1. Lecture: 2 Dr. Eyad M. Hussein Cerebral Hemispheres Ph.D of Neurology
Consultant in Neurology Department,
Nasser Hospital,
Assistant Professor,
Faculty of Medicine, Islamic University
Faculty of Dentistry, University of Palestine

2. الرجاء تحويل الجوال إلى وضع الصامت مع الشكر
الرجاء تحويل الجوال إلى وضع الصامت مع الشكر

3. The Cranial Fossa
The cranium is divided into three regions (fossa): 1. Anterior Cranial Fossa: house for frontal lobes. 2. Middle Cranial Fossa: house for temporal lobes. 3. Posterior Cranial Fossa: house for occipital lobes, cerebellum and brain stem.

4. Morphological Subdivisions of the Brain
- It is contains about one trillion cells (100 billion neurons and
900 billion neuroglial cells).
- The adult brain weight is about 1200 – 1500 g .
- The brain reaches full size about 18 year age.
- It is formed of:
Cerebrum:
- Is the largest part of the brain that located above the
tentorium cerebelli and orbit.
- It consists of two cerebral hemispheres connected
together by the corpus callosum.
2. Cerebellum:
- Is a large mass of brain tissue which located in the
posterior cranial fossa below the tentorium cerebelli
and behind brain stem.

5. 3. Diencephalon:
- Is located between the two cerebral hemispheres and
above the midbrain.
4. Brain Stem:
- Is the part of brain located below the diencephalon and in the front of the cerebellum.
- Is connected the cerebellum by three pairs of cerebellar
peduncles.
- Connects the two cerebral hemispheres with the spinal
cord.
- It consists of three parts, from below upwards:
a. Medulla oblongata
b. Pons
c. Midbrain

9. The Cerebrum (Cerebral Hemisphere)
Site: occupies most of cranial cavity and it is the large part of the brain.
The cerebrum formed of two cerebral hemispheres by a median longitudinal fissure, connected to each other by:
The corpus callosum.
Right and left cerebral peduncles: connected to upper part of the brain stem.
Anterior, posterior & habenular commissures

10. The Commissural Fibers

11. The Cerebrum (Cerebral Hemisphere)

12. Integrative Function of the Cerebral Cortex
Consciousness: (brain stem-reticular formation, frontal, temporal and deep structures of cerebrum).
Use of language: speech center present in frontal and temporal lobes (in 90-95% of population the centre is present in the left hemisphere).
Emotions: frontal and temporal lobes (limbic system).
Memory: frontal and temporal lobes
Orientation, thinking and intelligence: frontal lobe.

15. External Feature of the Cerebrum
Each cerebral hemisphere has:
Three surfaces.
Three poles.
Five borders.

16. Surfaces of Each Cerebral Hemisphere
Each cerebral hemisphere has 3 surfaces:
Lateral (superolateral) surface.
Medial surface.
Inferior surface.

17. Surfaces of Each Cerebral Hemisphere

19. Poles of Each Cerebral Hemisphere
Each cerebral hemisphere has 3 poles:
1. Frontal pole: at the anterior end of the frontal lobe.
2. Temporal pole: at the anterior end of the temporal lobe.
3. Occipital pole: at the posterior end of the occipital lobe.

20. Poles of Each Cerebral Hemisphere

21. Lobes of Each Cerebral Hemisphere
The surface of each cerebral hemisphere is divided by three main sulci or fissures into four lobes (which have been given the names of the skull bones under which they lie).
These four lobes are:
1. The frontal.
2. The parietal.
3. The temporal.
4. The occipital.
Each surface of lobes is divided by sulci into gyri.

