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39 Cards in this Set
- Front
- Back
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Ion Channels |
Effect of neurotransmitter (NT) depends on kind of channel that opens when NT binds to receptor on post-synaptic cell |
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Excitatory effect NT |
Channels allow positively charged ions in (Na+ or Ca+) Make post-synaptic cell more likely to fire |
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Inhibitory effect NT |
Channels allow negative ions to enter cell (Cl-) Make post-synaptic cell less likely to fire |
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Ligand |
Anything that binds or attaches to receptor Can be NT produced by cell and released from pre-synaptic neuron into synaptic cleft Can be drug that is artificially introduced into synaptic cleft |
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Ionotropic Receptors |
Immediately open channels into cell to allow positive or negative ions to enter Fast acting Alcohol, benzos, barbituates, steroids, and neurotransmitter GABA bind to ionotrpic Consists of five segments (each above binds to different segments) |
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Metabotropic receptors |
G-coupled receptor Formed of a protein chain that crosses cell membrane seven times Ligands bind by fitting into "pockets" on outside, moving 3D structure of protein which moves internally and starts chain of events inside cell |
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Activated metabotropic receptors |
Internal events may consist of opening a channel further along the membrane (indirect effect) DNA transcription factors are also initiated (getting certain genetic sequences read out and proteins are actively produced) Nitric oxide (NO) may also be released back to pre-synaptic cell - initiates transcription activities Result in more permanent changes in structure of receptor itself (synaptic connection between pre- and post- synaptic neurons is strengthened |
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Metabotropic learning process |
Strengthening of synapse - presynaptic more neurons releasing NT, postsynaptic more receptors receiving NT, strengthens connection |
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Agonists |
Anything (NT or drug) that facilitates action of receptor (makes receptor do what it normally does but moreso - excitatory or inhibitory) |
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Antagonist |
Anything (NT or drug) that diminishes action of receptor (less likely - excitatory or inhibitory) |
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Agonists and antagonists |
Facilitation or inhibition can take place at various steps in the process of neurotransmission |
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Partial agonist |
Ligand that does not fully activate receptor Can have facilitating effect Slightly activating effect but doesn't make it open up ion channels to extent it normally would If you have a partial agonist but a ligand comes with full agonist effect, it stops ligand from binding (indirect inhibitory effect) |
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Inverse agonist |
Activates receptor but produces opposite effect of what is normally produced Receptors responding to inverse agonist - activates receptor in way it normally doesn't behave |
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Receptor families |
NT act by binding to receptors but the effect of NT is determined by action of receptor Families of receptors to which same NT can bind Different neurotransmitters we produce (proteins) bind to different types of receptors distributed in different parts of brain/body Allows same NT to have different effects depending on receptor Equal opportunity binding |
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Five dopamine receptors |
D1, D2, D3, D4, D5, different effects in terms of which ions they allow into post synaptic cell Some excitatory, some inhibitory PFC - D1 receptors excitatory Other site - D2 receptors inhibitory |
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Distribution of different receptors in different structures |
Give system opportunity to send out NT and effects of NT determined in particular area of brain by kinds of receptor families located in structure One NT could have excitatory or inhibitory effect Selective involvement of different receptors in certain diseases |
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Opioid receptors |
Three types: mu, delta, kappa Each receptor has different effects Almost all NT have more than one type of receptor |
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Mu and delta receptors |
Reduce pain (narcotics) by inhibiting neurons that convey pain info (open Cl- channels, allow K+ to exit cell via K+ channels) Medications used to relieve severe pain (opioid crisis have affect on opioid receptor) |
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Disinhibition |
