What is a synapse?

When electrical impulses are fired around your body, they do so by travelling around in neurones as chemical/electrical impulses.


However, your neurones don't cover every inch of your body. To get over this issue, there are small gaps between the neurones - this is called the synapse. Technically speaking, it's a junction between the neurone and the next cell. , the gap itself is called the synaptic cleft. The neurone before the gap is given the name of a presynaptic neurone - it has a swelling on it called the synaptic knob. On the presynaptic neurone there's synaptic vesicles filled with chemicals called neurotransmitters.


When an action potential reaches the end of the neurone, neurotransmitters are released into the synaptic cleft. They diffuse across this gap and attach to the postsynaptic membrane - here they bind to specific receptors. When the neurotransmitter binds to the receptors, this could trigger an action potential, causing muscle contraction (perhaps) in the next cell. Alternatively, a hormone could be secreted if it's a gland cell.




Because these receptors are only on the post synaptic membrane, this makes action potentials unidirectional - i.e they travel in only one direction. If nerve signals travelled in multiple directions, things would get very confusing very quickly!

What is a receptor?

A receptor is an organ or cell which can respond to light, heat, or another external factor. They transmit an electrical impulse to the sensory nerve - this kick-starts the reflex arc.  There are many different kinds of receptors, all of which are specific to one kind of stimulus, they're all given names:

Mechanoreceptors - detect mechanical stimulus like pressure/vibrations

Thermoreceptors -  detect heat

Baroreceptors - detect high/low blood pressure in the heart

Chemoreceptors - detect chemical changes in the heart, so a change in oxygen, carbon dioxide or pH level

Fun Fact:

The retina of the octopus has up to 20 million light receptors :)

Why does a mint make ice cream even colder?

All mints contain the chemical menthol, which binds to the TRP-M8 receptors in your skin which sense cold, the temperature doesn't change it's the menthol that causes false cold signals to be sent to your brain. This feeling is intensified because the ice cream also sends cold signals to your brain and this increases the number of cold receptors that are firing at once. This is similar to the reaction caused by chilli which is caused by the chemical capsaicin which binds to the TRP-V1 receptors for heat.