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Chapter 4

PS101 Chapter 4,5,6.docx

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Wilfrid Laurier University
Kathy Foxall

Chapter 4 The Nervous System Function: gather & process info, produce responses to stimuli, and coordinate the workings of different cells The Central Nervous System (CNS): receives, processes, interprets and stores incoming sensory information about tastes, sounds, smells, colour, pressure on skin, state of internal organs, etc. & sends it to muscles, organs  Sends messages for muscles, glands & internal organs  Made of 2 components: 1. BRAIN: controls reflexes above the neck 2. SPINAL CORD: collection of neurons & supportive tissue running from the base of the brain down the centre of the back  an extension of the brain o Controls reflexes below the neck o acts as a bridge for brain & other body parts o Spinal reflexes: products of spinal cord & are automatic, not requiring any conscious effort  can sometimes be influenced by thoughts & emotions (e.g. erection/ejaculation) The Peripheral Nervous System (PNS): contains all portions of the nervous system outside the brain & spinal cord and handles the central nervous system’s input/output 1. Somatic Nervous System aka Skeletal Nervous System  Subdivision of PNS that connects to sensory receptors & skeletal muscles  Voluntary movement  Consists of nerves connected to sensory receptors  Sensory nerves: responsible for the intake of sensation & sending them to CNS  they carry messages from special receptors in internal/external sense organs which put us in touch with outside world and bodily activity  Motor nerves: carry orders from CNS to muscles, glands, and internal organs (interchange) – enable us to move & cause glands to secrete hormones 2. Autonomic Nervous System (self-governing)  Subdivision of PNS that regulates internal organs/glands A. Sympathetic Nervous System  Prepares body to expend energy for fight/flight/cope response: mobilizes bodily resources & increases output of energy during emotion/stree  Dilates pupils & bronchial tubes, increases heart rate, blood flow, epinephrine & norepinephrine secretion, stimulates sweat, relaxes bladder wall, inhibits digestion B. Parasympathetic Nervous System  Restores & conserves energy after emergency situation  Back to stasis to function adequately  Cortisol gets released Neurons/nerve cells: a cell that conducts electrochemical signals; the basic unit of the nervous system  transmits info to, from & within CNS  Fibres of neurons are connected together in bundles called nerves – human body has 43 pairs of peripheral nerves; 12 pairs in head called cranial nerves  The more neurons you have, the more you’ve experienced  The more axons & dendrites you have, the more complex learning connections have occurred  Neurogenesis: the production of new neurons from immature stem cells  Stem cells: immature cells that renew themselves & have the potential to develop into mature cells 1. Dendrite: incoming message (from neurotransmitters) is received by dendrite 2. From dendrite to cell body: initial processing is done in cell body 3. To axon: long thin fibre that transmits messages away from the cell body & to other neurons/muscle/gland cells; covered by: a. Myelin sheath: fatty insulation that may surround axon of a neuron  Protection: prevents signals from adjacent cells from interfering with each other – if not, results in loss of sense & lack of coordination  Speed: speeds up conduction of neural impulses  Made up of: i. Glia cells: cells that support, nurture & insulate neurons, remove debris when neurons die, enhance formation and maintenance of neural connections & modify neuronal functioning ii. Node: message jumps from node to node 4. To axon terminal – deposits info on the receiving neuron – doesn’t touch the receiving neuron, instead there is a synapse Communication between Neurons 5. Synapse: the site where transmission of a nerve impulse from one nerve cell to another occurs a. Synaptic cleft: where axon terminal of one neuron nearly touches the dendrite or cell body of another b. Synaptic vesicles house neurotransmitter cells: chemical substance that is released b a transmitting neuron at the synapse and that alters the activity of a receiving neuron 6. How do they open/close? Action potential: electrical impulse caused by changes in voltage that allow synaptic vesicle to open 7. Message is accepted by dendrite of receiving cell if neurotransmitter fits the receptor site  when molecules bind to receptor sites, the electrical state of the receiving neuron changes & neuron becomes either more likely to fire an impulse or less likely to  Neurons are either ALL or NONE/ON or OFF = they fire or they don’t  messages are either excitatory (positive voltage shift) or inhibitory (negative voltage shift).  Only when a cell reaches a certain threshold will it fire.  