Textbook Notes (362,809)
Canada (158,054)
Psychology (4,729)
Psychology 1000 (1,558)
Dr.Mike (659)

3 - Biological Foundations of Behaviour.docx

20 Pages
Unlock Document

Western University
Psychology 1000

Chapter 3 Biological Foundations of Behaviour 1 The Neural Bases of Behaviour  Brain: grapefruit-size mass of tissue that feels like jelly and looks like a greyish gnarled walnut Neurons  Neurons: specialized cells that are the building blocks of the nervous system  Linked together by circuits  At birth: 100 billion neurons  Soma: have biochemical structures to keep neuron alive o Nucleus – carries genetic information  Dendrites: branchlike antennas collect messages from 1,000 + neighbour neurons and processes them to send to the cell body o Surface of cell body also has receptors  Axon: conduct electrical impulses, soma  neurons, muscles, glands o Branch out to form several hundred axon terminals o Each axon may connect with dendritic branches from many neurons (soma) Node of Ranvier  pass many messages at once  more than 200 types and vary in size and shape o eg. Neuron in spinal cord: axon that extends almost a metre to one of fingertips o eg. Neuron in brain may be less than a mm long  Glial Cells: support neuron function o Forms myelin sheath that surround some axons &hold them in place o manufacture nutrient chemicals that neurons need o absorb toxins and waste materials that might damage neurons  Blood-brain Barrier: blood vessels smaller gaps, glial covered o 10 glial cells : 1 neuron  Horizontal cells - neuron of retina that helps integrate info before sent to brain  Ganglion cells o Large interneuron that conveys info from horizontal cells to brain o Easy to measure electric output The Electrical Activity of Neurons  Generate electricity to make nerve impulses  Release chemicals that allow them to communicate with other neurons, muscles, glands  Salty positive charged external fluid (Na ) and (Cl) and some K + + -  Inside neuron: Na , K , Cl, anions (negative charge)  Uneven distribution of charged protein ions inside (Na concentration is 10x higher outside) The Action Potential (Nerve Activation)  action potential - 70 mV  40 mV in 5 – 7 msec  Rest: Na and K channels are closed at 70 millivolt +  Stimulated: Na channels opened to allow depolarization through K pump (Na inflow, lose its polarity)  All-or-none law: o Action Potential Threshold: change from -70 mV  -50 mV by Na into axon before triggered  Threshold: -50 millivolts (all holes expand and sodium ions rush right in) o Graded Potentials: does not reach -50 mV o Only axons have action potential and it flows down to its axon terminals  Repolarization: bring back polarity until dips below resting period o Absolute Refractory Period: membrane is not excitable &cannot generate another action potential  Hyperpolarization: Asymptote back up to resting potential after o Relative Refractory period - (can stimulate neuron but need a stronger stimuli)  Reflex action: close Na channels so excess Na flows out and escaped K are recovered + +  For the neuron to function properly, Na and K must enter and leave the membrane at just the right rate 2 What happens when multiple neurons synapse?  Additive – see if it is enough to reach threshold (-50)  Excitatory and inhibitory fire at the same time o No change in electrical activity (cancel out) and stay at resting potential of -70 How does a neuron code intensity?  Neurons have different thresholds but fixed max  Strong stimulus  more neurons  higher frequency of firing  Intensity directly proportional to frequency of firing  No firing during absolute refractory period o Can’t be any faster than the time it takes to repolarize The Myelin Sheath  Fatty, whitish insulation layer (faster transmission speed) derived from glial cells during development  Nodes of Ranvier – where myelin is really thin or absent and generates electrical charge  Most commonly found in nervous systems of higher animals  Usually not fully formed until after birth when gain muscular coordination  Multiplesclerosis: person’s own immune system attacks the myelin sheath o Disrupts delicate timing of nerve impulses o Result: jerky, uncoordinated movements, paralysis How Neurons Communicate: Synaptic Transmission  Early history: thought axon made physical contact with dendrites, cell bodies of neurons to pass electricity  Descartes – reflex arc o Stimuli transferred from periphery to brain and reflected back through animal spirits o Mind and body interact through the brain’s tiny pineal gland o Sensory neuron  inter-neuron  motor neuron o Sherrington’s Experiment proved that neurons don’t touch  Swammerdam – frog experiment o Put frog leg in jar with water o Put battery, but water level didn’t