What Is A Brain Pathway
A brain pathway is like a power line between two brain regions. A brain pathway is made up of interconnected neurons, and signals travel along them from one area of the brain to another.
Neurotransmitters are molecules that allow a signal to travel from one neuron to another. All drugs of abuse interfere with neurotransmitter signaling in some way. Neurons in different brain pathways use different neurotransmitters. Depending on which neurotransmitters they interfere with, drugs have varied effects in the brain.
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Interconnected neurons form brain pathways, allowing different brain regions to communicate.
Oxytocin And Vasopressin Can Affect Behavior By Wireless Signaling
Let me use another example. The neuropeptides, oxytocin and vasopressin, are made by large neurons in the hypothalamus, a part of the brain that is important in regulating many physiological processes of the body. These large neurons have one axon that goes all the way to a specialized gland, the pituitary gland, which is attached to the bottom of the brain. From there, the neuropeptides are released from the axon terminals directly into the blood. Oxytocin travels through the body and has a role in childbirth and breastfeeding. Vasopressin affects blood pressure and regulates the bodys water balance through the kidneys. But both neuropeptides are also released into the brain, where they control several sorts of behavior. For example, oxytocin helps a mother to bond with her child, and vasopressin affects memory and aggression. However, the brain areas that control these behaviors are sometimes far from the cells that make the neuropeptides. Some of these areas have the right receptors but no axons and terminals nearby, so that wired signaling by oxytocin and vasopressin cannot occur.
- Figure 3
- Oxytocin is released into the blood from axons in the pituitary gland and into the brain from the dendrites of neurons in the hypothalamus . Oxytocin acts both in the body and in the brain to make sure the child gets food and love .
Gaba Diseases And Treatment
Increasing GABA in the brain has for years been the focus of drug development aiming to alleviate the severity of epileptic seizures . Initial studies examined the efficacy of administering GABA directly. One study reported a reduction in the amount of seizures in epileptic patients who were administered a very high dose of GABA . However, this result was found only in four out of twelve patients. Additionally, the patients in whom the administration of GABA did have an effect were children below the age of 15. This finding is in line with the suggestion that the BBB permeability to GABA decreases with age . Perhaps more importantly, GABAs half-life is about 17 min in mice . If the half-life has a similar short duration in humans, direct administration of GABA is unsuitable as pharmacological treatment of epilepsy.
Patients with Huntingtons disease also have reduced GABA levels in the brain , but administration of GABA to remedy this deficiency has shown mixed results with regards to the reduction of symptoms . Of course, that the administration of GABA does not consistently alter the symptoms in complex and multifaceted disorders such as epilepsy and Huntingtons disease, does not necessarily mean that GABA is unable to affect the brain.
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What Is The Function Of Gaba In The Brain
GABA is implicated in a wide variety of functions to fine tune neural processing. It is also broadly involved in supporting sleep and a disturbance in GABA signalling is one contributing factor in anxiety disorders, which can be treated using benzodiazepines which act to increase GABA signalling in the brain, therefore reducing unwanted brain excitability.
Diseases Due To Dysfunction In Neurotransmission
Myasthenia gravis is a disease that affects muscle functioning. It is caused by decreased levels of the neurotransmitter acetylcholine. In this disease, antibodies have formed that damage the receptor for acetylcholine at the neuromuscular junction.
The patient presents with drooping of eyelids and difficulty in performing daily activities like walking, talking, etc. Nerve conduction study is diagnostic for this disease.
Parkinson’s disease is caused by low levels of the neurotransmitter dopamine in the brain. In this disease, there is a loss of neurons in basal ganglia that are producing dopamine. The patient presented to us with tremors bradykinesia, stooped posture and masked faces. This disease is diagnosed on clinical examination.
Generalized anxiety disorder, stress, and depression are caused by low levels of serotonin. They are diagnosed with a medical history and in severe cases when leading to suicidal tendencies.
