Lecture 5 Neurotransmitter Review Synapse Problems and Lateralization Neurotransmitters o Neurotransmitters travel across the synaptic cleft o Excitatory neurotransmitters tell the receiving neuron to increase level of activation o Inhibitory neurotransmitters tell the receiving neuron to decrease level of activation o Neuron s response to these exciting and inhibitory influences is graded o Neuron s level of activation fluctuates o If neuron reaches a threshold depolarization at the base of the axon occurs and the neuron fires There are three types of problems that can occur at the synapse 1 Production End Problem something is wrong with the production or release of the neurotransmitter not enough of the transmitter is being produced or the release mechanism is broken 2 Receiving End Problem docking station isn t working properly it may be damaged or some other chemical agent may have docked and is blocking the neurotransmitter opiates work this way 3 Synaptic Cleft Problem neurotransmitters must survive the passage the chemical constituency of the fluid in the synapse can be either hostile to particular neurotransmitters it will break them down or conducive to particular neurotransmitters Example Muscle Relaxants The most often used muscle relaxant acts at the synapse between a motor neuron and the muscle it is connected to The neurotransmitter involved is acetylcholine The muscle relaxant contains curare which blocks acetylcholine by docking at acetylcholine s receptor The muscles cannot contract because the messages cannot be received All neurons your brain use a fuel source glucose sugar Muscles burn glucose You store glucose in your muscles and liver o The glucose is used only in the muscle in which it is stored o The glucose stored in the liver can be used in your entire body this glucose is volatile and doesn t last long Hypoglycemia is when you have no glucose your muscles shut down and your brain does not et enough fuel so your emotions are effected you become hostile irritable angry hostile or aggressive 1 Lateralization Outline Left Brain Right Brain Split Brain Research Visual Wiring General Experiment Results Intact Brain Research Some Popular Issues Left Brain Right Brain Where did these ideas come from Split Brain Research and Results The left brain is thought to be analytical verbal rational cold and calculating well suited to the fields of science and math while the right brain is thought to be good at synthesizing seeing patters and it response to emotion you would be well suited to the arts There is also a concept that you can exercise the two halves of the brains in different ways and that some people have one half of the brain larger than the other We did not know whether there was localization of tasks in the brain are particular areas of the brain specified for a certain task or is the brain largely undifferentiated and any part of the brain can perform any task What is largely agreed upon now is that particular areas of the brain process particular kinds of information there is localization specialization There is also plasticity but in the normal brain particular areas process particular information There is a language processing mechanism and a set of these mechanisms is located in the left hemisphere left hemisphere is called verbal Some of the mechanisms involved in pattern recognition are in the right hemisphere This was discovered with research that was done with epilepsy patients At the time patients with severe epilepsy were subject to grand mall seizers which are like an electrical storm in the brain there are not enough inhibitory signals so the neurons are firing out of control One extreme form of treatment was to sever the corpus callosum the connection between the left and the right hemispheres of the brain By severing the connection between the two halves of the brain you reduce the functional mass of the brain by half so if firing gets out of control in one hemisphere it cannot continue into the other hemisphere so the electrical storm is limited In the body the right half of the body is wired into the left half of the brain and the left half of the body is wired to the right half of the brain L R corpus callosum Essentially these patients have two separate brains information that is in the left hemisphere cannot get into the right hemisphere and vise versa So researchers 2 wanted to figure out if certain tasks can only be preformed if the information is in one hemisphere rather than the other They tested this in two ways 1 Tactilely easy let people feel stuff under a table with one hand and see if they can tell what it is 2 Visually hard each eye maps information to both the left and the right hemispheres there is a left visual field and a right visual field in each eye The eye moves rapidly back and forth so that information gets into both the left and right visual fields of each eye very easily To get the information into only one hemisphere you must have very precise control over the stimulus where in space it is located how long it lasts etc They would flash a picture into either the left hemisphere or the right hemisphere Left hemisphere If they routed a picture of a bicycle to the left hemisphere they would ask the person Do you know what that is the person would say yes and the person will with a high degree of accuracy point to a picture of the bicycle Then they would be asked to name the object and they can name the object Thus when an image is routed to the left hemisphere the person can identify the object pictorially and they can name the object Right hemisphere Now if we take the same person and route the picture to the right hemisphere Then they will ask Do you know what that is the person would say yes and the person will with a high degree of accuracy point to a picture of the bicycle Then they would be asked to name the object and they cannot name the object Thus when an image is routed to the left hemisphere the person can identify the object pictorially and they cannot name the object Why Because the processing mechanisms that are involved in naming stuff are in the left hemisphere if the information is in the right hemisphere and there is a severed corpus callosum the information cannot get to the left hemisphere even though they know what the thing is they can identify it accurately they cannot name it You have people feel shapes under a table and then ask them to point to a picture of the shape they just felt Left
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