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Neuroanatomy (PPT)

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    Neuroanatomy (PPT) Neuroanatomy (PPT) Presentation Transcript

    • Neuroanatomy
      • Components of this lecture:
      • Neurons & Glial Cells
      • Neurotransmitters & Psychopharmacology
      • 3. Functional Organization
    • Neurons, Glial Cells & Neurochemistry
    •  
      • Nervous System
      • Central Nervous Peripheral Nervous
      • System System
      • Brain Spinal Cord
    •  
    •  
    •  
    •  
      • 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**
    •  
      • 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 it’s Oligodendrocytes
      • B. In PNS it’s Schwann cells
      • 9. Nodes of Ranvier – spaces between myelinating cells along the axon
    •  
      • 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 NT’s – 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
    •  
      • 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
    •  
      • 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.
    •  
      • 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
    •  
      • 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
    •  
      • 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)
    •  
    • 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
      • 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
      • 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
    •  
    •  
    • Neurotransmitters and Psychopharmacology
    • 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)
    •  
    • 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
    • Not in Book
    • Monoamine NTs
      • Catecholamines
      • Dopamine
      • Norepinephrine
      • Epinephrine
      • Indolamines
      • Serotonin
      These NTs use both reuptake and enzymes (e.g. MAO) to terminate action
    • Not in Book
    • Acetylcholine
      • Two Receptors:
      • nicotinic receptor – uses ionotropic receptor
      • muscarinic receptor – uses metabotropic receptor
      • Degradation is through enzyme only:
      • acetylcholinesterase inhibitor
    • Neuropeptides
      • Long chains of amino acids
      • Numerous categories (see appendix VII)
      • One category is the ENDORPHINS
        • Enkephalins
        • Beta-endorphin
    • Soluble Gases
      • Nitric Oxide – involved in learning and memory (more on this later)
      • Neurotransmitters have 7 actions
      • Synthesized
      • Stored
      • Enzymatically destroyed if not stored
      • Exocytosis
      • Termination of release via binding with autorecptors
      • Binding of NT to receptors
      • NT is inactivated
      • Drugs are developed that address these actions as an AGONIST (mimic the NT ) or ANTAGONIST (block the NT)
    •  
    •  
    • Drugs that Block Reuptake
      • SSRIs (Selective Serotonin Reuptake Inhibitors)
      • Cocaine
      • - highly addictive, both physiologically and
      • psychologically
      • (see interactive CD ROM)
    • 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
    • Functional Organization
    •  
    •  
      • 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
      • c. Midbrain (Mesencephalon)
      • Superior Colliculus
      • Inferior Colliculus
      • Central Gray (periaqueductal gray)
      • Substantia Nigra
      • Ventral Tegmentum
      • Schizophrenia & Parkinson’s
      • disease
      • 3. Cerebellum (Metencephalon)
      • smooth coordination of practiced
      • movements
      • integrates sensory & motor
      • cognitive functions (with frontal lobe)
    •  
    •  
      • 4. Hypothalamus (Diencephalon)
      • 22 sets of nuclei
      • homeostasis, biological rhythms
      • drives
      • Thalamus (Diencephalon)
      • Relay Station
      • Topographic arrangement with cortex
    •  
      • Basal Ganglia (Telencephalon)
      • Striatum (Caudate & Putamen)
      • Globus Pallidus
      • “ Substantia Nigra”
    •  
      • Limbic System (Telencephalon)
      • Hippocampus
      • Amygdala
      • Nucleus Accumbens
      • “ Prefrontal Cortex, Cingulate Cortex
      • & Hypothalamus”
    •  
      • Cerebral Cortex (Telencephalon)
      • - 6 layered structure
      • - Four lobes: Frontal
      • Parietal
      • Temporal
      • Occipital
      • - sulcus (i) & fissure (s) (lateral, central)
      • - gyrus (i)
    •  
    •  
    •  
    •  
    •  
      • Features of the Cerebral Cortex
      • note: more on this later
      • Somatosensory Cortex (homunculus)
      • Motor Cortex (homunculus)
      • Visual Cortex
      • Auditory Cortex
    •  
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    •