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Chapter 1-6

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McGill University
PSYC 211
Yogita Chudasama

PSYC 211 – Chapter 1 1/20/2013 8:07:00 PM Chapter 1 – Introduction* (Lecture 1) *these notes are what is not added to the lecture slides Understanding Human Consciousness: A Physiological Approach  Consciousness  simple wakefulness o Can be altered by changes in the structure or chemistry of the brain (physiological function)  Verbal communication makes cooperation possible o Establish customs, laws of behavior Blindsight   damage to particular part of brain  our behavior can be guided by sensory information of which we are completely unaware o common belief that perceptions must enter consciousness to affect our behavior = WRONG.  More primitive system (fish and frogs) evolved first (eye movements and attention to sudden movements), more complex, second (that mammals have) o Mr. J was blind but could still grab things  Only mammalian system was damaged  Only mammalian visual system has direct connections with the parts of the brain responsible for consciousness  Blindsight  the ability of a person who cannot see objects in his or her blind field to accurately reach for them while remaining unconscious of perceiving them, caused by damage to ―mammalian‖ visual system in brain Split Brains  Corpus collosum  largest commissure of the brain, interconnecting the areas of the neocortex on each side of the brain  Split-brain operation  brain surgery that is occasionally performed to treat a form of epilepsy; the surgeon cute the corpus collosum, which connects the 2 hemispheres of the brain o Reduced frequency of epileptic seizures  Cerebral hemispheres  the 2 symmetrical halves of the brain; constitute the major part of the brain o Receive sensory info from opposite sides of the body o Send info between each other (after split-brain, they operate independently)  We become conscious of something only if information about it is able to reach the parts of our brain responsible for verbal communication (left hemisphere) Unilateral Neglect  Unilateral neglect  a syndrome in which people ignore objects located toward their left and the left sides of objects located anywhere; most often caused by damage to the right parietal lobe  2 major symptoms: o neglect of the left halves of things in the environment o neglect of the left half of one’s own body Perception of Self  Rubber hand illusion o If the subject’s hidden hand and the visible rubber hand are stroked synchronously in the same direction, the subject will come to experience the artificial hand as his or her own  Premotor cortex was activated o If the hands are stroked asynchronously or in different directions, the illusion will not occur  Premotor cortex was not activated o (experimenter stroked the real hidden hand and the rubber hand with a small brush) o people felt ownership to the rubber hand, when it was about to be stabbed in another experiment, the anterior cingulate cortex (anticipate pain) was activated The Nature of Behavioral Neuroscience  Ultimate function of the nervous system is behavior The Goals of Research  Scientific explanation takes 2 forms: o Generalization  a general conclusion based on many observations of similar phenomena o Reduction  a phenomenon is described in terms of the more elementary processes that underlie it Biological Roots of Behavioral Neuroscience  Descartes  see slides.  Luigi Galvani o Experiments leading to an understanding of the nature of the message transmitted by nerves between the brain and the sensory organs and the muscles  Johannes Müller o Experimenting!!  Removing or isolating animal organs, testing their responses to various chemicals and altering the environment to see how the organs responded o Doctrine of specific nerve energies  Müller’s conclusion that, because all nerve fibers carry the same type of message, sensory information must be specified by the particular nerve fibers that are active  Perceive the message of different nerves differently (messages occur in different channels) o Experimental ablation  the research method in which the function of a part of the brain is inferred by observing the behaviors an animal can no longer perform after that part is damaged  Broca performed this and found Broca’s area (responsible for speech production) o Hermann von Helmholtz  Devised math formula of the law of conservation of energy, invented ophthalmoscope (to examine retina)  First person to attempt to measure speed of conduction through nerves  Similar to wires Natural Selection and Evolution  *see slides Ethical Issues in Research With Animals  Need to use animals for scientific research o Prevent future human disease o People shit on it more than eating animals or getting fur from them, or even owning pets (animal rights)  Stupid because research is most important Careers in Neuroscience  Behavioral neuroscientist  a scientist who studies the physiology of behavior, primarily by performing physiological and behavioral experiments with laboratory animals o Allied with other scientists in the field of neuroscience Strategies for Learning  Learn research strategies, observations, reasonings PSYC 211 – Chapter 2 1/20/2013 8:07:00 PM Chapter 2 – Structure and Functions of Cells of the Nervous System (Lecture 2 and Lecture 3, Part I) • Sensory neuron  a neuron that detects changes in the external or internal environment and sends information about these changes to the CNS • Motor neuron  a neuron located within the CNS that controls the contraction of a muscle or the secretion of a gland • Interneuron  a neuron located entirely within the CNS  local interneurons form circuits with nearby