Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 3: Neural Communication A Resting Neuron If a neuron is not active receiving or transmitting information, it maintains a resting potential The cell keeps this negative charge by: 1. Only allowing certain ions (charged particles) the cell membrane 2. And by actively pumping other ions out of the cell = sodium-potassium pump. Concentration Gradient vs. Electrical Gradient 1. Concentration gradient is the difference in the AMOUNT of a given ion on either side of the membrane. 2. Electrical gradient describes the difference in the CHARGE on either side of the membrane. Picture of Both Gradients 1 2 The Key Players: Sodium (Na+) and Potassium (K+) 1. Na+ really wants into the cell because of both the concentration and electrical gradients 2. K+ wants into the cell because of the electrical gradient, but wants out of the cell because of the concentration gradient What purpose does the resting potential serve? Action Potential Three simple concepts: Rapid depolarization Short-lived hyperpolarization Role of the threshold of excitation How does the AP happen? • Back to the ions! And what happens next? • How does the cell get itself back to rest? All or Nothing The AP is not a graded response Refractory Period This is a short period of time following an AP where the cell cannot be made to fire again. Where does the AP start? It begins at the axon hillock and moves down the length of the axon How does it keep moving? Role of the refractory period Contribution of Myelin Not just electrical… Sherrington made several important observations about nervous control of muscles: 1. Muscular reflexes are slower than the speed of the AP 2. Summation 3. Synchrony of contraction & relaxation Proving Sherrington Right Leowi confirmed Sherrington’s suspicions about chemical communication in 1920 Frog heart experiment Chemical Events What happens in the neuron in order for neurotransmission to take place? 1. Neurotransmitters are made in the cell 2. When the AP reaches the terminals… Then What? The “hook-up” After the transmitter has its fun with the receptor, it: • It is degraded in the synapse or • It is taken back up into the cell and broken down there or • It is taken back into the cell and reused Post-Synaptic Activity 1. 2. There are two ways a neurotransmitter effects the post-synaptic cell Ionotropic Metabotropic The end result is a change in the resting potential of the post-synaptic neuron!! Types of Neurotransmitters 1. 2. 3. 4. 5. Amino acids Peptides Acetylcholine Monoamines Gases Drug Effects at the Synapse Agonists vs. Antagonists Affinity & Efficacy Next Time: Chapter 7 – Development of the Nervous System