rise so no animal spirit came out  Bell and Muller o Thought each sensory mechanism have different energy but they have same energy  Muller – not instantaneous speed – there’s a limit  Reaction time - Maskelyne and Kinnebrook  Cajal and Sherrington: communicate at synapse (functional; no physical connection between neuron, target) o Loewi: experiment proved that neurons released chemicals that carried the message to another  Synaptic Cleft: (synapse) tiny gap or spaced between axon terminal of neuron and dendrite of another Neurotransmitters  Receptor sites is where communication is happening  Synthesis – neurotransmitters: chemical molecules are formed inside neuron  Stored – synaptic vesicles filled with neurotransmitters in axon terminal  As action potential passes axon, synaptic vesicles goes towards gap and breaks it open o Release – chemicals into the synaptic gap and flow across to postsynaptic membrane (dendrites) o Bind – fit into same shaped receptor site  Presynaptic membrane - reuptake o Recycle, takes in all remaining neurotransmitter in synapse o MAO – monoaminooxidase neutralizes the synapse and gets rid of its remains  Sodium ion channels open o Depolarization  EPSP (excitatory post synaptic potential) – more positive  Potassium ion channels open o Hyperpolarization  IPSP (inhibitory post synaptic potential) – more negative 3 Excitation, Inhibition and Deactivation  Binding of transmitter and receptor site  chemical reaction o Depolarize (excite) postsynaptic cell membrane by stimulating inflow of positive charged ions o Excitatory transmitters = neurotransmitters that create depolarization o Excitatory transmitters or others may exceed action potential  Hyperpolarize + o Allow K to flow out or negatively charged ions to flow in o Make membrane potential even more negative o Inhibit function  Balance of excitatory & inhibitory processes must be maintained if the nervous system will function properly o Prevents uncoordinated discharge of nervous system (seizures: many neurons reach action potential)  Deactivation of transmitters (2 ways) o binds to its receptor until it shuts off o deactivated by other chemicals synapse that break them down into chemical components  Psychoactive drugs target transmitter’s receptor, binding to receptor instead of neurotransmitter o alter synaptic transmission influencing how transmitter is cleared from synaptic cleft after it released o Drug’s effects are not determined by its actions at synapse  by which specific chemical transmitter it targets Specialized Transmitter Systems  Nature has found a way to divide the brain into systems that are uniquely sensitive to certain messages  Transmitter molecules have many shapes recognized by certain chemical messengers to prevent “crosstalk”  Two types of neurotransmitters o Amino acids, glutamate or glutamic acid  Excitatory, important in learning and memory  Over activation esp within cerebral cortex does not improve memory, gives one seizures o Gamma-aminobutyric acid (GABA)  Motor control and the control of anxiety  Anxiety disorder drugs act by enhancing GABA activity  Common used drugs and alcohol intoxicate the brain and cause ↑ GABA-induced inhibition o Both found throughout nervous system o Role in mediating all behaviours  Acetylcholine (ACh): best understood neurotransmitter involved in memory and muscle activity o Underproduction in Alzheimer’s, weakens or deactivates neural circuitry that stores memories o Also excitatory transmitter at synapses where neurons activate muscle cells o Botulism blocks release of Ach paralysis of muscles esp in respiratory system o Black widow spider bite  venom produces a lot Ach  violent muscle movement and maybe death  Dopamine: mediates a wide range of functions o motivation, reward, feelings of pleasure, voluntary motor control, control of thought processes o In Parkinson’s Disease, basal ganglia producing neurons die  ↓ dopamine = loss of voluntary motor control  Treated with L-DOPA  ↑ amount of dopamine o In emotionally disturbed people, drugs attach to dopamine receptors and block it  Serotonin: influence mood, eating, sleep, sexual behaviour o depression involves abnormal sensitivity to this o anti-depressant drugs like Prozac increase serotonin by blocking reuptake o Others inhibit the activity of enzymes in the synaptic space that deactivate serotonin  Endorphins: reduce pain and increase feelings of well-being o bind to same receptors as morphine o analgesics = pain killers  Neuromodulators: substances in brain that ↑ or ↓ sensitivity of many neurons to their specific transmitters o Role in eating, sleep and stress 4 Understanding How Drugs Affect Your Brain  Agonist – drug that ↑ activity of neurotransmitters o Enhance a neuron’s