neurons and analyze small pieces of information  relay interneurons connect circuits of local interneurons in one region of the brain with those in other regions Cells of the Nervous System Neurons INTERNAL STRUCTURE  genome  sequence of nucleotide bases on the chromosomes that provide the information needed to synthesize all the proteins that can be produced by a particular organism  junk DNA  doesn’t have info needed to make proteins  what do non-coding sequences of DNA do? o Non-coding RNA (ncRNA)  Constituent of a spliceosome (splices mRNA)  Cytoskeleton – gives neuron its shape o Made of 3 kinds of protein strands linked to each other and forming a cohesive mass  Microtubules  Thickest  Bundles of 13 protein filaments arranges around a hollow core  Axoplasmic transport  an active process by which substances are propelled along microtubules that run the length of the axon o Accomplished by kinesin (protein molecule)  Legs and feet (Brouhard)  Energy supplied by mitochondria’s ATP o Dynein  Carries substances from terminal buttons to the soma (retrograde axoplasmic transport)  Anterograde  in a direction along an axon from the cell body toward the terminal buttons  Retrograde  in a direction along an axon from the terminal buttons to the cell body Supporting Cells  Glial cells  see slides.  Schwann Cells o Perform same functions as oligodendrocytes, but in the PNS o Each segment consists of a single Schwann cell, wrapped many times around the axon o Differences from oligodendrocytes:  Schwann cells arrange themselves in a series of cylinders that act as guides for regrowth of the axons  If axons in CNS are damaged, new sprouts will form, but in PNS, budding axons encounter scar tissue produced by astrocytes, and they cannot penetrate this barrier  During development, axons have 2 modes of growth:  First mode causes them to elongate so that they reach their target, which could be as far away as the other end of the brain or spinal cord (Schwann cells provide this signal to injured axons)  Second mode causes axons to stop elongating and begin sprouting terminal buttons because they have reached their target  Chemical composition of the myelin protein is different  MS only attacks the myelin protein produced by oligodendrocytes (CNS) Communication Within a Neuron  Sometimes inhibitory neurons interfere with excitatory neurons (reflexes) o not dropping the casserole dish even though it’s very hot… Measuring Electrical Potentials of Axons  Electrode  a conductive medium that can be used to apply electrical stimulation or to record electrical potentials  Microelectrodes  a very fine electrode, generally used to record activity of individual neurons  Membrane potential  the electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell  Oscilloscope  a laboratory instrument that is capable of displaying a graph of voltage as a function of time on the face of a cathode ray tube  Resting potential  the membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials; approximately -70 mV in the giant squid axon  Depolarization  reduction (toward 0) of the membrane potential of a cell from it normal resting potential  Hyperpolarization  an increase in the membrane potential of a cell, relative to the normal resting potential  Action potential  the brief electrical impulse that provides the basis for conduction of information along the axon  Threshold of excitation  the value of the membrane potential that must be reached to produce an action potential The Membrane Potential: Balance of Two Forces The Force of Diffusion  Diffusion  the process whereby molecules distribute themselves evenly throughout the medium in which they are dissolved o From high to low concentrations The Force of Electrostatic Pressure  Electrolyte  an aqueous solution of a material that ionizes— namely, a soluble acid, base, or salt (split into 2 parts, each with an opposing electrical charge (ions))  Electrostatic pressure  the attractive force between atomic particles charges with opposite sign or the repulsive force between atomic particles charges with the same sign Ions in the Extracellular and Intracellular Fluid  Intracellular and extracellular fluid contain different ions  Organic ions (negatively charged proteins and intermediate products of the cell’s metabolic processes) are only found in intracellular fluid The Action Potential  1. Threshold of excitation reached o sodium channels open and influx of Na in to cell (propelled by forces of diffusion and electrostatic pressure) o depolarization o voltage-dependent ion channels (channels opened by change in membrane potential from -70 mV to 40 mV)  2. Voltage-dependent potassium channels – less sensitive than sodium ones o need more depolarization to open, so begin to open later than the sodium channels  3. Around when a.p. reaches peak, sodium channels become refractory (channels become blocked and can’t open again until the membrane reached resting potential again) o no more Na can enter cell  4. By now, the K channels are open, letting K ions more freely through membrane o inside of axon is +, so K is driven out of cell by electrostatic pressure o this outflow of cations causes membrane potential to return toward its normal value (as it does, K channels start to close again)  5. Once membrane potential turns to normal, sodium channels reset so that another depolarization can cause them to open again  6. Membrane overshoots its resting value (-70 mV) and only gradually returns to normal as K channels finally close o eventually, sodium-potassium transporters remove the Na ions that leaked in and retrieve K ions that leaked out Conduction of Action Potential  Saltatory conduction  conduction of action potentials by myelinated axons. The