Neuroanatomy (PPT)

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  • 1.Neuroanatomy Components of this lecture: 1. Neurons & Glial Cells 2. Neurotransmitters & Psychopharmacology 3. Functional Organization

2. Neurons, Glial Cells & Neurochemistry 3. Nervous System Central Nervous Peripheral Nervous System System Brain Spinal Cord 4. ii. Structure of neurons 1. Cell body - contains nucleus 2. Nucleus contains DNA 3. Dendrites cell body (receives information) 4. Receptors receive information using a chemical signal. 5. Axons sends information 6. Axon hillock junction between cell body and axon **Lowest threshold for action potential** 5. 7. Terminal (buttons or boutons) swelling on the surface (see slide) - Inside buttons are synaptic vesicles, packaging of neurotransmitter 8. Myelin sheath insulation for axons - comprised of glial cells (see slide) A. In CNS its Oligodendrocytes B. In PNS its Schwann cells 9. Nodes of Ranvier spaces between myelinating cells along the axon 6. 11. Cell membranes cover all cells - Two layers of fat molecules - Tucked inside are channels made up of protein molecules (see slide) - Protein molecules a. Serve as receptors for NTs next slide b. Serve as channels for ions (Ca++, Na+, K+, and Cl-) - next slide c. Location along neuron differs in the type of channel protein d. Membranes are dynamic and alive 7. Two Types of Receptors (more again soon) 1. Ionotropic Receptors fast acting ion channel/receptor complex same only a few Neurotransmitter activate them 2. Metabotropic Receptors slower acting ion channel and receptor are different most Neurotransmitters act on them 8. 12. Cytoskeletons (Neurofilaments) inside cell provide structural support - Microfilaments - Microtubules Fairly large, play important role in transport a. Send vesicles to the buttons where they are filled with NT. Acts like a conveyor belt. 9. 13. Organelles within the cell a. Mitochondria Convert glucose into energy we can use: ATP (energy source for cell) b. Endoplasmic Reticulum Synthesis of fat molecules and protein molecules 10. 3. Synapse - the junction between cells (neurons). - synaptic cleft - space between cells a. synapse is made of 3 parts: 1. Presynaptic cell sending side of synapse 2. Postsynaptic receiving side of neuron 3. Synaptic Cleft b. Purpose: promote chemical-electrical signal c. Types of Synapses: axodendritic, axosomatic axoaxonic, dendrodendritic 11. 4. Chemical Milieu of Cellular Spaces when the neuron is at rest Intracellular space & extra cellular space (inside of cell membrane & outside of cell membrane) a. Cl- = Chloride (more outside than inside) b. Na+ = Sodium (more outside than inside) c. A- = Anions (more inside than outside) d. K+ = Potassium (more inside than outside) 12. Forces that maintain the chemical balance i. Concentration gradient lesser concentration ii. Electrostatic pressure attraction toward opposite charges iii. Na & K pumps Throws out sodium and takes in potassium to keep cell balanced 13. 5. Four states of neuronal electrical charge (potentials) a. Resting Membrane Potential -70 mV (transient state, constantly affected by forces that increase or decrease charge) b. Excitatory Post-Synaptic Potential or EPSP Charge across the membrane becomes less negative - depolarization of the neuron (i.e. decrease negative charge from 70mV to 65mV) - Leads to an action potential 14. c. Inhibitory Postsynaptic Potential or IPSP Charge across the membrane becomes more negative - hyperpolarization of neurons (i.e. increase in negative charge from 70mV to 90 mV) - Reduces the likelihood of an action potential d. Action Potential or AP Charge across the membrane becomes less negative - depolarization of neurons (i.e. decrease in negative charge from 65mV to +55 mV) - charge for the AP begins at Axon Hillock - significant shift in ions 15. Neurotransmitters and Psychopharmacology 16. Neurotransmitters 80 plus chemical substances that provide communication between cells. Some of these are actually NTs and others are neuromodulators (i.e. they augment the activity of the NT) 17. Amino Acid NTs Glutamate Uses both ionotropic and metabotropic receptors NT of the cerebral cortex Excitatory effect GABA Uses ionotropic receptors Most prevalent NT in the CNS Inhibitory effect Seizures disorders are the caused by overactive Glu and/or under active GABA 18. Not in Book 19. Monoamine NTs Catecholamines Dopamine Norepinephrine Epinephrine Indolamines Serotonin These NTs use both reuptake and enzymes (e.g. MAO) to terminate action 20. Not in Book 21. Acetylcholine Two Receptors: nicotinic receptor uses ionotropic receptor muscarinic receptor uses metabotropic receptor Degradation is through enzyme only: acetylcholinesterase inhibitor 22. Neuropeptides Long chains of amino acids Numerous categories (see appendix VII) One category is the ENDORPHINS Enkephalins Beta-endorphin 23. Soluble Gases Nitric Oxide involved in learning and memory (more on this later) 24. Neurotransmitters have 7 actions 1. Synthesized 2. Stored 3. Enzymatically destroyed if not stored 4. Exocytosis 5. Termination of release via binding with autorecptors 6. Binding of NT to receptors 7. NT is inactivated Drugs are developed that address these actions as an AGONIST (mimic the NT ) or ANTAGONIST (block the NT) 25. Drugs that Block Reuptake SSRIs (Selective Serotonin Reuptake Inhibitors) Cocaine - highly addictive, both physiologically and psychologically (see interactive CD ROM) 26. Tolerance & Dependence Tolerance state of decreased sensitivity to the drug as a result of exposure to it. functional tolerance (number of binding sites is reduced also called down regulation of receptors) note: opposite phenomenon: up-regulation Physical Dependence caused by withdrawal symptoms (not the reason that people continue to take most drugs) Psycholological Dependence (now called positive- incentive theory of addiction) e.g., intracranial self-stimulation studies & dopamine 27. Functional Organization 28. 2. Brainstem medulla, pons & midbrain a. Medulla (Myelencephalon) center for vital functions decussation of the pyramids crossing over for most nerve fibers b. Pons (Metencephalon) numerous cranial nerves reticular formation raphe nucleus and sleep 29. c. Midbrain (Mesencephalon) Superior Colliculus Inferior Colliculus Central Gray (periaqueductal gray) Substantia Nigra Ventral Tegmentum Schizophrenia & Parkinsons disease 30. 3. Cerebellum (Metencephalon) smooth coordination of practiced movements integrates sensory & motor cognitive functions (with frontal lobe) 31. 4. Hypothalamus (Diencephalon) 22 sets of nuclei homeostasis, biological rhythms drives 5. Thalamus (Diencephalon) Relay Station Topographic arrangement with cortex 32. 6. Basal Ganglia (Telencephalon) Striatum (Caudate & Putamen) Globus Pallidus Substantia Nigra 33. 7. Limbic System (Telencephalon) Hippocampus Amygdala Nucleus Accumbens Prefrontal Cortex, Cingulate Cortex & Hypothalamus 34. 8. Cerebral Cortex (Telencephalon) - 6 layered structure - Four lobes: Frontal Parietal Temporal Occipital - sulcus (i) & fissure (s) (lateral, central) - gyrus (i) 35. Features of the Cerebral Cortex note: more on this later Somatosensory Cortex (homunculus) Motor Cortex (homunculus) Visual Cortex Auditory Cortex