NEUROTRANSMITTERS

BYTIMOTHY AMEEFO

INTRODUCTION

• Neurotransmitters are chemicals which relay, amplify, modulate signals between a neuron and another cell.

• Basically they are chemicals that transmit signals from one neuron to the next across synapses.

• Neurotransmitters are produced by some glands such as the pituitary and adrenal glands.

INTRODUCTION

• The release of neurotransmitters usually follow the arrival of an action potential at the synapse and the released neurotransmitter then cross the synapse where they may be accepted by the next neuron at a specialised site called the RECEPTOR

DIAGRAM OF A TYPICAL NEURON

Examples of neurotransmitters

• In the midst of many chemicals that act as a neurotransmitter, below is a list of some.

• (Small molecule neurotransmitter substances). Acetylcholine,dopamine,norepinephrine,

serotinin,histamine,epinephrine.• (Amino Acids) Gamma-aminobutyric

acid(GABA),Aspartate,Glutamate

Types of Neurotransmitters

• (Neuroactive peptides-Partial list only)Bradykinin,gastrin,secretin,oxytocin,prolactin,ins

ulin,calcitonin,glucagon,vasopressin,lutenizing hormones

• (Purines)-Adenosine,ATP,GTP• (Soluble Gases)-Nitric Oxide,Carbon Monoxide

Mechanism of Action

• Within cells,small-molecules neurotransmitter are packaged in vessicle called synaptic vessicles.When an action potential travels to the synapse, the rapid depolarisation causes calcium ions channels to open.Calcuim then stimulates the transport of vessicles to the synaptic membrane leading to release of neurotransmitters via a process known as exocytosis.

Mechanism of action

Mechanism of action of neurotransmitters

Inactivation of Neurotransmitters

• 1. Diffusion: the neurotransmitter drifts away, out of the synaptic cleft where it can no longer act on a receptor.

• 2.Enzymatic degradation:specific enzyme changes the structure of the neurotransmitter so it is not recognized by the receptor. For example, acetylcholinesterase is the enzyme that breaks acetylcholine into choline and acetate

• 3. Glial cells: astrocytes remove neurotransmitters from the synaptic cleft.

• 4. Reuptake: the whole neurotransmitter molecule is taken back into the axon terminal that released it. This is a common way the action of norepinephrine, dopamine and serotonin is stopped...these neurotransmitters are removed from the synaptic cleft so they cannot bind to receptors.

Inhibitory and excitatory neurotransmitters

• There are two kinds of neurotransmitters – INHIBITORY and EXCITATORY. Excitatory neurotransmitters are not necessarily exciting – they are what stimulate the brain. Those that calm the brain and help create balance are called inhibitory. Inhibitory neurotransmitters balance mood and are easily depleted when the excitatory neurotransmitters are overactive.

Excitatory neurotransmitters

• DOPAMINE is our main focus neurotransmitter. When dopamine is either elevated or low – we can have focus issues such as not remembering where we put our keys, forgetting what a paragraph said when we just finished reading it or simply daydreaming and not being able to stay on task. Dopamine is also responsible for our drive or desire to get things done – or motivation. Stimulants such as medications for ADD/ADHD and caffeine cause dopamine to be pushed into the synapse so that focus is improved. Unfortunately, stimulating dopamine consistently can cause a depletion of dopamine over time.

Excitatory neurotransmitters

Other examples are• Epinephrine---regulates heart rate and blood

pressure• Norepinephrine----causes anxiety at elevated

levels and low levels causes decreased focus ability

Inhibitory neurotransmitters

• GABA is an inhibitory neurotransmitter that is often referred to as “nature’s VALIUM-like substance”. When GABA is out of range (high or low excretion values), it is likely that an excitatory neurotransmitter is firing too often in the brain. GABA will be sent out to attempt to balance this stimulating over-firing.

Inhibitory neurotransmitters

Other examples of inhibitory neurotransmitterAre Serotinin---This regulates many processes such carbohydrate cravings, appropraite digestion,pain control

Neurotransmitters, mental disorders, and medications

• Schizophrenia• Impairment of dopamine-containing neurons

in the brain is implicated in schizophrenia, a mental disease marked by disturbances in thinking and emotional reactions. Medications that block dopamine receptors in the brain, such as chlorpromazine and clozapine, have been used to alleviate the symptoms and help patients return to a normal social setting.

Mental disorders and application

• Alzheimer's disease• Alzheimer's disease, which affects an estimated four

million Americans, is characterized by memory loss and the eventual inability for self-care. The disease seems to be caused by a loss of cells that secrete acetylcholine in the basal forebrain (region of brain that is the control center for sensory and associative information processing and motor activities). Some medications to alleviate the symptoms have been developed, but presently there is no known treatment for the disease.

• Attention-deficit/hyperactivity disorder• People affected by

attention-deficit/hyperactivity disorder (ADHD) experience difficulties in the areas of attention, overactivity, impulse control, and distractibility. Research shows that dopamine and norepinephrine imbalances are strongly implicated in causing ADHD.