action potential appears to jump from one node of Ranvier to the next. o 2 advantages:  economic  myelinated axons expend less energy because Na only has to be pumped back out at the nodes (because less gets in)  speed  faster conduction of a.p. in myelinated axons because transmission between the nodes is very fast  faster thinking and reaction  increasing size also increases conduction (bigger diameter of axon – faster speed) Communication Between Neurons  Binding site  the location on a receptor protein to which a ligand binds  Ligand  a chemical that binds with the binding site of a receptor Structure of Synapses  Synapses can occur in 3 places: o Dendrites – axodendritic  Can occur on smooth surface surface of dendrite or on dendritic spines  small bud on the surface of a dendrite, with which a terminal button of another neuron forms a synapse o Soma – axosomatic o Other axons – axoaxonic  Synaptic vesicles  small, rounded objects in the shape of spheres or ovoids o Found in all terminal buttons o Contain NT o Transport proteins fill vesicles with NT o Trafficking proteins involved in release of NT and recycling of vesicles o Small synaptic vesicles produced in Golgi apparatus, carried by fast axoplasmic transport to the terminal button o Large synaptic vesicles only produced in soma, transported through axoplasm to the terminal buttons  Release zone  a region of the interior of the presynaptic membrane of a synapse to which synaptic vesicles attach and release their NT into the synaptic cleft  Postsynaptic density  caused by presence of receptors (specialized protein molecules that detect the presence of NT in the synaptic cleft) Release of a Neurotransmitter  Docking  when clusters of protein molecules attach to other protein molecules located in the presynaptic membrane  When terminal button is depolarized, calcium channels open and Ca flows into the cell (propelled by diffusion and electrostatic)  3 distinct pools of synaptic vesicles: o release-ready vesicles  docked against inside of presynaptic membrane, ready to release their contents when an a.p. arrives o recycling pool  for faster firing rates o reserve pool  for faster firing rates  kiss and run  vesicles release their NT, fusion pore closes, vesicles break away from presynaptic membrane and get filled with more NT o other vesicles merge and recycle and lose their identity  membranes of these vesicles merge with presynaptic membrane  little buds of membrane pinch off into cytoplasm and become vesicles  appropriate proteins fill these vesicles with NT  membranes of these vesicles recycles through bulk endocytosis Activation of Receptors  Postsynaptic receptor  a receptor molecule in the postsynaptic membrane of the synapse that contains a binding site for a NT  Neurotransmitter-dependent ion channel  an ion channel that opens when a molecule of a NT binds with a postsynaptic receptor  NT open ion channels by at least 2 methods: o Direct  Ionotropic receptor  a receptor that contains a binding site for a NT and an ion channel that opens when a molecule of the NT attached to the binding site o Indirect  Metabotropic receptors  a receptor that has a binding site for NT; activates an enzyme that begins a series of events that opens an ion channel elsewhere in the membrane of the cell when a molecule of the NT attached to the binding site  G protein  a protein coupled to a metabotropic receptor; conveys message to other molecules when a ligand binds with and activates the receptor  Second messenger  a chemical produced when a G protein activates an enzyme; carries a signal that results in the opening of the ion channel or causes other events to occur in the cell  Cyclic AMP – first to be discovered (synthesized from ATP)  = k, so basically a metabotropic receptor is coupled to a G protein, when a molecule of NT binds with this receptor, G protein gets activated and activated an enzyme that simulated the production of a chemical called a second messenger. Molecules of second messenger travel through cytoplasm and attach themselves to nearby ion channels, causing them to open. These potentials take longer to begin and last longer. Postsynaptic Potentials  Excitatory postsynaptic potential (EPSP)  an excitatory depolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button  Inhibitory postsynaptic potential (IPSP)  an inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button Termination of Postsynaptic Potentials  Reuptake  the reentry of a NT just liberated by a terminal button back through its membrane, thus terminating the PSP o From synaptic cleft directly into cytoplasm (no vesicles)  Enzyme deactivation  the destruction of a NT by an enzyme after its release—for example, the destruction of acetylcholine by acetylcholinerase  Acetylcholine  a NT found in the brain, spinal cord, and parts of the PNS; responsible for muscular contraction  Acetylcholinerase (AChE)  the enzyme that destroys acetylcholine soon after it’s liberated by the terminal buttons, thus terminating the PSP  Myasthenia gravis (muscle weakness from chapter’s case study)  from poison that blocks neural transmission at the synapses on muscles o Physostigmine  deactivates acetylcholinerase Effects of Postsynaptic Potentials: Neural Integration  Neural integration  the process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing a neuron Autoreceptors  Many neurons also process receptor that respond to NT that they themselves release  autoreceptors o Autoreceptors  a receptor molecule located on a neuron that responds to the NT released by that neuron  Can be located on the membrane of any part of the cell  Don’t produce changes in membrane potential  Regulate internal processes, including synthesis and release of