In Alzheimer’s disease, there is a loss of memory and the patient can’t take care of himself. In this disease, there are low levels of acetylcholine in the brain.
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How Do Neurotransmitters Work
To send messages throughout the body, neurons need to transmit signals to communicate with one another. But there is no physical connection with each other, just a minuscule gap. This junction between two nerve cells is called a synapse.
To communicate with the next cell, a neuron sends a signal across the synapse by diffusion of a neurotransmitter.
There Are Three Main Parts Of A Neuron
Neurotransmission is the interaction between these. From the neuron, the neurotransmitter is released and interacts with the dendrites of another neuron.
They are produced in the ribosomes of the presynaptic neuron. They are stored in vesicles. These vesicle’s location is cytoplasm of a neuron. When an action potential arrives at the pre-synaptic terminal, there is the entry of the calcium ions in pre-synaptic neurons.
Now, after calcium ions entry into the cell, synaptic vesicles merge with pre-synaptic membrane and neurotransmitter is released into the synaptic cleft. When neurotransmitter arrives at the cell membrane of a post-synaptic neuron, certain protein molecules are activated. These protein molecules are receptors for neurotransmitters.
After binding with receptors, neurotransmitters have two effects on the post-synaptic membrane.
Excitation of the postsynaptic membrane or its inhibition. During excitation, an action potential is generated. During inhibition, an action potential is inhibited.
Neurotransmitters are released in small amounts and produce minimal excitatory or inhibitory effects. This process takes place regardless of the action potential generated or not. This process is amplified when an action potential arrives and the required message is sent from neuron to its target through neurotransmission.
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Where Does Serotonin Act In The Brain
There are multiple families of serotonin receptors, with each family containing multiple subtypes. These include 5-HT1A/1B/1D/1E/1F, 5-HT2A/2B/2C, 5-HT3A/3B, 5-HT4A/4B/4C/4D, 5-HT5A/5B, 5-HT6 and 5-HT7A/7B/7C/7D. The receptors vary according to where they are expressed in the brain.
In addition, each one has a different genetic origin which means that two people can express a slightly different combination and pattern of serotonin receptors throughout their brain depending on their specific genetic makeup. Serotonin is released into the synaptic space and binds to the receptors which are typically located on the surface of the receiving cell.
Dopamine: A Neurotransmitter In The Brain Related To Depression
Alcohols effect on the dopamine system is one of the most addictive. Dopamine is closely tied to depression and is vital to chemical dependency treatment. Certain alcoholics specifically seek the feeling they get from the surge of dopamine that occurs once blood alcohol levels exceed a certain point. We call those alcoholics, Blackout drinkers.
So there you have it too much dopamine will cause one to hallucinate or become psychotic, but not enough can cause one to become depressed. There exists a fine balance between how much dopamine is necessary to feel good and how much will make a person delusional.
Chapter 3, Neurotransmitter Basics
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Desensitization And Neurotransmitter Concentration
Neurotransmitter receptors are subject to ligand-induced desensitization: That is, they can become unresponsive upon prolonged exposure to their neurotransmitter. Neurotransmitter receptors are present on both postsynaptic neurons and presynaptic neurons with the former being used to receive neurotransmitters and the latter for the purpose of preventing further release of a given neurotransmitter. In addition to being found in neuron cells, neurotransmitter receptors are also found in various immune and muscle tissues. Many neurotransmitter receptors are categorized as a serpentine receptor or G protein-coupled receptor because they span the cell membrane not once, but seven times. Neurotransmitter receptors are known to become unresponsive to the type of neurotransmitter they receive when exposed for extended periods of time. This phenomenon is known as ligand-induced desensitization or downregulation.
What Are Neurotransmitters
Neurotransmitters are chemical molecules synthesized within brain cells, which allow the transfer of signalling messages between brain cells. Whilst the signals which are carried within each cell are electrical, chemicals, such as neurotransmitters, are critical at the joins between cells to enable the transfer of information across the gaps.
