MIT 9.14 Class 9a. Autonomic nervous system structures. A sketch of the central nervous system and its origins

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1 A sketch of the central nervous system and its origins G. E. Schneider 2009 Part 5: Differentiation of the brain vesicles MIT 9.14 Class 9a Autonomic nervous system structures

2 Autonomic nervous system Overview of functions Schematic overview Formation of sympathetic ganglia from the neural crest (REVIEW) Sympathetic innervation pattern (thoracicolumbar system) Cf. parasympathetic innervation (cranio-sacral system); dual innervation of smooth muscles and glands. Chemical mediation at synapses: discovery by Otto Loewi in 1921.

3 Closure of neural tube; formation of sympathetic ganglia Neural plate Ectoderm Notochord Neural groove Neural tube and neural crest Roof plate Alar plate Basal plate Floor plate

4 Autonomic nervous system Overview of functions Schematic overview Formation of sympathetic ganglia from the neural crest Sympathetic innervation pattern (thoracicolumbar system) Cf. parasympathetic innervation (cranio-sacral system); dual innervation of smooth muscles and glands. Chemical mediation at synapses: discovery by Otto Loewi in 1921.

5 INTERNAL STRUCTURE OF THE SPINAL CORD Dorsal Root Fibers Nuc cornucommissuralis Posterior Fasc. Gracilis Substantia Gelatinosa Nuc. Posteromarginalis Internal Structure Spinal Cord Segment C1 Internal structure of Ventral Root Fibers Nuc. Motorii Medialis Zone of Lissauer Lat. Corticospinal Tr. Nuc. Proprius Cornu Dorsalis Nuc. Reticularis Nuc. Dorsalis (of Clarke) Ant. Spinocerebellar Tr. Lat. Spinothalamic Tr. Nuc. Motorii Lateralis Fasc. Proprius Ant. Spinothalamic Tr. Vestibulospinal Tr. Segment C5 Segment C8 Segment T2 spinal cord: II III IV I Segment T10 Note the V VI Segment L1 lateral horn X M VIII IX VII IX IX IX Segment L4 Segment S4 Figure by MIT OpenCourseWare.

6 Sympathetic nervous system axons, schematic section of spinal cord, thoracic level xxxxx xxxxx xx Descending reticulospinal fibers Paravertebral ganglion Prevertebral ganglion, e.g., celiac Dorsal root ganglion Spinal nerve Smooth muscle: Glands; intestinal tract; blood vessels, erector pili (hairs); sweat glands. Cardiac muscle To striated muscles

7 Sympathetic Innervation (P. Brodal) Figure by MIT OpenCourseWare.

8 Autonomic nervous system Overview of functions Schematic overview Formation of sympathetic ganglia from the neural crest Sympathetic innervation pattern (thoracicolumbar system) Parasympathetic innervation (cranio-sacral system); dual innervation of smooth muscles and glands. Chemical mediation at synapses: discovery by Otto Loewi in 1921.

9 Vagus nerve (10 th cranial nerve)

10 MESENCEPHALON Visceral Efferent Oculomotor Nucleus (Edinger-Westphal) Ciliary Ganglion Oculomotor Nerve MEDULLA OBLONGATA MEDULLA OBLONGATA Superior Salivary Nucleus Maxillary Nerve Intermediate Nerve Greater Petrosal Nerve Facial Nerve Chorda Dorsal Motor Tympani Vagus Nucleus Mandibular Nerve Glossopha- Ryngeal Nerve Vagus Nerve Tympanic Nerve Pterygopalatine Ganglion Lingual Nerve Submandibular Ganglion Otic Ganglion Pupillary Sphincter Muscle Ciliary Muscle Lacrimal Gland Nasal & Palatal Gland Submandibular Gland Sublingual Gland Parotid Gland Auriculo-Temporal Nerve Pharynx Esophagus Trachea, Bronchi Lungs Parasympathetic Innervation (P. Brodal) MEDULLA SPINALIS (S 3 - S 4 ) Ganglia & Plexuses Pelvic Nerve Sympathetic Trunk Heart Stomach Small Intestine Large Intestine Liver, Pancreas Gallbladder Large Intestine (Lower) Rectum Bladder Genitals Figure by MIT OpenCourseWare.

11 Autonomic nervous system Overview of functions Schematic overview Formation of sympathetic ganglia from the neural crest Sympathetic innervation pattern (thoracicolumbar system) Parasympathetic innervation (cranio-sacral system); dual innervation of smooth muscles and glands. Chemical mediation at synapses: discovered by Otto Loewi in 1921 (REVIEW)

12 Autonomic pathways with neurotransmitters showing accelerator & decelerator nerves of the heart

13 An advance in PNS anatomy in the late part of the 20 th century: The enteric nervous system The little brain in the gut: A semi-autonomous network that may contain as many neurons as the entire spinal cord. In the wall of the intestine, this network contains multiple plexi: Myenteric plexus (the outer plexus) Submucous plexus (the middle plexus) Villous plexus (inner plexus) Periglandular plexus (inner plexus) Innervation by vagus nerve Cf. Cardiac Ganglion: Does the heart have a brain? Various neurotransmitters are used in this system.

14 Levels of autonomic control The enteric nervous system shows autonomy at the lowest level, in control of the alimentary tract. Within the CNS, there are lower levels of control of the internal environment capable of some autonomy. Temperature regulation is a good example. For this function, each higher level adds more refinement.

15 Levels of control in the ANS: the temperature regulation systems Temperature is regulated by mechanisms operating at all levels: spinal, hindbrain, midbrain, hypothalamus of the tweenbrain. Each higher level adds refinements: for endothermic animals, this means speed and a narrower range of target temperatures. See reviews by Evelyn Satinoff. For other functions, there is probably a similar hierarchy.

16 A sketch of the central nervous system and its origins G. E. Schneider 2009 Part 5: Differentiation of the brain vesicles MIT 9.14 Class 9b Differentiation of the brain vesicles: Introduction to hindbrain and segmentation

17 The encephalon* (brain) Hindbrain (rhombencephalon) Midbrain (mesencephalon) Forebrain (prosencephalon) Tweenbrain (diencephalon) Endbrain (telencephalon) * In the head

18 The embryonic neural tube above the spinal cord What are the "flexures" in the neural tube? (See, e.g., Nauta & Feirtag, pp )

19 The flexures of the developing neural tube s rostral end, human (From Nauta & Feirtag) Figure by MIT OpenCourseWare.

20 Origin of the term rhombencephalon What happens to the roof plate where the pontine flexure (bend) forms? (See, e.g., Nauta & Feirtag, p. 162)

21 a. Spinal cord a. Spinal a. Spinal cord cord b. Hindbrain b. Hindbrain (rhombencephalon) b. Hindbrain (rhombencephalon (rhombencephalon c. Midbrain c. Midbrain (mesencephalon) c. Midbrain (mesencephalon) (mesencephalon) d. Tweenbrain d. Tweenbrain (diencephalon) d. Tweenbrain (diencephalon) (diencephalon) e. Endbrain e. Endbrain (telencephalon) e. Endbrain (telencephalon) (telencephalon) Forebrain Basic subdivisions, embryonic neural tube: Where is the rhombus? What is it? Reminder: Students should understand and know this figure! (prosencephalon)

22 Terminology: What is the obex? Find it in the previous picture.

23 The hindbrain (rhombencephalon) topics Basic structural organization compared with spinal cord Basic functions Cell groupings; origins Sensory channels and the trigeminal nerve The "distortions" in the basic organization

24 Basic organization: "a glamorized spinal cord" Alar and basal plates; widened roof plate (with widened ventricle the 4 th ventricle) No more law of roots; some cranial nerves are "mixed nerves" containing both sensory and motor components.

25 Cell groupings Secondary sensory nuclei (cell groups) in the alar plate Motor nuclei (groups of motor neurons) in the basal plate The arrangement can be understood as a simple modification of spinal cord organization.

26 Embyonic spinal cord & hindbrain compared Embryonic spinal cord (in cross section) Ventricular zone Intermediate zone Marginal zone Alar plate Basal plate Embryonic hindbrain Sulcus limitans Secondary sensory cell groups in intermediate zone of alar plate Alar plate Motor neuron cell groups in intermediate zone of basal plate Basal plate

27 Hindbrain functions Routine maintenance: the support services area of the CNS, for centralized control of spinal functions Vital functions (control of breathing, blood pressure & heart rate, & other visceral regulation) Motor coordination (cerebellum, vestibular system) Fixed Action Pattern generators: swallowing, vomiting, eyeblink, grooming, smiling, frowning, righting, etc. Widespread modulation of brain activity: sleep & waking; arousal effects [See following illustrations] Role in mammalian higher functions: movement control for functions of more rostral brain systems for speech (tongue, lip, breath control) for emotional displays, especially in facial expressions for eye movements

28 Neurons of the reticular formation Isodendritic core of the brainstem (Ramon-Moliner & Nauta) Neuropil segments Axons with very wide distributions Contrast: isodendritic & idiodendritic

29 Dendritic orientation of reticular formation neurons in hindbrain, forming a series of neuropil segments: Collaterals of pyramidal tract axons have similar distributions. For contrast, cells of the hypoglossal nucleus are also shown Figure removed due to copyright restrictions. Golgi stain, parasagittal section of hindbrain, young rat. From Scheibel & Scheibel, 1958

