Health and medicine
- Dementia and Delirium, including Alzheimer’s
- What are dementia and Alzheimer's
- Alzheimer's disease: Plaques and tangles
- Other types of dementia
- Risk factors for dementia
- Stages of dementia and Alzheimer's disease
- Diagnosis of dementia and Alzheimer's disease
- Treatment of dementia and Alzheimer's disease
- What is delirium?
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Tanner Marshall.
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- At the explanation of memantine at4:20, how can that NMDA channel open at all if memantine is bonded to the receptor? It seems to me that a complete blockage of those ions would be just as bad as an overabundance. Can the ions get in through other types of receptors?(6 votes)
- Hi, Andrew. Given a high dose of memantine, you are absolutely right. So beginning with a low dose, the medication is gradually titrated in such a way that patient learning and memory potential is optimized. Administration can a bit tricky, but if done properly, quality of life can be preserved (for at least a few months, anyway).(8 votes)
- At about5:30Tanner talked about an increased mortality rate. Does that mean the patient has more of a chance of dying?(1 vote)
- Can the NMDA receptors not be down-regulated? By the way, examples of acetylcholine esterase inhibitors are rivastigmine and galantamine (from the Snowdrops plant). The patient will also experience muscarinic adverse effects.(1 vote)
- [Voiceover] Scientists and physicians continue to learn more and more about Alzheimer's disease and dementia in general, but unfortunately, they still haven't found a cure. With that said, though, there are medications that can help lesson the symptoms of dementia, like memory loss and confusion. Currently, all the medications approved by the Food and Drug Administration or the FDA are aimed at either one of two neurotransmitters: acetylcholine or glutamate. The first class of drugs are cholinesterase inhibitors. Acetylcholine is a really important neurotransmitter in our brain and nervous system. Even though it has important functions in other parts of our body, in our brain, it helps our neurons communicate. And it's this communication of our neurons that allows our brain to think and do things like sustain attention, sense things, learn and remember things. Okay, so, say we have these two neurons here that are trying to communicate, one transmitting neuron and one receiving neuron. The transmitting neuron releases the neurotransmitter acetylcholine, which then binds to an acetylcholine receptor on the receiving neuron. And this is how these two neurons communicate, right? To sort of regulate this process, though, you have this enzyme that constantly breaks down the acetylcholine that's being released and this sort of makes sure that too much doesn't build up. And this guy is called acetylcholinesterase, and it breaks acetylcholine down into acetic acid and choline. Think of acetylcholinesterase like Pac-Man and all of these acetylcholines as the little dots that he eats. He's constantly going around eating the dots, but some of them may get by to communicate between the neurons. So, it's like this balance, right, of some of the dots being eaten and some communicating. Acetylcholinesterase is a type of cholinesterase. So, if we throw a cholinesterase inhibitor into the mix, like the ghost in Pac-Man, then we inhibit or stop our Pac-Man from doing his job of eating the dots, right? Which means more of these dots build up, and we tilt the balance in favor of the dots or acetylcholine. Now, patients with Alzheimer's disease, though, already have decreased levels of dots in the first place. So, with Pac-Man there, they have even less. But if we inhibit Pac-Man, then we have less dots being eaten, right? And so, we end up with more active acetylcholine. And by doing this, by stopping the enzyme that breaks down acetylcholine, we can help neurons communicate in people with Alzheimer's disease. And this medication can help delay worsening of dementia symptoms for about six to 12 months on average, for about half of the patients that take them. And although they're usually pretty well tolerated, some side effects can include nausea, vomiting, and loss of appetite. All right, so that's the first type of medication for Alzheimer's disease. The second type targets the neurotransmitter glutamate, and is called memantine. Just like acetylcholinesterase inhibitors, memantine is prescribed to help patients with symptoms related to memory, attention, reasoning, and language skills. Instead of acetylcholine, though, now we focus on this neurotransmitter called glutamate. Glutamate, when at normal levels, actually helps our learning and memory, and is considered an excitatory neurotransmitter. When glutamate levels get too high, though, it's actually toxic to the cell. And we use the word called excitotoxicity, where the cell gets actually too stimulated and may die as a result. Having too much glutamate is thought to be one possible way that people with Alzheimer's disease lose nerve cells and therefore have problems with learning and remembering new things. So, again, we've got our two neurons transmitting and receiving, right? And we have this receptor on the receiving neuron called the NMDA receptor, which is also like this channel or gateway that lets in ions to the receiving cell. Now, this gateway lets them in when glutamate binds to it. So, if there's too much glutamate and this gateway is always open, then the receiving neuron can suffer from excitotoxicity, because it's like always being stimulated. Now, memantine blocks this receptor for glutamate, so it keeps this channel closed more. And when it's closed more, we bring down the stimulation to normal levels and avoid killing the cell by overstimulating it. Think of glutamate like this key that opens the door to this party down here, letting all the ions in. If too many get in, though, the party gets too big and too crowded and out of control. If we put a different lock on the door, memantine, then the key won't open it, and the party stays at reasonable levels. Now, memantine is used most often to treat moderate to severe Alzheimer's disease, and will often be taken alongside cholinesterase inhibitors. Some side effects can be things like headache, confusion, and dizziness. So, switching gears a little bit, other forms of treatment often target behavioral symptoms, like agitation, irritability, aggression, and anxiety. Usually, it's preferred to focus on treatments that don't use medications for these, though, like behavioral modification, since a lot of medications intended to treat behavioral symptoms can actually increase confusion and can even be associated with increased mortality.