Introduction-to-Neural-Sciences.pdf

NEURAL SCIENCESpart I Introduction Functional Neuroanatomy Neural Development and Neurochemistry ABDULGAFFAR. ABDULHALIM. ABDULHAMID ABDULMANAN. ABEDIN. ACA. ACOB. ADOMA AGAKHAN. AGAO-AGAO. ALAVE ...

NEURAL SCIENCESpart I Introduction Functional Neuroanatomy Neural Development and Neurochemistry ABDULGAFFAR. ABDULHALIM. ABDULHAMID ABDULMANAN. ABEDIN. ACA. ACOB. ADOMA AGAKHAN. AGAO-AGAO. ALAVE  PSYCHOSOCIAL EMOTIONS 1990: decade of the brain ENVIRONMENT feel GENETICS DSM-5 COGNITIVE BEHAVIORS ICD think do no biological markers psychiatric in psychiatry ECT and research symptoms and study > objective tests limbic circuit by of the Chronobiology brain Papez ENDOCRINE IMMUNE psychoneuroendocrinology psychoneuroimmunology brain neural functions science in different researches conditions  PSYCHOPHARMACOLOGY & ENDOPHENOTYPES CLASSIFICATION OF PSYCHOPHARMACOLOGICAL TREATMENTS 1. Antipsychotic ENDOPHENOTYPE 2. Antidepressant set of objective characteristics not 3. Antianxiety visible to the unaided eye 4. Mood-stabilizer genes and the observable symptoms focuses on specific traits that are easier REGARDED AS INACCURATE BECAUSE: to study 1. drugs of one class are used to treat heritable disorders assigned to another class not symptoms or diagnostic markers 2. drugs are used to treat disorders not biological previously treatable by drugs 3. other drugs can effectively treat a variety research and treatment development of disorders and do not fit into the aforementioned classification  Psychiatry and human genome About 40-70% of cognitive traits and personality aspects are hereditary. Nature and Nurture in CNS - interactions between genetic and environmental factors shape brain development and function, illustrating biopsychosocial model of disease.  Mental disorders reflect abnormalities in neuro anatomical circuits and synaptic regulation. the downstream effects of abnormal genes are modification in discrete attributes such as axonal projections, synaptic integrity, and specific steps in intraneuronal molecular signaling  Functional Neuroanatomy Brain Organization Somatosensory System Soma, Dendrites, and Axon Intricate array of parallel point-to- Astrocytes, Oligodendrocytes, point connections from body Schwann Cells, and Microglia surface to brain cytoarchitecture Light touch, pressure, pain, temperature, vibration, and proprioception Sensory System Spatial relationships at all levels relevant stimuli Receptor nerve terminals internal image Thalamus' role hierarchical organization and Reciprocal connections neural processing Fine-tuning by activity-dependent mechanisms Development of the Somatosensory System Somatotopic organization Paradigm: Mouse Whiskers Homunculus...W.Penfield Cortical Mapping and Plasticity Visual System highly specialized brain cells cellular localization P. visual cortex and S. visual cortex I.T. lobe “What?” / P.P. lobe “Where?” hemispheric asymmetry Development of Visual System early postnatal period - Binocular visual input Ocular dominance columns Auditory System Sounds > Eardrum > Ossicles > Cochlea. Vibrations of the endolymph move the cilia The hair cells respond in a tonotopic manner within the cochlea. Dichotic listening tests demonstrate that most input from one ear activates the contralateral auditory cortex. Development of Auditory studies suggest that neuronal circuits required for auditory processing can be recruited Early intervention can help improve outcomes for children with speech and hearing delays.  OLFACTION TASTE AUTONOMIC MOTOR SYSTEM Autonomic system: (1) sensory component and (2) motor component. The autonomic motor system is divided into two branches: the sympathetic and the parasympathetic. Odorants enter the nose, are solubilized in the nasal mucus, and bind to odorant Soluble chemical cues in the Parasympathetic system slows the receptors displayed on the surface of the heart rate and begins the process sensory neurons of the olfactory epithelium. mouth bind to receptors in the of digestion. It generates neural impulses, which travel tongue and stimulate the along the axons of the sensory nerves gustatory nerves, which project Sympathetic system mediates the through the cribriform plate to the olfactory to the nucleus solitarius in the fight or flight response. bulb. brainstem.  MOTOR SYSTEMS - Body muscle movements are controlled by the lower motor neurons, which extend axons-some as long as 1 meter-to the muscle fibers. CEREBELLUM - The cerebellum consists of a simple six-cell pattern of circuitry that is replicated roughly 10 million times. Simultaneous recordings of the cerebral cortex and the cerebellum have shown that the cerebellum is activated several milliseconds before a planned movement.  Localization of Brain Functions Brodmann's Areas: 47 cytoarchitectonic regions Hemispheric lateralization Language Localization and Processing Three Processing Blocks: Brainstem & Thalamus: Left Hemisphere: Core for language functions. - Arousal and attention. Posterior Cortex: - Perception and language. left inferior frontal lobe, Frontal Cortex: Speech Production. - Planning and execution Right hemisphere handles emotional left superior temporal lobe, Language comprehension. tone of speech.  