Brain & Cranial Nerves

1. Brain & Cranial Nerves

2. The Brain • Ranges from 750 cc to 2100 cc • Contains almost 98% of the body’s neural tissue • Average weight about 1.4 kg (3 lb)

3. 6 Major Regions of the Brain • Cerebrum • Cerebellum • Diencephalon • Mesencephalon • Pons • Medulla oblongata

4. The Brain

5. Cerebrum • Largest part of brain • Controls higher mental functions • Divided into left and right cerebral hemispheres • Surface layer of gray matter (neural cortex)

6. Cerebral Cortex

7. 3 Functional Principles of the Cerebrum • 1. Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body

8. 3 Functional Principles of the Cerebrum • 2. The 2 hemispheres have different functions although their structures are alike

9. 3 Functional Principles of the Cerebrum • 3. Correspondence between a specific function and a specific region of cerebral cortex is not precise

10. Motor & Sensory Areas of the Cerebral Cortex • Where are the motor, sensory, and association areas of the cerebral cortex, and what are their functions?

11. Central sulcus separates motor and sensory areas

12. Motor Areas • Precentralgyrus of frontal lobe: • directs voluntary movements • Primary motor cortex: • is the surface of precentralgyrus • Pyramidal cells: • are neurons of primary motor cortex

13. Sensory Area • Postcentralgyrus of parietal lobe: • receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature) • Primary sensory cortex: • surface of postcentralgyrus

14. Special Sensory Cortexes • Visual cortex: • information from sight receptors • Auditory cortex: • information from sound receptors • Olfactory cortex: • information from odor receptors • Gustatory cortex: • information from taste receptors

15. Sensory Association Areas • Somatic sensory association area: • interprets input to primary sensory cortex (e.g., recognizes and responds to touch) • Visual association area: • interprets activity in visual cortex • Auditory association area: • monitors auditory cortex

16. Other Integrative Areas • Speech center: • is associated with general interpretive area • coordinates all vocalization functions • Prefrontal cortex of frontal lobe: • integrates information from sensory association areas • performs abstract intellectual activities (e.g., predicting consequences of actions)

17. Hemispheric Lateralization • Functional differences between left and right hemispheres • Each cerebral hemisphere performs certain functions not performed by the opposite hemisphere

18. The Left Hemisphere • In most people, left brain (dominant hemisphere) controls: • reading, writing, and math • decision-making • speech and language

19. The Right Hemisphere • Right cerebral hemisphere relates to: • senses (touch, smell, sight, taste, feel) • recognition (faces, voice inflections)

20. Cerebellum • Second largest part of brain • Coordinates repetitive body movements • 2 hemispheres • Covered with cerebellar cortex

21. The Cerebellum • An autonomic processing center

22. Functions of the Cerebellum • Adjusts postural muscles • Fine-tunes conscious and subconscious movements

23. Structures of the Cerebellum

24. Structures of the Cerebellum • Folia: • surface of cerebellum • highly folded neural cortex • Anterior and posterior lobes: • separated by primary fissure

25. Structures of the Cerebellum • Cerebellar hemispheres: • separated at midline by vermis • Vermis: • narrow band of cortex • Flocculonodular lobe: • below fourth ventricle

26. Purkinje Cells • Large, branched cells • Found in cerebellar cortex • Receive input from up to 200,000 synapses

27. Arbor vitae • Highly branched, internal white matter of cerebellum • Cerebellar nuclei: • embedded in arbor vitae • relay information to Purkinje cells

28. The Peduncles • Tracts link cerebellum with brain stem, cerebrum, and spinal cord: • superior cerebellar peduncles • middle cerebellar peduncles • inferior cerebellar peduncles

29. Cranial Nerves • I. – Olfactory – smell • II – Optic – sight • III – Oculomotor – eye movement • IV – Trochlear – eye movement • V – Trigeminal – mixed (sensory/motor) face • VI – Abducens – eye movement • VII – Facial - mixed (sensory/motor) face • VIII – Vestibulocochlear – balance, equilibrium, hearing • IX – Glossopharyngeal – mixed head & neck

30. Cranial Nerves • X – Vagus – mixed thorax and abdomen • XI – Accessory – motor muscles of the neck and upper back • XII – Hypoglossal – motor of the tongue