22. The Important Sulci of Cerebral Hemisphere
The longitudinal fissure divides the cerebrum into two hemispheres.
Each cerebral hemisphere is divided by sulci (grooves) into gyri.
1. The central sulcus (Roland sulcus): it separates the
frontal lobe (in front) from parietal lobe (behind).
2. The lateral sulcus (Sylvian sulcus): between frontal
and parietal lobes (above) and temporal lobe (below).
3. The parieto-occipital sulcus: it found mainly on the
medial surface of the hemisphere between parietal and
occipital lobes.

23. Sulci of Each Cerebral Hemisphere

26. Cortical Somatotopy

27. Cortical Somatotopy

28. The Important Sulci of Frontal Lobe
The important sulci of frontal lobe are:
The precentral sulcus: it present in front of the central sulcus.
The superior frontal sulcus: present in front of the precentral sulcus (superior part of the frontal lobe).
The inferior frontal sulcus: present in front of the precentral sulcus (inferior part of the frontal lobe).

30. Sulci of Each Cerebral Hemisphere

31. The Important Gyri of Frontal Lobe
1. The precentral gyrus: between the central and precentral sulci.
2. The superior frontal gyrus: above the superior frontal
sulcus.
3. The middle frontal gyrus: between the superior and
inferior frontal sulci.
4. The inferior frontal gyrus: below the inferior frontal

32. Lobes of Each Cerebral Hemisphere

34. The Important Functional Areas of the Frontal Lobe
Site
Areas
Voluntary motor activity of opposite 1/2 of the body
Precentral gyrus
Primary motor area (4)
Gives extrapyramidal fibers
Anterior part of precentral gyrus
Secondary motor (Premotor) area (6)
Voluntary conjugate deviation of eyes to opposite side
Middle frontal gyrus
Frontal eye conjugate (8)
Motor center of writing.
Inferior frontal gyrus in dominant hemisphere
Area (45)
Motor center of speech.
Brocca's area (44)
Higher center of memory, orientation, thinking and intelligence
Anterior pole
Prefrontal
Areas(9, 10, 11 & 12)

35. Areas of Cerebral Cortex

36. The Important Sulci of Parietal Lobe
The important sulci of parietal lobe are:
The postcentral sulcus: it present behind the central sulcus.
The intraparietal sulcus.

38. Sulci of Each Cerebral Hemisphere

39. Important Gyri of Parietal Lobe
The postcentral gyrus: its the main gyrus of parietal lobe, between the central and postcentral sulci.
The superior parietal gyrus: above the intraparietal sulcus.
The inferior parietal gyrus: below the intraparietal sulcus.
The supramarginal gyrus: small gyrus surrounding the upper end of lateral sulcus.
The angular: small gyrus surrounding the upper end of the superior temporal sulcus.

40. Lobes of Each Cerebral Hemisphere

41. The Important Functional Areas of the Parietal Lobe
Site
Areas
Perception of cortical sensation from opposite 1/2 of the body
Post central gyrus
Primary sensory area (1,2,3)
Knowing the meaning of the sensations felt (steriognosis) in absence of sensory loss
Superior parietal gyrus
Areas 5& 7
Visual psychic area for speech (recognition of letters & numbers).
Surround the upper end of superior temporal sulcus in dominant hemisphere
Angular gyrus,
area (39)
Associative area and center for complex movement.
Surround the upper end of lateral sulcus
Supramarginal
gyrus, area (40)

42. Areas of Cerebral Cortex

43. The Important Sulci of Temporal Lobe
The superior temporal sulcus: below the lateral sulcus.
The inferior temporal sulcus.

44. Important Gyri of Temporal Lobe
The superior temporal gyrus: lies between the lateral sulcus and the superior temporal sulcus.
The middle temporal gyrus: lies between the superior and inferior temporal sulcus.
The inferior temporal gyrus: lies below the inferior temporal sulcus.

