Anatomy of the Cerebrum

Understanding anatomy of the Cerebral organ

1. Cerebrum-ANATOMY
Shittu LAJ

2. Lerning objectives
Overview of the CNS
Cerebral anatomy
Discuss the various parts and functions
Applied anatomy

3. The human brain
The brain contains roughly ~20 billion neurons
- excitatory and inhibitory interactions ensure that the
Its response can vary to meet changing circumstances
- adaptability requires multiple processing steps
- every synapse adds to the delay between stimulus and
response
- spinal reflexes provide an immediate response

4. Organization of the Brain
• Adult human brain contains ~95% of all
neural tissue
- weighs about 1.4kg (~3lb)
- considerable individual variation exist
- brains of males are on average ~10% larger

5. Organization of the Brain
The basic parts of the brain are as follows:
The cerebrum
The diencephalon
The brain stem
The cerebellum
The brain is organized into groupings of cell bodies (the gray
matter) and fibers (the white matter).
The cerebrum & the cerebellum contain gray matter on the outer
edges w/white matter below this surface.
While the diencephalon & brain stem have the white matter
superficially surrounding internal pockets of gray matter

6. Cerebrum
Largest portion of brain (>=80% mass).
Responsible for higher mental functions..
The cerebrum is divided into left and right hemispheres by the
longitudinal fissure.
The cell bodies in the outer cortex require more surface area
than the underlying white matter which results in much
folding.
The upfoldings are called gyri (gyrus, singular).
The infoldings are called sulci (sulcus, singular).
Corpus callosum:
Major tract of axons that functionally interconnects right
and left cerebral hemispheres.

7. Other parts of the brain
The diencephalon:
The epithalamus
The thalamus
The hypothalamus
The brain stem
The midbrain
The pons
The medulla oblongata
The cerebellum

8. The Brain
Medulla
Pons
Cerebellum
Midbrain
Diencephalon
Cerebral hemisphere

9. Cerebrum
Largest part of the brain
Situated in the anterior and middle cranial
fossae
Two parts are involved embryologically:
Diencephalon – central core
Telencephalon – cerebral hemispheres
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11. Fig. 14-5, p. 422

12. Cerebral hemispheres

General Appearance:
Separated by a deep midline sagittal fissure –
longitudinal cerebral fissure
The fissure contains falx cerebri and the anterior
cerebral arteries
In the depth of the fissure, the corpus callosum
connects the hemispheres across the midline
Gyri – the folds of the surface of hemispheres
Sulci – the fissures separate the gyri
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17. 17

18. Cerebral Cortex-histology
Surface layer of gray matter -- 3 mm thick
Neocortex (six-layered tissue)
newest part of the cortex (paleocortex & archicortex)
layers vary in thickness in different regions of brain
2 types of cells
stellate cells
have dendrites projecting
in all directions
pyramidal cells
have an axon that passes
out of the area

20. Cerebral cortex -functions
The is particularly well developed in humans
is responsible for many higher brain functions,
including manual dexterity (eg to move the fingers
individually so as to play the piano);
conscious, discriminative aspects of sensation;
cognitive activity, including language, reasoning, and
many other aspects of learning and memory.

21. Lobes of Cerebral Hemispheres
Cerebral hemispheres are divided into lobes by
the central, parieto-occipital, lateral and
calcarine sulci
Lobes are named according to the cranial bones
under which they lie
Lobes are:
Frontal
Parietal
Temporal
Occipital
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22. The cerebral hemispheres
The cerebral cortex (consists of six lobes on
each side:
frontal,
parietal,
temporal,
occipital,
insular, and
limbic).
the underlying cerebral white matter,
the basal ganglia: a complex of deep gray
matter masses.

23. cerebrum

24. 24

25. 25

26. The main sulci include
1. Central sulcus:
Indents the superior medial border of the
hemisphere, 1 cm behind the mid-point
It runs downward, forward and toward the
lateral sulcus across the lateral aspect of the
hemisphere
The central sulcus is the only sulcus that
indents the superior medial border
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27. 27

28. cerebrum

29. 2. Lateral sulcus:
Deep cleft on the inferior and lateral surfaces of
the cerebral hemisphere
It consists of a short stem and three rami.
3. Parieto-occipital sulcus:
Begins on the superior medial border of the
hemisphere, about 5 cm anterior to the occipital
pole
It passes downward and anteriorly on the medial
surface to meet the calcarine sulcus
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30. 30

31. Calcarine sulcus:
Found on the medial surface of the hemisphere
It begins under the posterior end of the corpus
callosum
It ascends upward and backward to reach the
occipital pole
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32. 32

