PSY 301 1st Edition Lecture 6 Outline of Last Lecture I Love Relationships II Development of Relationships III Qualities of good marriages and other long term relationships Outline of Current Lecture I Biopsychology introduction II Neuron III Types of Neurons IV Structure of a Neuron V Path of Transmission Current Lecture Biopsychology introduction 1 This involves looking directly at biological processes involved in behaviour 2 The brain determines what we experience 3 Brain receives interprets and acts on information from the world 4 We are able to see what we see and experience what we experience because of our brains Neuron nerve cell 1 This is the basic element of the brain 2 The nervous system is a network of connections linking neurons to each other 3 A person almost has 100 billion neurons 4 We are born with more neurons than we have now neurons die as we live 5 If connections are not made in our brain they will eventually die and no longer be able to be made 6 The connections that are made in our brain enable us to function the way we do now new connections are made all throughout life 1 Example is when we were babies we learned how to walk Without this connection of being made at this critical time we would not know how to walk 2 Another example is our ability to hear if the connection of learning how to hear was not made during infancy then our ability to hear would be gone 7 Myelination of 50 neurons after birth Types of Neurons 1 Sensory neurons Neurons that enable us to touch hear see and smell 1 Carry information from receptor cells to the central nervous system 2 These are afferent neurons 2 3 4 Motor neurons Neurons that control our motor movements 1 Carry information from the central nervous system to muscles glands and organs 2 These are efferent neurons Interneurons Neurons in our brain that enable us to think and make conclusions 1 Make local connections within areas of the central nervous system Mirror neurons are found in the frontal and parietal lobes and have been identified in other species 1 They are activated when an organism engages in a behavior or observes another engage in that behavior 2 An example is when a gorilla sees fear in a snake the other gorillas recognize that fear and also too become afraid of a snake that they weren t initially afraid of Structure of a Neuron 1 Cell body soma provides life support for the neuron 2 Dendrites the branching extensions at the cell body which receives messages from other neurons 3 Axon the long extension of a neuron which transmits messages to other neurons 4 Function of a neuron is to send information Path of Transmission 1 When a neuron is not stimulated it is at resting state 1 An impulse neurotransmitter from a sending neuron is absorbed by a receptor on the dendrites or the soma of a receiving neuron 2 This produces an electro chemical impulse which will have one of two effects on the receiving neuron depending on the nature of the receptor 1 Excitatory this makes the receiving neuron more likely to generate an impulse down the axon 2 Inhibitory this makes the receiving neuron less likely to generate an impulse down the axon 3 The impulse travels along the cell membrane until it reaches the axon hillock at the top of the exon 1 2 3 4 5 6 Each neuron receives excitatory and inhibitory from many other neurons At the axon hillock these impulses are summated When the intensity of the excitatory signals the inhibitory signals exceed the threshold the neuron will fire an action potential signals minus intensity The action potential travels down the axon 1 All action potentials have equal intensity stimulus intensity is coded by firing rate 2 Unmyelinated axons the action potential moves smoothly down the axon 3 Mylineated axons the action potential jumps between segments of the mylien sheath creating a faster transmission When the action potential reaches the end of the axon the message must be transmitted to the next neuron across the synaptic cleft 1 Synaptic cleft fluid filled space between the axons of the firing neuron and the dendrites of the receiving neuron 2 Synapse the entire junction between presynaptic and postsynaptic neurons 7 At the end an axon branches into several axon terminals 1 Each axon terminal contains many vesicles each filled with molecules of neurotransmitter 2 When the action potential reaches the terminals It causes the vesicles to move to the presynaptic membrane at the tip of each branch 3 The molecules of neurotransmitter are then spilled into the synaptic cleft 8 The molecules of neurotransmitter travel across the synaptic cleft to contact the postsynaptic membrane of the receiving neuron which contains specialized receptors that bind with the molecules of neurotransmitter generating a new impulse in the postsynaptic neuron 9 Molecules of different neurotransmitters fit into different types of receptors 10 1 Each receptor can bind with only one kind of neurotransmitter 2 The receptor determines whether the impulse will be excitatory or inhibitory All excess neurotransmitter must be removed from the synaptic cleft 1 Enzymes deactivation cleanup enzymes the postsynaptic neuron break molecules of neurotransmitter into their chemical components with different enzymes breaking different kinds of NT released by 2 Reuptake molecules of neurotransmitter are from the receptors vacuumed back through pumps into the presynaptic neuron axon and repackaged into new synaptic vesicles ejected molecular terminals 3 Autoreceptors autoreceptors on the presynaptic membrane monitor how much neurotransmitter has been released from the presynaptic cell and sign al the cell when to stop the release down
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