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Lecture 1 - Neurophysiology and Anatomy

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Emis Akbari

PSY398H5S – Motivational Systems Lecture 1 – January 10, 2013 Introduction – Neurophysiology and Anatomy What is Motivation? - To be motivated is to be moved into action, or to decide on a change in action - Action does not occur spontaneously – but rather it is inducted by either internal motive or environmental incentives - Incentive – The anticipated reward or aversive event available in the environment - A motive is linked to an incentive, since attaining an incentive is the goal of a person’s motive - Hunger is a motive for eating - Interest changes is an incentive for timely bill paying o Some time interest charges are high so they are motivated to pay bill on time - A lot of individual differences in what motivates us and the levels needed to throw us into action Understanding the Biological Basis of Behavior  Describing Behavior: o It can be examined analytically or in terms of function  What is the function of sexual behavior?  Procreation + pleasure  Sexual behavior: o Analytically: mounts, intromissions, ejaculations, grooming etc. o Functionally: Three Approaches to Study Behavioral Neuroscience - Somatic Intervention – Manipulating a body structure or function and observing resulting behavior o Administering hormones - Behavioral Intervention – Intervening in behavior of an organism and looking for resulting changes in body structure or function o Opp of somatic int o Looking at behaviour and collecting samples of what it is doing naturally o Microdialysis – collects CSF and pumps it out. We can analyze the CSF DA increases before and during sex and decreases after sex - Correlations – How variables (brain and behavior) covary o How two variables are related o How long it took male to ejaculate o Longer it took to ejaculate, more DA released Study of Behavioral Neuroscience - Independent Variable – The factor that is being manipulated by the experimenter o What we change - Dependent variable – The factor that an experimenter measures to monitor a change in response to chances in an independent variable o What we measure Levels of Analysis in Biological Psychology - Simple molecular constituents to complex social interactions - Reductionism involves analysis on a more basic level than the function to be explained - Looking at complex behavior and reducing it o Example: Social behavior – how neurons come to each other – within each neuron what receptors are active PSY398H5S – Motivational Systems Lecture 1 – January 10, 2013 Animal Testing - 93% of all animal testing is conducted on rodents - All procedures attempt to minimize pain and discomfort - Local and national animal care committees - Is animal testing ethical and necessary? - By disconnecting the corpous coil can avoid seizures – split brain Origins of Neuroscience - Split Brain – Demonstrates the importance of communication and consciousness - Used with people with severe epilepsy - Nerves in one side of the brain become overactive, over-activity is transmitted to other side of the brain by the corpus collosum - Corpus Collosum – Bundle of nerve fibers that connect corresponding parts of one side of the brain with those of the other - Cutting the corpus collosum greatly reduces the frequency of seicues - After the split, two sides of the brain are independent o Language process is on the left side (80%) Origins of Physiological Psychology - Following the split brain operation (corpus callosotomy), 2 hemispheres are disconnected and operate independently - In most people, the left side of the brain controls speech – if you show a picture to the left visual field (processed by the right hemisphere) person unable to vocally tell you what it is - However, they can pick up and show recognition of an object (one within the left visual field) with their left hand (that hand is controlled by the right side of brain) - When speaking to a person with slit brain, you are only conversing with one hemisphere – the left - Gave us insight into hemispheric specialization - Biggest complaint in these patients: o Their left hand has a mind of it’s own o Reading a book, their left hand will put the book down o A case of a man beating his wife with his left hand and protecting her with his right The Nervous System - Neurons collect signals from several sources, integrate and transform information, and distribute information to other cells - Dendrites – The input zone-receives info from other neurons - Soma – Cell body, contains cell nucleus. May receive synaptic connections - Axon – A single extension leads away from the soma and transmits electrical signals away from the cell body - Axon Terminals – Swelling at the end of axons. They communicate the cell’s activity to other cells Central vs. Peripheral NS - Two main division of the NS: o Central NS: Consists of the brain and spinal cord o Peripheral NS: All parts of the NS that are outside the body skull spinal column - Peripheral NS: 3 Components: o Cranial Nerves: 12 pairs serve sensory and motor systems o Spinal Nerves: 31 pairs o The autonomic NS: spans both central and peripheral NS PSY398H5S – Motivational Systems Lecture 1 – January 10, 2013 The Autonomic Nervous System - Spans both CNS and PSN - Autonomic (independent) - There are 3 division of the autonomic NS: o Sympathetic NS: Preganglionic cells of the SNS found in the SC – prepares the body for action: blood pressure increases, pupils dilate, heart quickens  Thoaxic region o Parasympathetic NS: Preganglionic cells of the PSNS found above and below those of those SNS  Keeps body at homeostatic level by counteracting cervical and lumbar regions - Usually