Opioids inhibit action of inhibitory neurons that release GABA Taking of the breaks Opioids bind to GABA cells which bind to GABA ionotropic receptor which is inhibitory (bind to GABA neuron, stop GABA inhibiting next cell) |
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Kappa receptors |
Opposite effects of mu and delta - endogenous form of opioid bind to kappa |
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Dopamine system |
Dopamine has main pleasurable effect by stimulating nucleus accumbens Dopamine system releases dopamine to nucleus accumbens to activate structure (stimulate release of opioids) and reward pathway |
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Nucleus accumbens |
Pleasure center of brain Found in animals, stimulate --> person/animal feels intense pleasure and continues stimulating without stopping Important for high people experience with drugs/mood - need this to feel positive |
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Reward pathway |
Learning things, rewarding, help us to survive |
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Dopamine production |
Two areas of brain: 1. Substantia nigra 2. Ventral tegmental area (VTA) (3. hypothalamus) (4. retina) |
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Substantia nigra |
Neurons where cell body is in substantia nigra, but axons run to nucleus accumbens |
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Ventral tegmental area (VTA) |
Front of brain, important for production of dopamine in neurons that subtend to basal ganglia |
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Hypothalamus |
Dopamanergic neurons |
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Dopamine pathways |
Pathway - where cell body of neuron is and where axon/terminal buttons end up At least four main pathways: 1. Mesolimbic 2. Tuberoinfundibular path 3. Mesocortical 4. Nigrostriatal |
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Mesolimbic pathway |
Meso means midbrain, limbic means emotional control - starts in VTA to nucleus accumbens, then to PFC Important for reward and pleasure |
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Tuberoinfundibular path |
Dopamine released from hypothalamus into pituitary gland Regulates/inhibits production of prolactin |
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Mesocortical |
Midbrain to cortical area - VTA to PFC and other cortical areas Important in thinking |
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Nigrostriatal |
Substantia nigra (nigro midbrain) to striatum (basal ganglia - caudate and putamen) involved in motor functions and procedural learning |
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Midbrain reward (mesolimbic) pathway |
Dopamergic neurons send axon from VTA and project axonal fibers to nucleus accumbens (NAc), firings produce feelings of pleasure Stimulation (VTA or NAc) will continue without satiation Inhibitory GABA neurons synapse (connect) with VTA to regulate activity VTA send dopamine to NAc Opioid autoreceptors on GABA releasing neurons bind on own neuron to inhibit firing/reduce braking activity on DA neurons Less likely to inhibit dopamanergic receptors, GABA less likely to fire because of opioids and disinhibits dopamanergic neurons |
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Dopamine Reward Pathways of nucleus accumbens |
Drugs of abuse (e.g. cocaine) - lose ability to regulate use of substance, affect mesolimbic pathway |
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Disorders of mesolimbic pathway (Volkow, 2003) |
All addictive behaviors activate mesolimbic DA pathway |
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Disorders of nigrostriatal pathway |
Neurological disorders affecting movement, Parkinson's disease and Huntington's disease |
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Mesocortical Da pathway |
When things go wrong, mesocortical (VTA to cortical) role of DA in executive function DA from VTA to cortical areas (frontal lobes) DA critical in executive function - inhibition, working memory, etc. Disruption can result in schizophrenia and ADHD |
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Disorders of mesocortical pathway |
Excess DA - schizophrenia Positive symptoms (hallucinations, delusions) PFC overabundance creates hallucinations Treat with neuroleptics (medications that counteract DA efect) Side effects - tremor, anadonia, movement problem, disorder relating to PFC Reduce DA, reduce movement and abnormal tremors Basal ganglia relies on DA for function o motor system Agonist or antagonist side effects, impact on receptor family not meant to be affected If people don't experience side effects then it is because it is not being affected to degree of symptom expression Decrease in positive mood because less DA in reward pathway |
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AHD |
PET studies, three DA transmission problems - reduced production of DA - faster elimination of DA from synapse (COMT enzyme type - val or met) - fewer DA receptors *fewer DA neurons, fewer receptors for DA produced COMT enzyme metabolizes DA in synapse, fast acting and gobbles up DA before chance to bind Affects ability to inhibit behavior/impulsivity |
