Class Notes (811,155)
Canada (494,530)
Psychology (2,023)
PSYC 101 (392)

PSYC 101 CHPT. 4

9 Pages
Unlock Document

University of British Columbia
PSYC 101
Barbara Cox

Psych 101, 007 Jan. 22 Chpt. 4 The Biology of Behaviour Major structures of the Neuron: Cell body Contains the nucleus  nucleus is round, centrally located structure, contains DNA, controls protein manufacturing, directs metabolism, no role in neutral signalling Dendrites  Information collectors  Receive inputs from neighboring neurons  Inputs may number in thousands  If enough inputs the cell’s axon may generate an output Dendritic growth  Most of the neurons in our brain are the neurons we’ve had since we were born  What can change is that dendrites can grow, make new connections, lose connections  Mature neurons generally don’t divide  Provides room for more connections to occur Axon The cell’s output structure One axon per cell, 2 distinct parts  Axon terminal- tubelike structure branches at end that connect to dendrites of other cells Myelin Sheath  White fatty casing on axon  Acts as an electrical insulator  Not present on all cells, but on ones that have long processes  When present increases the speed of neural signals down the axon Jan . 24 How neurons communicate  Neurons communicate by means of an electrical signal called the action potential  Action potentials are based on movements of ions between the outside and inside of cell  When an action potential occurs, a molecular message is sent to neighboring neurons Ion channels Two types of channels: 1) Ion channels that don’t bind to a neurotransmitter (called Gap junctions and act as an electrical signal)  Ions flow from presynaptic membrane to post-synaptic membrane 2) Ion channels that bind to a neurotransmitter (called chemical synapses)  Neurotransmitters from the presynaptic membrane bind to and open ion channels on the post-synaptic membrane  Ion channels are in the postsynaptic membrane, they open & close  Ion channels are specific to certain ions  Ion channels and ion transporters regulate the number of ions inside and outside the axon Neural Firing  A resting neuron is negatively charged  If a portion is stimulated beyond its threshold, it briefly reverses polarity  This polarity reversal travels down the neuron  Neurotransmitters are released at the axon terminals The Action Potential  Sodium and potassium are both positive  At first, inside of the cell is negative with respect to outside  During an action potential, sodium channels open to let sodium ions enter, reversing membrane potential  Inside of cell becomes more positive than outside (depolarization)  After a brief period, sodium channels close  Next, potassium channels open and let potassium out  Inside of neuron becomes negative again (repolarization)  This causes the neuron to go back to resting potential  The height of the action potential is fixed  A neuron either fires or it fails to reach the threshold  Stimulus intensity is coded by frequency of firing -> Strong stimuli trigger a high rate of firing in axons  Intensity is directly proportional to frequency of firing The process of neural transmission  Within cells transmission is due to the action potential. Transmission between cells occurs at the synapse  A small amount of chemical is released by the first cell (presynaptic cell) onto the second cell (postsynaptic cell).  Receptors on the postsynaptic cell bind the neurotransmitter & transmit the signal to it.  Cell would only fire when there’s excitatory input than inhibitory input. Synapses -Tiny gap between an axon terminal & another neuron (or specialized cell)  Firing neurons release neurotransmitters that cross the synapse Synaptic vesicles:  Hold the neurotransmitter  Neural firing drives them to the synapse  The neurotransmitter binds to the receptor site on the target cell  Ion gates open  Excess neurotransmitter is reuptaken (taken up again) 1. Within the axons of the neuron neurotransmitters, which are held in storage-like vesicles until they are released when the neuron is stimulated 2. The small space between the axon terminal and the dendrite of another neuron Neurotransmitters  Ex. Glutamate, GABA, Acetylcholine, Monoamines, Peptides, Cannabinoids  Acetylcholine: important for learning, memory, muscle movement  Serotonin: influences mood and regulates food intake  Dopamine: important to movement and to frontal lobe activity  GABA: important in inhibiting neural activity  Norepinephrine: maintains alertness & wakefulness  Endorphins: regulate firing of pain neurons  After crossing the synapse the neurotransmitter is reuptaken or degraded  There are more than 40 known types  Different ones have different effects  Whether it’s inhibitory or excitatory is not necessarily because of the chemical compound, it’s the nature of the receptor that matters  Drugs, neural diseases often affect neurotransmission Drugs  A drug that is psychoactive is a drug that is affecting our brain  Many drugs influence synaptic transmission  Drugs can be agonistic or antagonistic  Antagonistic  interferes with release of neurotransmitter  acts as false transmitter, occupying receptor sites so that neurotransmitter can’t bind to it  Drug causes leakage of neurotransmitter from synaptic vesicles  Agonistic  drug induces increase in synthesis of neurotransmitter  increases synaptic release of transmitter  drug sits on the receptor and activates it, turns it up Drugs and Consciousness  Psychoactive drugs are chemicals that change perceptions and moods, they affect brain chemistry & user expectations  Stimulants-excite neural activity, arouse body functions  Ex. caffeine, nicotine, amphetamines  While stimulants are active, they increase heart rate & breathing rate, pupils dilate, appetite diminishes  After, get tiredness, headaches, irritability, depression  Amphetamines- drugs that stimulate neural activity, causing accelerated body functions and associated energy and mood changes  Depressants- calm neural activity, slow body functions  Ex. alcohol, barbiturates, opiates  Impairs judgement and inhibitions  Decreases sympathetic nervous system activity  Disrupts processing of info into memory (not short term recall or existing long-term memory)  Focuses attention on immediate situation  Opiates- opium & its derivatives (morphine & heroin) opiates depress neural activity, temporarily lessening pain & anxiety  Barbiturates- drugs that depress the activity of the central nervous system, reducing anxiety but impairing memory & judgement  Hallucinogens- psychedelic (mind-manifesting) drugs that distort perceptions, evoke sensory images in the absence of sensory input  Ex. LSD, Peyote, marijuana, magic mushrooms  Psychedelic s: LCD, PCP, marijuana  Common perceptual distortions & hallucinations: o Simple Geometric Forms o Meaningful Images / Tunnel o Feeling of Separation from Body  Loss of oxygen to the brain  THC- major active ingredient in marijuana, triggers a variety of effects, including mild hallucinations  LSD- lysergic acid diethylamide, a powerful hallucinogenic drug, also known as acid Summary Dependence and Addiction  Tolerance- continued use of a drug requires larger doses to equal the same effect  Withdrawal- in the absence of the drug, user may feel physical pain & cravings  Any drug that you take regularly that affects the brain, you can end up with withdrawal  2 kinds of dependence: physical dependence or psychological dependence  Physical dependence-physiological need for drug, marked by unpleasant withdrawal symptoms o brain adjusts to the drug  Psychological dependence –psychological need for drug, i.e. to relieve negative emotions o brain & body starts to learn the cues that the drug is coming, body starts to prepare for the drug & compensates for the drug even before it gets inside the body o If in different environment, body may not get the cues & cannot prepare for the drug , could die
More Less

Related notes for PSYC 101

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.