45. Lobes of Each Cerebral Hemisphere

46. The Important Functional Areas of the Temporal Lobe
Site
Areas
Auditory sensory area
In the superior temporal gyrus
Primary auditory (area 41,42)
Auditory association area (recognition & recall of sounds).
In the superior temporal lobe of dominant hemisphere
Sensory speech area or Wernicke's center (area 22)
Uncus: sense of smell
Hipocampus: mood & memory
Uncus and hypocampus in the medial and inferior surface of the temporal lobe
Limbic system

47. Areas of Cerebral Cortex

48. The Important Sulci of Occipital Lobe
The calcarine sulcus: lies on the medial surface of the occipital lobe and extends backwards to the occipital pole.
The lateral occipital sulcus: is a short horizontal sulcus running on the middle of the superolateral surface of the occipital lobe.

49. Sulci of the Cerebral Hemisphere

51. Important Gyri of Occipital Lobe
The superior occipital gyrus: above the lateral occipital sulcus.
The inferior occipital gyrus: below the lateral occipital sulcus.

53. Lobes of Each Cerebral Hemisphere

54. The Important Functional Areas of the Occipital Lobe
Site
Areas
Visual sensory area (perception of visual impulses)
Posterior medial part of occipital lobe (surrounds calcarine sulcus)
Primary visual sensory
area (17)
Visual association area (Recognition & recall of image).
Anterior to area 17 in dominant hemisphere
Secondary (psychic) visual area (18, 19)

55. The Occipital Lobe

56. Areas of Cerebral Cortex

57. Areas of the Occipital Lobe

58. The Insula
The insula is a part of the cerebral cortex which is hidden in the bottom of lateral sulcus.
The insula is subdivided two long gyri (behind) and 3-4 short gyri (in front).
Function of the insula: cortical taste center and some visceral activities (e.g. salivation).

60. Internal Structure of the Cerebrum
The cerebral hemispheres consists of :
Gray Mater (outer): composed of nerve cells (cerebral cortex). The cells of each area has specific functions.
White Mater (inner): composed of nerve fibers conducting impulses to and from the cortex.
Basal Nuclei: there are several groups of nuclei situated at various levels within the white mater.
Lateral Ventricle: the cavity of the cerebral hemisphere.

61. Internal Structures of the Cerebral Hemispheres

62. The Layers of the Cerebral Cortex
Molecular layer.
External granular layer.
External pyramidal layer.
Internal granular layer.
Internal pyramidal (ganglionic) layer.
Multiform layer.

63. The Layers of the Cerebral Cortex
Betz cells

64. The White Mater of the Cerebrum
Consists of myelinated nerve fibers .
There are three types of fibers in the white mater:
Projection fibers: They connect the cerebral cortex with the lower subcortical centers.
Association fibers: They connects different areas of the same cerebral hemisphere .
Commissural fibers: They connect similar areas of both hemispheres.

66. The Projection Fibers
Definition: they are afferent and efferent fibers (tracts) of the cerebral cortex which connect the cerebral cortex with the lower part of the brain and spinal cord (e.g. pyramidal tract).
Types of the Projection Fibers:
Ascending (afferent or sensory): to the cerebral cortex from the thalamus.
Descending (efferent or motor): from the cerebral cortex to lower centers.

67. The Association Fibers
Definition: they are fibers which connect the different cortical areas in the same hemisphere.
Types of Association Fibers:
Short association fibers: they connect adjacent gyri with one another.
Long association fibers: connect the different lobes of the hemisphere together.

68. The Commissural Fibers
Definition and function: is a band of white mater (nerve fibers) connecting and coordinating of activates of the right and left hemisphere.
The Commissural Fibers Include:
Corpus callosum.
Anterior commissure.
Posterior commissure.
Habenular commissure.
Hippocampal commissure.

69. The Commissural Fibers

70. Internal Capsule
It is a thick lamina of white matter made up of projection
fibers which pass to and from the cerebral cortex.
It is continuous superiorly with the corona radiata, and
inferiorly with pedunculi of midbrain.
Parts of Internal Capsule:
Anterior limb.
Genu.
Posterior limb.

72. Thank You