ability to synthesize, store or release neurotransmitters o Mimic the action of a neurotransmitter by binding with and stimulating postsynaptic receptor sites o Make it more difficult for neurotransmitters to be deactivated (inhibit uptake)  Antagonist – drug that ↓ activity of neurotransmitters o Reduce a neuron’s ability to synthesize, store or release neurotransmitters o Prevent a neurotransmitters from binding by fitting into and blocking the receptor site  Alcohol - depressant o Agonist – stimulates activity of inhibitory transmitter GABA, depressing neural activity o Antagonist – decreases activity of glutamate (learning and memory) o Slow neural activity inhibits normal brain functions (clear thinking, emotional & motor coordination)  Caffeine - stimulant o Increase the activity of neurons and other cells o Looks like adenosine molecules (that causes drowsiness) o Antagonist – caffeine takes up all receptors so can`t sense adenosine = ↑ rates of cellular activity  Nicotine o Agonist – looks like Ach and fits into its receptor cells to create action potentials o At other receptor sites, nicotine stimulates dopamine activity (addictive properties)  Amphetamines – stimulants o Boost arousal and mood by increasing dopamine and norepinephrine o Cause neurons to release lots of neurotransmitters and inhibit reuptake  Cocaine o Produce excitation of increased muscular strength and joy  Rohypnol and GHB o Drugs added to party drinks to lower drinker’s inhibitions, making non-consensual sexual conquest o Supress neural activity by enhancing the action of GABA o High doses  respiratory depression, loss of consciousness, coma, death o Decreases neurotransmission in areas of the brain involved in memory Neurotransmitter Major Function Disorders Associated with Malfunctioning Glutamate  Excitatory (Glutamic Acid)  Found throughout brain  Control all behaviour (learning, memory) Gamma  Inhibitory transmitter (hyperpolarization) Destroyed GABA-producing neurons Aminobutyric  Found throughout brain in Huntington’s  tremors, loss of Acid (GABA)  Control all behaviours (anxiety, muscle) motor control, personality changes Acetylcholine  Excitatory at synapse  Alzheimer’s (undersupply) (Ach)  Muscular movement and memory  Muscle contractions, convulsions (oversupply)  Inhibitory – lower heart rate Norepinephrine  Excitatory and inhibitory functions  Depression (undersupply) (NE)  Neural circuits controlling learning,  Stress and panic disorders memory, wakefulness, eating (oversupply) Serotonin  Inhibitory at most sites, excitatory  Depressions, sleeping, eating (5-HT)  Mood, sleep, eating, thermoregulation disorders (undersupply)  Pleasure and pain Dopamine  Inhibitory or excitatory  Parkinson’s disease and depression (DA)  Voluntary movement, emotional arousal, (undersupply) learning, motivation, experience pleasure  Schizophrenia (oversupply) Endorphin  Inhibits transmission of pain impulses  Insensitivity to pain (oversupply)  Pain hypersensitivity, immune problems (undersupply) 5 The Nervous System Intro  Sensory Neurons: afferent - carry input messages from the sense organs to the spinal cord and brain  Motor Neurons: efferent - transmit output impulses from brain & spinal cord to body’s muscles and organs  Interneurons: relay station; outnumbers sensory and motor neurons o perform connective or associative functions within sensory and motor neurons (allows complexity)  Central Nervous System: consisting of all the neurons in the brain and spinal cord  Peripheral Nervous System: neurons connecting central nervous system to muscles, glands, sensory receptors The Peripheral Nervous System  Contains all the neural structures that lie outside of the brain and spinal cord  neurons carry out functions to sense what’s going on in & outside our bodies & respond with muscles, glands The Somatic Nervous System  Sensory neurons transmit messages from the eyes, ears and other sensory receptors  Motor neurons send messages from brain and spinal cord to muscles to control our voluntary movements  Sensory nerves – axons of sensory neurons group together like many strands of a rope (similar for motor)  Tracts – nerves inside brain and spinal cord The Autonomic Nervous System  Involuntary functions o Respiration, circulation, digestion, motivation, emotional behaviour, stress responses  Subdivisions – work together to achieve homeostasis Sympathetic Nervous System Parasympathetic Nervous System  Activation or arousal function  Slows down body processes and maintains or  Fight or flight response returns you to a state of rest  Dilates pupils (enhance vision)  Contracts pupils  Relax bronchi (increase air to lungs)  Constricts bronchi  Accelerate, strengthen heart beat (increase2O )  Slows