Arousal, Attention, EMOTION, and Memory Arousal : managed by the Ascending Reticular Activating System (ARAS); synchronizes cortical oscillations, crucial for wakefulness. Attention : right frontal lobe; ADHD linked to hypometabolism in frontal lobes. Emotion : left hemisphere: analytical with limited emotional range right hemisphere: dominant for affect and socialization. Memory: Hippocampus: Critical for memory formation. Amygdala: Adds emotional significance to memories, enhancing retention. * 3 periods of memory: Frontal lobes: influence mood > Memory Immediate left: elevating mood > Recent right: depression > Remote *Temporal Lobe Epilepsy (TLE): impacts behavior left side: philosophical themes right side: emotionality and aggression  LIMBIC SYSTEM FUNCTION PAPEZ CIRCUIT (FMATCH) fornix Limbic system mammillary bodies James Papez, 1937 anterior thalamus originally just the Papez circuit cingulate gyrus now includes BONAS hippocampus basal forebrain orbitofrontal cortex nucleus accumbens amygdala septum amygdala mediates learned fear response WHEN DESTROYED, lose ability to distinguish fear & anger in others; might still recognize happiness, sadness, disgust LIMBIC SYSTEM & SCHIZOPHRENIA In schizophrenia... gray matter weight is reduced 4 A’s of in MRI, reduced volume of SCHIZOPHRENIA hippocampus affect amygdala associations parahippocampal gyrus ambivalence in voluntary action, autism decreased activation of frontal lobe increased activation of temporal lobe  FRONTAL NEURONAL LOBE DEVELOPMENT FUNCTION Embryology 4 sub-divisions PNS arises from neural motor strip crest supplemental CNS arises from neural motor area tube Broca’s area Both arise from prefrontal cortex ectoderm Frontal lobe Neurons develop inside syndrome neural tube caused by At peak, 250,000 bilateral lesions neurons/minute leads to change can be incorrectly in personality & placed → heterotopia thinking THE NEURAL PLATE AND NEURULATION Nervous system of human embryo appears between 2 1/2 and 4 weeks of gestation. First step in neurulation is formation of neural plate. Edges of neural plate fold and rise meeting in midline to form neural tube. Neural tube = CNS Neural crest = PNS REGIONAL DIFFERENTIATION OF THE EMBRYONIC NERVOUS SYSTEM Neural tube dimensions: Longitudinal - rostrocaudal Circumferential - two axes: dorsoventral and medial to lateral Radial - innermost cell layer to outermost VENTRICULAR PROLIFERATIVE ZONE (VZ) - crucial during early brain development. SUBVENTRICULAR PROLIFERATIVE ZONE (SVZ) - active during later stages of brain development and in some areas of the adult brain. RADIAL AND TANGENTIAL PATTERNS OF NEUROGENESIS AND MIGRATION Radial migration - excitatory pyramidal projection neurons migrate from the ventricular zone to the cortical plate in the developing brain. Tangential migration - interneurons originate from distinct proliferative zones in the developing brain.  SPECIFIC INDUCTIVE SIGNALS AND PATTERNING GENES IN DEVELOPMENT Neural Induction and Inhibition BMP (Bone Morphogenetic Proteins) promote skin cell formation. Chordin, Noggin, Follistatin, secreted by Hensen’s node block BMP. This allows etodermal cells to differentiate into neural cells. Spinal Cord Patterning Shh ( Sonic Hedgehog) from notochord and floor plate induces motoneurons and interneurons in the ventral spinal cord. BMP from the roof plate induces sensory neurons in the dorsal spinal cord. Cerebral Cortex Hippocampus Signaling Centers: FGF8, Roof plate, Signaling Centers: BMP, Wnt, Cortical Hem FGF Patterning Genes: Wnt3a, Lef1- essential for hippocampal development. Deletion causes severe defects Lhx5, Lhx2- affect organization and proliferation. Basal Ganglia contributes to GABAergic interneurons. Genetic Factors: Nkx2.1, Gsh2, Pax6 - regulate migration and differentation of interneurons.  miRNAs: New Mechanism of Regulating Gene Expression miRNAs - 21 to 23 nucleotide long single stranded RNA molecules. 475 miRNAs identified in humans e.g. miR-133B - inhibit apoptosis (degeneration) of dopaminergic neurons. Reduced miR-133B is seen in patients with Parkinson’s Processing and function of micro RNA Disease  Extracellular Factors in regulating Neurodevelopment Stimulate or inhibit proliferation of VZ precursors. Mitogenic - re-entry of cells to cell bFGF 30% increase cerebellar proliferation and and cycle hippocampus Trophic - enhance proliferation by survival of mitotic cells Timing of signals activity is important PACAP inhibited proliferation of cortical precursor by 26% Early Development - more nerve cells Late Development - glial cells  Neural Cell Migration Away from proliferative zones: Radial or Tangential < 25 syndromes with disturbed migration Reelin - guide neurons to proper positions. Extensive lissencepahlies Smooth Brain Disorder Neuregulins - glial protein; neuronal-glial migratory. Schizophrenia  Differentiation and neuronal process Neurodevelopmental outgrowth basis of disease Differentiation Critical Periods Genetic Factors Environmental Influences Process Outgrowth Neuronal Migration Defects Synaptic Development and Myelination Plasticity Neurodevelopmental Autism Spectrum Disorder Schizophrenia disorder (ASD) late adolescence or early Onset adulthood early childhood A ffect flattening ssociation looseness Avoids eye contact Interest in routines Symptoms mbivalence Unusual behaviors Speech delays utism Trouble with social skills Meltdowns Neurodevelopmental genetic vulnerability early disruptions in brain development Basis + environmental stressors Neurobiological Dopamine Hypothesis Synaptic dysfunction factors Structural abnormalities Brain overgrowth (+) strong genetic Genetic Influence component (+) strong genetic component