NEUROTRANSMITTERS

NARAINO MAJIE Nabiilah3rd April 2013

Introduction• Definition• Structure of Neuron• Transmission of chemical information• Release• Receptors• Inactivation

Types of neurotransmitters• Inhibitory• Excitatory

Conclusion References

CONTENT

NEUROTRANSMITTERS are the brain chemicals that communicate information throughout our brain and body.

They relay signals between nerve cells, called “neurons.”

The brain uses neurotransmitters to tell • your heart to beat,• your lungs to breathe, and• your stomach to digest. • They can also affect mood, sleep, concentration, weight,

and• can cause adverse symptoms when they are out of balance.

Neurotransmitters

This is a NEURON

Dendrites are branching fibers that receive information from other neurons

Soma is the cell body of a neuron. It contains a nucleus, ribosomes, mitochondria, and other structures. This is where much of the metabolic work takes place

Axon is a thin fiber where information is sent from the neuron to other neurons

Soma

Presynaptic terminalsPresynaptic

terminals are the point where the axon releases chemicals

Dendrites

Axon

Neurotransmitter comes from somaIt travels through the axon

From the pre-synaptic terminal it is taken through the synapse to the next neuron

Re-uptake sometimes occurs

Transmission of Neurotransmitters

Pre-synaptic Neuron

Post-synaptic Neuron

Neurotransmitters are sent through the axon to pre-synaptic terminals, and then to another neuron

Transmission of Neurotransmitters

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NEUROTRANSMITTERSChemical transducers released By electrical impulse Into the synaptic cleft From pre-synaptic membrane By synaptic vesicles.

Diffuse to the post-synaptic membrane React and activate the receptors present Leading to initiation of new electrical signals.

Across a small gap called the synapse. An electrical impulse will trigger the migration of

vesicles containing neurotransmitters toward the presynaptic membrane.

The vesicle membrane fuse with the presynaptic membrane releasing the neurotransmitters into the synaptic cleft.

Chemicals, called neurotransmitters, are released from one neuron at the presynaptic nerve terminal.

Release

Neurotransmitters then cross the synapse where they may be accepted by the next neuron at a specialized site called a receptor.

Either depolarization (an excitatory postsynaptic potential) or hyper polarization (an inhibitory postsynaptic potential).

A depolarization makes it MORE likely that an action potential will fire; a hyper polarization makes it LESS likely that an action potential will fire.

Release (cont’d)

It occurs in 4 steps:

◦ Synthesis of transmitter

◦ Storage & release of transmitter

◦ Interaction of transmitter with receptor in postsynaptic membrane

◦ Removal of transmitter from synaptic cleft

Release

Ca2+ Ca2+Release

There are 2 types of receptors:◦ Ion-Channel linked receptor◦ G- Protein linked receptor

Receptor

Inactivation of the transmitter happens in one of three ways:

Re-absorption of the neurotransmitter into the neuron. This is known as reuptake and is the normal process.

Destruction of the neurotransmitter with special chemicals called enzymes. This is known as enzymatic degradation.

By the neurotransmitter becoming detached from the receptor and drifting out of the synaptic cleft. This is known as diffusion.

Inactivation

Two types:◦ Inhibitory-inhibit nerve impulses and calm the

brain and help create balance.◦ Excitatory-propagate nerve impulses and

stimulate the brain.

Inhibitory neurotransmitters balance mood and are easily depleted when the excitatory neurotransmitters are overactive.

Types of Neurotransmitters

Action of Inhibitory Neurotransmitters Action potential goes down synaptic knobs of

another neuron Release of Inhibitory neurotransmitters Activation of receptor site on cell membrane Opening of potassium channels Flow of k⁺ out of cell Cell inside becomes –ve Leads to local hyper polarization Known as Inhibitory Post Synaptic Potential (IPSP)

Inhibitory N.Transmitters

Examples of Inhibitory Neurotransmitters

SEROTONIN is an inhibitory neurotransmitter – which means that it does not stimulate the brain. 