30 Neuron of hindbrain reticular formation: Axon has ascending and descending branches, each with widespread distribution of terminations Figure removed due to copyright restrictions. 2-day old rat, Rapid Golgi stain, from Scheibel & Scheibel, 1958

31 Notes on hindbrain origins: definitions Segmentation above the segments of the spinal cord: The somitomeres & branchial arches in the mesoderm, and the rhombomeres of the CNS See Nauta & Feirtag, ch.11, p. 170, on the branchial motor column -- in addition to the somatic and visceral motor columns. Sulcus limitans Visceral motor column Somatic motor column Branchial motor column Reticular formation Basal plate Alar plate

32 Three segmented systems, 3-day chick embryo: somites, branchial arches, rhombomeres s10 s2 r1 Rhombomeres r2 of Hindbrain r3 r4 r5 r6 r7 r8 Somites b1 b2 b3 b4 Limb Bud s20 MidBrain Branchial Arches Branchial arches of the mesoderm, innervated by the Trigeminal Motor & the Facial Nucleus and by Nucleus Ambiguus. (Functions of Nuc. Ambiguus: swallowing and vocalization) The branchial arches in humans form jaws, the auditory ossicles, the hyoid, and the pharyngeal skeleton including thyroid cartilage. Wolpert, 2002 Fig Figure by MIT OpenCourseWare.

33 Hox gene expression in the mouse embryo after neurulation The mesoderm below the head region becomes segmented: Somites, 2-day chick embryo Figure removed due to copyright restrictions. Somites, 2-day chick embryo Please see: Wolpert, Lewis, et al. Principles of Development. 2nd ed. Oxford, UK: Oxford University Press, 2002, p. 22. ISBN: (Photo from Wolpert, 2002, p. 22)

34 Genes underlying segmentation topics Ancient origins of segmentation along the A-P axis, with corresponding nervous system differentiation The homeobox genes: What are they? Examples of gene expression patterns

35 Homeobox genes in Drosophila, and 13 paralogous groups in 4 chromosomes of mouse Figure by MIT OpenCourseWare.

36 Hox gene expression along the antero-posterior axis of the mouse mesoderm Figure removed due to copyright restrictions. Please see: Figure 4.11 from Wolpert, Lewis, et al. Principles of Development. 2nd ed. Oxford, UK: Oxford University Press, ISBN: E 9.5 mouse embryos, immunostained using antibodies specific For the protein products of the indicated Hox genes. (Wolpert, 2002, fig. 4.11)

37 Hox gene expression along the antero-posterior axis of the mouse mesoderm Vertebral regions Posterior Caudal Sacral Lumbar Thoracic Anterior Cervical Hox genes d3 d4 d8 d9 d10 d11 d12 d13 c5 c6 c8 c9 b1 b4 b5 b9 b7 a1 a4 a5 a6 a7 a10 a11 Anterior margins of expression Figure by MIT OpenCourseWare. (Wolpert, 2002, fig. 4.12)

38 Figure removed due to copyright restrictions. Allman, John Morgan. "Scanning Electron Microscope Photo." In Evolving Brains. New York, NY: Scientific American Library: Distributed by W.H. Freeman and Co., ISBN: Rhombomeres: the 8 segments of the rhombencephalon (Scanning e.m. photo from Allman, 2000)

39 r7 r6 r5 r4 r3 r2 r1 r6 r5 r4 r3 r2 Gene Expression Kreisler Krox-20 Sek-1 Sek-2 Sek-3 Sek-4 Ebk Elk-L Elf-2 Elk-L3 Hoxa-1 Hoxb-1 Hoxa-2 Hoxb-2 Hoxa-3 Hoxb-3 Hoxd-3 Hoxd-4 Hoxb-4 Hoxa-4 and Rhombomeres (Lumsden & Krumlauf 96) Fgf-3 Follistatin CRABP-1 RAR α RAR β Figure by MIT OpenCourseWare.

40 The hindbrain neuromeres (= rhombomeres): A) Expression of transcription factor genes; B) Fate of embryonic precursor cells injected before and after rhombomere formation r1 r2 r3 r4 r5 r6 r7 hox d4 hox b2 hox b3 hox b1 krox 20 A) Gene Expression boundaries B) Lineage restriction boundaries Figure by MIT OpenCourseWare. From Striedter (2005), p. 79

41 MIT OpenCourseWare Brain Structure and Its Origins Spring 2009 For information about citing these materials or our Terms of Use, visit:

Autonomic pathways: a selective schematic view

Autonomic pathways: a selective schematic view Thoraco -lumbar Courtesy of MIT Press. Used with permission. Schneider, G. E. Brain Structure and its Origins: In the Development and in Evolution of Behavior