Forebrain, diencephalon. Meninges of the brain. Cerebro-spinal fluid. The diencephalon The diencephalon is the region of the embryonic vertebrate neural tube that gives rise to posterior forebrain structures including the thalamus, hypothalamus, posterior portion of the pituitary gland, and pineal gland. The hypothalamus performs numerous vital functions, most of which relate directly or indirectly to the regulation of visceral activities by way of other brain regions and the autonomic nervous system. THE DIENCEPHALON EPITHALAMUS THALAMUS SUBTHALAMUS HYPOTHALAMUS Diencephalon Thalamus dorsal thalamus Hypothalamus pituitary gland
Epithalamus habenular nucleus and commissure pineal gland Subthalamus ventral thalamus subthalamic nucleus (STN) field of Forel Diencephalon Hypothalamus Command for the Thalamus
control of autonomic functions such as heart rate, blood pressure, hunger, thirst. Role in emotions and motivation (e.g., thoughts about fear get translated into arousal through hypothalamus.) Thalamus Chief relay centre for directing sensory messages Helps regulate awareness Relays commands going to the skeletal muscles from the motor cortex. Hypothalamus also controls sexual desire.Together with the pituitary systems (a structure located close to the hypothalamus, the hypothalamus helps regulate the endocrine system (I.e., hormones such as adrenaline and noradrenaline). Classification of Thalamic Nuclei
I. Lateral Nuclear Group II.Medial Nuclear Group III.Anterior Nuclear Group IV.Posterior Nuclear Group V.Metathalamic Nuclear Group VI.Intralaminar Nuclear Group VII.Thalamic Reticular Nucleus Summary of Thalamic Connectivity
I.Sensory Input general sensation special sensation taste, equilibrium, hearing, vision II.Motor Input cerebellum, basal ganglia III. Reticular Formation IV.Limbic System mammillary nucleus hippocampal formation Thalamus Functions of the thalamus I. Relay functions fromthe spinal cord, brainstem, cerebellum basal ggl. to the cortex II. Modulatory functions Influences the excitability of the cx, synchronised vs. desynchronised states (repetitive and burst firing) III. Integrative functions 1. Sensory connections (sensory relay station) 2. Motor coordination 3. Psychological functions (instinct, affection, limbic functions etc) 4. Autonom function control 5. Cortical activation Clinical Syndromes of the Thalamus
Posterolateral thalamic syndromes sensory disorders Thalamic (Dejerine-Roussy) syndrome ----- VP nucleus - pain Medial thalamic syndromes disorders of consciousness thalamic neglect, thalamic amnesia, akinetic mutism Anterolateral thalamic syndromes motor disorders paresis, ataxia, motor incoordination, dysphagia Visual (Optic) Pathway
Modality:Vision Receptor: Photoreceptor Cell of Retina Cranial Nerve: II (Optic nerve) 1stNeuron: Bipolar Cell 2nd Neuron: Ganglion Cell optic nerve optic chiasm optic tract 3rdNeuron: Lateral Geniculate Nucleus optic radiation Termination: Visual Areas (V I, V II) Brodmann area 17 (V I), 18, 19 (V II) Visual Pathway 1. Optic nerve 2. Optic chiasm 3. Optic tract
4. Lateral geniculate body 5. Optic radiation 6. Visual cortex Visual (Optic) Pathway Clinical Features of Visual Pathway Lesion
1. optic nerve 2. optic chiasm 3. optic tract 4. 5. optic radiation A. unilateral blindness B. bitemporal hemianopsia C. left homonymous hemianopsia D. left inferior homony- mous quadranopsia E. left superior homony- Signs of Visual Pathway Lesion
Optic nerve - ipsilateral blindness Optic chiasm - bitemporal hemianopsia Optic tract - contralateral homonymous hemianopsia Optic radiation - contralateral homonymous quadranopsia - intact light reflex Visual Cortex - macular sparing left inferior optic radiation lesion right superior quadranopsia
Visual Field Defect left inferior optic radiation lesion right superior quadranopsia Hypothalamus Limbic System Diencephalon 3rd ventricle Surrounded by cerebrum Thalamus
Intermediate mass Pineal body Hypothalamus Epithalamus Mammillary body Pituitary gland epithalamus Located at dorsal part of the diencephalons, it includes the pinieal body. It secretes melatonin which signals the nighttime stage of the sleep-wake cycle. pineal body internal secretion gland habenular triangle habenular nucleus habenular commissure thalamic medullary stria posterior commissure subthalamus subthalamic nucleus participate in the function of extracorticospinal tract