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How does a molecule have an effect on a cell?  An organism?  An ecosystem?  Have you thought about following a molecule across the many levels of biological organization? Let’s follow a protein, the voltage-gated sodium channel, and see how it exerts its effects across a wide swath of biology…. Slide 1 – Title page Slide 2 Voltage-gated Na+ channels are found in all animals… Slide 3 – … found in the plasma membranes of neurons and muscle cells Slide 4 – They are transmembrane proteins that selectively allow Na+ through the pore when it is opened by a depolarization of the membrane potential. Slide 5 – When these channels open, action potentials can be generated on the membranes of both neurons and muscles. Slide 6 – These action potentials can transmit information from sensory organs (eyes, ears, smell, taste, touch)…. Slide 7 – … or information to the muscles …. Slide 8 – … where the neuron releases acetylcholine (ACh) into the synapse, which then activates the nicotinic acetylcholine receptors (NAChR) that then starts a muscle action potential. Slide 9 – The muscle action potential then initiates the contraction of the muscle…. Slide 10 – … which results in movement and locomotion Slide 11 – When voltage-gated Na+ channels are defective, these issues have been linked to epilepsy, chronic pain, as well as other neurological diseases. Slide 12 – … these channels underpin movement and behavior, which are under natural selection, so if the channels and the animal aren’t quick…. Slide 13 – … the animal can become dinner for a predator, or…. Slide 14 – … survive to reproduce, changing the ecology of where they live. Slide 15 – Sources