act in opposition to each other o Enteric NS: A local network of sensory and motor neurons that regulate the functioning of the gut. Innervated by both the SNA and the PSNS. Plays a key role in maintaining fluid and nutrient balances in the body The Brain – Lateral View The Brain – Midsagittal View The Brain – Basal View PSY398H5S – Motivational Systems Lecture 1 – January 10, 2013 The Mammillary Bodies: - This area is particularly vulnerable to alcohol abuse and damage subsequently causes Wenicke-Korsakoff’s syndrome that is characterized by severe memory loss. This area is also implicated in autism - Uncus: Continuation of the hippocampus - Seizures are preceded by hallucinations of odours often originate in the uncus Organization of the Brain - Neocortex o Center of human cognition o Arranged in 6 layers o Well developed for humans o Rates have patterns of rough vs. smooth not developed Telencephalon – The Limbic System - Widespread network of structures involved in emotions and learning - Amygdala – involved in emotional regulation and odour perception - Hippocampus and Fornix – Important in learning and memory - Cingulate Gyrus – Which we discussed - Olfactory Bulb – Involved in the sense of smell - Mammillary Bodies – Very important in motor control - Includes: - Caudate Nucleus and Glutamen – Major input station for the basal ganglia - Globus Pallidus – Major part of this system - Substantia Nigra – Dopamine production and therefore also important in reward and addiction o Depletion of DA results in Parkinson’s (motor) Diencephalon - Thalamus – Almost all sensory information enters the thalamus and sends information to cortex PSY398H5S – Motivational Systems Lecture 1 – January 10, 2013 - Hypothalamus – “hypo” under the thalamus o Has many distinct nuclei that control: o Thirst, huner, temperature, reproduction, pituitary function Mesencephalon – Midbrain - Superior Colliculi – Receives visual information - Inferior Colliculi – Receives auditory information - There are 2 important motor centers in the midbrain: o The Substantia Nigra o The Red Nucleus: communicates with motoroneurons in the spinal cord - Also apart of the midbrain is the reticular formation: stretches form midbrain down to medulla and is implicated in the sleep and arousal o How two variables are releated o How long it took male to ejaculate o Longer it took to ejaculate, more DA released Hindbrain - Cerebellum: Composed of 3 layers o Purkinje cells: middle layer o Granule cells: axons extend to the outer most layer o Parallel fibers: outer most layer - Pons: Part of the brainstem also important in motor control - Medulla: Transition from brainstem to spinal cord regulates breathing and heart rate – damage is often fatal Communication – Synapses - There are 3 components of a synapse - (1) The presynaptic membrane: in the axon terminal - (2) The postsynaptic membrane: on the surface of the dendrites or cell body of the postsynaptic neuron - (3) The synaptic cleft: the gap that separates the 2 membranes - Neurotransmitters: Chemical messengers Neurophysiology - Ions: A charged molecule dissolved fluid - Anion: A negatively charged ion - Cation: A positively charged ion - A neuron contains many anions and fewer cations - All of these ions are dissolved in the intracellular fluid Electrical Balance - A neuron is more negatively charged inside a cell and positively charged outside the cell - A neuron at rest exhibits a resting membrane potential: an electrical potential difference across the membrane; of about -50 to -80 mV - Lipid Bilayer: this is 2 layers of linked fatty molecules – where many proteins float Ion Channel - Ion Channel: A tube-like pore that allows ions of a specific type to pass through the membrane - Some of these channels are gated and some are ot - Selective Permeability: only a specific substance (K+) can freely cross the membrane PSY398H5S – Motivational Systems Lecture 1 – January 10, 2013 Ionic Force - Diffusion: particles move from areas of high concentration to areas of low concentration – move down the concentration - Diffusion (Semi Permeable Membrane): certain membranes permit some substances to pass through but not others - Electrostatic Forces: like charges repel each other; opposite charges are attracted to each other - They eventually reach and equilibrium – balances each other out – this corresponds to the resting potential Depolarization and Hyperpolarization - Action Potential: Nerve impulses that are very brief but a large changes in neuronal polarization that arise initially at the axon hillock - The nerve impulse then rapidly travels down the axon - The information that is sent by a neuron is encoded in patterns of these action potentials - Depolarization: a decrease in membrane potential, makes the inside closer to the outside (i.e. -60mV to -50mV) o Makes the cell more positive - Hyperpolarization: an increase in membrane potential, so neuron becomes even more negative inside (i.e. from-60mV to -70mV) o Makes the cell more negative Action Potential - APs are therefore a rapid depolarization and repolarization of the membrane - In order for an action potential to be fired, depolarization must be large enough
 - This is referred to as the threshold: The value of the membrane potential to which the axon must be depolarized to initiate an action potential - All-or-none: The amplitude of the AP once initiated, does not depend on the size of the initial depolarization Voltage-Gated Ion Channels - Voltage-gated ion channels are of prime importance in generating action potentials
 - Open and close according to the membrane potential. They are closed at the resting potential and open as membrane depolarizes Refractory Per
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