Human Physio Notes Week 4 - IA Adrian Bahn BIPN 100 Dr...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
IA: Adrian Bahn BIPN 100 – Dr. Fortes 01/25/16 Last time we left off on G-protein coupled receptors. To expand on them, these G- protein coupled receptors, upon binding acetylcholine, will activate the trimeric G- protein it is linked to that is on the inner part of the cell membrane. Thus the receptor transmits the chemical signal from the outside to the inside through the activation of the G-protein. The G-protein then catalyzes a second messenger cascade (e.g. cAMP) that can affect the opening or closing of ion channels. It is important to note that GPCRs are ubiquitous and highly conserved; you can find them in many more places than just the nervous system. Rhodopsin, for example, is a GPCR in the eyes that upon getting hit by a photon activates its G-protein to catalyze a reaction that allows you to detect light. As mentioned before, epinephrine/norepinephrine bind to adrenergic receptors, which are GPCRs, and dopamine and serotonin also have receptors that are GPCRs. Note that in the nervous system, the main adrenergic neurotransmitter is norepinephrine and NOT epinephrine. We can categorize dopamine and norepinephrine as both hormones and neurotransmitters, but epinephrine is mainly a hormone. The distinction can be blurry, but it is a definition of function. Hormones are released into the blood stream and act on distant parts of the body . Neurotransmitters are supposed to be used in synapses as a chemical signal between neurons . Norepinephrine does circulate in the blood, but most of it is from the norepinephrine escaping the synaptic cleft during a neurotransmission. There is an enzyme, monoamine oxidase (MOA), which is located on the mitochondria, which breaks down the catecholamines (epinephrine, norepinephrine, dopamine) and serotonin. This is important for terminating the synaptic transmission as the neurotransmitters get reabsorbed and metabolized. There have been a class of antidepressants developed called selective-serotonin reuptake inhibitors (SSRIs) that can prevent the reuptake of serotonin and the catecholamines , with different drugs having varying affinities for specifically serotonin absorption. This is because there are unique transporters for dopamine, norepinephrine and serotonin, but different drugs have varying specificities for just the serotonin transporter. Thus SSRIs not only keep the serotonin levels in the synaptic cleft higher, they can also keep dopamine and norepinephrine concentrations elevated as well. Now that we’ve talked about all the different receptors and their ligands, what do they do? Well, when the neurotransmitters bind to the receptors on the receiving neuron, they cause ion channels to open. If the receptor is ionotropic then there is a fast, immediate response as the receptor’s ion channel opens, and if they’re metabotropic and open other channels through secondary messengers the response is slower and longer as it takes time for the second messengers to elicit a response.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern