Chapter 10 Central & Somatic Nervous Systems

1. Chapter 10Central & Somatic Nervous Systems p.233

2. Spinal Cord • Protection & Coverings: Vertebral Canal & Meninges • Vertebral canal – ring of bones • Epidural space • Meninges • Dura mater • Arachnoid mater • Subarachnoid space • Meninx • Pia mater

3. General Features of the Spinal Cord • Length • 16-18 inches • From foramen magnum of occipital bone to superior border of the 2nd lumbar vertebra • Cauda equina • Nerves angling down the vertebral canal below the spinal cord • Enlargments • Cervical ~ Nerves supply upper limbs • Lumbar ~ Nerves supply lower limbs • Spinal segments • 31 segments • Each gives rise to a pair of spinal nerves

4. Spinal CordStructure in Cross Section • Central canal • Contains CSF • Gray matter (H) • Horns (anterior, lateral, posterior) • Consists mainly of • Interneurons • Motor neurons

5. Spinal CordStructure in Cross Section (cont.) • White matter • Columns (anterior, lateral, posterior) • Consists of • Myelinated and unmyelinated axons • Organized into tracts • Sensory • Motor • Spinal nerves • Dorsal root • Sensory • Ganglions contain cell bodies • Ventral root • Motor

6. Spinal Cord Functions • Impulse conduction along pathways • Sensory • Motor • Spinal reflexes

7. Spinal Cord Functions (cont.) • Impulse conduction along pathways • Sensory • Anterolateral pathways • Convey impulses for sensing: • Pain • Temperature • Crude touch • Pressure • Tickle • Itch • Posterior column-medial lemniscus pathway • Carries impulses for sensing: • Proprioception • Fine touch • Stereognosis • Weighth discrimination • Vibratory sensations

8. Spinal Cord Functions (cont.) • Impulse conduction along pathways • Motor • Direct pathways • Convey impulses for precise, voluntary movements of skeletal muscles • Indirect pathways • Convey impulses that • Program automatic movements • Help coordinate body movements with visual stimuli • Maintain skeletal muscle tone and posture • Play a major role in equilibrium

9. Spinal Cord Functions (cont.) • Spinal reflexes • Reflex arc • Sensory receptor • Sensory neuron • Integrating center • Motor neuron • Effector

10. Spinal Cord Functions (cont.) • Spinal reflexes • Somatic reflexes • Involve skeletal muscles • Examples: • Patellar reflex • Withdrawal reflex • Autonomic reflexes • Involve smooth muscle, cardiac muscle, and glands • Example: • Swallowing

11. Spinal Nerves • Names • Number • According to region and level • Roman numerals • Name • Composition and Coverings • Dorsal root and ventral root unite at intervertebral foramen • All spinal nerves are mixed nerves • Bundles of axons are wrapped in connective tissue and supplied with blood vessels

12. Spinal Nerves (cont.) • Distribution • Branches • Rami (sing. = ramus) extend in different directions • Plexuses • Rami that join with adjacent nerves to form networks • Principle plexuses • Cervical • Brachial • Lumbar • Sacral • Nerves emerge from the plexuses to supply various body parts • Intercostal nerves • Extend directly to the structures they supply • Spinal nerves T2 to T11

13. Brain - Principal Parts (Figure 10.7, p.240-241) • Brain stem • Medulla oblongata • Pons • Midbrain • Diencephalon • Thalamus • Hypothalamus • Cerebrum • Cerebral cortex • White matter • Cerebellum

14. Brain – Blood Supply • Cerebral arterial circle (circle of Willis) brings • Oxygen • 20% of body’s oxygen supply (but only 2% of body weight) • Nutrients • Glucose • Substances pass through the blood-brain barrier (BBB)

15. Brain – Protective Coverings • Cranial meninges • Dura mater • Arachnoid mater • Pia mater

16. Brain – Cerebrospinal Fluid (CSF) • Formed in choroid plexus • Circulates through • Subarachnoid space • Around the brain • Around the spinal cord • Through the 4 ventricles in the brain • Continuously formed and reabsorbed at an equal rate