There are many major and minor signalling chemicals in the brain. The major neurotransmitters in your brain include glutamate and GABA, the main excitatory and inhibitory neurotransmitters respectively, as well as neuromodulators including chemicals such as dopamine, serotonin, norepinephrine and acetylcholine.
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Getting The Message Across
The task in neurotransmission is to convey a signal from a sending neuron to a receiving neuron across an open space known as a synapse. All neurons accomplish this in approximately the same way.
The sending cell manufactures neurotransmitter molecules and stores them in packets called vesicles. When stimulated sufficiently, the neuron generates an electric signal and causes some vesicles to migrate to the neuron membrane, merge with it, open up, and release their contents into the synapse. Some of the released molecules drift across the synapse and link up, lock-and-key fashion, with molecules called receptors on the surface of the receiving neuron. If the neurotransmitter is stimulatory , its interaction with the receptor will raise the receiving neurons level of electrical activity and thereby increase the likelihood that it will, in turn, mobilize its vesicles and emit its own neurotransmitter. If the neurotransmitter is inhibitory , it will dampen the receiving neurons electrical activity and reduce its likelihood of releasing the neurotransmitter.
In this way, neurotransmitters relay information about the environment and our internal states from neuron to neuron through the brains circuits and, ultimately, shape how we respond. Neurotransmitters interactions with receptors can also set processes in motion that can alter the structure of receiving neurons, or raise or lower how strongly neurons respond when neurotransmitters link to their receptors in the future.
How Neurotransmitters Help Your Body Communicate
Communication is key to your health. Neurotransmitters do that work, sending instructions from one brain cell to the next and transferring information throughout the brain and body.
The process starts where these chemical messengers are stored in tiny compartments at the end of neurons. These are called synaptic vesicles. Neurotransmitters live here until your brain needs to relay a message.
When a neuron makes a command neurotransmitters spring into action. These action potentials temporarily boost neurons into a higher energy state. More energy means brain cells can dump chemical neurotransmitters into the space between them and the next neuron. This gap between neurons is called the synapse.
Neurotransmitters are then collected from the synapse by neighboring neurons after an action potential sparks. A chain reaction follows. Each brain cell releases neurotransmitters to spread the message. When the command is completed, the neurotransmitters break down, float away, or are taken back up by the synaptic vesicles they came from.
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How Does The Drug Alter Neurotransmission
As described above, neurotransmission is a cyclic process that transpires in several steps utilizing specialized components of the sending and receiving neurons. Identifying the precise step that a drug disrupts, and how, provides crucial insight into its impact on users, and is key to developing medical and behavioral interventions to inhibit, counter, or reverse the disruption.
Some drugs mimic neurotransmitters. Heroin and prescription opioids, for example, chemically resemble the brains natural opioids sufficiently to engage and stimulate their specialized receptors. Since heroin stimulates many more receptors more strongly than the natural opioids, the result is a massive amplification of opioid receptor activity. Marijuana mimics cannabinoid neurotransmitters, the most important of which is anandamide. Nicotine attaches to receptors for acetylcholine, the neurotransmitter for the cholinergic system.
Finally, some drugs alter neurotransmission by means other than increasing or decreasing the quantity of receptors stimulated. Benzodiazepines, such as diazepam or lorazepam, produce relaxation by enhancing receiving neurons responses when the inhibitory neurotransmitter GABA attaches to their receptors.
Why Is It Important To Understand Neurotransmitter Signaling
Some of the behavior disorders hardest to treat, for which new therapies are urgently needed, affect behaviors in which vasopressin and oxytocin are involved . As mentioned above, oxytocin is involved in childbirth, breastfeeding, and the mothers behavior toward childcare. But oxytocin is also important for the child to develop and maintain complex interactions with others. Some children with autism often have difficulties in understanding and responding to those interactions, and scientists are trying oxytocin as a potential treatment .
Other examples include disorders associated with stress and anxiety, disorders of eating, disorders of substance misuse , and disorders of sexual behavior. These are major health problems with a considerable impact on humans. By better understanding how brain cells and neuropeptides interact, we may find ways to control some of these disorders and improve the quality of our lives.
