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Lecture 3

PSYC 211 Lecture 3 Notes

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PSYC 211
Yogita Chudasama

PSYC 211 – Lecture 3 January 16 2011 How do Neurons communicate with each other? Synapse – junction between the terminal buttons of the sending neuron and a portion of the dendritic neuron of the receiving neuron. Synapse can be on membrane of Soma or on dendrite. Synaptic Transmission – transmission of messages from one neuron to another through the synapse through neurotransmitters, which diffuse across the synaptic cleft. Synaptic vesivles – contain molecules of neurotransmitter. They attatch to the presynaptic membrane and relase neurotransmitter into the synaptic cleft. Synaptic Cleft – is the space between the pre and postsynaptic membranes. It is filled with an extracellular fluid. Presynaptic membrane – is the membrane of the terminal button (the sending cell). This is where the neurotransmitter is released. (Calcium channels here) Postsynaptic membrane: is the membrane of the receiving cell Neurotransmitters facilitate the opening of channels for ions on the membrane by binding onto the presynaptic membrane. Movement of ions affect the potential of the postsynaptic membrane. PostSynaptic Potentials (PSP) -determined by the type of ion that the receptor opens. Four types of ion channels Na, K, Cl, Ca2+. Each Ion does a different thing: -Sodium potassium transporter keeps Na outside the cell. When the channels are open, the influx of sodium causes a depolarisation. (Excitatory Postsynaptic Potential – EPSP) -If potassium channels open, K+ leave the cell. Potassium is positively charged, it’s efflux causes a hyperpolarization. (Inhibitory Postsynaptic Potential – IPSP). -PSP’s are influenced by other ions depending on the state of the membrane. If the membrane is resting, Cl ions will not have any effect because diffusion and electrostatic will maintain the healthy balance. If the membrane has been depolarized, however, the chloride ion channels will permit CL to enter the cell, causing depolarization, trying to neutralize the EPSP. -However you can make the membrane very neg, leading to an IPSP. -Calcium ions affect membrane potential, acting in the same way as Na+ ions. Depolarize membrane, EPSP. Special role in activating enzymes and organelles which can cause changed to the postsynaptic membrane. NEURAL INTEGRATION: The interaction of the excitarory and inhibitory synapses on a particular neuron is called neural integration. If several excitatory synapses are active at the same time, 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 EPSP and prevent the axon from firing. Travels down the soma to axon hillock, the junction between soma and axon. Neural inhibition does not always produce behavioural inhibiton. For example. A group of neurons may prevent me from putting my hand in the fire. If, however, those neurons are inhibitied (prevented from producing 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, during dreams, a group of inhibitory neurons are activated to prevent us for acting out our dreams. If activation fails to occur, people will act out dreams. -excitation of neurons that inhibit a behaviour, suppress that behaviour. *AUTORECEPTORS – on a neuron, detects neurotransmitters that are released by that neuron. Do not open and close ion channels, but control regulatory processes, such as synthesis of neurotransmitters. *axoaxonic synapses – between two terminal buttons. Modulate the amount of neurotransmitters released by the terminal butons. PSYCHOPHARMACOLOGY – DRUGS Drug: A chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to enhance physical or mental well being, (Pharmacological) A chemical substance that has perceived beneficial effects on perception, consciousness, personality and behaviour (ex narcotics) some drugs can cause addiction if abused, (Recreational) An exogenous substance chemical that significantly alters the function of certain cells when taken in relatively low doses. (anything in high doses alters the general functioning of cells) Psychopharmacology is the study of the effects of drugs on the nervous system and behaviour. Routes of 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 (synapse). Drugs must cross the blood brain barrier. i) IV (intravenous injection) – into the vien ii) IP (intraperitoneal Injection) – into the abdominal wall (peritoneal
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