Transcript PPT
Neurotransmitters Neural transmitters • Acetylcholine – one of the most common transmitters • Used at neuromuscular junctions (excitatory) • Used to slow down heart rate (inhibitory) – How can the same NT have two different results? • Different types of receptors • Many insecticides use either neural transmitters or chemicals that destroy enzymes such as cholinesterase. With their nerves continuously firing or remaining in a depolarized state their bodies shut down. Inhibitory neurotransmitters Inhibitory neurotransmitters cause neurons to become unable to fire – K+ channels open causing K+ to rush out to the outside of the membrane causing it to become even more positive. • At this point the membrane is said to be hyperpolarized Other Neurotransmitters in the CNS • Epinephrine (adrelalin) • Norepinephrine (noradrenaline) – Also functions in PNS (autonomic) • Dopamine • Serotonin Dopamine • Dopamine – Dopamine is critical to the way the brain controls movements and is also associated with pleasure and motivation – Shortage of dopamine, or the death of dopamine producing neurons causes Parkinson's disease, in which a person loses the ability to execute smooth, controlled movements • To help relieve these symptoms, people with Parkinson’s take L-DOPA, a drug that can be converted in the brain to dopamine Serotonin • Serotonin • Serotonin is believed to have an important role in depression, and anxiety sexuality and appetite. – Most medication to help depression contain drugs to improve production of serotonin Drugs and Transmittters • Botulinum (Botulism) – toxin produced by a bacteria (Clostridium botulinum) that interferes with the release of ACh at neuromuscular junctions – cause fatal muscular paralysis – antiwrinkle drug for facial cosmetic enhancement Drugs and Transmittters • Cocaine – prevents reabsorption of the dopamine after release – dopamine builds up in the synapse, • results in strong feelings of pleasure and even euphoria. The excess dopamine that accumulates in the synapse causes the neurons that have dopamine receptors to decrease the number of receptors they make Drugs and Transmittters • Tetrodotoxin, (Puffer fish) • much larger than the sodium ion, acts like a cork in a bottle, preventing the flow of sodium until it slowly diffuses off. • Death can result from a single milligram. Drugs and Transmittters • opiates (morphine, codeine, heroin) – very effective pain killers • more powerful that the bodies natural system that uses endorphins – Increase release of dopamine – Heroin – moves quickly through the blood brain barrier once taken, gets converted into morphine and binds to opioid receptors that produce the euphoric high • Causes the body to reduce or stop endorphin production causing dependency (addiction)