BIO 311D 2nd Edition Lecture 32 Outline of Last Lecture I. Ion channels and Membrane PotentialII. Action Potential is “all-or-none”III. Chemical Synapse Outline of Current Lecture I. Chemical SynapsesII. Neuromuscular junctionIII. Neuron networksCurrent LectureI. Chemical SynapsesA. Membrane communication at the end of an axon triggers the releases of neurotransmitters into the synapse; NT binds receptor, causing response a. Signaling: specific signal and receptorb. Clearing the synapse: to prevent from over-simulating II. Neuromuscular junctionsA. Some neurotransmitter receptors are ligand-gated channelsa. The AChR protein is a ligand-gated Na+ ion channelb. Some GABA receptors are ligand-gated Cl- ion channelsB. Some neurotransmitter receptors activate signal transduction pathwaysa. Could open ion channels, etc. C. IClicker Question1. Into cell2. Into cell3.4.5. HyperpolarizeIII. Neuron NetworksA. Most neurons receive multiple excitatory postsynaptic potentials (EPSPs) to reachthreshold for an action potential a. This decision making process is called summationb. Depolarization sufficient to get to threshold to lead to action potential B. Some neurotransmitters cause postsynaptic cell to hyperpolarize. These inhibitory postsynaptic potentials (IPSPs) reduce the chance of an action potential. The cell body integrates these signalsC. Sensory neurons take non-neural signals and turn them into neural responses a. Responds to change in pressureb. Responds to heatc. Responds to taste receptor (i.e. small molecule of sugar)d. Responds to light e. Their output can talk to neurons such as interneurons other interneurons motor neurons D. How does the action potential go along the entire length of the axon? That is, how is it propagated without any loss of magnitude?a. Action potentials (depolarization wave followed by receptor, travel along axons with no loss of signal amplitude)b. Axon membrane: E. The sodium ion concentration the neuron membrane is usually much higher outside than inside. Which of the following contribute to this steep gradient?a. Voltage-gated sodium channelsb. Ligand-gated sodium channelsc. Sodium-potassium pumps [Channels are passive and do NOT create a gradient] F. Stimulation at the neuromuscular junction generates an action potential on the muscle membrane that triggers the release of Ca++ stored in the sarcoplasmic reticulum, flooding the cytosol of the sarcoplasm where the muscle fibers lie G. Skeleton muscles made of bundles of overlapping fibers, each with numerous thick myosin fibers and thin actin fibersa. Actin- microfilaments | Myosin- motor protein b. “Sliding filament mechanism” 1. Overlapping - contraction2. Separation, lengthen – retraction 3. ATP hydrolysis provides the energy4. Myosin is a motor protein. When phosphorylated in ATP hydrolysis it changes shape.5. Activated myosin (thick filament) binds to action (thin filament), forming a cross bridge, and pulling (shoving) the thin filament6. Depolarization opens voltage-gated Ca++ channels, calcium ions trigger contraction H. Knee-Jerk Reflex1. Neuron that releases acetylcholine (acetylcholine receptors open sodium ion channels2. Muscle cell that contracts when acetylcholine binds to its receptors3. Neuron, that when stimulated, inhibits the release of acetylcholine into its synapse4. Neuron that an receive sensory information (touch stimulus)5. Neuron that releases neurotransmitters that depolarize the post-synaptic membrane Pathway: #4 #5 1/3
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