Lecture 4[1].Chap 3

Lecture 4[1].Chap 3 - Physiological Psychology Lecture 4- -...

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Unformatted text preview: Physiological Psychology Lecture 4- - - - - Chapter 3 Do we use only 10% of our brains Some Clarifications Changing Thresholds of the Neuron- - - - - - Refractory Periods Fig. 2-16, p. 41 Saltatory Conduction The neural impulse appears to jump from node to node Flow of ions between nodes is considerably faster than the regeneration of the action potential at each point along the axon Speed of neural conduction The thicker the neuron the faster the impulse conduction 1m/sec to 10m/sec I mpulse from giraffe foot to brain = .5 sec With myelin sheath speed is 100m/sec Types of Synpses Axodendritic normal transmission Axoaxonic alters amount of neurotransmitter Dendrodentritic perform regulatory functions Dendritic Action The Concept of the Synapse Neurons can have thousands of synapses. Both temporal and spatial summation can occur within a neuron. The likelihood of an action potential depends upon the ratio of I PSPs to EPSPs at a given moment. Spark school vs soup school. By 1950s it was realized that transmission is mostly chemical. Graded potentials are electrical. Chemical Events at the Synapse German physiologist Otto Loewi was the first to convincingly demonstrate that communication across the synapse occurs via chemical means in the 1920s Neurotransmitters are chemicals that travel across the synapse and allow communication between neurons. Loewi stimulated the vagus nerve to one frogs heart, decreasing the heartbeat. When he transferred fluid from that heart to another frogs heart he observed a decrease in its heart rate Chemical Events at the Synapse The major sequence of events allowing communication between neurons across the synapse: 1. The neuron synthesizes chemicals that serve as neurotransmitters. 2. Neurons store neurotransmitters in axon terminals or transport them there. 3. An action potential triggers the release of neurotransmitters into the synaptic cleft. Chemical Events at the Synapse (cont.) 1. The neurotransmitters travel across the cleft and attach to receptors on the postsynaptic neuron. 2. The neurotransmitters separate from the receptors. 3. The neurotransmitters are taken back into the presynaptic neuron, diffuse away, or are inactivated by chemicals. 4. The postsynaptic cell may send negative feedback to slow the release Chemical Events at the Synapse Major categories of neurotransmitters include the following: Amino acids. Neuropeptides. Acetylcholine. Monoamines. Purines. Gases. Neurotransmitters Amino Acids: glutamate, GABA, glycine, aspartate, maybe others A Modified Amino Acid: acetylcholine Monoamines (also modified from amino acids): indoleamines: serotonin catecholamines: dopamine, norepinephrine, epinephrine Peptides (chains of amino acids): endorphins, substance P, neuropeptide Y, many others Purines: ATP, adenosine, maybe others Gases: NO (nitric oxide), maybe others Chemical Events at the Synapse Transmission across the synaptic cleft...
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Lecture 4[1].Chap 3 - Physiological Psychology Lecture 4- -...

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