NEUROTRANSMITTERS
BY
TIMOTHY 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 neurotransmitter
Are
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 attentiondeficit/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.