Biopsychology Revision
Neurons
Neurons communicate via electrical signals
Cells use electrical signals to communicate information and neurons can only transmit and
receive information.
- Electrical signals are called nerve impulses (or action potentials)
Neuronal structure
There are four main components of a neuron:
1. Dendrites
➔ Tree like structures
2. Cell body
➔ Next to the dendrite (big round body)
3. Axon
➔ Long stick coming off the cell body
4. Axon terminal
➔ Next to the axon, end of the neuron
Neural transmission
The electrical signals change in voltage
- It changes if there are more or fewer charged particles in the neuron
Small waves of positively charged particles flow into the neuron through the dendrites
causing small positive changes inside the cell. It then travels to the cell body. If the change
in voltage, caused by the positively charged particles, is big enough when it reaches the
cell body it then triggers a bigger change in voltage, being the action potential (triggered
in the cell body).
Action potentials then travels down the axon until it reaches the axon terminal
- Action potentials only travel in one direction, from the dendrite to the axon terminal
Structure of the synapse
The presynaptic terminal is at the end of the axon terminal. The wall around this is called
the pre synaptic membrane. The end of the dendrite is called the postsynaptic terminal
,and the wall around it is called the postsynaptic membrane. The gap between the
presynaptic terminal and the postsynaptic terminal is called the synaptic cleft.
- In the presynaptic terminal there are synaptic vesicles (looks like little white bags)
filled with neurotransmitters
Synaptic transmission
The gap between the axon terminal and the next dendrite is called the synapse
- Neurons communicate through the synapse
The process through which nerve processes are transmitted across the synapse is called
synaptic transmission:
1. When nerve impulses travel to the presynaptic terminal it tells synaptic vesicles to
travel down to the presynaptic membrane
2. When the synaptic vesicles reach the presynaptic terminal, the synaptic vesicle and
the presynaptic membrane fuse (join together)
3. This causes the neurotransmitters to be released into the synaptic cleft
4. The neurotransmitters then diffuse across the synaptic cleft towards the
postsynaptic terminal
5. The neurotransmitters then bind to the receptors on the postsynaptic membrane
6. The neurotransmitters that bind to receptors means more positively charged
particles can flow into the dendrite, causing large changes in voltage (normally the
positively charged particles can't get through to the dendrite but when the
neurotransmitters do, they also)
7. The neurotransmitters then go back into the synaptic cleft but are removed by
reuptake proteins making them enter back into the pre synaptic terminal where
they can be recycled.
➔ The presynaptic terminal is responsible for the reuptake of
neurotransmitters
Summation
Action potentials are usually caused by summation and it can occur in two ways:
1. If multiple action potentials occur in the presynaptic neuron in close succession
then there are multiple waves of neurotransmitters which are released to the
synapse in very close succession. This means that the first small change in voltage
is quickly followed by the second change which adds onto the first one. It is quickly
followed by another change which adds up to the second change which causes a
large change in voltage causing an action potential.
, 2. If the postsynaptic neuron forms synapses with more than one neuron and action
potentials occur at the same time then the neurotransmitters will be released at
both synapses at the same time. The positively charged particles will flow in both of
the synapses causing small changes in voltage and will add up (summate) making
it more likely for a action potential to be triggered
Excitatory and Inhibitory neurons
Not all neurotransmitters cause positively charged particles to enter the postsynaptic
terminal, some are negatively charged and create small negative changes in voltage
making action potentials less likely to occur
The small positive changes in voltage are called Excitatory postsynaptic potentials
(EPSPs). The negative changes in voltage are called Inhibitory postsynaptic potentials
(IPSPs)
The neurotransmitters that create excitatory postsynaptic potentials are called Excitatory
neurotransmitters, causing positively charged particles to enter and an action potential is
more likely.. However, the neurotransmitters that create inhibitory postsynaptic potentials
are called inhibitory neurotransmitters, causing negatively charged particles to enter and
an action potential is less likely.
Excitatory and Inhibitory neurons in summation
At the synapse sometimes both excitatory and inhibitory neurotransmitters might bind to
receptors at the same time this causes both EPSPs and IPSPs to occur in the postsynaptic
neuron at the same time. They then summate and cancel each other out making an action
potential less likely to occur.
- For an action potential to occur there needs to be more EPSPs than IPSPs and for it
to occur it depends on the balance of excitatory and inhibitory neurotransmitters
Types of neurotransmitters
1. Acetylcholine
➔ Released by neurons controlling muscles and makes action potentials more
likely to happen (excitatory)
2. GABA
➔ Main inhibitory neurotransmitter in the brain and makes action potentials
less likely to happen
Neurons
Neurons communicate via electrical signals
Cells use electrical signals to communicate information and neurons can only transmit and
receive information.
