The A2 SNAB EDEXCEL BIOLOGY

Contains bullet point summary for Topic 8.

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  • Created on: 12-04-09 17:56
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Parkinson's disease
Dopamine is a neurotransmitter secreted by neurons.
The axons of the neurons extend throughout the frontal cortex, brain stem and spinal cord.
They are important in control of muscular movements and also linked with emotional
responses.
In Parkinson's disease, dopamine secreting neurones in the basal ganglia die, leading to
reduced dopamine in the brain.
The symptoms of the disease are stiffness of muscles, tremor of the muscles, slowness
of movement , poor balance, walking problems, depression, difficulty with speech
and breathing
Treatments
Drug selegiline used to slow the loss of dopamine from the brain. The drug inhibits an
enzyme called monoamine oxidase, which is responsible for breaking down dopamine in the
brain.
Ldopa, a precursor in the manufacture of dopamine, can be given. Once in the brain
Ldopa is converted into dopamine therefore increasing the concentration of dopamine and
controlling the symptoms of the disease.
Use of dopamine agonists (activate the dopamine receptor directly) to mimic the role of
dopamine in the brain, binding to dopamine receptors at synapses and trigger action potentials.
Activates dopamine receptors in the presence of dopamine.
Depression
Serotonin is a neurotransmitter and plays a part in determining a person's mood.
Group of neurons that secrete serotonin are in the brain stem.
Their axons extend into the cortex, cerebellum and the spinal cord.
Lack of serotonin is linked to depression clinical depression can last for months or years and
can have profound effect on work or relationship.
Symptoms include sadness, anxiety, and hopelessness, loss of interest in pleasurable
activities, low energy levels, insomnia, restlessness and thoughts of death.
The causes are not completely understood:
There may be a genetic element because it runs in families.
It could be environment for some people.
Fewer never impulses than normal are transmitted around the brain, which may be
related to low levels of neurotransmitter being produced.
A number neurotransmitter may have a role to play in depression, including dopamine and
noradrenalin reduced serotonin levels are commonly involved.

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Treatment for depression
In treating the symptoms the drug selective serotonin reuptake inhibitor (SSRI) is used. It
inhibits the uptake of serotonin from synaptic cleft.
SSRIs increase the extracellular level of the neurotransmitter serotonin by inhibiting its
reuptake into the presynaptic cell, increasing the level of serotonin available to bind to the
postsynaptic receptor.
One of the more common drugs of this type is Prozac.…read more

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