17. Brain Stem • Medulla Oblongata • Continuation of spinal cord • Contains all sensory and motor tracts extending between the spinal cord and other parts of the brain • Most fibers cross to the opposite side • Governs several autonomic functions • Cardiovascular center • Medullary rhythmicity area of respiratory center • Contains nuclei for 5 pairs of cranial nerves

18. Brain Stem (cont.) • Pons • “bridge” • Contains nuclei for: • 4 pairs of cranial nerves • Regulating breathing • Midbrain • Cerebral peduncles connect cerebral cortex to pons and spinal cord • Sensory fibers connect the spinal cord to the thalamus • Contains nuclei for 2 pairs of cranial nerves

19. Brain Stem (cont.) • Reticular formation • Extend throughout brain stem and diencephalon • Netlike arrangement of small areas of gray matter • Alerts cerebral cortex to incoming sensory signals • Helps regulate muscle tone

20. Diencephalon • Thalamus • Principal relay station for sensory impulses from the spinal cord, brain stem, cerebellum, and other parts of the cerebrum to the cerebral cortex • Allows crude perception of some sensations • Plays an essential role in awareness and acquisition of knowledge (cognition)

21. Diencephalon (cont.) • Hypothalamus • Functions • Control of the ANS • Control of the pituitary gland • Regulation of emotional and behavioral patterns • Regulation of eating and drinking • Control of body temperature • Regulation of circadian rhythms and states of consciousness

22. Reticular Activating System, Consciousness, & Sleep • Stimulation  state of wakefulness • Inactivation  sleep (consciousness) • Damage or disease  coma (lack of consciousness)

23. Cerebrum • Lobes • White matter • Basal ganglia • Limbic system • Functional areas of the cerebral cortex • Hemispheric lateralization • Memory • Electroencephalogram (EEG)

24. Cerebrum (cont.) • Lobes • Frontal • Parietal • Temporal • Occipital • Also important: • Central sulcus • Precentral gyrus • Postcentral gyrus • Insula (lies within lateral cerebral fissure)

25. Cerebrum (cont.) • White matter • Transmits impulses: • Across hemispheres (via corpus callosum) • From cerebrum to other parts of brain/spinal cord • Basal ganglia • Paired masses of gray matter within white matter • Control large subconscious movements of skeletal muscles • Regulate muscle tone required for specific body movements • Damage results in tremors, muscular rigidity, involuntary muscle movements (Parkinson’s)

26. Cerebrum (cont.) • Limbic system • Wishbone-shaped group of structures around brain stem • “Emotional” brain • Controls most involuntary aspects of behavior related to survival • Functional areas of the cerebral cortex • Sensory areas • Motor areas • Association areas

27. Cerebrum (cont.) • Hemispheric lateralization • Structurally mostly symmetrical • Functionally asymmetrical • Control opposite sides of body • Left hemisphere • Spoken/written language • Numerical & scientific skills • Sign language • Reasoning • Right hemisphere • Musical/artistic awareness • Spatial & pattern perception • Facial/emotional language content recognition • Generation of mental images of sensations • Less pronounced in females

28. Cerebrum (cont.) • Memory • Involves: • Association cortex • Limbic system • Diencephalon • Explanation: • No one knows! • Requires changes in the CNS • Categories: • Short-term • Long-term

29. Cerebrum (cont.) • Electroencephalogram (EEG) • Record of brain waves • Used to: • Study brain functions • Diagnosing disorders • Establish brain death

30. Cerebellum • 2nd largest portion of brain • Consists of: • 2 hemispheres • Cerebellar cortex (surface) • White matter tracts • Cerebellar nuclei (gray matter) • Functions: • Compares intended movements with actual movements • Help smooth and coordinate complex sequences of skeletal muscle contractions • Regulates posture and balance • Makes all skilled motor activities possible

31. Cranial Nerves • Part of SNS • Consist of 12 pairs • 10 originate from the brain stem • 10 are mixed • 2 are sensory • Identified by: • Roman numerals • Order – anterior to posterior • Names • Distribution/function