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Lecture

Biological Psychology- Lecture 3

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Department
Psychology
Course
PSY 324
Professor
Tara M Burke
Semester
Fall

Description
Chapter 3 – Synapses *Alcoholism not on midterm* - Threshold of excitation reached  Ion channels open at axon hillock  signal moves down axon (non-decrementing)  signal reaches terminal buttons - Neurons communicate with one another via synaptic transmission of neurotransmitters (Ligand will bind to a specific binding site which will produce postsynaptic potential) - Presynaptic Membrane: Lies opposite to the postsynaptic membrane, where the neurotransmitters are released - Dendritic Spine: Increases surface area Components of the Synapse - Synaptic cleft, synaptic vesicle, release zone, post-synaptic density - Neurotransmitters are produced in the cell body and in the terminal buttons Communication Between Neurons - Structure of the synapses: Synapses occur in 3 places… 1) On dendrites= axodendritic synapse 2) On the soma= axosomatic synapse 3) On other axons= axoaxonic synapse How do we know a synapse exists? Properties of a synapse: 1) Reflexes are slower than conductions along and axon (there must be a gap causing this time lapse) Synaptic Delay: Something is slowing down the transmission of communication 2) Many weak stimuli presented at slightly different times/ locations around the same time produce a stronger reflex than a single stimulus alone (multiple is better than single)- Temporal Summation: neuron A should repeatedly apply stimulation to help neuron B to reach the required threshold (depolarization). Spatial Summation: If there are 3 points of stimulation it will also help the neuron to reach threshold (depolarization) 3) Law of Reciprocal Innervation: When one set of muscles becomes excited, a different set becomes relaxed - Excitatory: tells muscle to flex - Inhibitory: tells antagonistic muscle to relax - EPSP= excitatory post-synaptic potentials Depolarization, increase Na+ into the cell - IPSP= inhibitory post-synaptic potentials Hyperpolarization to prevent stimulation of the neuron, increasing flow of K+ or out or Cl- into cell Steps for Synaptic Neural Communication 1) Synthesis and release of neurotransmitters from presynaptic terminals - Synthesis in soma/ terminal buttons - Calcium channels open (calcium is waiting for depolarization in order for the gates to open and allow for calcium to enter)- if the terminal button is not stimulated, calcium will not enter - Exocytosis: synaptic vesicle fuses with membrane - Vesicles break open and release neurotransmitters into synaptic cleft 2) Activation of the Postsynaptic receptors - Postsynaptic receptor - Neurotransmitter-dependent ion channel 2 Ways neurotransmitters open ion channels… 1) Ionotropic receptor: contains a binding site for neurotransmitters & ion channel that opens when a molecule of the neurotransmitter attaches to binding site (fast acting) 2) Metabotropic receptor: activates an enzyme that begins a series of events that opens ion channels somewhere else in the cell (Slow acting)- effect is stonger and lasts longer even though it is a slower process - G protein: conveys messages to molecules when a ligand binds with & activates the receptor Binding of ligand to receptor  G protein inside membrane activates  activates enzyme that stimulates second messenger  second messenger travels through cytoplasm to ion channel  Opening of ion channel - Second messenger: che
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