Neurons & Synaptic Transmission

What are neurons?

Neurons are cells within the nervous system that are the building blocks of communication within the body. They send electrical and chemical messages to sense organs, glands and other organs.

What is the cell body?

The cell body contains the nucleus, where the DNA of the neuron is stored.

What are dendrites?

Dendrites receive electrical signals from other neurons and transmit them to the cell body.

What is the axon?

The axon carries the electrical charge away from the cell body down the length of the neuron.

What is the myelin sheath?

The myelin sheath is a protective fatty covering around the axon that helps speed up the transmission of electrical signals.

What are Nodes of Ranvier?

Nodes of Ranvier are gaps in the myelin sheath that speed up the transmission of electrical signals.

What is the axon terminal?

The axon terminal is found at the end of the neuron and plays a role in chemical transmission across the synaptic cleft to the next neuron.

What are the three main types of neurons?

Sensory neurons, motor neurons and relay neurons.

What is the role of sensory neurons?

Sensory neurons send information from the peripheral nervous system towards the central nervous system and keep the brain informed about the external and internal environment.

What is the structure of a sensory neuron?

Sensory neurons have long dendrites and short axons, with the cell body usually located to the side of the cell.

How do sensory neurons transmit information?

Sensory neurons can only transmit messages one way and cannot receive messages.

What is the role of motor neurons?

Motor neurons carry signals from the central nervous system towards organs, muscles and glands in the peripheral nervous system.

What do motor neurons control?

Motor neurons control physical movements such as the contraction and relaxation of muscles.

What is the structure of a motor neuron?

Motor neurons have short dendrites and long axons.

How do motor neurons transmit information?

Motor neurons can both transmit and receive messages.

What is the role of relay neurons?

Relay neurons connect sensory neurons to motor neurons.

Where are relay neurons located?

Relay neurons are located in the central nervous system and carry signals across this part of the nervous system.

What is the structure of relay neurons?

Relay neurons have short axons and short dendrites.

How do relay neurons transmit information?

Relay neurons can both transmit and receive messages.

What is a synapse?

A synapse is the junction where two neurons meet.

What are the three main components of a synapse?

The presynaptic knob, synaptic cleft and postsynaptic membrane.

What is the presynaptic knob?

The presynaptic knob is a swelling at the end of the presynaptic neuron containing vesicles that hold neurotransmitters.

What is the synaptic cleft?

The synaptic cleft is the space between the axon of one neuron and the dendrites of another. It is where the electrical signal is converted into a chemical messenger.

What is the postsynaptic membrane?

The postsynaptic membrane receives the signal and contains receptor sites that bind neurotransmitters from the presynaptic neuron.

What is an action potential?

An action potential is an electrical impulse travelling within a neuron.

What is the first stage of synaptic transmission?

An electrical impulse, or action potential, begins within the presynaptic neuron.

What happens when the action potential reaches the presynaptic knob?

Neurotransmitters are released from vesicles at the presynaptic membrane.

What are neurotransmitters?

Neurotransmitters are chemical messengers released by the presynaptic neuron into the synaptic cleft.

What happens to neurotransmitters after they are released?

They diffuse across the synaptic cleft and temporarily bind to receptor sites on the postsynaptic membrane.

What happens when neurotransmitters bind to postsynaptic receptors?

This stimulates the postsynaptic neuron to generate another electrical impulse, which travels down its axon.

How is continued stimulation prevented?

Neurotransmitter molecules are destroyed by enzymes or recycled so that repeated impulses are not continually sent.

What happens to reabsorbed neurotransmitters?

They may be used again by the presynaptic neuron.

What are neurotransmitter receptors?

Receptor sites are structures that specifically bind particular neurotransmitters.

What is serotonin associated with?

Serotonin plays an important role in regulating mood, particularly depression and anxiety.

What is dopamine associated with?

Dopamine receptors play an important role in movement and the experience and anticipation of reward.

Where are dopamine receptors located according to the notes?

Dopamine receptors are located in the hippocampal dentate gyrus.

What are excitatory neurotransmitters?

Excitatory neurotransmitters stimulate an action potential in the postsynaptic neuron.

How do excitatory neurotransmitters affect the neuron's charge?

They increase the neuron's positive charge, making it more likely to fire.

What example of an excitatory neurotransmitter is given?

Adrenaline.

What are inhibitory neurotransmitters?

Inhibitory neurotransmitters inhibit an action potential in the postsynaptic neuron.

How do inhibitory neurotransmitters affect the neuron's charge?

They increase the neuron's negative charge, making it less likely to fire.

What example of an inhibitory neurotransmitter is given?

Serotonin.