- Electrical signals are called nerve impulses (or action potentials)
Neuronal structure
There are four main components of a neuron:
1. Dendrites
➔ Tree like structures
2. Cell body
➔ Next to the dendrite (big round body)
3. Axon
➔ Long stick coming off the cell body
4. Axon terminal
➔ Next to the axon, end of the neuron
Neural transmission
The electrical signals change in voltage
- It changes if there are more or fewer charged particles in the neuron
Small waves of positively charged particles flow into the neuron through the dendrites
causing small positive changes inside the cell. It then travels to the cell body. If the change
in voltage, caused by the positively charged particles, is big enough when it reaches the
cell body it then triggers a bigger change in voltage, being the action potential (triggered
in the cell body).
Action potentials then travels down the axon until it reaches the axon terminal
- Action potentials only travel in one direction, from the dendrite to the axon terminal
Structure of the synapse
The presynaptic terminal is at the end of the axon terminal. The wall around this is called
the pre synaptic membrane. The end of the dendrite is called the postsynaptic terminal
,and the wall around it is called the postsynaptic membrane. The gap between the
presynaptic terminal and the postsynaptic terminal is called the synaptic cleft.
- In the presynaptic terminal there are synaptic vesicles (looks like little white bags)
filled with neurotransmitters
Synaptic transmission
The gap between the axon terminal and the next dendrite is called the synapse
- Neurons communicate through the synapse
The process through which nerve processes are transmitted across the synapse is called
synaptic transmission:
1. When nerve impulses travel to the presynaptic terminal it tells synaptic vesicles to
travel down to the presynaptic membrane
2. When the synaptic vesicles reach the presynaptic terminal, the synaptic vesicle and
the presynaptic membrane fuse (join together)
3. This causes the neurotransmitters to be released into the synaptic cleft
4. The neurotransmitters then diffuse across the synaptic cleft towards the
postsynaptic terminal
5. The neurotransmitters then bind to the receptors on the postsynaptic membrane
6. The neurotransmitters that bind to receptors means more positively charged
particles can flow into the dendrite, causing large changes in voltage (normally the
positively charged particles can't get through to the dendrite but when the
neurotransmitters do, they also)
7. The neurotransmitters then go back into the synaptic cleft but are removed by
reuptake proteins making them enter back into the pre synaptic terminal where
they can be recycled.
➔ The presynaptic terminal is responsible for the reuptake of
neurotransmitters
Summation
Action potentials are usually caused by summation and it can occur in two ways:
1. If multiple action potentials occur in the presynaptic neuron in close succession
then there are multiple waves of neurotransmitters which are released to the
synapse in very close succession. This means that the first small change in voltage
is quickly followed by the second change which adds onto the first one. It is quickly
followed by another change which adds up to the second change which causes a
large change in voltage causing an action potential.
, 2. If the postsynaptic neuron forms synapses with more than one neuron and action
potentials occur at the same time then the neurotransmitters will be released at
both synapses at the same time. The positively charged particles will flow in both of
the synapses causing small changes in voltage and will add up (summate) making
it more likely for a action potential to be triggered
Excitatory and Inhibitory neurons
Not all neurotransmitters cause positively charged particles to enter the postsynaptic
terminal, some are negatively charged and create small negative changes in voltage
making action potentials less likely to occur
The small positive changes in voltage are called Excitatory postsynaptic potentials
(EPSPs). The negative changes in voltage are called Inhibitory postsynaptic potentials
(IPSPs)
The neurotransmitters that create excitatory postsynaptic potentials are called Excitatory
neurotransmitters, causing positively charged particles to enter and an action potential is
more likely.. However, the neurotransmitters that create inhibitory postsynaptic potentials
are called inhibitory neurotransmitters, causing negatively charged particles to enter and
an action potential is less likely.
Excitatory and Inhibitory neurons in summation
At the synapse sometimes both excitatory and inhibitory neurotransmitters might bind to
receptors at the same time this causes both EPSPs and IPSPs to occur in the postsynaptic
neuron at the same time. They then summate and cancel each other out making an action
potential less likely to occur.
- For an action potential to occur there needs to be more EPSPs than IPSPs and for it
to occur it depends on the balance of excitatory and inhibitory neurotransmitters
Types of neurotransmitters
1. Acetylcholine
➔ Released by neurons controlling muscles and makes action potentials more
likely to happen (excitatory)
2. GABA
➔ Main inhibitory neurotransmitter in the brain and makes action potentials
less likely to happen
