problems with synapses Flashcards
where is dopamine normally secreted?
midbrain & motor cortex
what happens in parkinson’s
dopamine secreting neurones in the basal ganglia die
-> motor cortexes get less dopamine & there is a loss of control of muscular movements
symptoms of parkinson’s
stiffness & tremors of muscles
slowness of movement
poor balance
how can parkinson’s be treated?
slowing dopamine loss
drugs
dopamine antagonists
deep brain stimulation
how is the loss of dopamine slowed?
MAO inhibitors
they inhibit monoamine oxidase, the enzyme that is responsible for the breakdown of dopamine
MAOB is used
how is parkinson’s treated with drugs?
can’t use dopamine itself - can’t cross from blood to brain.
- > L-dopa ( precursor in the manufacture of dopamine ) can be given
- > converted into dopamine in the brain
what are dopamine agonists?
drugs that directly activate the dopamine receptor, mimic the role of dopamine but triggering action potentials
what is the problem with too much dopamine?
cause of schizophrenia
how can excess dopamine be treated?
drugs that block the binding of dopamine to its receptor sites
side effect: induce the symptoms of parkinson’s
what does seratonin do ?
plays an important part in defining someone’s mood
where are the neurones that secrete seratonin?
brainstem
-> axons extend into the cortex, cerebellum & sc
what has a lack of seratonin been linked to?
depression
what is the cause of depression
no one cause, it’s multi factorial
-> several genes may be involved, but probably only confer a susceptibility to the condition, with environmental factors also contributing
what gene is known to increase the susceptibility to depression
5-HTT -> codes for a transporter protein that controls seratonin reuptake
people with the short version are more likely to develop depression after a stressful life event
what does depression depend on?
environmental factors to act as triggers
during depression, what may be related to to low levels of neurotransmitters being released?
fewer nerve impulses than normal are being transmitted around the brain
-> seratonin pathways have a number of abnormalities in people with depression
what is a measure of the influence of genes on characteristics?
degree of similarity between monozygotic twins
what are SSRIs and how do they help?
selective serotonin reuptake inhibitor
- > blocks only the reuptake of serotonin from the synaptic cleft
- > maintains a higher level of and so increase the rate of nerve impulses in serotonin pathways, reducing some symptoms
how can drugs affect synaptic transmission?
- a chem with similar molecular structure to a neurotransmitter is likely to bind to the same receptor sites, perhaps stimulating the post synaptic neurone
- others may prevent neurotransmitter release
what does MDMA affect?
thinking mood and memory
anxiety & altered perceptions
short term- changes in behaviour and brain chemistry
long term- changes in behaviour and brain structure
what does MDMA do?
increases the serotonin concentration in the cleft by binding to molecules in the presynaptic membrane that are responsible for transporting the serotonin back into the cytoplasm
-> prevents it’s movement from the cleft
what are some negative side effects if MDMA?
clouded thinking
disturbed behaviour
dry mouth
muscle spasms & hyperthermia
repeated use - irregular heartbeat, muscle breakdown, kidney failure
why can MDMA lead to depression
the drug has stimulated so much serotonin release that the cells cannot synthesise enough to meet the demand one it has gone
what has helped us understand the way genes control phenotype
HGP
what is a genome
all the DNA of an organism
what other genomes have been sequenced?
yeast
worms
flies
which was the 1st chromosome to be fully sequenced?
22
how many bases is the human genome?
3 200 000 000
what is an SNP?
a DNA seq variation that occurs when a single nucleotide in the genome sequence is altered in at least 1% of the species population
-> scientists think the possession of certain SNPs predispose them to a disease
what does BCRA2 code for
breast cancer
what causes total colour blindness?
CNGA3 + CNGB3
code for subunits of a protein channel in photoreceptor cells in the retina
what genes are associated with parkinson’s?
DJ1 + PINK1
knowing genes that predispose means what?
it is possible to locate a candidate gene on DNA and screen it for mutations in affected individuals
having 2 alleles of APOE4 mean what
10x more likely to get alzheimer’s
what is a drug target?
a specific molecule that a drug interacts with to bring about its effect
what issues need to be adresssed regarding drugs / genetics
- implications ( ie. applying for health insurance )
- who should decide when they’re used
- confedentiality
- expense