the NT (metabotropic, through G proteins)  Usually, effects of autoreceptor activation is inhibitory Other Types of Synapses  Axoaxonic synapses work differently o Do not contribute directly to neural integration, instead they alter the amount of NT released by the terminal buttons of the postsynaptic axon  Presynaptic inhibition  the action of the presynaptic terminal button in an axoaxonic synapse, reduces the amount of NT released by the postsynaptic terminal button  Presynaptic facilitation  the action of the presynaptic terminal button in an axoaxonic synapse; increases the amount of NT released by the postsynaptic terminal button  Small neurons form dendrodendritic synapses (between dendrites) o Some large neurons also  Gap junction  a special junction between cells that permits direct communication by means of electrical coupling Nonsynaptic Chemical Communication  Neuromodulators  a naturally secreted substance that acts like a neurotransmitter except that it is not restricted to the synaptic cleft but diffuses through the extracellular fluid o Most are peptides  chain of amino acids joined together by peptide bonds  Hormones (has effects on target cells in other organs) are secreted by endocrine glands (secretes into extracellular fluid around capillaries and hence into the bloodstream) o Target cell  type of cell that is directly affected by a hormone or other chemical signal  Steroid  a chemical of low molecular weight, derived from cholesterol, affect their target cells by attaching to receptors found within the nucleus o Lipid soluble, so they pass easily through cell membrane PSYC 211 – Chapter 3 1/20/2013 8:07:00 PM Chapter 3 – Structure of the Nervous System The Central Nervous System Development of the CNS  Begins early in embryonic life An Overview of Brain Development  Development of the human nervous system tarts around 18 thday after conception  Part of ectoderm (outer layer) of back of embryo thickens and forms a plate, edges of this plate form ridges that curl toward each other along a longitudinal line, running in a rostral-caudal direction st  By 21 day, these ridges touch each other and fuse together, forming a rube—the neural tube, which gives rise to the brain and spinal cord  Top part of ridges break away from the neural tube and become the ganglia of the ANS  By 28 thday, neural tube is closed, and its rostral end has developed three interconnected chambers o Chambers become ventricles and the tissue that surrounds them becomes the three major parts of the brain  Forebrain, midbrain, hindbrain o Rostral chamber (forebrain) divides into 3 parts  2 lateral ventricles and the third ventricle o region around third ventricle becomes diencephalon Prenatal Brain Development  Cerebral cortex  the outermost layer of gray matter of the cerebral hemispheres o Larger in humans than other species  Progenitor cells  cells of the ventricular zone that divide and give rise to cells of the CNS  Ventricular zone (VZ)  a layer of cells that line the inside of the neural tube; contains progenitor cells that divide and give rise to cells of the CNS  Subventricular zone (SVZ)  a layer of progenitor cells located just inside the ventricular zone; thicker in mammals with large brains  Symmetrical division  division of a progenitor cell that gives rise to 2 identical progenitor cells; increase the size of the ventricular zone and hence the brain that develops from it  asymmetrical division  division of a progenitor cell that gives rise to another progenitor cell and a neuron, which migrates away from the ventricular zone toward its final resting place in the brain  five layers of neurons and their migration takes about 5 weeks  apoptosis  death of a cell caused by a chemical signal that activates a genetic mechanism inside the cell  genetic duplications responsible for evolution of more complex brains  ultimate size of brain determined by ventricular zone o each symmetrical division doubles the number of progenitor cells, and thus doubles the size of the brain o ventricular zone gives rise to more neurons than are needed (they have to compete to survive) Postnatal Brain Development  Different regions of cerebral cortex perform specialized functions  Neurogenesis  production of new neurons through the division of neural stem cells; occurs in the hippocampus and olfactory bulb and appears to play a role in learning The Forebrain   most rostral of the 3 major divisions of the brain, includes telencephalon and diencephalon Telencephalon  Includes most of the 2 symmetrical cerebral hemispheres o Covered by cerebral cortex, contain limbic system and basal ganglia  Basal ganglia are in subcortical regions of the brain (located within the brain, beneath cortical surface)  Cerebral Cortex: o Sulci (small groove) and fissures (large groove) o Gyri (bulges between adjacent sulci and fissures o Enlarge surface area o Gray matter (cell bodies give it gray tint) o Primary visual cortex  receives input from visual system (region of posterior occipital lobe)  On calcarine fissure  located in occipital lobe on the medial surface of brain, most of it located along its upper and lower banks o Primary auditory cortex  received auditory info, region of superior temporal love  Located on lower surface of deep fissure in the side of brain (lateral fissure  separates temporal love form overlying frontal and parietal lobes) o Primary somatosensory cortex  vertical strip of cortex just caudal to the central sulcus  Gets into from body senses o Insular cortex  info concerning taste o Primary motor cortex  region of posterior frontal lobe that contains neurons that control movements of skeletal muscles  Contralateral c
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