neurons and synaptic transmission Flashcards
Where are the neurons located?
The central nervous system contains all neurons in the body. A neuron is a nerve cell. Neurons carry “messages” or signals electrically and chemically. They are the building blocks of the body’s communication system
What is the structure of a neuron?
Dentrites on the end of the cell body which contains a nucleus
Myelin sheath with node of ranvier in between
Axon on the end of the
What is the function of the dendrites?
Branch like structures which carry impulses from neighbouring neurons towards the cell body
What is the cell body?
Includes a nucleus
What is the cell nucleus?
Contains the genetic material
What is the axon?
Tube - like structure that carries the impulses away from the cell body down the length of the neuron
What is the myelin sheath?
A fatty layer which covers the axon - it protects the axon and speeds up electrical impulses
What is the terminal buttons?
At the end of the axon terminal from where the neurotransmitters is released
What are vesicles?
Small packets of neurotransmitter
What is action potential?
When a neuron is in a resting state the inside of the cell is negatively charged relative to the outside. When a neuron is sufficiently activated by a stimulus, the inside of the cell becomes positively charged for a split second. This rapid switch from negative positive charges called depolarisation and it creates an electrical impulse (action potential)that travels down the axon towards the terminal buttons of the neuron.
This is sometimes called firing an action potential. The action potential is generated once depolarisation reaches a certain threshold. It is always the same intensity, regardless of the size of the stimulus that originally generated it. If the threshold is not reached, there is no action potential, therefore an action potential is an all or nothing prevent. Most myelinated neurons are capable of conducting up to 500 action potentials a second.
What is the synaptic transmission?
New ones communicate with each other within groups known as neural networks. They do not physically touch, but are separated by a tiny called synaptic cleft.
Signals within a neuron are transmitted electrically
Signals between neurons are transmitted chemically
Synaptic transmission is a chemical process using biochemical substances called neurotransmitters. The sign transmission process starts with an action potential, the electrical impulse by which the messages passed down the axon of the neuron, which triggers the release of neurotransmitters from tiny sacs called vesicles.
Explain the process of synaptic transmission
- When the action potential reaches the presynaptic terminal button, it triggers the release of neurotransmitters from tiny sacs called vesicles.
- These neurotransmitters (chemicals) then diffuse across the synapse
- Neurotransmitters then fit into matching receptor sites on the post synaptic neuron (where the signal is converted back into an electric signal)
- Neurotransmitters that remain in the synapse are re absorbed into the presynaptic neuron (reuptake) which means they can be used again
Neurotransmitters
Neurotransmitters are the chemical messengers that act between the neurons in the brain.
Each neurotransmitter has its own specific molecular structure and fits perfectly into a specific type of postsynaptic receptor (like a key and lock)
Have different roles and functions
What is noradrenaline?
- fight or flight response
- sleeping - dreaming
- learning
- attention
- emotion, especially mood control
What is dopamine?
- posture and control of movement
- dependency behaviour- addiction
- cognitive functions
- emotion
What is serotonin?
- regulates body temperature
- sleep - wakefulness
- hunger
- feeling pain
- mood control - happiness and good mood
What is acetylcholine?
- stimulates muscle contraction and key function in motor control and movement
- cognitive functions including memory and thinking
- expressions of some emotions e.g anger and sexuality
What is GABA?
- stands for gamma-aminobutyric acid
- this is an inhibitor in the brain so it blocks messages rather than taking a message on
- it calms nerves that are firing so producing feelings of relaxation
- low levels are associated with anxiety
