Good afternoon all,
Now that our second exam is completed, we will spend a bit of time discussing the nervous and endocrine systems as we start into the 3rd unit of our course. These are the two primary regulatory systems in the body, which makes their place in our homeostatic control very important. Accordingly then, when these systems are dysregulated or hijacked, the problems that arise can be very severe.
We do not have a chapter assigned for tomorrow (Friday 18 Oct), so I would like to give you some supplemental reading, instead. You can review this material on your own, so we will not have to meet in person on Friday (tomorrow).
In lecture yesterday, we outlined the cellular basis of the nervous system, and the method by which neurons communicate with each other and their targets at synapses. Synapses are points of communication between cells, but are not actual points of physical contact between cells. The communication is achieved not by direct cell-to-cell transfer of materials, but rather through neurotransmitters, chemical signals that are released from the 'signaling' cell, drift across the synapse space, and bind to receptors on the 'receiving' cell.
If you think back to early in the term about our discussions of how cells can communicate with each other, you will picture that these neurotransmitters can have effects on their target cells by binding to receptors on the cells, and causing some change: perhaps ion channels open or close, ions move in or out of the cell (or stop flowing), or some enzyme is activated that changes the metabolism of the target cell. These changes might have the effect of stimulating the target cell (causing it to perform more of its cellular function), or inhibiting it.
As I pointed out in lecture yesterday, synapses also are the place where most of our drugs (both legal and illegal) influence nervous system function. Our drugs may change the amount of neurotransmitter that is released, or cause it to stay in the synapse for a longer or shorter time. Some drugs block neurotransmitters from binding to their receptors, or artificially activate the receptors even when no neurotransmitter is present. These all are potentially very powerful effects on synaptic function, and thus brain function. If the effects of medications are targeted to specific neural systems (sensory, motor, motivation, reward, or other), they can drastically alter our behavior and our capabilities.
When we quickly reviewed some some common drugs and their effects at the end of lecture yesterday, I noted that heroin is among our most dangerous drugs, for its ability to cause very high levels of dependence (users can't bear to be without the drug) and tolerance (users need successively larger doses to feel the same effect). Heroin is one of the opioid drugs, a class of drugs long known for their ability to relieve pain and provide pleasure/euphoria. This class of drugs includes morphine, long used clinically for pain relief.
Historically, heroin was derived from natural (plant) sources, and humans have been cultivating and using opioids for thousands of years. Poppy plants have long been grown for their opium sap, which can be consumed as-is, or refined into more-potent forms. With the advent of global travel, poppies grown in Afghanistan can produce opium sap, which can be refined into heroin and trafficked for thousands of miles. This wave of heroin across the planet initiated the opioid crisis, decades ago.
More recently, pharmaceutical advances have led to the development of many other opioids: hydrocodone, oxycodone, fentanyl, and others. They are so effective at providing pain relief that they have been heavily marketed, and heavily prescribed. Black-market sourcing and illegal use of synthetic opioids now far outstrips that of heroin, as the pharmaceuticals are typically cheaper, easier to obtain, and preferred by users because they are, in many cases, more potent. Fentanyl, for example, is estimated to be 20x as potent as heroin. Other synthetic opioids may be as much as 500x as potent.
Prescription and illegal use of opioids now has reached a crisis point in our country. One cannot listen to the news without hearing of opioid uses and deaths (even here at IUP). Opioids do target the pleasure and pain centers of the brain, but they also serve as a general depressant of respiratory function. As users become dependent upon and more tolerant of these drugs, they acquire and use them in higher amounts. This puts them more and more at risk of respiratory failure: their brains simply stop signaling enough breathing. This is especially problematic when users consume illegal drugs, for their contents may not be well-regulated. Far too often, users overdose on drugs which are more concentrated, or in higher doses, than expected.
And so, for your reading on this topic, I'm offering here below a link not to a recent news story, but rather to a more comprehensive news report that was issued last Fall. It describes some of the biology and the neuroscience of opioid addiction, but also presents a variety of personal perspectives from addicted individuals. In many ways, addiction can be considered to be a disease, and the viewpoints and anecdotes describing addiction are both powerful and scary.
This article also includes links to a few other resources on the topic of opioid addiction.
But let us add to this discussion some good news: Because the action of opioids is relatively well-understood, pharmaceutical advances have made available a very effective antidote to opioid overdose. Commonly referred to by its product name (Narcan), naloxone is a substance that binds to opioid receptors, in place of the opioids themselves. But, naloxone does not activate the receptor in the same way as do the opioids; rather, it blocks the receptor from being activated by the opioids.
Naloxone is remarkably effective, and many first responders and emergency personnel now carry it. They find themselves using more frequently than they would like, but there is no doubt that it has saved thousands of lives.
Naloxone is so important in the fight against opioid abuse that the Pennsylvania Department of Health has issued a standing order that allows public citizens to obtain it, if they believe that having Narcan might help them prevent an opioid overdose. If you think that having it would benefit you or those around you, I'd encourage you to consider obtaining it. You can start at the PA Department of Health web site, especially the text pertaining to ACT 139, which described how private citizens might obtain naloxone, through a standing prescription order:
There also are opioid resources available here at IUP, through IUP's Center for Health and Well-Being:
I can help you navigate these resources, if you like.
I hope that these materials help to put our discussions of brain structure/function and synapses into some context. I'd be happy to provide more material on these topics, if anyone is interested.
Have a great weekend - see you on Monday.