The Central Nervous System: Part A

1. The Central Nervous System: Part A

2. Central Nervous System (CNS) • CNS consists of the brain and spinal cord • Cephalization • Evolutionary development of the rostral (anterior) portion of the CNS • Increased number of neurons in the head • Highest level is reached in the human brain

3. Functions of the Nervous System • Sensory input • Information gathered by sensory receptors about internal and external changes • Integration • Interpretation of sensory input • Motor output • Activation of effector organs (muscles and glands) produces a response

4. Sensory input Integration Motor output Figure 11.1

5. Divisions of the Nervous System • Central nervous system (CNS) • Brain and spinal cord • Integration and command center • Peripheral nervous system (PNS) • Paired spinal and cranial nerves carry messages to and from the CNS

6. Peripheral Nervous System (PNS) • Two functional divisions • Sensory (afferent) division • Somatic afferent fibers—convey impulses from skin, skeletal muscles, and joints • Visceral afferent fibers—convey impulses from visceral organs

7. Motor (efferent) division • Transmits impulses from the CNS to effector organs

8. Motor Division of PNS • Somatic (voluntary) nervous system • Conscious control of skeletal muscles

9. Peripheral nervous system (PNS) Central nervous system (CNS) Cranial nerves and spinal nerves Brain and spinal cord Communication lines between the CNS and the rest of the body Integrative and control centers Sensory (afferent) division Motor (efferent) division Somatic and visceral sensory nerve fibers Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands) Conducts impulses from receptors to the CNS Somatic sensory fiber Autonomic nervous system (ANS) Somatic nervous system Skin Visceral motor (involuntary) Somatic motor (voluntary) Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands Conducts impulses from the CNS to skeletal muscles Visceral sensory fiber Stomach Skeletal muscle Motor fiber of somatic nervous system Sympathetic division Parasympathetic division Mobilizes body systems during activity Conserves energy Promotes house- keeping functions during rest Sympathetic motor fiber of ANS Heart Structure Function Sensory (afferent) division of PNS Bladder Parasympathetic motor fiber of ANS Motor (efferent) division of PNS Figure 11.2

10. Embryonic Development Don’t copy • Neural plate forms from ectoderm • Neural plate invaginates to form a neural groove and neural folds

11. Surfaceectoderm Head Neuralplate Tail The neural plate forms from surface ectoderm. 1 Figure 12.1, step 1

12. Neural folds Neuralgroove The neural plate invaginates, forming the neuralgroove, flanked by neural folds. 2 Figure 12.1, step 2

13. Embryonic Development don’t copy • Neural groove fuses dorsally to form the neural tube • Neural tube gives rise to the brain and spinal cord

14. Neural crest 3 Neural fold cells migrate to form the neural crest,which will form much of the PNS and many otherstructures. Figure 12.1, step 3

15. Head Surfaceectoderm Neuraltube Tail 4 The neural groove becomes the neural tube, whichwill form CNS structures. Figure 12.1, step 4

16. Anterior (rostral) Posterior (caudal) Metencephalon Mesencephalon Midbrain Flexures Diencephalon Cervical Telencephalon Spinal cord Myelencephalon (a) Week 5 Figure 12.3a

17. Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Pons Medulla oblongata Spinal cord (b) Week 13 Figure 12.3b

18. Cerebral hemisphere Cerebellum Pons Medulla oblongata Spinal cord (c) Week 26 Figure 12.3c

20. *Regions and Organization of the CNS • Adult brain regions • Cerebral hemispheres • Diencephalon • Brain stem (midbrain, pons, and medulla) • Cerebellum

21. Cerebral hemisphere Diencephalon Cerebellum Brain stem • Midbrain • Pons • Medullaoblongata (d) Birth Figure 12.3d

22. Regions and Organization of the CNS • Spinal cord • Central cavity surrounded by a gray matter core • External white matter composed of myelinated fiber tracts

23. Regions and Organization of the CNS • Brain • Similar pattern with additional areas of gray matter • Nuclei in cerebellum and cerebrum • Cortex of cerebellum and cerebrum

24. Cortex of gray matter Central cavity Migratory pattern of neurons Inner gray matter Outer white matter Cerebrum Cerebellum Gray matter Region of cerebellum Central cavity Inner gray matter Outer white matter Gray matter Brain stem Central cavity Outer white matter Inner gray matter Spinal cord Figure 12.4

25. Ventricles of the Brain • Connected to one another and to the central canal of the spinal cord • Lined by ependymal cells

26. Ventricles of the Brain • Contain cerebrospinal fluid • Two C-shaped lateral ventricles in the cerebral hemispheres • Third ventricle in the diencephalon • Fourth ventricle in the hindbrain, dorsal to the pons, develops from the lumen of the neural tube

27. Lateral ventricle Septum pellucidum Anterior horn Posterior horn Inferior horn Interventricular foramen Lateral aperture Median aperture Third ventricle Inferior horn Lateral aperture Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view (b) Left lateral view Figure 12.5

28. *Cerebral Hemispheres • Surface markings • Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) • Five lobes • Frontal • Parietal • Temporal • Occipital • Insula

29. *Cerebral Hemispheres • Surface markings • Central sulcus • Separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe • Longitudinal fissure • Separates the two hemispheres • Transverse cerebral fissure • Separates the cerebrum and the cerebellum PLAY Animation: Rotatable brain

30. Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons Medulla oblongata Fissure Spinal cord (a deep sulcus) Gyrus Cortex (gray matter) Sulcus White matter (a) Figure 12.6a

31. Central sulcus Frontal lobe Gyri of insula Temporal lobe (pulled down) (b) Figure 12.6b

32. Anterior Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid mater Parietal lobe Right cerebral hemisphere Left cerebral hemisphere Occipital lobe Posterior (c) Figure 12.6c

33. Left cerebral hemisphere Transverse cerebral fissure Brain stem Cerebellum (d) Figure 12.6d

34. *Cerebral Cortex • Thin (2–4 mm) superficial layer of gray matter • 40% of the mass of the brain • Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding • Each hemisphere connects to contralateral side of the body • There is lateralization of cortical function in the hemispheres

35. *Functional Areas of the Cerebral Cortex • The three types of functional areas are: • Motor areas—control voluntary movement • Sensory areas—conscious awareness of sensation • Association areas—integrate diverse information • Conscious behavior involves the entire cortex

36. Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Thalamus (encloses third ventricle) Interven- tricular foramen Posterior commissure Pineal gland (part of epithalamus) Anterior commissure Corpora quadrigemina Mid- brain Cerebral aqueduct Hypothalamus Optic chiasma Arbor vitae (of cerebellum) Pituitary gland Fourth ventricle Mammillary body Choroid plexus Pons Cerebellum Medulla oblongata Spinal cord Figure 12.12

38. *Motor Areas • Primary (somatic) motor cortex • Premotor cortex • Broca’s area • Frontal eye field

39. Motor areas Sensory areas and related association areas Central sulcus Primary motor cortex Primary somatosensory cortex Premotor cortex Somatic sensation Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Taste Prefrontal cortex Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Primary visual cortex Working memory for object-recall tasks Vision Visual association area Solving complex, multitask problems Auditory association area Hearing Primary auditory cortex (a) Lateral view, left cerebral hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8a

40. *Primary Motor Cortex • Allows conscious control of precise, skilled, voluntary movements • Motor homunculi: upside-down caricatures representing the motor innervation of body regions

41. Posterior Motor Anterior Motor map in precentral gyrus Toes Jaw Primary motor cortex (precentral gyrus) Tongue Swallowing Figure 12.9

42. *Premotor Cortex • Anterior to the precentral gyrus • Controls learned, repetitious, or patterned motor skills • Coordinates simultaneous or sequential actions • Involved in the planning of movements that depend on sensory feedback

43. *Broca’s Area • Anterior to the inferior region of the premotor area • Present in one hemisphere (usually the left) • A motor speech area that directs muscles of the tongue • Is active as one prepares to speak

44. *Frontal Eye Field • Anterior to the premotor cortex and superior to Broca’s area • Controls voluntary eye movements

45. Motor areas Sensory areas and related association areas Central sulcus Primary motor cortex Primary somatosensory cortex Premotor cortex Somatic sensation Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Taste Prefrontal cortex Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Primary visual cortex Working memory for object-recall tasks Vision Visual association area Solving complex, multitask problems Auditory association area Hearing Primary auditory cortex (a) Lateral view, left cerebral hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8a

46. *Primary Somatosensory Cortex • In the postcentral gyri • Receives sensory information from the skin, skeletal muscles, and joints • Capable of spatial discrimination: identification of body region being stimulated

47. Posterior Sensory Anterior Sensory map in postcentral gyrus Genitals Primary somato- sensory cortex (postcentral gyrus) Intra- abdominal Figure 12.9

48. Motor areas Sensory areas and related association areas Central sulcus Primary motor cortex Primary somatosensory cortex Premotor cortex Somatic sensation Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Taste Prefrontal cortex Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Primary visual cortex Working memory for object-recall tasks Vision Visual association area Solving complex, multitask problems Auditory association area Hearing Primary auditory cortex (a) Lateral view, left cerebral hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8a

49. Cingulate gyrus Primary motor cortex Premotor cortex Central sulcus Corpus callosum Primary somatosensory cortex Frontal eye field Parietal lobe Somatosensory association cortex Prefrontal cortex Parieto-occipital sulcus Occipital lobe Processes emotions related to personal and social interactions Visual association area Orbitofrontal cortex Olfactory bulb Primary visual cortex Olfactory tract Fornix Uncus Calcarine sulcus Temporal lobe Primary olfactory cortex Parahippocampal gyrus (b) Parasagittal view, right hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8b