a. Social influence a. Approaches a. Issues and debates
b. Memory b. Biopsychology b. Relationships
c. Attachment c. Research methods c. Schizophrenia
d. Psychopathology d. Aggression
BIOPSYCHOLOGY
NEURONS
What is a cell?
All living things are made up of cells,
the cell membrane is a wall around
the cell. Different cells have different
functions, like transmitting
information.
Information is transmitted through
electrical signals.
Neuronal cells (neurons) are cells
that receive and transmit nerve
impulses or action potential.
Nerve impulses are triggered in the cell body of a neuron, only if there is a large change in
voltage. Once a nerve impulse is generated at the cell body, the nerve impulse then travels
down the axon, finally reaching the axon terminal.
Nerve impulses only travel in one direction, from the dendrite to the axon terminal.
(A nerve impulse travels in one direction. It is first created at the cell body and moves
through to the axon terminal. This is then picked up by the next neuron’s dendrites, where it
then travels via the cell body, and so on to the next neuron.)
The gap between one
neuron's axon terminal and a
second neuron's dendrite is
called the synapse.
Synaptic transmission is
the process through which
nerve impulses are
transmitted across the
synapse.
,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 where the nerve impulse first arrives is called the pre-synaptic terminal, and the
membrane around it is called the pre-synaptic membrane. The bit on the other side is the
post-synaptic terminal, and the membrane around it is the post-synaptic membrane.
SYNAPTIC TRANSMISSION
1. the nerve impulse arrives at the pre-synaptic terminal, causing the synaptic
vesicles to travel down to the pre-synaptic membrane.
2. the synaptic vesicles and the pre-synaptic membrane fuse, causing the
neurotransmitters to be released into the synaptic cleft.
3. neurotransmitters diffuse across the synaptic cleft towards the post-synaptic
terminal.
4. Once released, neurotransmitters diffuse across the synaptic cleft where they
bind to the receptors allowing positively charged particles to flow into the
post-synaptic terminal, creating small electric signals in the neurons.
5. After the neurotransmitter binds to the receptor, and positively charged particles have
flowed into the post-synaptic membrane, the neurotransmitters are released back out
into the synaptic cleft, where the pre-synaptic terminal re-uptakes neurotransmitters.
Re-uptake is the process of removing neurotransmitters from the synaptic cleft.
The nerve impulse arrives at the pre-synaptic terminal, causing the synaptic vesicles to travel down to
the pre-synaptic membrane. The pre-synaptic membrane and synaptic vesicle fuse, causing the
release of neurotransmitters into the synaptic cleft. The neurotransmitters diffuse across the synaptic
cleft towards the post-synaptic terminal, where they bind to post-synaptic receptors.
As a result, the receptors allow positively charged particles to flow into the post-synaptic terminal,
creating small, positive changes in voltage in the neuron. Once there is a large enough change in
voltage, a nerve impulse is triggered. Meanwhile, the neurotransmitters are released back into the
synaptic cleft, where they are sucked back into the pre-synaptic membrane by re-uptake proteins.
Summation is when successive changes in voltage add up in the post-synaptic neuron, and
it occurs when multiple nerve impulses occur in the pre-synaptic neuron, in close
succession.
Excitatory neurotransmitters cause positively charged particles to enter the post-synaptic
neuron making a nerve impulse more likely to occur, and inhibitory neurotransmitters
cause negatively charged particles to enter the post-synaptic neuron making a nerve
impulse less likely to occur.
- Acetylcholine released by motor neurons makes nerve impulses more likely to
happen, so it is an excitatory neurotransmitter.
- GABA is the main inhibitory neurotransmitter used in the brain, so it makes nerve
impulses less likely to happen.
Some neurotransmitters can be either excitatory or inhibitory depending on the receptors
they bind to:
- Dopamine is released between neurons that help control the brain’s response to
reward.
, - Serotonin is released between neurons that help control the mood.
The excitatory post-synaptic potentials and inhibitory post-synaptic potentials can summate,
but inhibitory post-synaptic potentials cancel out or negate the excitatory post-synaptic
potentials. Whether a nerve impulse occurs, depends on the balance of excitatory and
inhibitory neurotransmitters binding to post-synaptic receptors.
TYPES OF NEURONS:
Sensory neurons, located near the sensory
receptors, pick up information from the sensory
receptors and send it towards the brain.
Sensory neurons form synapses
with sensory receptors and have a
coating on their axon called the
myelin sheath.
Motor neurons, are positioned next to muscles and form synapses with
them. They carry information away from the brain to the muscles, they control
muscle movement. (they are coated with a myelin sheath and form synapses
with the muscle fibres)
Relay neurons, relay between the sensory and motor neurons, process and transform
information.
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