Thousands of messages are received by cell & it must average them  The message that reaches a final destination depends on rate at which neurons are firing, how many are firing, what types are firing, their location & degree of synchrony among neurons, NOT how strongly the individual neurons are firing. Plasticity: the brain’s ability to change and adapt in response to experience – for example, by reorganizing or growing new neural connections – rewiring of the brain to adapt to damage (e.g. adapting to blindness by recruiting visual areas to take part in activities involving hearing)  Brain is a dynamic organ: its circuits are continually being modified in response to info, challenges, & changes in environment Chemical Messengers in the Nervous System TYPE FUNCTION EFFECTS WHERE PRODUCED Neuro- Enable neurons to Diverse, depending on which Brain, spinal cord, transmitters excite or inhibit each circuits activated/suppressed. Can peripheral nerves, other. affect mood, memory, and well- certain glands Travel through axons, being – level of effect depends on fast/short distance. level or neurotransmitter, location, type of receptor it binds with. Endorphins Usually modulate the Reduce pain, promote pleasure; Brain, spinal cord effects of linked to memory & other neurotransmitters functions Hormones Chemical substances Diverse, rangeing from promotion Primarily produced and that affect functioning of digestion to metabolism secreted by endocrine of target organs & regulation glands. Released tissues. directly into bloodstream, which carries them to organs/cells. Neurotransmitter Hormones Seratonin: sleep,apetitie,sensory Melatonin: "dracula"hormone, perception,temperatureregulation, secretedy pineal gland & helps pain suppression& mood(too little = regulate daily biologicalrhythm & depression) promotes sleep Dopamine:voluntary movement, Oxytocin: secretedby pituitarygland. learning, memory,emotion,pleasure highestpeak at orgasm & releasedin or reward & responseto novelty (too pair-bondingsituationsalong with little = parkinsons,too much= vasopressinwhichpromotoes schizophrenia) attachment/trust Acetylcholine:muscleaction,cognitive Adrenals: secretedby adrenal glands & functionung,memory& emotion(too releasedduring emergency response little = alzheimer's) (cortisol,epinephrine& noreinephrine) Norepinephrine:emergency response & learning, memory,deaming, waking, Sex hormones:secretedby tissuesin emotion gonads & by adrenal glands GABA: amjor inhibitory testosterone:enhances sexualdesire neurotransmitterin brain (too much= in both sexes & masculinizationof sleep disorders,too little = anxiety) body Glutamate:major excitetory neurotransmitterin brain, long-term estrogen: physicalfeminization memory Endorphins:body's natural morphine, body's pain killer. Role in apetitie, progesterone:present when egg is sexual activity,blood pressure,mood, fertilized,responsibleto make uterine learning & memory. wall comfy Mapping the Brain Method What is Learned Case studies of person How damage to or loss of neural circuits affects behaviour/cognition with brain damage Lesion studies How damage to or loss of neural circuits affects behaviour from (animals) destroying a part of the brain to examine subsequent behavioural deficit Electrical recordings Patterns of electrical activity in the brain – done by putting electrical (EEGs) contacts on head & measuring activity Needle electrodes and More precise info about electrical activity in small groups of microelectrodes neurons/single neurons Transcranial magnetic What happens behaviourally when a brain area is temporarily inactivated stimulation (TMS) – done by putting a wire coil on person’s head & producing a magnetic field PET scans Visually displayed info about active/quiet areas during and activity/response and about changes associated with disorders as they are happening – done by injections of glucose laced with radioactive element MRI Visually displayed info about brain structures – done through powerful magnetic fields & radio receivers Functional MRI Visually displayed info about active/quiet areas during and activity/response and about changes associated with disorders Parts of the Brain 1. Cerebral cortex: thin cap that goes over cerebrum – the outer layer, has c-shaped structures, grey matter (cell bodies) and white matter (myelin-covered axons), contains 3/4s of cells 2. Cerebrum: largest part of the brain, covered by cerebrum cortex – made of left & right cerebral hemispheres connected by corpus callosum  Where higher-order thinking takes place a. Corpus callosum 3. Thalamus (aka traffic cop): sends sensations (except smell – it has olfactory bulb) to appropriate place, relays sensory info to cortex (e.g. hearing goes to auditory cortex) 4. Hypothalamus: regulates hunger, thirst, sex drives, emotion, reproduction, body temperature, hormones & operations of autonomic nervous system. It sends messages to pituitary gland and then pituitary gland tell other endocrine glands. 5. Pituitary gland: controlled by hypothalamus and tells other endocrine glands to release hormonal messages 6. Limbic system: encompasses hypothalamus, amygdala and hippocampus – all of which are implicated in emotional reactions and motivated behaviour but not for sure controlling them 7. Amygdala: evaluates if you should really be afraid of something. Evaluates “is this really an emergency?” Involved in the arousal and regulation of emotion & initial response to sensory info. Formation and retrieval of emotional memories. Damage to the amygdala can result in anxiety disorders. 8. Hippocampus: evaluates sensory information & linked memory. (e.g. hearing a bird chirp does not trigger a reaction because body is used to it). Also enables us to form spatial memories to accurately navigate through environment. Information about memory directed to appropriate areas. Olfactory bulb & hippocampus are strongly linked = smell/memory have strong relationship. 