Serotonin are necessary for a stable mood and to balance any excessive excitatory (stimulating) neurotransmitter firing in the brain.

Stimulant medications or caffeine can cause a depletion of serotonin over time. 

Serotonin also regulates many other processes such as carbohydrate cravings, sleep cycle, pain control and appropriate digestion. 

Low serotonin levels are also associated with decreased immune system function.

Inhibitory N.Transmitters

GABA (Gamma-Amino Butyric Acid) When brain experiences an abundance of nervous

tension and stress, it can be caused by a surplus of norepinephrine or epinephrine (adrenaline).

To neutralize this extra adrenaline, the brain produces neurotransmitters, one of which is GABA.

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 N.Transmitters

DOPAMINE is a special neurotransmitter because it is considered to be both excitatory and inhibitory. 

Plays a critical role in the control of movement. It has a stimulating effect on the heart, the circulation, the

rate of metabolism, and is able to mobilize many of the body’s energy reserves.

It helps to modulate brain activity, control coordination and movement, and regulate the flow of information to different areas of the brain.

Dopamine is believed to release chemicals that allow us to feel pleasure (e.g. endorphins).

A massive disturbance of dopamine regulation in the brain can result in a person no longer being able to respond emotionally or express his or her feelings in an appropriate way (e.g. schizophrenia).

Inhibitory N.Transmitters

Action of Excitatory Neurotransmitters Action potential goes down synaptic knobs of

another neuron Release of Excitatory neurotransmitters Activation of receptor site on cell membrane Opening of ligand-gated sodium ion channels. Flow of Na⁺ in the cell Cell becomes less –ve Leads to to a local depolarization Known as Excitatory Postsynaptic Potential

(EPSP).

Excitatory N. Transmitters

Examples of Excitatory Neurotransmitters

Norepinephrine also known as noradrenaline is a excitatory neurotransmitter that is produced by the adrenal medulla or made from dopamine.

High levels of norepinephrine are linked to anxiety, stress, high blood pressure, and hyperactivity.

Low levels are linked to lack of energy, focus, and motivation.

Excitatory N. Transmitters

Histamine is most commonly known for it's role in allergic reactions but it is also involved in neurotransmission and can affect your emotions and behavior as well.

Histamine helps control the sleep-wake cycle and promotes the release of epinephrine and norepinephrine.

High histamine levels have been linked to obsessive compulsive tendencies, depression, and headaches.

Low histamine levels can contribute to fatigue and medication sensitivities.

Excitatory N. Transmitters

Acetylcholine same as Dopamine can be both Inhibitory and Excitatory.

Acetylcholine (often abbreviated ACh) is the most common neurotransmitter. It is located in both the central nervous system (CNS) and the peripheral nervous system (PNS).

In the central nervous system, acetylcholine acts as part of a neurotransmitter system and plays a role in attention and arousal.

In the peripheral nervous system, this neurotransmitter is a major part of the autonomic nervous system and works to activate muscles.

Acetylcholine is also involved in memory and learning and is in particularly short supply in people with Alzheimer's disease.

Excitatory N. Transmitters

All chemical messengers in the brain have immense interconnectivity.

Their function relies on a system of checks and balances during each moment of life. If one part of the system fails, others can’t do their job properly.

Panic disorder is just one of many physical and psychological illnesses that are believed to be influenced by the complex interacting of neurotransmitters.

Neurotransmitter levels can now be determined by a simple and convenient urine test collected at home. Knowing your neurotransmitter levels can help you correct a problem today or prevent problems from occuring in the future.

Conclusion

http://www.neurogistics.com/thescience/whatareneurotransmi09ce.asp

http://antranik.org/actions-of-excitatory-and-inhibitory-neurotransmitters/

http://neurogenesis.com/neuro-transmitters/dopamine/

http://faculty.washington.edu/chudler/chnt1.html

http://www.integrativepsychiatry.net/neurotransmitter.html

REFERENCES

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