PSY 301 1st Edition Lecture 6 Outline of Last Lecture I. Love RelationshipsII. Development of RelationshipsIII. Qualities of good marriages and other long-term relationshipsOutline of Current LectureI. Biopsychology introductionII. NeuronIII. Types of NeuronsIV. Structure of a NeuronV. Path of TransmissionCurrent LectureBiopsychology introduction:1. This involves looking directly at biological processes involved in behaviour2. The brain determines what we experience3. Brain receives, interprets, and acts on information from the world4. We are able to see what we see and experience what we experience because of our brainsNeuron (nerve cell):1. This is the basic element of the brain2. The nervous system is a network of connections linking neurons to each other3. A person almost has 100 billion neurons4. 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 made6. The connections that are made in our brain enable us to function the way we do now, new connections are made all throughout life1. 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 walk2. 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 gone7. Myelination of 50% neurons after birth Types of Neurons:1. Sensory neurons: Neurons that enable us to touch, hear, see, and smell1. Carry information from receptor cells to the central nervous system2. These are afferent neurons2. Motor neurons: Neurons that control our motor movements1. Carry information from the central nervous system to muscles, glands, and organs2. These are efferent neurons3. Interneurons: Neurons in our brain that enable us to think and make conclusions1. Make local connections within areas of the central nervous system4. 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 behavior2. An example is when a gorilla sees fear in a snake, the other gorillas recognize thatfear and also too become afraid of a snake that they weren’t initially afraid ofStructure of a Neuron:1. Cell body (soma) provides lifesupport for the neuron2. Dendrites: the branchingextensions at the cell body whichreceives messages from otherneurons3. Axon: the long extension of aneuron which transmits messagesto other neurons4. Function of a neuron is to send information Path of Transmission:1. When a neuron is not stimulated, it isat resting state 1. An impulse (neurotransmitter) from asending neuron is absorbed by areceptor on the dendrites or the somaof a receiving neuron2. This produces an electro-chemicalimpulse which will have one of twoeffects 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 axon2. Inhibitory: this makes the receiving neuron less likely to generate an impulse down the axon3. The impulse travels along the cell membrane until it reaches the axon hillock at the top of the exon1. Each neuron receives excitatory and inhibitory signals from many other neurons2. At the axon hillock these impulses aresummated3. When the intensity of the excitatory signals minus the inhibitory signals exceed the threshold intensity,the neuron will fire an action potential4. The action potential travels down the axon 1. All action potentials have equal intensity; stimulus intensity is coded by firing rate2. Unmyelinated axons: the action potential moves smoothly down the axon3. Mylineated axons: the action potential jumps between segments of the mylien sheath creating a faster transmission5.6. When the action potential reaches the end of the axon, the message must be transmitted to the next neuron across the synaptic cleft1. Synaptic cleft: fluid filled space between the axons of the firing neuron and the dendrites of the receiving neuron2. Synapse: the entire junction between presynaptic and postsynaptic neurons7. At the end, an axon branches into several axon terminals1. Each axon terminal contains many vesicles, each filled with molecules of neurotransmitter2. When the action potential reaches the terminals. It causes the vesicles to move to the presynaptic membrane at the tip of each branch3. The molecules of neurotransmitter are then spilled into the synaptic cleft8. 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 neuron9. Molecules of different neurotransmitters fit into different types of receptors1. Each receptor can bind with only one kind of neurotransmitter2. The receptor determines whether the impulse will be excitatory or inhibitory10. All excess neurotransmitter must be removed from the synaptic cleft:1. Enzymes deactivation: “cleanup” enzymes released bythe postsynaptic neuron break molecules ofneurotransmitter into their chemicalcomponents, with different enzymes breaking down different kinds of NT 2. Reuptake: molecules of neurotransmitter are ejected from the receptors, vacuumed back through molecular pumps into the presynaptic neuron axon terminals and repackaged into new synaptic vesicles 3. Autoreceptors: autoreceptors on the presynapticmembrane monitor how much neurotransmitter has been released from the presynaptic cell, and sign al the cell when to stop the
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