neurons and synaptic transmission

• All living things are made up of cells. All cells have a fatty wall around them called a cell membrane
• Different cells have different functions such as transmitting information around the body by using electrical signals to communicate information
• Neuronal cells are cells that receive and transmit electrical signals
• The electrical signals are called nerve impulses
• The four main components of the neuron are the dendrite, cell body, axon, and axon terminal
• Small waves of positively charged particles flow into the neuron at the dendrite. These waves of positively charged particles travel down to the cell body where nerve impulses are triggered.
• A neuron only generates a nerve impulse if there is a large change in voltage at the cell body
• Once a nerve impulse is generated at the cell body, the nerve impulse then travels down the axon to the axon terminal
• Nerve impulses only travel in one direction, from the dendrite to axon terminal
• When charged particles enter a neuron, the voltage within the cell changes. The voltage inside the cell determines whether a nerve impulse is triggered. A nerve impulse occurs only if there is a sufficiently large positive change in voltage.
• the gap between the axon terminal of one neuron, and the dendrites of a second neuron is called the synapse
• Neurons communicate with each other through the synapse, through a process called synaptic transmission
• The pre-synaptic terminal is the part of the axon terminal where a neuron forms a synapse with a second neuron.
• The post-synaptic terminal is the part of the dendrite where the second neuron forms a synapse with the first neuron.
• The part of the synapse where the nerve impulse arrives is called the pre-synaptic terminal, and the membrane around it is called the pre-synaptic membrane. The gap between the pre-synaptic and post-synaptic terminal is the synaptic cleft. The membrane around the post-synaptic terminal is called the post-synaptic membrane.
• The little round bags in the pre-synaptic terminal are called synaptic vesicles. The synaptic vesicles are filled with chemicals called neurotransmitters.
• Nerve impulse arrives at pre-synaptic terminal, causing synaptic vesicles to travel to the pre-synaptic membrane. Synaptic vesicle and pre-synaptic membrane fuse. Neurotransmitters released into synaptic cleft. Neurotransmitters diffuse across synaptic cleft to the post-synaptic terminal and bind to receptors on the post-synaptic membrane
• 1. Nerve impulse arrives at pre-synaptic terminal, causing synaptic vesicles to travel to the pre-synaptic membrane.
  2. Synaptic vesicles fuse with the pre-synaptic membrane, releasing neurotransmitters into synaptic cleft.
  3. Neurotransmitters diffuse across synaptic cleft to post-synaptic terminal and bind to post-synaptic receptors, allowing particles to flow into it
  4. Neurotransmitters are released into the synaptic cleft and are removed through the process of re-uptake.
• The more neurotransmitters released by the pre-synaptic neuron, the more neurotransmitters will bind to receptors allowing more positively charged particles to enter the neuron and a bigger change in voltage. This makes it more likely for a nerve impulse to be triggered.
• receptors usually block positively charged particles from entering the post-synaptic neuron, however, when neurotransmitters bind to post-synaptic receptors, the receptors change shape to allow flow into the post-synaptic terminal.
• The more positively charged particles flow into the post-synaptic terminal, the more likely it is that a nerve impulse is generated at the cell body.
• After the neurotransmitter binds to the receptor, and positively charged particles have flowed into the post-synaptic membrane, the neurotransmitter is released back out into the synaptic cleft
• Re-uptake is the process of removing neurotransmitters from the synaptic cleft
• The pre-synaptic terminal re-uptakes neurotransmitters using re-uptake proteins.
• Nerve impulse arrives at pre-synaptic terminal, causing synaptic vesicles to travel to pre-synaptic membrane. Pre-synaptic membrane and synaptic vesicle fuse. Neurotransmitters released into synaptic cleft. Neurotransmitters diffuse across synaptic cleft to post-synaptic terminal and bind to receptors. Positively charged particles flow into post-synaptic terminal, creating small, positive changes in voltage. Nerve impulse triggered once there is large enough change in voltage. Neurotransmitters released into synaptic cleft and sucked back into pre-synaptic membrane by re-uptake proteins.
• Most of the time, only a small amount of neurotransmitter is released into the synapse meaning only a small number of positively charged particles flow into the post-synaptic neuron and there will be a small change in voltage in the post-synaptic neuron.
• Summation is a process that makes it more likely a nerve impulse will be triggered. It is when multiple small changes in voltage, triggered by neurotransmitter release, add up together.
• Summation occurs if multiple nerve impulses occur in the pre-synaptic neuron in close succession or multiple nerve impulses occur at multiple synapses at the same time.
• Excitatory neurotransmitters cause positively charged particles to enter the post-synaptic neuron, and inhibitory neurotransmitters cause negatively charged particles to enter the post-synaptic neuron.
• excitatory neurotransmitters make a nerve impulse more likely to occur. inhibitory neurotransmitters make a nerve impulse less likely to occur.
• excitatory neurotransmitters create excitatory post-synaptic potentials. inhibitory neurotransmitters create inhibitory post-synaptic potentials.
• For a nerve impulse to occur, there needs to be more excitatory neurotransmitter release than inhibitory neurotransmitter release and more excitatory post-synaptic potentials than inhibitory post-synaptic potentials.
• excitatory post-synaptic potentials and inhibitory post-synaptic potentials can summate, but inhibitory post-synaptic potentials cancel out the excitatory post-synaptic potentials.
• Acetylcholine makes nerve impulses more likely to happen, so it is an excitatory neurotransmitter. It is used to control our muscles.
• GABA is the main inhibitory neurotransmitter used in the brain and makes nerve impulses less likely to happen
• Dopamine can be both an excitatory and inhibitory neurotransmitter, and controls our responses to rewards.
• serotonin can be both an excitatory and inhibitory neurotransmitter, and controls our response to mood.
•  Sensory neurons pick up information from sensory receptors which they transmit towards the brain. Sensory neurons are located near our sensory receptors
• Motor neurons are responsible for carrying information away from the brain to the muscles and controlling muscle movement
• Relay neurons process and transform sensory information. They can form synapses with both sensory and motor neurons