Cerebrum

Cerebrum

1. Cerebrum

2. Cerebrum
•Largest part of brain
•Divided into 2 hemispheres
•Controls all conscious thoughts &
intellectual functions
•Processes somatic motor and sensory
information

3. External features
•Poles
•Surfaces
•Borders
•Sulci & gyri

4. Poles
•3 poles
•Frontal
•Occipital
•Temporal

5. Surfaces
•3 surfaces
•Superolateralsurface
•Medial surface
•Inferior surface

6. Borders
•3 borders
•Superomedial
•Inferolaeral
•Inferomedial
•Medialorbital
•Medialoccipital
•

7. Gyrus & sulci
•To increase surface area
•To accommodate more neurons
•Sulcus
•Indentation (groove)
•Gyrus
•Ridge (elevation)

8. Fissures
•Deep groove
•Longitudinal fissure
•Separates two hemispheres

9. Grey & white matter
•Outside
•Cortex
•Neurons present
•White
•Axons present
Axons present

10. Main Sulci
•On superolateralsurface
•Two prominent sulci are present
•Posterior ramus of the lateral sulcus
•Central sulcus
•On medial surface -near occipital pole
•Parietooccipitalsulcus
•Upper end of this sulcus reaches
superomedialborder
•Small part of it can be seen on superolateral
surface

11. Lobes
•Frontal lobe
•Anterior to central sulcus and
•Above posterior ramus of lateral sulcus
•Parietal lobe
•Behind central sulcus
•Bounded below by posterior ramus of the
lateral sulcus and by the second
imaginary line and
•Behind by the upper part of the first
imaginary line

12. Lobes
•Occipital lobe
•Area lying behind the first imaginary
line connecting parieto-occipital sulcus
and pre-occipital notch
•Temporal lobe
•Below posterior ramus of the lateral
sulcus and the second imaginary line
•Separated from the occipital lobe by the
lower part of the first imaginary line

13. Sulci and gyri of frontal lobe
•Precentral sulcus
•Superior frontal sulcus
•Inferior frontal sulcus
•Precentral gyrus
•Superior frontal gyrus
•Middle frontal gyrus
•Inferior frontal gyrus

14. Sulci and gyri of parietal lobe
•Postcentral sulcus
•Intraparietal sulcus
•Postcentral gyrus
•Superior parietal lobule
•Inferior parietal lobule
•Supramarginalgyrus
•Angular gyrus
•Arcus temporo-occipitalis

15. Sulci and gyri of temporal lobe
•Superior temporal
sulcus
•Inferior temporal
sulcus
•Superior temporal gyrus
•Middle temporal gyrus
•Inferior temporal gyrus
•Transverse temporal gyri

16. Sulci & gyri of occipital lobe
•Lateral occipital sulcus
•Divides the lateral surface into
•Superior occipital gyrus
•Inferior occipital gyrus
•Lunate sulcus
•Transverse occipital sulcus
•Lies posterior to parieto-occipital sulcus
•Gyrus descendens
•Arcus parietooccipitalis

17. Sulci & gyri on medial surface
•Callosalsulcus
•Cingulate sulcus
•Short sulcus
•Cingulate gyrus
•Paracentral lobule
•Medial frontal gyrus

18. Sulci & gyri on medial surface
•Suprasplenialsulcus
•Parietooccipitalsulcus
•Calcarinesulcus
•Cuneus
•Precuneus
•Isthmus

19. Structures in inferior surface
•In centre
•Interpeduncular fossa
•Between 2 cerebral
hemispheres
•Inferior surface of
hemisphere can be
divided into
•Orbital & tentorial
surfaces

20. Interpeduncularfossa
•Lies anterior to midbrain
•Boundaries
•In front by
•Optic chiasma
•Anterolatealrlyby
•Right and leftoptic tracts
•Posterolaterally
•Crus cerebri
•Posteriorly
•Pons

21. Sulci & gyri on orbital surface
•Olfactory sulcus
•Antero posterior sulcus near medial border
•Olfactory bulb & tract
•Gyrus rectus
•Medial to olfactory sulcus
•Orbital sulcus
•H –shaped
•Anterior, posterior, medial & lateral orbital gyri

