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University of Toronto Scarborough
Steve Joordens

Chapter 3 Neurons: cells in the nervous system that communicate with one another to perform information processing tasks Discover of How Neurons Function: -Scientist originally thought that brain looked as it were composed of a continuously connected lattice of fine threads -Saniago Ramon y Cajal stained neurons in the brain. He was the first to see the structure of neuron components of the neuron (figure 3.2) -3 basic parts: *cell body: contain nucleus; part of a neuron that coordinates information processing tasks and keeps the cell alive *dendrite: part of a neuron that receives information from other neurons and send it to the cell body *axon: part of the neuron that transmits information to other neurons, muscles or glands -myelin sheath: an insulating layer, composed of glial cells which help the axon transmit information more efficiently -other functions of glial cells include: support cells found in the nervous system that digest dead neuron, provide physical and nutritional support -demyelinating disease is the deteriorates of myelin sheath which caused problem in coordinated movement and cognition -snapse: the gap between the axon of one neuron and the dendrites or cell body of another major types of neurons 3 major types of neuron: 1. sensory neuron: receive information from the external world and send information to brain through spinal cord 2.motor neuron: carry signals from the spinal cord to the muscle to produce movement 3.interneuron: connect sensory neuron, motor neuron or other interneurons neuron specialized by location -the size and shape of neurons vary depending on their location and their task the electrochemical actions of neurons; information processing -the communication of information within and between neurons proceeds in 2 stages (conduction and transmission) which are refer to as electrochemical action of neuron -conduction : an electric signal pass along dendrite, cell body and axon -transmission: send chemical signals between neurons over synapse The resting potential: the origin of the neuron's electrical properties -resting potential is the difference in electric charge between the inside and outside of a neuron's cell membrane, it creates the environment for a possible electrical impulse. -resting potential is caused by difference in concentration of ions inside and outside of neuron's cell membrane. -action potential is an electric signal that is conducted along a neuron's axon to a synapse *it only occurs when electric shock reaches a certain level, the strength of electric shock above the threshold did not increase the strength of the action potential -refractory period is the time allowing an action potential during which a new action potential cannot be initiated -the process of how each works in on pg 84, figure 3.5 -electric charge move down the axon by generating action potentials one after another along the path in the axon -myelin sheath facilitate the transmission of the action potential, it clumps around the axon with little break points between clumps, the break points are called nodes of ranvier -salutatory conduction is the process in which the electric impulse jumps from node to node in order to speed the conduction of information down the axon chemical signaling: transmission between neurons -terminal button are knob like structure that branch out from the axon, it is filled with tiny pockets contain neurotransmitter -neurotransmitter are chemicals that transmit information across the synapse to a receiving neuron's dendrite -receptors are found on the dendrites of the receiving neuron, it receive neurotransmitters and initiate or prevent a new electric signal -process: 1.action potential travels down the length of the axon to terminal button 2.stimulates the release of neurotransmitter from vesicles 3. neurotransmitters are released into the synapse where they float to bind with receptor sites on a dendrite of postsynaptic neuron to create new action potential *what tells dendrites which of the neurotransmitters flooding into the synapse to receive? 1.neuron tends to form pathways in brain that are characterized by specific types of neurotransmitters 2. by lock and key systems, only certain molecules fit in to receptor site -the neurotransmitters are cleared out of the synapse by 1.reuptake into the sending neuron or 2. being broken down by the enzyme in synapse or 3.binding to auto receptors on the sending neuron Types and Functions of Neurotransmitters 1.acetylcholine: involved in voluntary motor control; regulation of attention, learning, sleeping dreaming, memory *first neurotransmitter discovered 2.dopamine: regulates motor behavior, motivation, pleasure and emotional arousal 3.glutamate: information transmission throughout the brain 4.GABA gamma aminobutyric acid: stop the firing of neurons 5.norepinephrine: influence mood and arousal, involved in heightened