Introduction to Psychobiology - Part 6 (A Neurotransmitter known as Acetylcholine)

-
For more information about psychobiology, please check out "Physiology of Behavior," by Neil Carson

In this post we will cover a neurotransmitter known as Acetylcholine (ACh)



Acetylcholine (ACh)



This is thought to be the first discovered neurotransmitter by Otto Loewi (1).  To the right a drawing of a rat's brain and its acetylcholine pathway can be seen. ACh can be found in the peripheral nervous system(PNS) and the central nervous system (CNS). In the PNS it is involved with neuromuscular junction (2). This is where an axon reaches a muscle (3). Here the ACh causes EPSPs. This is excitatory postsynaptic potential and it refers to the action that increases the probability of an action potential occuring. On the other hand, IPSPs inhibit postsynaptic potentials (4). In the CNS, ACh in the basal forebrain is involved in perceptual learning and memory. In the Medial Septum, specifically the Hippocampus, ACH is also involved in learning and memory. In the Dorsolateral Pons, it can be found when individuals are passing through their REM sleep (Rapid eye movement). Finally, in the Putamen, Nucleus Accumbens, and the Caudate Nucleus Acetylcholine is involved in motor functions.

Biosynthesis of ACh

We will now look at the synthesis of acetylcholine (synthesis is the construction of a complex chemical (5)). As you can see the synthesis starts with two substances: Acetyl coenzyme A (acetyl-CoA) and Choline. Then, Choline acetyltransferase (ChAT), which is an enzyme (remember that enzymes are catalysts that either help break or unite two substances) transfers the acetate ion to Choline, thus, ending up with acetylcholine (6).



Two Subtypes of Receptors

Both of the subtypes are found in the CNS. They are nicotinic and muscarinic. The former is ionotropic, which is a receptor that is linked to an ion channels (7), is only found on muscle fibers (8). The latter is metabotropic, which obtained this name because the "movement of ions through a channel depends on one or more metabolic steps" (7).

Six Cholinergic Drugs

  1. Black Widow Spider Venom: This venom triggers the release of acetylcholine.
  2. Hemicholinium: This prevents the uptake of choline
  3. Atropine: This is a direct muscarinic antagonist. It produces dilated eyes.
  4. Curare: This comes from a plant and it prevents muscle contraction. It is a nicotinic antagonist that is direct.
  5. Neostigmine: This is an indirect agonist that blocks AChe
  6. Botulinum Toxin: Also known as Botox, it prevents release the release  of acetylcholine (8).





References
1. http://neuroscience.uth.tmc.edu/s1/chapter11.html

2. http://neuroscience.uth.tmc.edu/s1/chapter04.html

3. http://education.ucf.edu/litsymposium/resources2013/crittenden_handout1.pdf

4.http://www.ncbi.nlm.nih.gov/books/NBK11117/

5. http://www.britannica.com/science/chemical-synthesis

6. http://www.ncbi.nlm.nih.gov/pubmed/10594838

7.http://www.ncbi.nlm.nih.gov/books/NBK10855/

8. "Physiology of Behavior," by Neil Carson.

Comments

Post a Comment

Popular posts from this blog

Psychoanalytic Therapy

-
Image
A comparison between psychoanalysis, medication, and cognitive-behavioral therapy. The effectiveness of medication, cognitive-behavioral therapy, and psychoanalysis will be compared to each other in order to describe the most helpful form of treatment. Effectiveness is going to be measured by the effect sizes and the limitations of each treatment; success is going to be measured by relapse and remission rates as well as the increase or decrease of benefits over time and side effects. The first form of treatment that will be explored revolves around psychopharmacology. The article “Selective Publication of Antidepressant Trials and Its Influence on Apparent Efficacy” will provide the effect sizes of antidepressants, the number of positive and negative published and unpublished studies done by the FDA, and it will compare the long--term outcomes of using medication as a form of treatment. Turner, along with the other authors, looked at all registered FDA antidepressant studie
Read more

The Five Lectures of Freud: An Introduction to Psychoanalysis

-
Image
     Sigmund Freud, a neurologist and the founder of psychoanalysis, made his first and only trip to the United States in 1909  (Jay, 2016).  Stanley Hall, who  was the first person to receive a PhD degree in psychology in the U.S., and the first president of the American Psychological Association, had invited Freud to  Clark University to lecture on psychoanalysis ( Encyclopædia Britannica, 2016c) . The lectures were part of the university celebrating its twentieth anniversary in which prominent figures spoke about their field (Burnham, 2012). The purpose of this essay is to explore each of Freud’s lectures in detail  in order to introduce psychoanalysis.      Before describing the lectures, it is important to understand how Freud mapped the mind. He divided it into three parts twice. The first time, he categorized it into the conscious, preconscious, and unconscious (Freud, 1938). The conscious layer contains everything that an individual is aware of, such as immediate physica
Read more

Introduction to Neuroanatomy - Part 3 (Brain Structures - Telencephalon and Diencephalon)

-
Image
Brain Structures and their Functions To learn more about neuroanatomy, please check out: "Neuroanatomy Text and Atlas," by John H. Martin. In the last post, we ended explaining the development of the spinal cord. We will continue this discussion by exploring the structures of the brain from a bottom-up perspective and describe their functions.  Cranial and Non-cranial Nerves If you read the last post (Here is the link:  http://hbookreviews.blogspot.com/), you should remember that the spinal cord was divided by two plates: basal and alar. When we move up from the spinal cord into the brain we would observe a collection of structures known as the brainstem. In here, the plates become nerves. The alar plate becomes the cranial nerve sensory nuclei and the basal becomes the cranial nerve motor nuclei. Remember that a nerve is a bundle of axons in the central nervous system (CNS) and that nuclei are a collection of cell bodies that are also located in the CN
Read more