Intro to Psych Book Notes Chapter 3.1
Intro to Psych Book Notes Chapter 3.1 100
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This 7 page Study Guide was uploaded by Sophomore Notetaker on Thursday September 29, 2016. The Study Guide belongs to 100 at Washington University in St. Louis taught by Rice, Duchek, Carpenter in Fall 2016. Since its upload, it has received 38 views. For similar materials see Intro to Psychology in Psychology at Washington University in St. Louis.
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Date Created: 09/29/16
3.1 How Does the Nervous System Operate? Neurons – the basic units of the nervous system Cells that receive, integrate, and transmit information in the nervous system They operate through electrical impulses, communicate with other neurons through chemical signals, and form neural networks The Nervous System Has 2 Basic Divisions Central Nervous System (CNS) – brain and spinal cord Peripheral Nervous System (PNS) – all the other nerve cells in the rest of the body that are not CNS o Includes somatic and autonomic systems The CNS and PNS are anatomically separate, but functions are interdependent PNS sends a variety of information to the CNS CNS organizes and evaluates that information and then directs the PNS to perform specific behaviors or make bodily adjustments Neurons Are Specialized for Communication Neurons are specialized for communication o Excitable – powered by electrical impulses and communicate with other nerve cells through chemical signals Neuron Phases o Reception – neurons take in the chemical signals from neighboring neurons o Integration – incoming signals are assessed o Transmission – pass their own signals to other receiving neurons Type of Neurons o Sensory Neurons – detect information from the physical world and pass that information along to the brain, usually through the spinal cord Somatosensory neurons – provide information from the skin and muscles o Interneurons – communicate with local or short-distance circuits Integrate neural activity within a single area rather than transmitting info to other brain structures or body organs o Motor Neurons – direct muscles to contract/relax, producing movement o Sensory and motor neurons work together to control movement o Sensory receptors in skin sensory neurons interneuron motor neuronmuscle contraction -if touch something pointy Neuron Structure o Dendrite – short, branchlike, appendages that detect chemical signals from neighboring neurons o Cell body – where information from thousands of other neurons is collected and integrated o Axon – long narrow outgrowth of a neuron by which info is transmitted to other neurons Vary in length Nerve – bundle of axons that carry away info between the brain and other parts of the body o Terminal buttons – at the ends of the axons; small nodules that release chemical signals from the neuron into the synapse o Synapse – site where chemical communication occurs between neurons Neurons communicate by sending chemicals into synapse – a tiny gap between the axon of the “sending” neurons and the dendrites of the “receiving” neurons Chemicals leave 1 neuron, cross the synapse, and pass signals along to the other neuron’s dendrites o Messages are received by the dendrites processed in the cell body transmitted along the axon sent to other neurons via chemical substances released from the terminal buttons across the synapse. o A neuron is covered by a semipermeable membrane, a fatty barrier that does not dissolve in the watery environment inside and outside the neuron Membrane has ion channels – allows ions to pass in/out of cell when the neuron transmits signals down axon By controlling movement of ions, membrane plays an important role in communication between neurons; it regulates concentration of electrically charged molecules that are basis of neuron’s electrical activity The Resting Membrane Potential Resting membrane potential – the electrical charge of a neuron when it is not active o Electrical charge inside and outside the membrane is different; this is because the ratio of (-) and (+) ions is greater inside the neuron than outside it o It is more (-) inside the neuron than outside (-70 mV) = polarized o The polarized neuron (at rest) creates electrical energy necessary to power firing of neuron Roles of Na+ and K+ o Each channel matches a specific type of ion: Na+ channels allow Na+ but not K+ (same for K+ channels) o The flow of ions through each channel is controlled by a gating mechanism When the gate is open, ions flow in/out; closed gate prevents this o Ion flow is affected by cell membrane’s selective permeability; b/c of this, more K+ is inside the neuron than Na+ Na+ and K+ Pump: increases K+ and decreases Na+ inside the neuron o Helps maintain resting membrane potential o Contributes to polarization Action Potentials Cause Neural Communication Action potential (neural firing) – the electrical signal that passes along the axon o The signal causes the terminal buttons to release chemicals that transmit signals to other neurons o Signals arrive at dendrites by the thousands; 2 types of signals: Excitatory – depolarize the cell membrane (decrease polarization by decreasing (-) charge inside the cell) Increases the likelihood that neuron will fire Inhibitory – hyperpolarize cell (increase polarization by increasing (-) charge inside the cell) Decreases the likelihood that neuron will fire Excitatory and inhibitory signals received by dendrites are combined with the neuron It total amount of excitatory input surpasses neurons firing threshold (-55 mV), an action potential is generated When a neuron fires, the Na+ gate in the cell membrane opens allows Na+ to rush into neuron causes the inside of the neuron to become more (+) than outside K+ channels open up to allow K+ inside the cell to rush out The change from (-) (+) inside the neuron is the basis for an action potential As Na+ channels close, Na+ stop entering the cell (same for K+ channels) o The electrical charge inside the cell starts out slightly (-) in initial resting state o As cell fires and allows more (+) ions inside, charge becomes (+) o Through natural restoration, charge returns to slightly (-) resting state Na+ channels open (-) K+ channels open (gets more positive) depolarization Na+ channels close repolarization (gets more negative) K+ channels start to close (-) When neurons fire, the cell membrane’s depolarization moves along axon like a wave; Na+ channels open in a series; action potentials always move down the axon away from the cell body terminal buttons Electrical signals travel quickly down the axon because of fatty myelin sheath myelin sheath – encases and insulates the many axons o made up of glial cells; sheath grows along on axon in short segments; between