PHYSIOLOGY UNIT 10

what is a reward? 1 pt

an appetitive stimulus that produces a pleasant or positive affective experience that drives learning and behavior through reinforcement

dopaminergic system: reward and reinforcement? 5 pts

1. involved in the neurobiological mechanisms of motivation and addiciton

2. nihrostriatal pathway- movement coordination

3. hypothalamic pathway- hormonal secretion

4. mesolimbic/cortical pathway- emotional memory, attention, motivation

5. mesocortical pathway- starts at the VTA and ends in teh cortex; regulates executive functions e.g. decision making, motivation, attention

dopaminergic system: mesolimbic pathway? 3 pts

1. ventral tegmental area (VTA)- contains cell bodies of dopaminergic neurons

2. nucleus accumbens- receives dopaminergic synapses from neurons in the VTA, is the center of reward in the brain, found in the ventral striatum

3. limbic system- receive axons from the VTA modulatinf emotiona responses, memory, etc

first experimental procedure of intracraneal self stimulation (ICSS)? 1 pt

level pressing→ electrical stimulation of mesolimbic pathway→ rat presses the lever for sustained periods→ reinforcemnt mechanism

dopaminergic system: dopamine function in reinforcement? 5 pts

1. facilitates reward related learning by modulating synaptic plasticity (LTP)

2. DA neurons in the VTA release dopamine when something pleasurable happen

3. if a sensory cue predicts reward DA neurons learn through LTP to fire in response to the cue rather than the reward itself

4. if an expected reward doesn’t come DA neurons decrease firing (extinction)

5. surprise rewards result in max DA releases and strongest reinforcement

dopaminergic system: dopamine function in motivation? 3 pts

1. assigns incentive salience to cues to drive reward seeking

2. mesolimbic pathways increase the motivational value/salience of cues that predict rewards

3. connections with the prefrontal cortex and hippocampus drive anticipation and craving

pleasure pathway: wanting vs liking? 6 pts

1. motivation to seek reward and the pleasure obtained from getting it are different processes

2. liking something is not a prerequisite for generating motivation

3. wanting = dopamine while liking = opioids/endocannabinoids

4. hedonic centers increase the feellng of conscious pleasure when stimulated

5. there are several hedonic opioid hotspots in the brain including in the nucleus accumbens shell

6. the DA reward and motivation system is different from the pleasure pathway

neural circuits affected by drugs? 6 pts

rewarding properties of all drigs are tied to the dopaminergic circuit directly/indirectly

1. dopaminergic/reward system- stimulants

2. cannabinoid system- THC

3. GABA- alcohol

4. acetylcholine- nicotine

5. opioid system- heroin

6. serotonergic system- LSD MDMA

mechanism of action of natural rewards? 4pts

food, water, sex, love etc

1. fewer DA released

2. shorter effect

3. repetition/learning inhibits DA release

4. satiety (habituation)

mechanism of action of exogenous substances? 5 pts

cocaine, THC, alcohol, nicotine

1. abnormally high amount of DA released

2. longer lasting effect

3. DA is released every time

4. sensitization to the reward

5. drugs can bypass the brain’s natural regulatory feedback mechanisms that limit DA for natural stimuli

addiction? 4 pts

1. involves neuroadaptations similiar to those that occur in mem and learning as there are structural changes in the brain circuits involved

2. induction phase- initial exposure and reinforcement; emergence of sensitization and early associative learning of drug effects/context and reward

3. expression phase- consolidation of addiction; sensitization and tolerance coexist and there is greater amygdala involvement (emotional association)

4. results in cravings, loss of control over consumption, and abstinence syndrome

what is tolerance? 1 pt

reduced response after repeated exposure caused by adaptation mechanisms and can result from exposure to one drug causing a tolerance to another

what is sensitization? 1 pt

increase in some of the pharamacological and behavioral effects of a substance after repeaed use

what are neuroadaptations? 2 pts

structural and functional changes in the CNS that can remain for a long time after withdrawal and are responsible for craving and relapse; cellular and molecular modifications are induced that modify synaptic function and allow the consolidation of changes in various dopaminergic circuits that reinforce addiction

dopaminergic receptors? 3 pts

1. D1- present mostly at the synpatic level and are excitatory

2. D2- present at the pre- and post- synpatic level and are typically inhibitory and filter what stimuli deserves the brain’s attention

metabotropic type

effects of chronic drug use on dopaminergic receptors? 5 pts

1. increased expression of D1 receptors

2. increased reward value of the drug

3. dominance of D1 activity makes behavior more driven to seek strong rewards associated with the drug and a higher presence reinforces addiction

4. decrease in D2 receptors in areas associated with the DA system (nucleus accumbens, dorsal striatum) and is linked to a decreased sensitivity to natural rewards aka anhedonia

5. populational variations in the D2 receptors may be the reason why some individuals are more prone to being addicts

what is reward deficiency syndrome? 1 pt

predisposition to seek intense rewards through addictions or compulsive behaviors to compensate for the discomfort cuased by the underactive dopamine pathway

effects of chronic drug consumption of the prefrontal cortex? 5 pts

1. cognitive impairment and reduced executive functions

2. overvalue of drug rewards

3. lowered impulse control and an increased risk of relapse

4. loss of gray matter

5. increased DA activity in the prefrontal cortex