awareness of dangers in the environment 6.serotonin: regulation of sleep and wakefulness 7.endorphins: dull the experience of pain and elevate moods how drugs mimic neurotransmitters -agonist are drugs that increase the action of a neurotransmitter by binding to a receptor -antagonist are drugs that block the function of a neurotransmitter by blocking the action of the neurotransmitter -figure 3.8 pg 88 structure of the brain -major division of the brain: 3 parts, moving from bottom to top, the brain perform simpler function to more complex(hind brain , midbrain, forebrain) 1.hindbrain:an area of the brain that coordinate information coming into and out of the spinal cord. There are 3 anatomical structure that make up the hind brain: medulla, cerebellum, pons (fig 13.15 pg 96) -medulla: extension of the spinal cord into the skull that coordinate heart rate, circulation and respiration *reticular formation is a cluster of neuron inside medulla which regulate sleep, wakefulness -cerebellum: control fine motor skills, smooth out the action -pons: recieve and send information from cerebellum to the rest of the brain 2.middle brain: sitting on top of the hind brain, contains two structure: tectum and tegmentum orient you towards and away from pleasurable and threatening stimuli in the environment -tectum: receives stimulus input from eyes ears, skin and moves the organism towards the stimulus -tegmentum: involved in movement (also helps to orient an oragnism towards stimuli) and arousal(central location of the neurotransmitter invovled in arousal, mood, motivation) 3.Foredbrain: -highest level of brain both figuratively and literally -control cognitive, emotional, sensory and motor function. -the three main division: cerebral cortex, subcortical structure, basil ganglia 1.subcoritcal structure: area of the forebrain under cerebral cortex -division of subcoritcal structure: 1. thalamus, hypothalamus, pituitary gland function: relay signals, regulation 2.limbic system: hypothalamus, amygdala, hypocampus function: involved in motivation, emotion, learning , memory *thalamus, hypothalamus, pituitary gland: thalamus: -pass on and filter information from sense and send information to cerebral cortex -actively filters sensory information, give more weight to some -close pathways of incoming sensation during sleep -receives input from all major senses except small(which directly connect to cerebral cortex) hypothalamus: -located under thalamus -regulate hunger, thirst body temperature and sexual behaviour *key role in regulating food intake pituitary gland -located directly below hypothalamus -master gland of body's hormone, producing system, release hormone that direct the functions of many other glands in body -hypothalamus send hormonal signal to pituitary gland which then send hormonal signal to other glands in the body -control stress, digestive activities, reproductive process *limbic system: -involved in motivation, emotion learning and memory -include hypothalamus, amygdala, hypocampus hypocampus: -creating, storing, combing information so that they can be stored in other parts of cerebral cortex for long period of time -information limited to facts and events amygdala: -central role in emotional processes, forming emotional memories - stimulate hypocampus to remember details of the situation when we are in a very emotional state Cerebral cortex and basal ganglia basal ganglia: -set of subcortical structure that directs intentional movements -receive input from cerebral cortex and set out put to motor center in brain stem *striatum is part of basal ganglia that is involved in control posture and movement cerebral cortex: outermost layer of the brain, it covers the brain -responsible for most complex aspect of perception, emotion, movement -gyri is the smooth surface of cortex/ sulci is the indentation -divided into 3 levels:1. organizaiton acroos the hemisphere 2.organization within hemisphere 3.organization within specific lobes 1.organization across hemisphere: divide cerebral cortex into left and right hemisphere -similar in appearance and function -contralateral control: each hemisphere controls the functions of the opposite side of the body -cerevral hemisphere connected to each other by commisure (bundle of axons allow each hemisphere to communicate with each other) *corpus callosum is the largest commisure that connects each cerebral cortex and support communication of information across hemispheere 2.organization within hemisphere: -distinguish the functions of different regions within each hemisphere -each hemisphere is divided into 4 areas: occipital lobe, parietal lobe, temporal lobe, frontal lobe 1.occipital lobe -process visual information, comprehend what is being seen sensory receptor in eye->thalamus->occipital lobe *damage in occipital lobe cause person to be blind since person can no longer interpret 2.pariental lobe -process information about touch -contain somatosensroy cortex : strip of brain