BIO AND COG WEEK 2 Flashcards
SYNAPTIC TRANSMISSION AND NEUROPHARAMACOLOGY
what can neurotransmitters be?
- Excitatory- allow sodium to flow into the postsynaptic neuron
- inhibitory- allow chloride to flow into the postsynaptic neuron
what are the seven processes in neurotransmitter action?
1- Neurotransmitter molecules are synthesized from precursors under the influence of enzymes
2- neurotransmitters molecules are stored in vesicles
3- neurotransmitter molecules that leak from their vesicles are destroyed by enzymes
4- then action potentials cause vesicles to fuse with the presynaptic membrane and release their neurotransmitter molecules into the synapse
5- then the released neurotransmitter molecules bind with auto receptors and inhibit subsequent neurotransmitter release.
6- Then the released neurotransmitter molecules bind to postsynaptic receptors
7- thus the released neurotransmitter molecules are deactivated either by reuptake or enzymatic degrdation.
what are the four categories of neurotransmitter?
- Amino acids- Molecular subcomponents of proteins e.g glutamate, GABA, glycine
- Monoamines- synthesised from an amino acids e.g. dopamine ,noradrenaline, adrenaline,serotonin,
histamine
peptides- shorts chains of amino acids- e.g oxytocin, somatostatin opioids
others- other organic or inorganic molecules
e.g acetylcholine, adenosine and nitric oxide
what are some amino acid neurotransmitter pathways ?
- glutamate- the most prevalent excitatory neurotransmitter
(glutamatergic pathways)
Gaba- the most prevalent inhibitory neurotransmitter
(GABAergic pathways)
whats functions does dopamine pathways have?
- IN THE FRONTAL CORTEX
- Functions
- Reward(motivation)
- pleasure,euphoria
- motor function
- compulsion
- perseveration
what function does serotonin pathways do?
- IN THE STRIATUM , SUBSTANTIA NIGRA
function
- mood
- memory
- processing
- sleep
- cognition
HOW DO PHARMACOLOGICAL AGENTS WORK ON THE BRAIN?
what does direct and indirect binding mean?
DIRECT- binding to the neurotransmitter binding site
INDIRECT- the neurotransmitter binds elsewhere
what are the names of the two agents?
- AGONIST- a drug tat increases the effect of a neurotransmitter
- Antagonist - a drug that decreases the effect of a neurotransmitter
Describe the agonistic drug effect processes?
1- drug increases the synthesis of neurotransmitter molecules e.g by increasing the amount of precursor.
2- the drug then increases the number of neurotransmitter molecules by destroying degrading enzymes
3 - thus increasing the release of neurotrasmitter molecules from terminal buttons
4- then the drug binds to postsynaptic receptors and blocks their inhibitory effect on neurotransmitter release
5- then the drug binds to postsynaptic receptors and either activates them or increases the effect on them of neurotransmitter molecules
6- then the drug blocks the deactivation of neurotransmitter molecules by blocking degradation or reuptake
what are the antagonistic drug effect processes ?
1- the drug blocks the synthesis of neurotransmitter molecules e.g by destroying synthesizing enzymes
2- the drug then causes neurotransmitter molecules to leak from the vesicles and be destroyed by degrading enzymes
3- The drug then blocks the release of the neurotransmitter molecules from terminal buttons
4- the drug then activates auto receptors and inhibits neurotransmitter release
5- due to the drug being a receptor blocker it binds to the postsynaptic receptors and blocks the effect of the neurotransmitter
what is CURARE?
- an arrow poison
- a direct acetylcholine antagonist
- it blocks a subtype of the acetylcholine receptor at neuromuscular junctions by binding to the site where the neurotransmitter should
- results in complete paralysis ( death results from asphyxia)
what is FLUOXETINE?
- known as Prozac- antidepressant
- a SELECTIVE SEROTONIN REUPTAKE INHIBITOR (SSRI)
- ensures that endogenous serotonin remains in the synaptic cleft for longer by blocking this channel
APPROACHES TO STUDYING THE BRAIN
Describe MRI?
- uses a strong magnetic field and radio waves to produce an image of the brain based on hydrogen ions in the body
- used to produce several kinds of image
describe functional - fmri ?
- uses mri scanner to measure task related changes in blood flow
- measures the protons which are released when the haemoglobin in oxygenated blood releases its oxygen in the working brain
- highly correlated with brain activity levels
what are the strengths and weaknesses of MRI and fMRI?
MRI
- high spatial resolution
- can discern brain structure
fmri
- low temporal resolution - because it relies on the changes7 in blood flow that occur in response to the stimulus
-
which techniques are invasive or non invasive ?
non invasive
- EEG
- MEG
invasive
- ECoG
- SEEG
describe the features of ECoG and intracortical?
- only done on humans in the case of medical need
- recordings are relatively hard to come by and only done on atypical brains
- THEY HAVE EXQUISITE TEMPORAL AND SPATIAL RESOLUTION
What are the strengths and weaknesses of EEG?
- EEG =excellent temporal resolution - directly measuring the electrical activity in the brain ( miliseconds)
- poor spatial resolution because signals has to pass through several insulating layers before it reaches the electrodes
describe MEG
- The brains electrical currents are associated with magnetic fields
- highly sensitive sensors in the MEG system record the magnetic fields from outside the head.
- better spatial resolution that EEG
what can you measure EEG and MEG?
- brain oscillations - specific oscillations in specific areas cortex reflect particular function
e.g - alpha in occipital lobe
=visual processing and attention
theta= in the frontal lobe
- memory
beta above motor cortex
= planning and execution of movements
what are the strength and weaknesses of MEG and EEG ?
- both= excellent temporal resolution =direct measures of the electrical activity in the brain
- weakness= EEG- poor spatial resolution = insulating effects of the intervening tissues
strength= MEG- great spatial resolution= magnetic fields pass through these tissues
Name some examples Antagonists and agonists?
Antagonists= fenclonine (PCPA) = prevents enzymes from adding = used in symptoms of certain tumours.
- reserpine
Agonists= MAO inhibitor= blocks enzyme called monoamine oxidise which converts dopamine to an inactive substance in the pre-synaptic neuron
COMPETITIVE ANTAGONISTS= Naloxone= binds to any opioids receptors at the same site as the opioid would preventing it from binding.
DIRECT AGONISTS= morphine binds to …-opioids receptors in brain and fully activates them.= decreases feeling of pain.