33. Surfaces of Cerebral Hemisphere
Three surfaces are identifiable:
Superolateral surface
Inferior surface
Medial surface
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34. Superolateral surface
Frontal lobe – anterior to central sulcus
and superior to lateral sulcus
Superolateral surface of frontal lobe is
divided by three sulci into four gyri
Precentral sulcus and gyrus
Superior and inferior frontal sulci
Superior, middle and inferior frontal gyri
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35. Cerebral Cortex
Frontal lobe:
Anterior portion of each cerebral hemisphere.
Precentral gyri:
Contains upper motor neurons.
Involved in motor control.
Body regions with the greatest number of motor
innervation are represented by largest areas of
motor cortex.

36. 36

39. Superolateral surface
Temporal lobe – inferior to lateral
sulcus
Two sulci and three gyri
Occipital lobe – small area behind the
parieto-occipital sulcus
39

40. 40

41. Cerebral Cortex
Temporal:
Contain auditory centers that receive sensory fibers from
cochlea.
Interpretation and association of auditory and visual
information.
Occipital:
Primary area responsible for vision and coordination of eye
movements.
Insula:
Implicated in memory encoding.
Integration of sensory information with visceral responses.
Coordinate cardiovascular response to stress.

42. Superolateral surface
Parietal lobe –
posterior to central
sulcus and superior to
lateral sulcus, extends
upto the parieto-
occipital sulcus
Two sulci and three
gyri
42
Lateral
sulcus

44. Parietal Lobe
Primary area
responsible for
perception of
somatesthetic
sensation.
Body regions with
highest densities of
receptors are
represented by
largest areas of
sensory cortex.
Figure 8-7

45. Medial and Inferior Surface
Important areas are:
Corpus callosum
Cingulate sulcus and gyrus
Paracentral lobule
Precuneus and cuneus
Occipitotemporal, collateral and calcarine sulcus
Parahippocampal, medial and lateral
occipitotemporal gyrus and uncus
Olfactory sulcus, gyrus rectus and orbital gyri
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46. inferior-medial surface of Cortex
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47. Inferior view of cortex

49. Internal structure of Cerebral Hemispheres
Gray matter – cerebral cortex
Lateral ventricles
Basal nuclei – masses of gray
matter
White matter – nerve fibers
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50. 50

51. Lateral ventricles
Two lateral ventricles – one is in each cerebral
hemisphere
It communicates with the third ventricle through
interventricular foramen
C – shaped
Body – lies in the parietal lobe
Anterior horn – frontal lobe
Posterior horn – occipital lobe
Inferior horn – temporal lobe
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52. 52

53. Basal ganglia
Anatomically, the basal ganglia include
the caudate nucleus,
the putamen, and the globus pallidus.
(Together they are called the corpus
straitum)
Functionally, the basal ganglia and their
interconnections and neurotransmitters
form the extrapyramidal system.

54. Basal nuclei
Corpus striatum
Amygdaloid
nucleus
Claustrum
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55. Basal ganglia nuclei

58. White matter
Composed of mylinated nerve fibers
Classified into three groups:
Commissural fibers
Association fibers
Projection fibers
NB: “ CAP”
58

59. Corpus callosum
Largest
commissure
Parts:
Rostrum
Genu
Body
Splenium
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Rostrum
Genu
Body
Splenium

60. Fig. 14-5, p. 422

61. Commissural fibers
Connect corresponding
regions of two hemispheres
They are:
Corpus callosum
Anterior commissure
Posterior commissure
Fornix
Habenular commissure
Hippocampal commissure
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63. Association fibers
Connect various cortical regions within the same
hemisphere
They are:
Short association fibers - connect adjacent gyri
Long association fibers – collected into named
bundles. They are:
Uncinate fascicullus
Cingulum
Superior longitudinal fascicullus
Inferior longitudinal fascicullus
Fronto-occipital fascicullus
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64. Association fibers
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65. Projection fibers
Afferent and efferent nerve fibers passing to
and from the brainstem to the entire
cerebral cortex
They are:
Internal capsule
Corona radiata
Optic radiation
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66. Projection fibers

67. Areas of the cerebrum
Brodmann numbers to identify functions-
down to individual sulci
Question localisation now that we know
more about connectionism and we have a
more dynamic view of how the brain works

68. Broadman number of brain

69. Broadman number of brain

70. Broadman number of brain

71. Homunculus
Map of motor and sensory control
Reflects the body
Sizes indicate the amount of ‘brain’ needed
for various functions
Note vast area for the face- why?