The Central Nervous System

1. PART 3 The CentralNervous System

2. The Diencephalon • Forms the center core of the forebrain • Surrounded by the cerebral hemispheres • Composed of three paired structures • Thalamus • Hypothalamus • Epithalamus • Border the third ventricle • Primarily composed of gray matter

3. The Diencephalon and Brainstem Figure 13.16

4. The Diencephalon – The Thalamus • Makes up 80% of the diencephalon • Contains approximately a dozen major nuclei • Act as relay stations for incoming sensory message • Every part of brain communicating with cerbral cortex relays signals through thalamic nuclei! • Send axons to regions of the cerebral cortex • See figure 13.18b for nuclei

5. The Diencephalon – The Thalamus • Afferent impulses converge on the thalamus • Synapse in at least one of its nuclei • Is the “gateway” to the cerebral cortex • Nuclei organize and amplify or tone down signals

6. The Diencephalon Figure 13.17a

7. The Diencephalon Figure 13.17b

8. Relationship of Thalamus to Cerebrum Figure 13.18a

9. The Thalamus (note nuclei) Figure 13.18b

10. The Diencephalon – The Hypothalamus • Lies between the optic chiasm and the mammillary bodies • Pituitary gland projects inferiorly • Contains approximately a dozen nuclei • Main visceral control center of the body • The master gland’s master!!

11. The Diencephalon – The Hypothalamus • Functions include the following • Control of the ANS • Control of emotional responses • Regulation of body temperature • Regulation of hunger and thirst sensations • Control of behavior • Regulation of sleep-wake cycles • Control of the endocrine system • Formation of memory

12. Nuclei of the Hypothalamus Figure 13.19

13. The Diencephalon – The Epithalamus • Forms part of the “roof” (top) of the third ventricle • Consists of a tiny group of nuclei • Includes the pineal gland (pineal body) • Secretes the hormone melatonin • Under influence of the hypothalamus • Aids in control of circadian rhythm

14. The Cerebral Hemispheres • Account for 83% of brain mass • Fissures – deep grooves, which separate major regions of the brain • Transverse fissure – separates cerebrum and cerebellum • Longitudinal fissure – separates cerebral hemispheres

15. The Cerebral Hemispheres • Sulci • Grooves on the surface of the cerebral hemispheres • Gyri • Twisted ridges between sulci • Prominent gyri and sulci are similar in all people

16. The Cerebral Hemispheres • Deeper sulci divide cerebrum into lobes • Lobes are named for the skull bones overlying them • Central sulcus separates frontal and parietal lobes • Bordered by two gyri • Precentral gyrus • Postcentral gyrus

17. The Cerebral Hemispheres Figure 13.20a

18. The Cerebral Hemispheres • Parieto-occipital sulcus • Separates the occipital from the parietal lobe • Lateral sulcus • Separates temporal lobe from parietal and frontal lobes • Insula – deep within the lateral sulcus

19. The Cerebral Hemispheres Figure 13.20b, c

20. The Cerebral Hemispheres • Frontal section through forebrain • Cerebral cortex • Cerebral white matter • Deep gray matter of the cerebrum (basal ganglia)

21. The Cerebral Hemispheres Figure 13.21

22. The Cerebral Cortex • Home of our conscious mind • Enables us to • Be aware of ourselves and our sensations • Initiate and control voluntary movements • Communicate, remember, and understand

23. The Cerebral Cortex • Composed of gray matter • Neuronal cell bodies, dendrites, and short axons • Folds in cortex – triples its size • Approximately 40% of brain’s mass • Brodmann areas • 52 structurally distinct areas

24. The Cerebral Cortex • Functional regions • Traditionally – studied brain-injured people and animals • New discoveries – PET and fMRI • Regions of the cerebral cortex • Perform distinct motor and sensory functions • Memory and language spread over wide area

25. Functional and Structural Areas of the Cerebral Cortex Figure 13.23a

26. Functional and Structural Areas of the Cerebral Cortex Figure 13.23b