November 20 Lecture - November 20, 2008 Synapses - Two...

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November 20, 2008 Synapses - Two types of synapses o Electrical Synapses Represent the minority of synapses in the nervous system o Chemical Synapses When action potential reaches the sole foot, it brings about a variety of changes which prompts synaptic vesicles to move to edge of membrane, and the chemicals diffuse across to the post synaptic fibre across the synaptic cleft The chemical stimulus (transmitter) will induce changes in sarcolemma, which causes it to generate an action potential in the post synaptic fibre Types of Chemical Transmitters - Excitatory o Causes depolarization of post synaptic membrane o Will generate across an action potential in the postsynaptic membrane - Inhibitory o Opposing effect to excitatory o Increases state of polarization, increasing the threshold of stimulus that is required to activate the cell o Less likely to become activated o Will suppress or inhibit action potential in postsynaptic membrane Neurotransmitters - Upwards of 50 neurotransmitters known at this time - Acetylcholine o Synapses that use this neurotransmitter are referred to a cholinergic synapses Found in all of the neuromuscular junctions, many of the synapses seen in the central nervous system of the body In peripheral nervous system the synapses between neurons are cholinergic Many synapses between parasympathetic synapse are also chlinergic o Considered “generic synapse” because it is so prominent in the body o Excitatory: brings about depolarization of post synaptic membrane - Time delay between action potential reaches the sole foot and when the post synaptic membrane is 2-5 ms o Interval between when action potential reaches the sole foot and when the post synaptic membrane is activated is known as synaptic delay o If used repeatedly over time, the chemical transmitter may be depleted (being used at a faster rate than being formed), sole foot will still form action potential and post synaptic membrane is still capable of being stimulated Referred to as post synaptic fatigue - Norepinephrine o Found in the brain and portions of the autonomic nervous system
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o Excitatory transmitter o Synapses that depend on epinephrine are adrenergic - Dopamine o Found in central nervous system o May have excitatory or inhibitory effects depending on the circuitry that is involved o Parkinsons disease: Disorder that manifests itself as muscular tremours or irratick involuntary movement Basis: some of neurons are not creating enough dopamine to function Synapses are unable to suppress the stimulas - Serotonin o Attentionan and emotional state in Central Nervous System o Great deal to do with emotional state, biological rhythms - Gamma aminobutric acid (GABA) o Inhibitory transmitter o Reduced levels of GABA can cause Huntington’s Chorea Hereditary disease that is generally fatal that usually only displays symptoms once the individual is 40-50 years old - Various links between neurons in the nervous system and neurons and muscle tissue have
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This note was uploaded on 10/23/2011 for the course BIOL 2125 taught by Professor Dr.park during the Winter '02 term at A.T. Still University.

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November 20 Lecture - November 20, 2008 Synapses - Two...

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