heart beat  Contracts vessels (increase blood pressure)  Dilates vessels  Inhibit activity in stomach, intestines (blood  Stimulates activity in stomach and intestines sent to muscles) The Central Nervous System  This distinguishes us from other creatures  Spinal cord connects most parts of peripheral nervous system with brain The Spinal Cord  Most nerves enter and leave the central nervous system by the spinal cord  Neurons are protected by vertebrae (bones of the spine)  Central portion of spinal cord resembles an H o Myelinated axons surround neuron cell bodies o Along its length are sensory nerves o Motor nerves exit the spinal cord’s front side  Spinal reflexes triggered at the level of the spinal cord without any involvement of the brain o Reduces reaction time o Trigger sensory nerve  spinal  interneurons  excite motor neurons  send impulses  The Brain o Most active energy consumer of all body organs o Consumes 20% of oxygen in resting state o When you dream, the brain’s metabolic rate increases 6  Unlocking the Secrets of the Brain o Neuropsychological tests - psychological function linked to a particular brain structure or pathway o Destruction and Stimulation Techniques  Researches produce brain damage (lesions) under carefully controlled conditions  specific nervous tissue destroyed with electricity, cold, heat or with chemicals  Surgically remove parts of the brain and watch consequences  Brain stimulated by mild electric current or chemicals that excite neurons o Electrical Recording  Electrodes record and stimulate brain activity by inserting into brain or neurons  Electroencephalogram – measure the activity of large groups of neurons  Use it to determine abnormal electrical patterns o Brain Imaging  Computerized Axial Tomography – use 360 degree x rays to study visual brain structure  Focus beam of x rays to take pictures of narrow slices of cortex  Positron Emission Tomography  Inject radioactive glucose  Check neuron activity, metabolism, blood flow  More glucose used = more neuron activity  Colour coded; (white, yellow, red (intense colours) = lot of activity where)  Magnetic Resonance Imaging  Combine features of CT and PET view structure and brain activity  Expose to strong magnetic field  Good structural info  Angiogram  X rays enhanced with dye  See blood vessels (check blot clots for stroke)  Not good for showing detailed structure The Hierarchical Brain: Structures and Behavioural Functions The Hindbrain  The brain stem: Life support systems o attached to major portion of hindbrain and cerebellum o Medulla  cause vital body functions to occur automatically  sensory and motor nerve tracts cross over medulla up from spinal cord and down from brain  left side of brain receive sensory input  right side exert motor cells o Suppression of medulla  Alcohol intoxication  Result in death by heart or respiratory failure o Pons: above medulla; bridge carrying nerve impulses between higher, lower levels of nervous system  Clusters of neurons that help to regulate sleep and involved in dreaming  Help control vital functions esp. respiration  The Cerebellum: Motor Coordination Centre o Regulates muscular movement coordination, learning and memory o Motor control functions easily disrupted by alcohol  Damaged – uncoordinated movements eg. walk in straight line The Midbrain  Contains clusters of sensory and motor neurons  Sensory and motor fibre tracts that connect higher and lower portions of the nervous system  Sensory portion – contain important replay centres for the visual and auditory systems o Nerve impulses from eyes and ears are organized and sent to forebrain structures  Motor neurons that control eye movement 7  The Reticular Formation: The Brain’s Gatekeeper o Acts as lookout, alerting higher centres of brain that messages are coming  then either block or allow those messages o Ascending part – sends input to higher regions of the brain  Without this, messages do not register in conscious awareness o Descending portion – higher brain centres can either admit or block out sensory input  Do not want to be overwhelmed by a situation o Role in consciousness, sleep and attention o Severe damage  coma The Forebrain (cerebrum)  Two large cerebral hemispheres (left and right)  Wrap around brain stem (similar to wrapping hands around spoon)  Cortex surrounds cerebrum  The thalamus: The brain’s sensory switchboard o Sensory, visual, auditory relay station o Nerve tracts from sensory receptors  thalamus  appropriate areas in brain o Damaged – confused thinking, disordered attention  The basal ganglia: movement o Group of at least 5 distinct structures surroun
More Less

Related notes for Psychology 1000

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.