these segments are nodes of Ranvier – small gaps of exposed axon o action potential skips along axon; pauses briefly to be recharged at each node along the axon o for axons without myelin, Na+ channels along each part of the membrane must open (speed decreased) loss of myelin sheath means that visual information is disrupted and motor actins become jerky and uncoordinated All-or-None Principle – dictates that a neuron fires with the same potency each time; it does not fire in a way that can be described as weak/strong o How the neuron fires: the stronger the stimulation, the more frequently it fires action potentials Neurotransmitters Bind to Receptors Across the Synapse Presynaptic neuron – the neuron that sends the signal Postsynaptic neuron – the neuron that receives the signal How Neurotransmitters Work o Inside each terminal button are neurotransmitters – chemicals that are made in the axon and stored in vesicles; transmit signals from 1 neuron to another When released by the vesicles, the neurotransmitters convey signals across the synapse post synaptic cells o After the action potential travels to terminal buttons, it causes the vesicles to attach to the presynaptic membrane and release their neurotransmitters into synapse o Neurotransmitters then travel across the synapse and bind to receptors on postsynaptic neuron Receptors – specialized protein molecules on the postsynaptic membrane o Binding of neurotransmitters and receptors causes ion channels to open/close more tightly, producing an excitatory/inhibitory signal in postsynaptic neuron Neurotransmitters are made in the axon they are stored in vesicles action potentials cause vesicles to fuse to the presynaptic membrane and release their contents into the synapse neurotransmission is terminated by reuptake, enzyme deactivation or autoreception released neurotransmitters bind to postsynaptic receptors Neurotransmitters also block new signals until its influence is terminated 3 major events that terminate its influence: o Reuptake – when the neurotransmitter is taken back into the presynaptic terminal buttons; an action potential prompts terminal buttons to release the neurotransmitter into the synapse and then take it back for recycling Cycle of reuptake and release repeats continuously o Enzyme deactivation – when an enzyme destroys the neurotransmitter in synapse; different enzymes break down different neurotransmitters o Autoreception – autoreceptors monitor how much neurotransmitter has been released into the synapse; when excess is detected, the autoreceptors signal the presynaptic neuron to stop releasing the neurotransmitter Receptor has specific response (excitatory/inhibitory); same neurotransmitter can send excitatory/inhibitory postsynaptic signals Neurotransmitters can produce different effects, depending on properties of the receptor and receptors location in the brain Neurotransmitters Influence Mental Activity and Behavior Agonists – drugs and toxins that enhance the actions of neurotransmitters o Increase how much neurotransmitter is made o Block the reuptake of neurotransmitters o Mimic a neurotransmitter activating/increasing its effects Antagonists – drugs and toxins that inhibit these actions o Decrease the release of neurotransmitters o Destroy neurotransmitters in synapse o Mimic a neuro. blocking neurotransmitter binding Drugs and toxins can minimize neurotransmitter and bind with their receptors as if they were the real thing; the receptor/lock can’t tell if neurotransmitter/key from a forgery and activate it Types of Neurotransmitters o Acetylcholine (Ach) – responsible for motor control at junctions between nerves and muscles After moving across synapses, Ach binds with receptors on muscle cells, making the muscles contract/relax Ex: Ach excites skeletal muscles and inhibits heart muscles Involved in complex mental processes: learning, memory, sleeping and dreaming Because it affects memory and attention, drugs that are Ach antagonists can cause temporary amnesia Alzheimer’s associated with diminished Ach functioning o Monoamines – same basic molecular structure; regulate arousal, regulate feelings and motivate behavior Epinephrine – (adrenaline) a burst of energy caused by a release of it that binds receptors throughout the body; helps prepare body for dealing with threats Norepinephrine – states of arousal and alertness; useful for clarity of attention Serotonin – important for emotional states, impulses control and dreaming Low levels = sad/anxious moods, food cravings, aggressive behavior Some drugs block serotonin reuptake and leave more serotonin at synapse to bind with postsynaptic neurons; treat mental disorders Selective Serotonin Reuptake Inhibitors (SSRIs) – treat depression Dopamine – motivation and reward; communicates which activities may be rewarding Activates us to eat, have sex, drink when thirsty Also involved in motor control and planning; helps guide behavior toward things –objects and experiences – that will lead to additional reward Lack of dopamine – problems with movement o Parkinson’s disease – neurological disorder marked by muscular rigidity, tremors, difficulty with voluntary action; dopamine- producing neurons slowly die off; people alter on suffer from cognitive and mood disturbances Injecting with L-DOPA, helps surviving neurons produce more dopamine; only temporarily Deep brain stimulation – involves surgically implanting electrodes deep within brain and then using mild electrical stimulation in regions affected by disorder; reverse many of movement problems associated o Successful, for as long as 11 years; helps with motor symptoms, but other symptoms get worse over time o GABA – primary inhibitory neurotransmitter in the nervous system; more widely distributed throughout brain than other neurotransmitters Without inhibitory effect of GABA, synaptic excitation might get out of control and spread through brain chaotically Epileptic seizures caused by low GABA levels GABA agonists – used to treat anxiety disorders o Glutamate – primary excitatory neurotransmitter in nervous system; involved in fast acting neural transmission throughout brain Glutamate rectors aid learning and memory by strengthening synaptic connections Excessive glutamate release overexcitement of brain seizures Linked to diseases, brain damage o Endorphins – natural pain reduction and reward; body’s natural defense against pain Pain is useful because it alerts of danger but also interferes with adaptive functioning; endorphins painkilling effects help animals perform behaviors even when they are in pain Morphine – bind with endorphin receptors reducing experience of pain Alters way pain is experienced rather than blocking nerves that transmit pain signals
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