

71
Q

describe the parietotemporopontine tract

A

originates in the parietal lobe and travers the retrolentiform part of the internal capsule

72
Q

describe the corticostriate fibres

A

-Originate in all parts of the neocortex and terminate in the striatum
-The caudate and putamen receive these fibres from the internal capsule

73
Q

describe the fibres of the corticorubral fibres

A

Motor areas of the frontal lobe to the red nucleus

74
Q

describe the corticoreticular fibres

A

-motor cortex and primary somaesthetic area of the parietal lobe to the reticular nuclei

75
Q

describe the cortico-olivary fibres

A

motor cortex to the inferior olivary complex

NEUR532 (14 decks)

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