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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 • Superolateral surface • Medial surface • Inferior surface
- 6. Borders • 3 borders • Superomedial • Inferolaeral • Inferomedial • Medial orbital • Medial occipital •
- 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
- 10. Main Sulci • On superolateral surface • Two prominent sulci are present • Posterior ramus of the lateral sulcus • Central sulcus • On medial surface - near occipital pole • Parietooccipital sulcus • Upper end of this sulcus reaches superomedial border • 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 • Supramarginal gyrus • 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 • Callosal sulcus • Cingulate sulcus • Short sulcus • Cingulate gyrus • Paracentral lobule • Medial frontal gyrus
- 18. Sulci & gyri on medial surface • Suprasplenial sulcus • Parietooccipital sulcus • Calcarine sulcus • 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. Interpeduncular fossa • Lies anterior to midbrain • Boundaries • In front by • Optic chiasma • Anterolatealrly by • Right and left optic 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 parahippocampal gyrus • Rhinal sulcus • Separates uncus from medial occipito temporal gyrus • Occipitotemporal sulcus • Lateral one • Divides the remaining gyri into • Medial & lateral occipito temporal gyri
- 23. Insula • Submerged part of cerebral cortex • Found in depth of lateral sulcus • Surrounded by circular sulcus Lentiform nucleus lies deep to it
- 24. Functional Areas of Cerebral Cortex • In 1909, Brodmann’s areas were described based on cytoarchitecture • Later they were found to be functionally significant • Cytoarchitecture is 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 – Marinoti cells & multipolar
- 25. Functional areas in frontal lobe • Primary motor • Premotor • Frontal eye field • Supplementary motor • Prefrontal • Broca’s area
- 26. Functional areas in frontal lobe • Precentral motor cortex (area 4) • Infront of 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 infront of motor cortex • In posterior parts of superior middle and inferior frontal gyri • Inferiorly upto lateral 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’s area)
- 28. Functional areas in frontal lobe • Frontal eye field (8) • Ability of the eyes to work together • To follow an object • Lies infront of 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 • Somesthetic association 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 calcarine sulcus
- 38. Functional areas in occipital lobe • Second visual area (18) • Lies close to primary visual area • Function • Understand the written language