Neurotransmitters & Neuromodulators Flashcards
KKDP 2
The Synapse:
The neural synapse (or neural junction) is the site where communication typically occurs between adjacent neurons
Role of Neurotransmitters:
Neurotransmitters: are a chemical substance produced by neurons that carry a message to other neurons or cells in muscles, organs or other tissue.
● Neurotransmitter is sent across the synaptic gap (cle ) - the tiny space between the pre-synaptic and post-synaptic neuron - enabling communication between a pre-synaptic and post-synaptic neuron at the synapse
● To successfully send a message, the neurotransmitter will bind itself to the receptor site of the post-synaptic neuron if no receptor site re-uptake ➡➡
will occur
● Once the post-synaptic neuron has received the neurotransmitter, excess neurotransmitter is also reabsorbed by the presynaptic neuron
Effects of Neurotransmitters:
Neurotransmitters have one of two effects…
1. EXCITATORY: make the post synaptic neuron more likely to fire
2. INHIBITORY: make the post synaptic neuron less likely to fire
Common Neurotransmitters
Glutamate & Gamma-Aminobutyric Acid (GABA)
Glutamate: is the primary excitatory neurotransmitter in the CNS (it makes the post-synaptic neuron more likely to fire).
● Second most abundant neurotransmitter in the brain
● Involved in most brain functions (EG: perception, learning, memory,
movement and thinking
● Balance is essential not enough or too much can be harmful to the neuron ➡
Gamma-Aminobutyric Acid (GABA): is the primary inhibitory neurotransmitter in the CNS (it makes the post-synaptic neuron less likely to fire).
● Its role is to fine-tune neurotransmitter function in the brain
● Low levels of GABA could result in;
○ Seizures such as those associated with epilepsy
○ Anxiety
● Together GABA and glutamate counteract the acti ties of each other to
create a harmonious system
Neuromodulators:
Neuromodulators are neurotransmitters that ‘modulate’, or influence, the effects of other neurotransmitters
● Neuromodulators can team up and work together with another neurotransmitter in a synapse to make the other more or less potent.
● However, their acti ty is not restricted to the synaptic gap between two adjacent neurons. Neuromodulators do not release their chemical messengers into a single synapse. Instead, they are released into far broader areas, where they can affect a large number of neurons at once, as many as 100,000 or more.
● Consequently, an entire neural tissue, brain area, pathway or multiple pathways may be influenced by exposure to a neuromodulator action.
● Neuromodulators also exert their influence over a slower time period than excitatory and inhibitory neurotransmitters at synapses with fast-acting receptors. Their effects take longer to become established and last longer
Common Neuromodulators ⤵ Dopamine & Serotonin:
● Although dopamine and serotonin work differently and differ in function, they do not work in isolation. Dopamine and serotonin can also interact by counterbalancing each other’s effects.
Dopamine:
Dopamine is a modulatory neurotransmitter known to have multiple functions
● For example, it has important roles in voluntary movements, the experience
of pleasure, motivation, appetite, reward-based learning and memory.
● It has also been implicated in various mental conditions, including
Parkinson’s disease, addiction and schizophrenia.
Brain Areas involved in Dopamine Activity:
● The brain has several distinct dopamine producing areas and neural pathways along which dopamine travels to convey information to different areas and exert its influence.
● These form the dopamine (dopaminergic) system. Two of the pathways are the nigrostriatal pathway which originates from the substantia
nigra (orange) and the mesolimbic pathway (purple). The dopamine reward system is located between the ventral tegmentum and nucleus accumbens
Dopamine Pathways involved in Movement:
This pathway (nigrostriatal) has its origins in the midbrain structure called the substantia nigra. Dopamine produced by neurons in this structure carries messages that allow smooth, coordinated function of the body’s muscles and movements. When the substantia nigra is diseased or damaged, the amount of dopamine available is reduced. This means that other brain structures receive slower, fewer and/or irregular dopamine messages about motor acti ty.
This can result in conditions that make it difficult for a person to move, as occurs in Parkinson’s disease.
Symptoms of Parkinson’s disease include:
● Slow voluntary movements
● Tremors
Drugs commonly used to treat these motor symptoms of the disease target dopamine and try to mimic the role of dopamine.
Dopamine Reward System:
● When someone experiences something that is rewarding, the brain tends to respond by releasing dopamine, resulting in feelings of pleasure and possibly even euphoria. This primarily occurs in the pathway (mesolimbic) that originates deep within the midbrain.
● When experiencing a beha our with a pleasurable consequence, it becomes more likely to repeat that beha our and eventually learn to associate that rewarding experience with whatever is thought to have caused it.
● In addition, the anticipation of recei ng a rewarding stimulus can be a motivating influence on beha our and can trigger dopamine release.
Downside of Dopamine:
● Dopamine stimulation in this pathways has been found to be strongly associated with addictive beha ours
○ E.g: taking drugs, gambling, or other harmful beha ours ● Schizophrenia has also been linked to dopamine
Dopamine on its own is not responsible for these issues but rather its associated with these problems
Serotonin:
A modulating neurotransmitter that has a wide range of functions.
It has important roles in mood, emotional processing, sleep onset, appetite and pain perception.
● Serotonin only has inhibitory effects
Brain structures and neural pathways that form the serotonin (serotonergic) system. Within the brain, serotonin is mostly produced in the brain stem, within the Raphe nuclei. The serotonin created by the brain comprises around 10% of the body’s total amount of serotonin.
Serotonin explained:
Serotonin is widely described as a mood stabiliser, with low levels associated with mood disorders such as depression and seasonal affective disorder.
● Reduced levels of serotonin in the brain have also been associated with a
number of anxiety disorders, particularly obsessive-compulsive disorder.
● Serotonin also seems to play an important role in the regulation of the daily
sleep–wake cycle, too little may result in insomnia
● TOO MUCH Serotonin can lead to Serotonin syndrome; a collection of
symptoms that includes fever, elevated heart rate, restlessness, agitation, confusion, hallucinations, delirium and seizures.
