Download Problems with synapses File

Problems with
Synapses
Topic 8.7
Specification
• 17 Explain how imbalances in certain, naturally occurring,
brain chemicals can contribute to ill health (e.g. dopamine in
Parkinson’s disease and serotonin in depression) and to the
development of new drugs.
• 18 Explain the effects of drugs on synaptic transmissions,
including the use of L-Dopa in the treatment of Parkinson’s
disease and the action of MDMA in ecstasy.
• 19 Discuss how the outcomes of the Human Genome Project
are being used in the development of new drugs and the
social, moral and ethical issues this raises.
• 20 Describe how drugs can be produced using genetically
modified organisms (plants and animals and micro organisms).
• 21 Discuss the risks and benefits associated with the use of
genetically modified organisms.
Forebrain- cerebral cortex, corpus collosum,
hippocampus, thalamus and hypothalamus
Midbrain
Hindbrain- pons, cerebellum, medulla
Brain Stem
Cerebral Cortex
The Brain
• About 100 different neurotransmitters
• Some can inhibit, some excite the post synaptic neurone
• Some only occur in certain areas eg. parts of the brain
• Difficult to treat brain disorders because of the blood
brain barrier
• The endothelial layer of brain capillaries are tightly joined
together
• Not “leaky” as in other capillary beds
• Form a barrier
• Controls what can enter the brain
The synapse
Problems with Synapses
• Natural imbalances in neurotransmitters
• Parkinson’s
• Schizophrenia
• Hyperactivity
• Depression
• Imbalances caused by drug use
• Cocaine
• Ecstacy
Parkinson’s Disease
• Degenerative disease of the motor system
• Not fatal but no cure
• Symptoms
• Muscle stiffness and tremor
• Slow movement
• Poor balance
• Walking problems
• Due to problems with the neurotransmitter
dopamine
Parkinson’s Disease
• Dopamine is a neurotransmitter of sympathetic nervous
system, released by neurones of the midbrain and neurones
in the basal ganglia.
• Axons in the midbrain extend to the frontal cortex, brain stem
and spinal cord.
• Axons in the basal ganglion extend to the motor cortex.
• Where is the motor cortex? What is its function?
• In the frontal lobe. Neurones connect from there to the
spinal cord and brain stem and from there via motor
neurones to the muscles relaying information to the body
about movement.
Parkinson’s Disease
• What causes Parkinson’s?
• Dopamine-secreting neurons in basal
ganglia, which usually release dopamine in
the motor cortex, die.
• The motor neurones there receive little
dopamine
• Less action potentials are fired
• Muscle contraction is no longer smooth
Parkinson’s Disease
• Treatments
• What are some of the treatments of Parkinson’s
disease? Explain how each work. Activity 8.20a
• What is an agonist? What shape might they have?
• Drugs which act in the same way as the
neurotransmitter – bind to a receptor.
• They must have a similar shape to dopamine.
• Why can dopamine not be given as a treatment?
• Can’t cross the blood brain barrier
• Q 8.56
Schizophrenia
Read the “Did you know?” box on page 251
• What is schizophrenia? What causes it?
• Caused by excess dopamine in the brain leading to multiple
personalities (excess action potentials are fired)
• How is Schizophrenia treated?
• It can be treated by drugs which block the binding of
dopamine in the post-synaptic neurons- less action
potentials are fired.
• How is the treatment for schizophrenia similar/different to the
dopamine agonists used in treatment of Parkinson’s?
• They have a similar shape/structure to dopamine but can
NOT stimulate the post-synaptic receptors. Dopamine
agonists also have a similar shape/structure to dopamine
but they DO stimulate the post-synaptic receptors
Hyperactivity
• What causes hyperactivity?
• Hyperactivity is associated with low levels of
dopamine. ( this seems surprising- It is much more
complex than this, however, it can be thought of like
this- dopamine is a stimulant needed to focus- without
it focusing is hard and the child is hyperactive.)
• How is hyperactivity treated?
• It is treated with drugs (ritalin) which prevent
dopamine from being taken back into the presynaptic neuron- therefore more stays in the cleft
stimulating post-synaptic neurons.
•
What other drug is ritalin similar to?
•
cocaine
Activity 8.20b Depression pages 252-253
• What are the main symptoms of depression?
• Feelings of sadness, anxiety, hopelessness
• What is serotonin and where is it produced?
• Seratonin is a neurotransmitter associated with mood.
Neurons releasing it are situated in the brain stem with axons
extending into the cortex, cerebellum and spinal cord
• Lack of serotonin is linked to depression.
• Depression is multifactorial. What is meant by this term? Can
you name another condition which is multifactorial?
• Several genes and other factors are involved in this condition.
CVD
• Answer Question 8.57 on page 253• a) Polygenic inheritance
• b) CHD, some cancers, Alzheimer’s, shizophrenia, diabetes
• Which other neurotransmitters have also been linked to depression?
• Dopamine and noradrenaline
• Describe the brain of a person suffering from depression.
• Fewer nerve impulses than normal are transmitted in the brain
possibly due to low levels of neurotransmitter (mostly serotonin)
being produced. There may be a lack of the molecules needed to
produce serotonin. There may be an abnormally high number of
the serotonin binding sites to compensate for the low levels of the
serotonin.
• What is the role of twin studies in general?
• Allows us to determine the genetic component of a disease
• What have twin studies told us about depression?
• Several genes do play a role but so do other non genetic factors.
• What drugs can be used to treat depression and how do they work?
• It inhibits the reuptake of serotonin into the presynaptic neuronsSSRI. It blocks the reuptake of serotonin alone. Prozac- raises the
level of serotonin- increasing the rate of nerve impulses.
Various drugs affect the synapse
• http://learn.genetics.utah.edu/content/addiction/mouse/
• Cocaine
• What is the job of dopamine? What is the
function of the dopamine transporters
• Dopamine is a neurotransmitter. It binds to
postsynaptic receptors to stimulate the opening
of cation channels. Dopamine transporters take
dopamine back up into the presynaptic neurone.
• What does cocaine do? What can you suppose
about the shape of a cocaine molecule?
• Complementary in shape to dopamine
transporters
The effect of cocaine
Cocaine blocks the
reabsorption of
dopamine
Cocaine stays bound
to the transporter
molecule
Dopamine levels in
the synapse increase
Ecstasy pages 253-254
• Complete Activity 8.20