tissue running from top of the brain down to side -represents skin areas of particular parts on the cortalateral side of the body (fig 3.22 pg 101) -large part of somatosensory cortex is devoted to the more sensitive part of the body -illustrated by homunculus in which the size of the body parts correspond to how much somatosensory cortex is devoted toit 3.temporal lobe: -responsible for hearing and language -contain primary auditory cortex: -receive sensory information from ear then process information into meaningful units -also contain visual association areas that interpret the meaning of visual stimuli and help us recognize common object 4.frontal lobe: -specialize area for movement, abstract thinking, planning, memory -contains motor cortex: parallel strip of brain tissue to somatosensory cortex -different part of motor cortex correspond to different body parts -starts voluntary movements and sends message to basal ganglia, cerebellum, spinal cord -control different skin and body areas on the contralateral side of the body -other areas coordinate thought process that help us manipulate information, retrieve memories (thinking, imaging, planning, anticipate) Organization within specific lobe -representation of information within specific lobe in cortex -pimary area: handles fine details of information/ association area contains neuron that help provide meaning to information coming in cortex -neuron in association area is less specialized than primary area Brain plasiticity -sensory neuron in cerebral cortex are not fixed -area of assigned sensory neuron can be reassigned to respond to other regions of the body to adapt to changes the organization of the nervous system Nervous system is an interacting network of neurons that send electrochemical information throughout the body division of the nervous system 2 major divisions: 1.central nervous system, composed of brain and spinal cord. It receives sensory information from the external world and processes the information and send commands to body connect to the spinal cord 2.peripheral nervous system connects the central nervous system to the body's organs and muscles -divide in to somatic nervous system(controls voluntary movements of muscles; human has conscious control over this system ) and autonomic nervous system(controls self regulated actions of internal organs and glands; human do not have control over this system) 3. autonomic nervous system divided in to parasympathetic( calming; helps the body return to a normal resting state) and sympathetic (arousing; nerves that prepares the body for action in threatening situations) systems -parasympathetic nervous system mirror the connections of the sympathetic nervous system (figure 3.11 pg 93) components of central nervous system -spinal reflexes is simple pathways in the nervous system that rapidly generate muscle contraction which do not require the brain's input (sensory neuron-> spinal cord-> motor neuron) - for complicated tasks, the peripheral nervous system communicates with the central nervous system through sensory neuron; brain sends commands for voluntary movement through the spinal cord to motor neurons to conduct movement -patients with at particular damaged area of spinal cord will lose sensation and motor control to the corresponding body parts Prenatal (before birth) Development of the Central Nervous System -first important bodily system developed in an embryo -ridge form on one side of the "sphere" and then builds up at its edges to become a deep groove. The deep grooves fuse together to become neural tube: *the tail end will remain a tube and form the basis of the spinal cord *the head end will expand to form the three basic levels of the brain -first, three basic levels of the brain are visible, then the brain differentiate into subdivision of forebrain, midbrain, hindbrain. -as embryonic brain continues to grow, each subdivision folds onto next one (ex. hindbrain forms cerebellum and medulla ex.) -the cerebral cortex doesn't develop until the middle of the pregnancy and cerebral hemispheres undergo most of their development in the final months -ontogeny( how it develops with in a given individual) of the brain is fast process -phylogeny (how it developed within a particular species) of the brain is slow process Genes and the Environment Gene and environmental influence play a role in directing behavior. The two factors are compared relatively with respect to their influence. What are gene? -Units on the a strand of DNA that encodes for the production of protein -Chromosome are condensed threads of DNA, each strands composed of two DNA wound around each other in a double helix configuration -Human have 23 pairs of chromosomes, you inherit one of each pair from your parents and selection of the pairs are random (for example, determination of sex is random) -degree of relatedness is the probability of sharing genes most genetically related people are monozygotic twins (identical twin) second