22. Sulci & gyri on tentorial surface
•Collateral sulcus
•Near medial border
•Posteriorly forms lateral boundary for Lingual gyrus
•Anteriorly forms lateral boundary for parahippocampalgyrus
•Rhinalsulcus
•Separates uncus from medial occipitotemporal gyrus
•Occipitotemporalsulcus
•Lateral one
•Divides the remaining gyri into
•Medial & lateral occipitotemporal gyri

23. Insula
•Submerged part of cerebral cortex
•Found in depth of lateral sulcus
•Surrounded by circular sulcus
Lentiformnucleus lies deep to it

24. Functional Areas of Cerebral Cortex
•In 1909, Brodmann’sareas
were described based on
cytoarchitecture
•Later they were found to be
functionally significant
•Cytoarchitectureis based on
•Density of different cortical
neurons and thickness of layers
•
•6 layers are present in cortex
•Molecular –outermost
•Outer granular –stellate & granule cells
•Outer pyramidal –small & medium
•Inner granular –stellate cells
•Inner pyramidal –medium & large
•Polymorphous–Marinoticells & multipolar

25. Functional areas in frontal lobe
•Primary motor
•Premotor
•Frontal eye field
•Supplementary motor
•Prefrontal
•Broca’sarea

26. Functional areas in frontal lobe
•Precentral motor cortex (area 4)
•Infrontof central sulcus including anterior
wall of central sulcus
•Anterior part of paracentral lobule
•Has large pyramidal cells of Betz
•Opposite side body is topographically
represented
•In upside down manner (head is lower and leg
is up
•Lower limb and perineum are on medial side
•Controls highly skilled voluntary
movement of opposite half of body
•Voluntary control of micturition &
defecation are in anterior part of
paracentral lobule

27. Functional areas in frontal lobe
•Premotor cortex (area 6)
•Lies infrontof motor cortex
•In posterior parts of superior middle and
inferior frontal gyri
•Inferiorly uptolateral sucus
•Superiorly extends into medial surface
•Anterior to paracentral lobule
•Upper part –writing centre
•Lower part & around ascending ramus
of lateral sulcus
•Motor speech area (44 & 45) (Broca’sarea)

28. Functional areas in frontal lobe
•Frontal eye field (8)
•Ability of the eyes to work together
•To follow an object
•Lies infrontof upper part of premotor
area
•In posterior part of middle frontal gyrus
•Controls conjugate movements of eye
•Prefrontal cortex (9, 10 & 11)
•Essential for thought process
•Examples
•Solving mathematical problems
•Having foresight
•Giving judgments

29. Functional areas in frontal lobe
•Supplementary motor area (24)
•Primary motor area (6) continues on
medial surface
•Function
•Programming sequential motor
movements
•Lesion
•Results loss in coordination in
movements of two limbs

30. Functional areas in parietal lobe
•Primary somatosensory
•Secondary somatosensory
•Gustatory
•Association

31. Functional areas in parietal lobe
•Primary somatosensory area (3, 1 & 2)
•Lies in
•Posterior wall (3) and lip of central sulcus (1)
•Post central gyrus (2)
•Extends into paracentral lobule
•Receives sense of bladder & rectum fullness
•Functions
•Tactile localization between the 2 points discrimination & tactile
discrimination between 2 objects

32. Functional areas in parietal lobe
•Secondary somatosensory
•Lies along
•Upper lip of Posterior ramus of
lateral sulcus
•Functions
•Responds to stroking the skin
by brush or tapping

33. Functional areas in parietal lobe
•Somestheticassociation area (5)
•Lies in
•Anterior part of superior parietal lobule
•Function
•Integrates tactile & visual stimuli
•To determine shape & size of an object

34. Functional areas in temporal lobe
•Primary auditory (41 & 42))
•Auditory association (22)
•Visual association
•Limbic

35. Functional areas in temporal lobe
•Primary auditory area (41 & 42)
•Located in
•Transverse temporal gyrus
•In floor of posterior ramus of lateral sulcus &
adjoining superior temporal gyrus
•Function
•Detecting the direction of the sound

36. Functional areas in temporal lobe
•Auditory association area (22)
•Lies around primary auditory area
•In middle of superior temporal gyrus

37. Functional areas in occipital lobe
•Primary visual cortex (17)
•Called as striate cortex
•Lies in
•Lips & walls of
•Posterior part of calcarinesulcus

38. Functional areas in occipital lobe
•Second visual area (18)
•Lies close to primary visual area
•Function
•Understand the written language