8: The Central Nervous System

1. 8: The Central Nervous System

2. Nervous System Map Central Nervous System CNS Peripheral Nervous System PNS Effectors Receptors

3. The CNS • The brain and spinal cord

4. The PNS – All the stuff not CNS Contains: • SENSORY information within afferent division • Motor COMMANDS within efferent division • SNS – Somatic NS • ANS – Automatic NS • Parasympathetic Division (-) • Sympathetic Division (+)

5. Cellular Organization in Neural Tissue • Neurons • Neuroglia

6. Neurons • STRUCTURAL (POLAR) TYPES • Multi-: 2+ dendrites; most common in CNS • Uni-: most common in PNS • Bi-: rare; occur in special sense organs • FUNCTIONAL TYPES • Sensory: external and proprioceptors (visceral and internal) • Motor: somatic and visceral • Inter-/association: brain and spinal cord only

7. Neuroglia • Glial cells: present in CNS and PNS, but the CNS has a greater variety: • Astrocytes • Oligodendrocytes • Microglia • Ependymal

8. Neuroglia in the CNS

9. Astrocytes ASTROCYTE • Most numerous neuroglia. • Don’t confuse its shape with a neuron! • Maintain the blood-brain barrier, isolating the CNS from general circulation • Done via secretions • Structural framework for CNS neurons • Perform repairs in damaged neural tissue

10. Oligodendrocytes Wrap around axons, creating an insulating sheath of myelin • Myelin: • Lipid-rich; light yellow to glossy white • The myelinated axons in the CNS form the white matter of the CNS, while grey matter is dominated by neuron cell bodies • Can myelinate multiple axons

11. Microglia • Smallest and rarest of neuroglia in the CNS. • Phagocytic cells derives from white blood cells that came into the CNS as the nervous system formed. • Get rid of waste and pathogens

12. Ependymal • Line the central canal of the spinal cord and the chambers/ventricles of the brain. • These are filled with cerebrospinal fluid (CSF) • In some regions, the ependymal produces CSF

13. Neuroglia in the PNS • Satellite: surround/support cell bodies in the PNS, similar to astrocytes in the CNS. • Schwann: cover every axon outside the CNS. • Can fullymyelinate 1 portion 1 axon OR • Can partiallymyelinate several axons

14. Anatomical Organization of Neurons I • PNS: • Cell bodies (gray matter) are found in ganglia • White matter contains nerves; bundled axons • Sensory and motoraxons can be on the same nerve

15. Anatomical Organization of Neurons II CNS: • Center: collection of neuron cell bodies with a common function. • Nucleus: a center with an actual boundary • Neural cortex: thick layer of gray matter • White matter contains tracts: bundles of axons with a common origin, destination, and function • Pathways: link centers with the body • E.g. sensory and motor

16. THE CNS • The Meninges • Dura mater • Epidural space • The arachnoid • Subdural space • Arachnoid • Subarachnoid space

17. The Brain • Contains 35 billion neurons • Contains 98% of neural tissue

18. Brain Anatomy • 6 main regions: • Cerebrum • Diencephalon • Midbrain • Pons • Medulla Oblongata • Cerebellum

20. THE CEREBRUM • The top portion

21. THE CEREBELLUM • The smaller portion on the bottom

22. THE DIENCEPHALON • The Thalamus, hypothalamus, and pineal gland

23. THE PONS AND MEDULLA OBLONGATA The PONS is “upons” the medulla oblongata…

24. MIDBRAIN • The very mid-dle of the brain… • Between the PONS and DIENCEPHALON

25. Ventricles • Enable the circulation of CSF • About 500mL of CSF is produced a day. • The Total volume is about 150mL, so the CSF is getting constantly replenished carefully each day.

26. Superficial Anatomy • Cerebral Cortex • Gyri – peaks • Sulci – shallow depressions • Fissures – deep grooves

27. Areas of the Brain • The Brain can be divided multiple ways in order to illustrate multiple things related to anatomy and physiology.

28. The LIMBIC system • establishing emotional states and related behavioral desires • linking the conscious with the unconscious • long-term memory storage/retrieval

29. Physiology of the Brain • The CEREBELLUM: • This is an automatic processing center. It has 2 functions: • 1. Adjust the postural muscles for balancing • 2. Program/fine-tune movements controlled at the sub- and conscious levels

30. The Diencephalon • Hypothalamus • subconscious skeletal muscle control • Adjusting autonomic, voluntary activity • coordinating nervous and endocrine activity • Secreting hormones • behavioral drives • Body temperature regulation • Daily activity cycles • thalamus • Last call for sensory info • epithalamus & pineal gland

31. The Cerebellum • conscious thought and intellectual functions originate here.

32. The Arthur PONSarelli • Hit jukeboxes and hey “Hey!” a lot. • Tracts passing through the pons and link the cerebellum to the brain stem. • Lol, jk, that’s the Fonze.

34. The Midbrain • Processes visual and auditory sensations • Controls the reflexes of the eyes, head, and neck in response to visual stimuli • Control the reflexes of the head, neck and trunk in response to auditory stimuli • Reticular formation regulates a lot of involuntary functions

35. The Medulla Oblongata • Connects the brain and spinal cord • Heart rate adjustment and basic pace for breathing

36. Reflexes • Simple and Complex • Stretch and withdrawal • Reflex arcs

37. Motor Pathways • Corticospinal: conscious, voluntary control of skeletal muscles. • Posterior Column: fine touch, proprioception information • Medial/Lateral: Subconcous, involuntary control of muscle tone and movements of neck, trunk, and limbs • Coordinate learned movement patterns and other voluntary motor activities