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Lecture 3

Lecture 3 - Jan 16.pdf

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PSYC 211
Yogita Chudasama

PSYC211 Lecture 3 - Jan. 16 The Synapse: • A synapse is a junction between the terminal button of the sending neuron and a portion of the dendritic membrane of the receiving neuron • Synapse can occur on the soma or the dendrite • Synaptic transmissionDetail of the Synapseof messages from one neuron to another through a synapse Synaptic vesicles contain molecules oft by neurotransmitters which are released out of the terminal button neurotransmitter. They attach to themicals diffuse through synaptic cleft presynaptic membrane Dand releasee Synapse: Detail of the Synapse neurotransmitter into the synaptic cleft Synaptic vesicles contain molecules of neurotransmitter. They attach to the the presynaptic membranec membranes. It is filled with an extracellular fluid.ransmitter into the synaptic cleft Synaptic cleft is the space between the Presynaptic membrane is Postsynaptic membrane is pre- and postsynaptic the membrane of the the membrane of the membranes. It is filled terminal button (the receiving cell either on the with an extracellular sending cell). This is soma or the dendrite fluid. where neurotransmitter is released Presynaptic membrane is Postsynaptic membrane is the membrane of the the membrane of the terminal button (the receiving cell either on the sending cell). This is soma or the dendrite where neurotransmitter is Postsynaptic Potreleased(PSP) Postsynaptic Potentials (PSP): Postsynaptic Potentials (PSP) • Neurotransmitter diffuses across synaptic cleft, it will bind to a receptor on the postsynaptic membrane • Binding of neurotransmitter to binding site opens the ion channel (open/close PSM) • Sodium-potassium channels keep sodium ions outside the cell. When sodium channels are opened, the influx of sodium ions causes a depolarization - Excitatory Postsynaptic Potential (EPSP) • If potassium channels open, potassium ions leave the cell. Potassium is positively charged. It’s efflux causes a hyper-polarization - Inhibitory Postsynaptic Potential (IPSP) PSP’s are influenced by other ions depending on the state of the membrane. E.g. If • the membrane is resting, chloride ions will have no effect, but if the membrane has be depolarized, chloride ion channels will permit chloride ions to enter the cell thus neutralizing the EPSP • Calcium ions play an important role in activating certain enzymes and other organelles (chemicals) which can cause structural changes to the postsynaptic potentials Neural Integration: • The interaction of the excitatory and inhibitory synapses on a particular neuron is called neural integration If several excitatory synapses are active at the same time, the EPSP will travel • toward the axon and the axon will fire • If several inhibitory synapses are active at the same time as the EPSP, the IPSP will diminish the size of the EPSP and prevent the axon from firing • The rate at which a neuron fires is controlled by the relative activity of excitatory and inhibitory synapses • If the activity of the excitatory synapses goes up, the rate of firing goes up • If the activity of the inhibitory synapses goes up, the rate of firing goes down Neural Inhibition Does Not Always Produce Behavioural Inhibition: • For example, a group of neurons may prevent me from putting my hand in the fire. If, however, those neurons are inhibited (i.e. Prevented from producing an IPSP), those neurons will NOT suppress my behaviour and I will put my hand in the fire • Inhibition of inhibitory neurons makes the behaviour more likely to occur Neural Excitation Does Not Always Produce Behavioural Excitation: • For example, when we are dreaming, a group of inhibitory neurons are activated to prevent us from acting out our dreams. If this activation fails to occur, people will act out their dreams • Excitation of neurons that inhibit a behaviour, suppresses that behaviour Autoreceptors: • Located on a neuron which detects neurotransmitters that have been released by that very same neuron • Do not control opening/closing of the ion channel Regulate a variety of internal processes including synthesis of neurotransmitters • What is a Drug? • A chemical substance used in the treatment, cure, prevention or diagnosis of disease or used to enhance physical or mental well being • A chemical substance that has “perceived” beneficial effects on perception, consciousness, personality and behaviour (e.g. Narcotics, hallucinogens). Some drugs can cause addition if abused (e.g. Cocaine, heroin) • An exogenous chemical that significantly alters the function of certain cells when taken in relatively low doses • Exogenous chemical - chemical produced outside of the body (basically consumed) • Psychopharmacology is the study of the effects of drugs on the nervous system and behaviour Routes of Drug Administration: • Drugs have to reach their site of action which is the point where drug molecules interact with molecules located on or in cells of the body • Intravenous (IV) injection - into the vein • Intraperitoneal (IP) injection - into the abdominal wall (peritoneal cavity) • Intramuscular (IM) injection - into the muscle Subcutaneous (SC) injection - into the space between the skin • • Oral administration - by mouth • Sublingual administration - under the tongue • Intrarectal administration - as suppositories • Inhalation - by smoking Topical administration - through the skin • • Intracerebral administration - directly into the brain *Bold* = in humans *italics* = in animals Dose Response Curve: Dose Respo
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