Neurons and synaptic transmission- Biopsychology

What are synaptic transmissions?

The process by which neighbouring neurons communicate with each other by sending chemical messages across the synaptic cleft that separates them.

What are the types of neurons?

sensory neurons, relay neurons, motor neurons

What are electrical transmissions in the synapse?

- Neurons communicate with each other within groups known as neural networks. Each neuron is separated from the next by a synapse. - The synapse includes the space between them (synaptic cleft) as well as the presynaptic terminal and post synaptic receptor sites. - Signals within neurons are transmitted electrically; but signals between neurons are transmitted chemically by synaptic transmission. - When the electrical impulse reaches the end of the neuron (the presynaptic neuron) it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles.

What is the structure of a neuron?

- Neurons vary in size from less than a millimetre to up to a metre long, but all share the same basic structure. - The cell body (or soma) includes a nucleus, which contains the genetic material of the cell. Branch-like structures called dendrites protrude from the cell body, these carry nerve impulses from neighbouring neurons towards the cell body. - The axon carries the impulses away from the cell body down the length of the neuron. The axon is covered in a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse. - If the myelin sheath was continuous this would have the reverse effect and slow down the electrical impulse. So the myelin sheath has is segmented by gaps called nodes of Ranvier. These speed up the transmission of the impulse by forcing it to 'jump' across the gaps along the axon. - At the end of the axon on terminal buttons that communicate with the next neuron in the chain across a synapse.

What are electrical transmissions?

- 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 of a split second causing an action potential to occur. This creates an electrical impulse that travels down the axon towards the end of the neuron.

What is a neurotransmitter?

Brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another. - Can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function. - Are chemicals that diffuse across the synapse to the next neuron in the chain. - Once it has crossed the gap it is taken up by the postsynaptic neuron. Here the chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neuron. - Several dozen types of neurotransmitter have been identified in the brain. Each neurotransmitter has its own specific molecular structure that fits perfectly into a post-synaptic receptor site. - Neurotransmitters also have specialist functions.

What are neurons?

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

What are sensory neurons?

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

What are motor neurons?

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

What are relay neurons?

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

What is excitation?

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

What is inhibition?

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