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PSYB65H3 (479)
Ted Petit (185)
Chapter 2

PSYB65 - chapter 2.docx

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University of Toronto Scarborough
Ted Petit

Chapter 2: Neuroanatomy Cells of the Nervous System - What makes the human a higher-functioning organism is the fact that humans have aggregates of specialized cells that perform specialized functions - Neurons (communicators) and glia (support functions) are the specialized cells of the nervous system in both structure and function Neurons and Glia: Structure and Function - Gross Anatomy of the Neuron:  Shape related to function (to receive, conduct, and transmit)  3 main components: dendrites (receive info), soma (cell body containing genetic machinery), and the axon (sends info to other neurons)  Synapse: gap in which info is passed from axon to dendrite  Info is sent in the form of an electrical charge, or action potential  Myelin: many axons in the mammalian nervous system are covered with insulation (speeds rate of info transfer)  Terminal button: where info is sent from, across the synapse to the dendrite  Neurotransmitter: neurochemical message passed from the axon across the synapse - Internal Anatomy of the Neuron: plasma membrane (separates the 2 fluid membranes – inside or outside the cell)  Processes: genetic, synthetic, and metabolic keep the neuron functioning - Structure and Function of Neurons:  Structure: unipolar, bipolar, multipolar (number of processes extending from the cell body)  Interneurons: neurons with no axon or only short axons, and tend to integrate information within a structure  Function: motor, sensory, interneurons o Afferent: bring info to the central nervous system o Efferent: send info from brain - Glia: perform support functions  Satellite cells: support cells outside of the brain and spinal cord  3 types of glia: o Astrocytes (largest, fill space between neurons): also perform nutritive and metabolic functions of neurons, and are also essential for the regulation of the chemical content of the extracellular space o Oligodendrocytes: make myelin (some provided by Schwann cells) o Microglia (smallest): are phagocytes that remove debris from the nervous system. Excessive activation of microglia has been implicated in neurodegenerative disease such as multiple sclerosis and Alzheimer’s disease Chapter 2: Neuroanatomy Communication within the Neuron: The Action Potential - The electrical events that underlie the transmission (or inhibition) of information rely on the balance of ions between the inside of the neuron (intracellular) and the outside of the neuron (extracellular) - Resting potential: an electrical charge of -70 mV, or the electrical charge on the inside of the neuron is 70 mV less than the charge on outside - Sodium ions (NA+) and Potassium ions (K+): at rest, extracellular fluid contains high levels of Na+, and intracellular fluids contain high levels of K+ (sodium-potassium pump) - Depolarization and Action potential: when the change in the membrane potential moves from its resting state of about -70 mV to about +50mv - Repolarization soon occurs, and often hyperpolarization is a result. - In myelinated neurons, ion channels and sodium-potassium pumps occur only at the nodes of Ranvier (saltatory conduction – moves down axon) Communication between Neurons: The Synapse - Within neurons, communication is largely electrical, however between neurons, communication is largely chemical - Synapses: axodendritic, axosomatic, dendrodendritic, and axoaxonic synapses - The terminal button of an axon contains dozens of small packages (vesicles) that contain neurotransmitters - Two types of receptors are located on the postsynaptic membrane: transmitter-gated ion channels (ionotropic receptors- fast response required) and G-protein-coupled receptors (metabotropic receptors – produce slower more sustained responses, and occur more frequently in the nervous system)  Excitatory postsynaptic potential (EPSP): when a dendrite is depolarized by the release of a neurotransmitter from the presynaptic site  Inhibitory postsynaptic potential (IPSP): when a dendrite is hyperpolarized by the release of a neurotransmitter from the presynaptic site - Two mechanisms are responsible for terminating the activity of neurotransmitters: reuptake and enzymatic degradation Neurotransmitters - Small-molecule neurotransmitter group (fast responses)  Acetylcholine, monoamines, soluble gases, and amino acids - Large-molecule neurotransmitter group (slower, long lasting response)  Neuropeptides: made, storied, and transported differently from the small-molecule neurotransmitters, and adjust sensitivity of neurons (modulates effects of other neurotransmitters) Chapter 2: Neuroanatomy The Nervous System - The brain is approximately 3 pounds, and has 50-100 billion neurons - Sylvian fissure (or many other names): the large fissure that runs between the temporal lobe and frontal/parietal lobes - Chapter 8, the terms primary auditory cortex, the posterior portion of the superior temporal gyrus, Heschl’s gyrus, and Brodmann’s area 41 all refer to the same structure - The brain is complex and inconsistent Positional Terms - Neuroanatomical directions are always given in relation to the spinal cord - Neuraxis: an imaginary line running along the length of the nervous system, extending from the bottom of the spinal cord to the most frontward portion of the brain(humans have a 90 degree bend) - Dorsal: toward the back (top of the brain, back of spinal cord) - Ventral: toward the front (bottom of the brain, front of the spinal cord) - Anterior (rostral): toward the head (front of the brain, top of the spinal cord) - Posterior (caudal): toward the tail (back of the brain, bottom of the spinal cord) - Superior: above or topmost - Inferior: below or bottommost - Media: toward the middle - Lateral: away from the middle (toward the outside) - Ipsilateral: on the same side - Contralateral: on opposite sides - Cuts of the brain:  Horizontal se
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