Download Neurotransmitters: Acetylcholine and Dopamine

Neurotransmitters:
Acetylcholine and Dopamine
Ms. Carmelitano
Acetylcholine
• First Neurotransmitter to be identified and
most common in the human body
• Function:
– Helps control muscle contraction
– Plays a role in the development of memory of the
hippocampus
• Hippocampus: Part of the brain responsible for
converting short-term memory into long-term memory
Acetylcholine
• Acetylcholine and memory formation
– It is still not fully understood how memory
formation occurs
– However, research has shown that when a shortterm memory is converted into long-term storage
in the hippocampus, neurons in the brain help to
synthesize protein molecules and new
connections between neurons are formed
Acetylcholine
• So, what does this have to do with psychology
you ask??
– Over or underproduction can cause us to act in
certain ways!
Malfunction of Acetylcholine
• Underproduction on Memory
– Because acetylcholine plays a huge role in
memory, an underproduction can cause memory
loss or inhibit the formation of new memories
– It has been discovered that people who suffer
Alzheimer's have a deterioration in the dendrites
in neurons that play a role in memory, and
therefore a deterioration in the amount of
acetylcholine
Martinez and Kesner (1991)
• Aim: To investigate the role of Acetylcholine
on memory
• Procedure:
Can
– 1. Rats were trained to go through a maze and get
to the end, where they received food. you
solve
the
maze?
Martinez and Kesner (1991)
• Procedure:
– 2. Once the rats were able to do this, the researchers
injected one group of rats with scopolamine, which
blocks acetylcholine receptor sites decreasing
available acetylcholine.
– 3. Then the second group of rats was injected with
physostigmine, which blocks the production of
cholinesterase which does the “clean-up” of
acetylcholine from the synapse and returns the
neuron to its “resting state”
– 4.The third group, control group, were not given any
injections.
Second Place
WINNER!
Martinez and Kesner (1991)
• Findings:
– The rats that were injected with scopolamine
were slower at finding their way round the maze
and made the most errors
– The physostigmine group ran through the maze
and found the food more quickly and took fewer
wrong turns.
– The researchers concluded that acetylcholine
played an important role in creating a memory of
the maze.
Nicotine and Acetylcholine
• When a person smokes a cigarette, they will
put nicotine into their system
• Nicotine will stimulate neurons to release
more acetylcholine
• The overproduction of Acetylcholine will give
a person an “energized” feeling, muscles react
faster and the brain functions faster
• Smokers become addicted, and need a
cigarette in the morning to “wake-up”
Dopamine
• Function:
– voluntary muscle movement
– Learning
– Feelings of emotion: pleasure
Dopamine
• Dopamine and voluntary muscle movement
– When the body reacts to a stimuli that calls for
muscle movement (example: I hear a noise and
turn my head to see what it was) Dopamine will
be released over the synapses of nerve cells.
– The Dopamine will bind with receptors that cause
a chemical reaction to move smooth muscles in
the basil ganglia – the portion of the brain that
coordinates smooth muscle movement
Dopamine
• Dopamine and learning and emotion
– Dopamine controls the transfer of messages in the
frontal cortex of the brain which controls memory,
attention, and problem solving ability
– When dopamine is released, it creates a “feelgood” feeling within the individual
• The individual learns what behaviors will create this
feel good feeling
• They will learn that if they continue this behavior, the
feeling will continue
Malfunction of Dopamine
• Malfunction of Dopamine and muscle
movement
– When dopamine receptors are blocked, or not
enough dopamine is produced, a person will find
muscle coordination difficult
– People who do not produce enough dopamine
develop Parkinson
• Parkinson is degenerative – this means that it
progressively gets worse. A person with Parkinson's
Disease will gradually produce less and less dopamine
over time
Malfunction of Dopamine
• Malfunction of Dopamine in learning and emotion
– Because Dopamine regulates connections between
neurons responsible for concentration in the frontal
lobe, a person without enough dopamine may develop
ADD
– Low dopamine may also cause dementia because the
neurotransmitter helps make connection with learning
and memory. This usually occurs with age as the
neurons that produce dopamine begin to degrade
– Low dopamine may also be a reason for depression, low
dopamine will decrease the pleasure feeling
Malfunction of Dopamine and
Schizophrenia
• Schizophrenia is a mental illness
– People suffering from Schizophrenia report feeling
paranoid, having hallucinations, and even hearing
voices that are not there
• An overproduction of Dopamine in one area
of the brain has been linked to Schizophrenia.
This overproduction of Dopamine can cause
the hallucinations linked to Schizophrenia
Drugs and Dopamine
• Drugs prescribed to help people with ADD
concentrate increase the amount of dopamine
that is released in the brain
• People with Schizophrenia will be given drugs
to inhibit dopamine production, however, as a
side effect, this makes it hard for the person to
concentrate, reduce feelings of pleasure, and
reduce motor function
Drugs and Dopamine
• Most drugs, such as alcohol, cocaine, and
amphetamines increase the production of
dopamine in the brain
– This is why people get addicted to drugs
– They feel good when they take them
– They become used to the over production of
dopamine in their brain, and find it hard to
concentrate or feel pleasure without the drug as
they become dependent on it
Cardinal et al (2001)
• Procedure:
– Researchers gave a set of rats choices between bowls
of food containing large and small portions
– Rats chose the larger consistently
– The researchers split the rats into two groups
• Lesioned their nucleus accumbens (Where Dopamine and
Serotonin is produced) This caused excess Dopamine to be
produced
• One group received an anti-psychotic on did not
– When presented a choice between large and small
portions of food, the rats were more impulsive and
simply chose the bowl closer to them. They appeared
hyper-active
• Findings:
– Excess Dopamine in the brain lead the rats to be
more impulsive
– This could be why drug addicts are impulsive
Laurelle et al (1996)
• Procedure:
– Researchers gathered participants who were and
were not diagnosed with Schizophrenia
– Researchers gave participants an amphetamine, a
drug, that increased levels of dopamine in the
brain
– Researchers observed patients and interviewed
them about how they were feeling
• Findings:
– Observations and interviews confirmed that the
“healthy” patients began to experience symptoms
of Schizophrenia when their Dopamine levels
were forced to rise
– Patients tested who were diagnosed with
Schizophrenia had their symptoms worsen