Neuron and Synaptic Transmission

Neurotransmitters

Chemicals which diffuse across the synapse to the next neuron in the chain. Every transmitter has its own specific molecular structure that fits perfectly into a post-synaptic receptor site. Neurotransmitters also have specialist functions. for instance, acetylcholine is found at each point where a motor neuron meets a muscle, upon its release, it will cause muscles to contract.

Types of neuron

Motor, sensory and relay

Chemical transmission (from the neuron to the synapse)

Neurons communicate with each other within neural networks. Each neuron is separated from the next by a synapse, the synapse includes a space between them (synaptic cleft) as well as the presynaptic terminal and the postsynaptic receptor site. Signals within neurons are transmitted electrically, however, between neurons they are transmitted chemically (synaptic transmission). When the electrical impulse reaches the end of the neuron (presynaptic terminal) it triggers the release of neurotransmitters from tiny sacs called synaptic vesicles.

Chemical transmission (from the synapse to the next neuron)

Once the neurotransmitter crosses the gap, it is taken up by the post synaptic receptor sites (dendrites of the next unit). Here, the chemical message is converted back into an electrical impulse and then the process of transmission begins again.

Neuron

The basic building blocks of the nervous system, neurons and nerve cells that process and transmit messages through electrical and chemical signals.

Sensory Neuron

These carry messages from the PNS to the CNS. They have long dendrites and short axons.

Motor Neuron

These connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.

Relay Neuron

These connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons.

Electric transmission

When a neuron is in a resting state, the inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur. This creates an electrical impulse which travels down the axon towards the end of the neuron.

Excitation

When a neurotransmitter such as adrenaline, increases the positive charge of the post-synaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse.

Inhibition

When a neurotransmitter such as serotonin, makes the charge of the post-synaptic neuron more negative. This decreases the likelihood the neuron will fire and pass on the electrical impulse.