Psyc 4640 1st Edition Lecture 4 Current Lecture Space btwn terminal bulbs and dendrites is a synapse synaptic cleft Sender presynaptic neuron Receiver postsynaptic neuron Information moves slower in synapse than in neuron That info is similar to a graded potential closeness matters in amount of info transferred Graded potentials summate over time and space Stimulation of dendritic spines EPSP excitatory postsynaptic potential opens Na gate IPSP inhibitory postsynaptic potential K leaves cell hyperpolarizing OR Cl enter hyperpolarizing The net effect of all EPSPs and IPSPs on neuron decides whether or not it fires Almost all neurons in brain are constantly firing They have a spontaneous firing rate EPSPs and IPSPs alter this rate They occur equally Neurotransmitters Mode of transmission differs synaptically Chemical sent by neurotransmitters amino acids NH2 group peptides gases Neuron sends NTs to terminal bulbs When NTs reach axon terminals Ca2 goes in and NTs leave NT goes to dendrite Results can be o Uptaken by presynaptic neuron o Actually make it to dendrite and be used o Changed to inactive material NT components come from diet You can run out of NTs until they are regenerated They are stored in vesicles Some are free floaters The process of NT release travel to terminal bulbs then to dendrites takes 2 microseconds A single neuron can create and send more than 1 type of NT Can receive diff types as well Ionotropic effects gates open and stuff happens quickly o EX Vision o Glutamate most abundant NT Causes EPSP and ionotropic effects Metabotropic effects slower to occur Second messenger systems Take longer o EX Hunger o Gaba results in IPSPs Metabotropic effects Neuromodulatory effects always use 2nd messenger systems and metabotropic effects They modulate effects of other neurons but don t do anything on their own Autoreceptor a neuron releases an NT and has receptors on it for that same NT Retrograde messengers released by a postsynaptic dendrite or cell body and travels backwards across a chemical synapse to bind to the axon terminal of a presynaptic neuron Some NTs are broken down at receptor site o EX Acetylcholine ACh is broken down into acetate and choline acetylcholinesterase is the enzyme that breaks it down Other NTs go through reuptake Detach from neurons and transporters take them back up to the presynaptic terminals and are reused Many NTs act by altering spontaneous firing rate NTs have diff receptor subtypes Monoamines serotonin dopamine norepinephrine epinephrine o Serotonin does not directly excite other neurons but instead modulates the responses of neurons to other neurotransmitters o Catecholamines dopamine norepinephrine epinephrine Have a catechol group o Serotonin and the catecholamines undergo reuptake Electrical transmission when one neuron actually touches another neuron Where they meet is a gap junction Where synchronized activity is necessary you find them Transmit info electrically Drugs alter neurotransmission NTs get info from presynaptic neuron to postsynaptic neuron Drugs alter NT o Production o Storage o Release o Postsynaptic receptor effects Drug availability dependent on location and other common factors o EX Terminal cancer patients get morphine in US heroin in UK Any drug that can easily transverse the BBB will be very strong and probably addictive Endogenous substance something body already makes o EX Endorphins mute pain Exogenous substance synthesized substance o EX Heroin Psychopharmacology study of effects of drugs on behavior Research drugs are closely monitored by DEA Anytime a pharm industry develops a new drug they determine its abuse potential Determine if it s reinforcing animal works to get it likes it o EX Lever press how many times it will press to get it o EX CPP conditioned place preference rat heroin experiment Box with three areas black grey white Different floors in each Heroin in white area Rat placed in grey Decides where he wants to go Rats are nocturnal should like black room If they re going to the white room more often they are addicted