9. Cerebellum: important for smooth movement, balance, time keeping. Alcohol impairs it from functioning (e.g. why they have sobriety road tests) 10. Brain stem: includes pons, medulla and reticular activating system 11. Pons: involved in sleeping, walking, dreaming 12. Medulla: responsible for autonomic functions like breathing and heart rate. If damaged = dead. 13. Reticular activating system: alertness, consciousness, arouses cortex and screens incoming information. If damaged = coma. Cerebral Cortex 1. C-shaped structures 2. Hills and valleys Both result in a greater mass of neurons to fit in a smaller space Hemispheres: both share functions, but one is often more dominant: left = language, right = spatial ability, humour. However, most behaviours require both hemispheres (e.g. understanding language in order to get humour). Left hem controls right side, right hem controls left. Lateralization: specialization of the two cerebral hemispheres for particular operations 3. Frontal Lobe: complex decision making, involved in short-term memory, higher-order thinking, social judgment, emotion, ability to make plans, think creatively, take initiative, ability to do a series of tasks in proper sequence & stop doing them at the right time a. Pre-frontal cortex: has ability to control emotions, reasoning, decision making & planning (speculation on association to personality) b. Motor cortex (movement): more is allotted to parts that require more movement c. Broca’s area: handles speech production 4. Parietal Lobe: pain, pressure, touch, attention a. Somatosensory cortex: what allows us to sense – receives signals from body parts, large area dedicated especially to hands and face 5. Occipital Lobe: contains areas that receive visual information a. Visual cortex: if damaged, can cause impaired visual recognition or blindness 6. Temporal Lobe: involved in memory, perception & emotion a. Auditory cortex: processes sound b. Wernicke’s area: involved in language comprehension Example: Listening to music activates the whole brain  Temporal lobe: hearing the song  Frontal lobe: process info in patterns  If it’s familiar: hippocampus is remembering the song  Cerebellum: if you want to dance  Parietal lobe: slow-dance, touching someone  Hypothalamus: dopamine release from hearing music we like Understanding the Hemispheres VIA Split Brain Split brain: happens because of a severed corpus colosum, done sometimes to prevent severe epilepsy 1. Images in left visual field get sent to right hemisphere. Images in right visual field get sent to left hemisphere. 2. R Hem  L body Verbal left hem. L Hem  R body He saw nothing because the image went to the hemisphere less capable of processing language. He can pick it up with left hand because the right hemisphere controls the left hand. He can answer here because the image is sent to the hemisphere that allows him to answer verbally & process language. The Brain and… …The “Self” “is the brain the self?” (e.g. hippocampus & memories, limpic system & emotions related to those memories) The self exists in that many parts of the brain are activated by it. …Culture Culture is an experience that creates neural connections (e.g. bilingual brains are different than monolingual brains) What we focus on or learn can affect brain organization. Different cultures show different areas of the brain responsible for difference behaviours. …Sex No statistical differences between math skills, etc. Evolution: environment changes your biology. If we culturally impose experience on men & women, their physical brain structure can change (e.g. teaching women to focus on emotions & men not to) Chapter 5: Body Rhythms and Mental States Consciousness: awareness of oneself and the environment Biological rhythm: a periodic more or less regular fluctuation in a biological system; may or may not have psychological implications Circadian Rhythms: a biological rhythm with a period of about 24 hours  Entrainment: the synchronization of biological rhythms with external cues, (e.g. wake up when daylight, sleep to darkness)  Endogenous: generated from within rather than by external cues o Alertness o Body temperature (increase then sharp decline before sleeping) o Secretion of growth hormones Your Biological Clock Suprachiasmatic nucleus (SCN) aka master pacemaker: an area of the brain containing a biological clock that governs circadian rhythms  Eye sends message to SCN [light/darkness sends message to eye receptor (SCN)].  SCN sends message to brain/body to release hormones (e.g. melatonin secreted by pineal gland) which has effect on brain and behaviour & receives feedback from neurotransmitters & hormones that affect its functioning.  Melatonin in older adolescents kicks in an hour later than younger adolescents.  These rhythms affect us on a daily. Internal desynchronization: a state in which biological rhythms are not in phase with one another (e.g. jetlag affects energy level, mental skills and motor coordination) Sleep Stages (Ultradium Rhythms) – 90 minutes Awake: Small rapid brainwaves, inconsistent (up & downy) Stage 1: small irregular waves, drifting in/out of sleep, heart rate & breathing slows down, where jerky muscle thing happens  Easily woken, where lucid dreams occur Stage 2: less easily awoken, if woken, won’t remember sleeping or having been asleep  Sleep spindles: some brain activity  consolidation of memory of muscles, brain puts motions together smoothly & works out how muscles come together in a pattern *important for athletes, dancers, kids Stage 3 (deep sleep): Delta waves appear; more relaxation of waves  deep breathing, muscles start to relax Stage 4 (deep sleep): Delta waves have taken over; need a big noise to awaken you  sleepwalking occurs in this stage (or 3) because paralysis hormones have not yet been released in the body  Delta brain waves only occur when drunk, have dementia or schizophrenia REM stage: Rapid Eye Movement (dream stage)  Where we dream & where dreams are remembered  Brain waves are mostly similar to awake waves but body is acting very different (sometimes called paradoxical sleep): paralysis hormone has been secreted = no sleepwalking  Heart rate & blood pressure increases  Genitals are very active (wet dreams)  REM sleep may be necessary for memory: consolidation  When people are deprived of REM, they will make up for it when the
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