Student 2 Stx and Fx of the NS SP25 PDF

Module 1: Foundations Principles of Pharmacology Structure and Function of the Nervous System Chemical Signaling of Neurotransmitters Structure and Function of the Nervous System A. Organization of the Nervous System B. Cells of the Nervous System C. Electric Transmission within a Neuron A. Organ...

Module 1: Foundations Principles of Pharmacology Structure and Function of the Nervous System Chemical Signaling of Neurotransmitters Structure and Function of the Nervous System A. Organization of the Nervous System B. Cells of the Nervous System C. Electric Transmission within a Neuron A. Organization of the Nervous 1. CNS and PNS 2. Development of the NS System 3. Divisions of the NS Organization of the Nervous System Central nervous system (CNS) Peripheral nervous system (PNS) Peripheral Nervous System Autonomic NS Controls organs and glands Sympathetic division Parasympathetic division A. Organization of the Nervous 1. CNS and PNS 2. Development of the NS System 3. Divisions of the NS Development of the Nervous System A. Organization of the Nervous 1. CNS and PNS 2. Development of the NS System 3. Divisions of the NS Divisions of the CNS Limbic System- 3D Brain Hippocampus Memory Amygdala Fear and reward Hypothalamus Hormones and sleep Basal Ganglia Motivation and voluntary motion Cingulate Gyrus Connectivity to the cerebral cortex  Limbic System Ventral tegmental area (VTA) Midbrain structure Regulates reward, learning, memory Releases dopamine (DA) and Glutamate in the Limbic System and Cortical area Mesolimbic Pathway Bundle of neurons beginning in the VTA and terminating on the Nucleus Accumbens (NAcc) Dopamine and glutamate Mesocortical Pathway Bundle of neurons beginning in the VTA and terminating in the Frontal Lobe Dopamine and glutamate A. Ventral Tegmental Area B. Nucleus Accumbens C. Hippocampus D. Amygdala E. Frontal Cortex Primary Cortices Initial processing of stimuli Association Cortices Integration of information Divisions of the Nervous System Rats are commonly used as research models. Brain structures have been highly conserved during mammalian evolution so the basic brain plan is similar for rats and humans. Lissencephalic vs gyrencephalic  B. Cells of the 1. Types of Cells 2. Features of the Neuron Nervous System 3. Cell Membrane A. Cells of the Nervous System Two primary cell types: 1. Glial cells provide metabolic support, protection, and insulation for neurons. 2. Neurons transmit information in the form of electrical signaling. Cells of the Nervous System Types of glial cells: Oligodendrocytes Astrocytes/astroglia Microglia Schwann cells Cells of the Nervous System Glial cells provide metabolic support, protection, and insulation for neurons. Play central role in neural communication 90% of the brain composed of glial cells Types of glial cells: Oligodendrocytes Astrocytes Microglia Schwann cells  1. Types of Cells B. Cells of the 2. Features of the Neuron Types of Neurons Nervous System Structure of a Neuron Pathways 3. Cell Membrane Types of Neurons Primary Types of Neurons 1. Sensory neurons Convert physical stimuli into electrical signals. 2. Interneurons Found in brain and spinal cord Form interacting neural circuits Responsible for conscious sensations, recognition, memory, decision-making, cognition. 3. Motor neurons Direct bio-behavioral responses appropriate for the situation. Primary Types of Neurons Sensory, Interneuron, Motor Neurons form the reflex arc Structure of a Neuron Main regions of a Neuron: Soma or Cell Body Contains nucleus and other organelles. Dendrites Projections from the soma that receive information. Axon Extension that conducts electrical signals from the cell body to the terminal buttons. Axon Terminal Contain vesicles filled with neurotransmitters Structure of a Neuron Soma and Dendrites Receive information from other cells across the gap between them, the synapse. There are thousands of neurotransmitter receptors on the dendrites and soma. Effect of activating a neurotransmitter receptor can be excitatory or inhibitory. Structure of a Neuron Dendrites Covered with short dendritic spines that increase surface area. Dendrites and their spines are constantly modified Can change shape rapidly in response to changes in synaptic transmission. Mental illness, mental impairment, and drug addiction are associated with lessening of dendritic spines in specific regions Structure of a Neuron Dendrite Spines Structure of a Neuron Axon Transmits electrical signal from soma to the axon terminals  Structure of a Neuron Myelin Sheath A fatty insulation created by layers of glial cells. Oligodendroglia (oligodendrocytes) myelinate nerves in the central nervous system Schwann cells myelinate peripheral in the peripheral nervous system Structure of a Neuron Nodes of Ranvier Breaks in the myelin sheath Sites at which action potentials are regenerated. The myelin sheath increases speed of conduction along the axon Structure of a Neuron Axon Transmits electrical signal from soma to the axon terminals Axon Terminal Contain vesicles filled within neurotransmitter chemicals. Structure of a Neuron Pathways Neurons create networks or pathways Convergent Information received by a neuron from many different cells Divergent Information that is passed from one neuron to many other neighboring neurons Convergent and Divergent Pathways Pathways: Mesolimbic & Mesocortical  B. Cells of the 1. Types of Cells 2. Features of the Neuron Nervous System 3. Cell Membranes Cell Membrane The rate of passage through cell membranes is the largest factor on bioavailability Cell membranes: Made of Phospholipids- arranged in a bilayer Head: negatively charged region (hydrophilic) Tails: two uncharged lipid regions (hydrophobic) tes Attract: Positive hydrogen region on water molecule attracts negatively charged head of phospholipid  Cell Membrane and Neuronal Function Characteristics of cell membrane: Receptors- sites of action of neurotransmitters, hormones, and drugs. Cell Membranes Cell membrane proteins: Receptors Binding site for neurotransmitters, hormones, and drugs Does not allow for movement across the membrane Transporters Transporters use energy to move molecules across the membrane Ion Channels Proteins that form a channel and which allow molecules to selectively and passively move across the membrane. Cell Membranes Ion channels Specific for one or a few ions, which will pass through. Gated channels, opened by: Ligand-gated channel (Ionotropic Receptor) opens when a ligand (NT) binds to a receptor. Voltage-gated channel opens when the electrical potential across the membrane is altered. Cell Membranes Ion channels When open, ion channels allow ions to move along their concentration gradient either into or out of the cell. Selectively Permeable Cell Membranes Ion channels Channel opening can be modified by adding/removing a phosphate group to the intracellular protein. This process is called phosphorylation   Resting Membrane Potential (RMP)  Ion Distribution & RMP C. Electrical Transmission   Ion Movement The Action Potential within a Neuron  Localized potentials Electrical Transmission within a Neuron  Resting Membrane Potential (RMP)  Ion Distribution & RMP  Ion Movement  The Action Potential  Localized potentials Resting Membrane Potential (RMP) Resting membrane potential Difference in electrical charge between inside and outside of cell. Inside of cell is more negative than the outside –70 millivolts (mV) It is polarized. There are more negative ions (and amino acids) inside the cell, and more positive ions outside. Ion Distribution & RMP Resting membrane potential exists due to the distribution of ions inside vs outside the cell Ions are particles that carry a + or - charge Ion Distribution & RPM Ion movement across the cell membrane Cell membrane is selectively permeable Rules for ion movement when channels are open: 1. Diffusion: Ions move along their concentration gradient Ions move from areas of high concentration to areas of low concentration Ion Movement Ion movement across the cell membrane Cell membrane is selectively permeable Rules for ion movement when channels are open: 1. Ions move along their concentration gradient 2. Ions move according to electrostatic pressure Opposites attract: Positively charged ions are attracted to negatively charged spaces Negatively charged ion are attracted to positively charged spaces Ion Distribution & RPM Equilibrium potential for potassium (K+) K+ is moving both out of the cell (passive diffusion) and into the cell (electrostatic pressure) Na+/K+ pump works to move K+ ions out of the cell and Na+ into the cell Rules apply when cell is at rest The Action Potential (AP) The Action Potential (AP) Rapid depolarization (movement toward zero) Is propagated down the length of the axon Threshold membrane potential for the generation of an AP is –50 mV. Voltage-gated Na+ channels at the axon hillock open when the RMP reaches -50mv, beginning the AP The Action Potential (AP) The Action Potential (AP) The Action Potential (AP) Rapid depolarization (movement toward zero) Is propagated down the length of the axon Factors influencing the propagation of an AP: 1. Absolute Refractory Period No AP can be generated because Na+ channels are in the locked position 2. Relative Refractory Period It is less likely an AP can be generated because the membrane is hyperpolarized. This occurs because excessive K+ has left the cell. Takes time for the Na+/K+ pump to move K+ back into the cell, thus resetting the RMP The Action Potential (AP) (absolute refractory due to Na+ channel) (relative refractory due to K+ concentration) (Leaky) The Action Potential (AP) The Action Potential (AP) Myelin Sheath Glial cells: Oligodendrocytes Form myelin sheaths on neurons in the central nervous system (CNS) Schwann cells Form myelin sheath on neurons in the peripheral nervous system (PNS) The Action Potential (AP) Action potentials are “all or none” Size is unrelated to amount of stimulation. Saltatory conduction Describes the propagation of the AP in a meylinated neuron Conduction “jumps” from one node of Ranvier to the next. Less energy is needed because Na+–K+ pumps are only at the nodes. Local Potentials Local Potential: small, local changes in membrane polarity (RMP) Ligand (neurotransmitter) can bind to (neurotransmitter) receptor and open channels momentarily, Local Potentials 1. Local Depolarization Excitatory postsynaptic potentials (EPSPs) -Intracellular environment becomes less negative as compared to the extracellular environment Example: Neurotransmitter binds to receptor and allows Na+ to enter the cell 2. Local Hyperpolarization Inhibitory postsynaptic potentials (IPSPs) - Intracellular environment becomes more negative as compared to the extracellular environment Example: Neurotransmitter binds to receptor and allows Cl- to enter the cell Neurotransmitter binds to receptor and allows K+ to leave the cell Local Potentials Local potentials are graded The larger the stimulus, the greater the magnitude of hyperpolarization or depolarization They also show summation Small depolarizations/hyperpolarizations that can add up to larger changes in membrane potential. Temporal Summation Spatial Summation Integration of the signal occurs at the Axon Hillock  Shift from -70mV to -90mV Application Local anesthesia (e.g., Novocain) Blocks voltage-gated Na+ channels