most related people are dizygotic twin (fraternal twin) and siblings born separately The Role of Environmental Factors -Heritability is a measure of the variability of the behavioral traits that are genetically pass down to the individual. -heritability is calculated as a proportion and its numerical value ranges from 0 to 1.00. It is based on the relatedness between the individuals. (A heritability of 0 means that genes do not contribute to individual differences in the behavioral trait, A heritability of 1.00 means that genes are the only reason for the individuals differences.) -The scores indicated that individuals differences are caused by varying degrees of genetic and environmental contributions. (for human behavior, it is within the range of 0.3-0.6) -4 important points about heritability: tells us nothing about the specific genes the contribute to a trait (abstract concept) tells us nothing about an individual (population concept) is dependent on the environment( heritability is meaningful only for the environmental conditions in which it was computed) 4. it is not useful for determining how individuals will respond to particular environmental conditions Learning about Brain Organization by Studying the Damaged Brain -research in neuroscience correlates the loss of specific perceptual, motor, emotional, or cognitive functions with specific areas of brain damage and theorize about the functions those brain areas normally perform -modern history of neuroscience can be dated to the work of Paul Broca, he described patient who lost the ability to talk but still understand sentences due to damage in left frontal lobe -Cal Wernicke described a patient who lost the ability to understand sentences but still can talk due to damage in temporal lobe The emotional Functions of the Frontal Lobes Phineas Gage case: an iron rod went through his skull while he was working on the railroad. ( figure 3.26) The connections between the frontal lobe and the subcortical structures of the limbic system were damaged in his brain. His case study was the first to allow researchers to investigate the hypothesis that the frontal lobe is involved in emotion regulation, planning, decision making. The distinct roles of the left and right hemisphere -When patients suffer severe seizure that goes across two hemisphere through the corpus callsosum, surgeons produce the split brain procedure (cut the corpus callosum) to isolate seize in one side of the brain only. -Roger Sperry studies the patients with split brain procedure and finds the independent functions of the cerebral hemisphere( experiments figure 3.27, figure 3.28, pg 114) -the studies reveal that the two hemisphere perform different functions and can work together as long as the corpus callosum is there, without corpus callosum, the information gets stuck in the hemisphere it initially entered. From this Sperry found the independent functions of each hemisphere Listening to the brain: Single Neurons and the EEG electroencephalograph is a device used to record electrical activity in the brain . the recording allow researcher to make discoveries about the nature of sleep and wakefulness structural brain imaging -ct scan and mri are used to provide information about the structure of the brain but do not reveal anything about the function of the brain MRI produce better resolution than CT, clearer picture of the structure of the brain -pet and fmri scans provide inforamtion about the functions of the brain by revealing which brain areas become more or less active in different conditions. fmri does not requre any exposure to radioactive substance and localize changes in brain activity across a shorter period of time. Chapter4 Sensation and Perception -Synaesthesia is the perceptual experience of a sense that is evoked by another sense -some people with synaesthesia link their perceptions of letters with certain colors and perceive letters as printed in different colours. Study shown that in synaesthesia, brain regions for different forms of sensation cross active one another Our senses encode the information our brains perceive -sensation and perception are related but two separate events -sensation is stimulation to a sense organ; perception is to interpret the stimulation into meaningful representation -human have five senses: vision, hearing, touch, taste, smell -all sense depend on the process of transduction, it is the process when sensors in the body convert stimulus from the environment into neural signals and sent to central nervous system (convert physical energy from the world into neural energy and sent to the brain. table 4.1 pg 128) Psychophysics -structuralism tried using introspection to measure perceptual experiences. It failed since observer cannot directly perceive experimenter's feeling towards the event and the perception of the event is based on personal experiences, thus it is unique to individuals. -Fechner deve
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