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This 2 page Class Notes was uploaded by Adrianna Elbon on Tuesday February 16, 2016. The Class Notes belongs to BIOL 1114, 001 at University of Oklahoma taught by Dr.Lee in Spring 2016. Since its upload, it has received 17 views.
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Date Created: 02/16/16
Unit 2- Neurons, Neurotoxins Chapter 26- A neuron is a cell with tiny arms and one long leg, they communicate via electrical impulses. An action potential is the movement of ions, chemical gradient, and electrical gradients. Transport proteins have gates that open and close. If enough Na ions go to inside the neuron, that is when an action potential occurs. The myelin sheath covers the axon that connects the neurons and it speeds up electrical impulses. Axons connect neurons. Dendrites (hair like things) receive signals The signals converge on the cell body Axons signal by using action potentials Action potential- movement of ions across the cell membrane. The resting membrane is negative on the inside and positive on the outside A stimulus to the neuron could be pain, pH (acid or base), etc) The stimulus is received by the dendrite, channel proteins open, ions move into the cell. Graded potential: when the ions fuse across the axon. If the graded potential reaches the axon hillock, an action potential occurs (a flood of Na). It also weakens with distance, the magnitude of the graded potential depends on the size of the initial stimulus. An axon hillock is the trigger zone (you can have both inhibiting and prohibiting ions) Measuring the voltage of a neuron- 1) resting mP (-70 mV) 2) depolarization (-50/-55 mV) 3)repolarization (35 mV), 4)hyperpolarization (-90 to -94 mV) When the neuron is at rest, impermeable proteins inside the neuron have negative charge. The Na+ is delayed and the K is closed at rest (channels) Myelin sheath info: it is a layer of fatty cells, insulates the axon, has no channels, the ions are locked in and it speeds up the action potential. Nodes of Ranvier- spaces in between myelin sheath, are not insulated. *** Action potential cannot move backwards because the Na channel is still inactive and the K channel is not open. The steps to completing 1 action potential: 1) resting (-70) 2) depolarization 3) repolarization 4) hyperpolarization 5) resting Here are what is happening with the ion mechanisms during an action potential: 1) resting: Na/K pumps and K leaks, depolarization: Na opens, repolarization: K opens, Na closes, hyperpolarization: K closes slowly, resting (Na/K pumps, K leaks) Chapter 3.4/3.5- The process for proteins destined for exocytosis- 1. Nucleus: DNA RNA 2. Endoplasmic reticulum: RNA protein 3. Golgi apparatus: protein vesicles 4. Cell membrane: vesicles exocytosis Exocytosis of neurotransmitters: neurotransmitters travel across synapses (chemical signal) 1. Synapse: presynaptic neuron, synaptic cleft, post synaptic cell (neuron, muscle, or gland). 2. Axon terminal: synaptic terminal: Ca channels open, Ca ions enter, Ca ions activate vesicles, neurotransmitters leave post synaptic cell via exocytosis. 3. Synaptic cleft: neurotransmitters diffuse in post synaptic cell, NTs bind to ion channels, ion channels open, ions enter post synaptic cell. 4. Post-synaptic side: graded potential generated. – excitatory=increase chance of AP at trigger zone. –inhibitory= decreases chance of AP at trigger zone. Neurotransmitters are recycled!!! (note: in a depressed person, they have over active reuptake). Neurotoxins: 1. Blowfish toxin (TTX)- prevents voltage gated Na channels from opening in both motor neurons and nociceptors (causes paralysis). 2. Scorpion venom- prevents voltage-gated Na channels from closing into both nociceptors and motor neurons. 3. Cone snail toxin (conotoxins)-prevents opening of voltage-gated Ca channels in nociceptors (causes numbness). 4. Bacterium toxin (botulinum)-prevents exocytosis and neurotransmitters in both nociceptors and motor neurons (prevents muscle movement). 5. Mamba snake (dendrotoxin)- prevents K channels rom opening in motor neurons 6. Plant toxin (curare)-prevents neurotransmitters released by motor neurons from binding to receptors on the post-synaptic cell.
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