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Gaba As A Food Supplement
In recent years researchers have reported a number of placebo-controlled studies in which GABA was administered as a food supplement to healthy participants and participants with a history of acrophobia. One study found an increase in alpha waves in healthy participants and reduced levels of immunoglobulin A in participants with a history of acrophobia when they were exposed to heights . However, the sample size for the second finding was very small . Another study reported reduced heart rate variability and salivary chromogranin A during an arithmetic task compared to a control group after the administration of GABA-enriched chocolate . A third study reported less salivary cortisol and CgA than a control group during a psychological stress-inducing arithmetic task. Additionally, participants who received 50 mg of GABA dissolved in a beverage reported less psychological fatigue after completion of the task . Finally, in a fourth study, participants were found to show a decrease in alpha waves over time while performing an arithmetic task. This decrease was smaller in the group that orally received GABA compared to a control group . By way of comparison, one would have to eat 2.34 kg of uncooked spinach in order to consume a similar amount of GABA, and spinach is relatively rich in GABA compared to other foods .
The Central And Peripheral Nervous Systems
The central nervous system consists of the brain and the spinal cord and controls the majority of bodily and mental functions. The peripheral nervous system makes up the part of the nervous system that is outside of the brain and spinal cord, including the cranial nerves, spinal nerves, peripheral nerves, and neuromuscular joints. The peripheral nervous system makes it possible for the brain and spinal cord to receive and send messages to other parts of the body.
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Examples Of Important Neurotransmitter Actions
As explained above, the only direct action of a neurotransmitter is to activate a receptor. Therefore, the effects of a neurotransmitter system depend on the connections of the neurons that use the transmitter, and the chemical properties of the receptors that the transmitter binds to.
Here are a few examples of important neurotransmitter actions:
Ways To Balance The Neurotransmitters In Your Brain
The neurotransmitters in your brain are responsible for so much of your daily functioning that its best for your well-being to have them in a state of balance in your brain. In this article we will look at 5 ways you can help your brain to help your body function at its best throughout the day.
Neurotransmitters are brain chemicals floating around your brain that send signals from one neuron to another and communicate what needs to happen. Sometimes the need that is being communicated is to store a memory, and sometimes it is the need to eat or hide from danger.
The neurotransmitters control so much of our healthy functioning that when they are out of balance, we can experience many negative health effects. These can include mood disorders like depression and anxiety, to eating disorders like obesity, and sleep disorders like insomnia.
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Neurotransmitters Involved In The Brain
Neurotransmitters are the language of your brain. They allow neurons to communicate to other brain cells. Thats not it, though. Muscles receive cues from neurotransmitters, too. In fact, these chemical messengers send information throughout the body.
The different types of neurotransmitters vary widely. Some manage your heart rate and blood pressure. Others make you feel motivated, stabilize your mood, or help you fall asleep.
To understand how neurotransmitters work in your body, lets study the most notable chemical messengers. And youll learn how important they are for your brain and body.
How Is Gaba Synthesized In The Brain
GABA is synthesized from glutamate, the brain’s main excitatory neurotransmitter by the enzyme glutamic acid decarboxylase . Its synthesis also requires a supporting chemical – a cofactor – called pyridoxal phosphate, which is derived from vitamin B6 taken in from your diet. As GABA levels rise in the brain, it inhibits the action of GAD, therefore regulating its own rate of synthesis.
GABA is released not only from inhibitory cells, but also from supporting brain cells called glia, and is also often co-released together with other neurotransmitters. The mechanism of GABA release in the brain is further complexified by the fact that it can be released from both ends of a brain cell .
The multiple modes of GABA release helps to ensure that it can dynamically fine tune its response according to the ongoing neural environment. Again, like glutamate, GABA finds it difficult to cross the blood-brain barrier when it is not required, therefore helping to keep levels of GABA in the brain tightly regulated.
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