Neurotransmitters & Neurons

 

Neurotransmitters & Neurons

Neurons receive, process, and transmit information via both electrical and chemical signals.

A neurotransmitter is a chemical that is used to communicate between the nervous system. Neurons work within the brain for communication compared to hormones which are usually secreted to certain areas or throughout the bloodstream.

The Anatomy Of A Neuron:

1. Presynaptic Receptors (1) - contains vesicles (2) (sacs) that store neurotransmitters (3).

2. Dendrites (4) - the “ears” of the neuron, which receive incoming signals.

3. Soma (cell body) (5) - contains the nucleus (6) where its DNA is stored.

4. Myelinated Axon Trunk (7) - The axon trunk carries the signals forward. The axon hillock is the section of the neuron that decides if signals continue.

5. Axon Terminal (8 ) - This is where information is passed on to the next neuron.

The Flow Of A Neurotransmitter:

Step 1: A presynaptic cell releases neurotransmitters into the synapse from its vesicles. Once the “threshold” is met, this results in an “action potential”.

Step 2: The neurotransmitters released into the synapse now bind to specific receptors, designed to their specific form. This causes a change in the electrical potential within the post-synaptic cell.

Step 3: If the post-synaptic cell receives a strong enough signal, it will reach its own threshold resulting in yet another action potential. This signal travels down the post-synaptic neuron and can impact cells in its proximity.

Extra Details For You Nerds:

When a neuron is at its resting potential there is a higher concentration of negatively charged ions (Proteins and Potassium Ions). Outside the neuron, there is a higher concentration of positively charged ions (sodium and calcium ions).

When stimulated sodium channels open, rushing sodium into the cell which makes it less negative (depolarizing). Action potentials are met around -55 to -50 millivolts (mV). This action is an “All-or-Nothing” process. This results in a large positive charge shift within the neuron.

After this depolarization, voltage-gated potassium channels open, allowing potassium ions (K+) to exit the neuron. This exit of positive charge causes the membrane potential to return to a negatively charged value, repolarizing the neuron.

Following an action potential, neurons enter a refractory period which makes the neuron less responsive to further stimulation. This prevents neurons from “backfiring”.

Modulators are usually neurotransmitters. These modulators do not directly affect action potentials but can increase or decrease the sensitivity of neurons. Common examples include serotonin, dopamine, and norepinephrine.

What Happens If The Neuron Doesn’t Fire:

If the threshold is not met in the post-synaptic cell, the neurotransmitters may not initiate an action potential. In this case, various outcomes can occur.

Transporters are proteins in the presynaptic cell that function to recycle, reuptake, or store unused materials for future use. Unused neurotransmitters can also diffuse into the surrounding tissues. These transporter proteins also clear out the synapse, preventing continuous firing. Transporters can also help control the releasing concentration/rate of neurotransmitters.

Some Other Facts:

• Glial cells support and interact with neurons in the central nervous system.
• Amino acids are the building blocks for neurotransmitters and proteins.
• Some neurons can speed up or slow down the transmission of signals through neurons.
• The difference between neurotransmitters and hormones is that neurotransmitters are released into synapses, where hormones are released into the bloodstream.
• The combination of environment, body, and chemistry results in differing behaviors.
• There are over 100 different types of neurotransmitters!
• The are more neurons in your brain than stars in our galaxy!
• The synaptic cleft is less wide than a single strand of hair!