the effect of recreational drugs on the transmission process in the cns

Question 1

define recreational drugs

Answer 1

• taken for pleasure
• have effect of the cns, so they’re called ’psychoactive’
• eg cocaine, heroin, cannabis, ecstasy etc

Question 2

mode of action of drugs at the synapse

Answer 2

• drugs have a specific mode of action at the synapse
• so they act in a specific way

Question 3

describe the reward pathway

Answer 3

• located in septum area of brain
• where pleasure seems to be desires
• desire for the pleasure over-rides other drives

Question 4

what neurotransmitter is released when exposed to a rewarding stimulus?

Answer 4

dopamine

Question 5

what pathway is MOST ASSOCIATED with reward?

Answer 5

mesolimbic dopamine pathway

Question 6

where do dopamine levels rise when reward pathway is activated?

Answer 6

nucleus accumbens

Question 7

what is another important pathway in the reward pathway?

Answer 7

mesocortical dopamine pathway

Question 8

where does the mesocortical dopamine pathway originate and travel to?

Answer 8

orignates in ventral tegmental area
travels to cerebral correx

Question 9

why is the mesolimbic pathway the main structure of the reward system?

Answer 9

it is consistently activated during rewarding experiences

Question 10

what is nicotine

Answer 10

• highly addictive chemical compound naturally found in the tobacco plant

Question 11

describe the effect of nicotine

Answer 11

• works on the reward pathway to give pleasure - leads to addiction due to organism acting in order to stimulate reward pathway
• affects dopamine receptors in area of brain that is reward pathway
• dopamine: neurotransmitter that relates to rewards and feelings of pleasure
• mimics actions of acetylcholine, natural neurotransmitter
• binds to certain type of acetylcholine receptors, nicotinic receptors
• when either acetylcholine or nicotine binds to these receptors, same thing happens
• nicotine receptors cause impulse in neuron and ’excite’ neuron which gives action potential down the axon of neuron, realising more neurotransmitter (dopamine)
• dopamine gives feelings of pleasure, hence the effects of taking nicotine

Question 12

how does nicotine lead to addiction?

Answer 12

• binding over time affects receptors and causes decrease in dopamine receptors
• also a change in shape of cell
• when nicotine is absent, because there’s not so many receptors on postsynaptic neuron, more dopamine will be required to stimulate postsynaptic neuron to ‘normal’ level
• known as desensitisation, when more of a substance is required to achieve same response
• leads to addiction as nicotine is needed just to maintain what was normal functioning

Question 13

what is cocaine

Answer 13

• 15-30 mins of euphoria, energy and alertness
• white powder

Question 14

describe the effect of cocaine

Answer 14

• also works on reward pathway and dopamine receptors, but different to nicotine
• draws on idea that there’s reuptake by presynaptic neuron of neurotransmitter left in synaptic gap
• blocks binding site on reuptake receptor and stops the reuptake of dopamine back into the presynaptic neuron
• means excess dopamine in the synapse which leads to over-stimulation at postsynaptic receptors
• more dopamine than usual
• same feeling achieved as with nicotine (euphoria)
• desensitisation and addiction
• acts on receptors in reward pathway within seconds
• ’feel good’ neurotransmitter

Question 15

what is cannabis

Answer 15

• psychoactive drug
• marijuana weed, pot, ganja

Question 16

describe the effect of cannabis

Answer 16

• acts by binding on to cannabinoid receptors
• one type of receptor (CB1) found in many regions of brain (hippocampus)
• consuming = affect in memory function
• binds to cannabinoid receptors, blocking them meaning there’s less activity in neuron in hippocampus
• making memories may be affected by taking cannabis
• however, in reward system more dopamine is released and it’s this excess dopamine in reward system that gives ‘high’ feeling

Question 17

strength PEE
- compliment of methodology PET

Answer 17

• brain (PET) scans
• directly assess neurotransmission
• compare drug abusing and non drug abusing individuals
• correlate a drugs transit through the brain by monitoring fluctuations of a neurotransmitter

Question 18

strength PEE
- compliment of methodology fMRI

Answer 18

• monitors metabolic activity in selected brain regions
• each neurotransmitter has a unique distribution among brain regions so locations with heightened or decreased activity levels help provide clues as to the nt involved
• objective and scientific
• controlled conditions

Question 19

strength PEE
- compliment of methodology lab

Answer 19

• researchers compare individuals with drug exposure history compared to those who dont
• may compare a behaviour or symptom
• high control over extraneous variables

Question 20

strength PEE
- application

Answer 20

• drugs have been developed to help heroin withdrawal
• naloxone blocks opiate receptors and prevents heroin occupying them
• does not produce euphoria so helps reduce symptoms
• compliments learning approach as shows that people take drugs to stop withdrawal which is neg reinforcement and this approach forms a foundation for why this occurs

Question 21

weakness PEE
- generalisability

Answer 21

• higher control over animals as unethical to test on humans
• low generalisation
• significant differences in terms of relative size and developments

Question 22

weakness PEE
- reductionist

Answer 22

• brain and nt functioning are very complex
• one explanation is too simplistic
• too simple to say that drugs inhibit or excite
• ignores social factors of why we initially take drugs

Question 23

weakness PEE
- criticism of methodology

Answer 23

• brain scans cannot get to level of synaptic transmission
• hard to study mode of action of drugs at synapses

Question 24

strength PEE and CA
- supporting evidence Olds and Milner

Answer 24

• electrodes in rats brain
• rats press lever and self stimulate
• suggests that there are places in the brain where stimulation is rewarding enough that animals stimulate themselves frequently
• cannot be generalised to humans
• but good EV controls

Question 25

strength PEE and CA
- supporting evidence Volkow

Answer 25

• PET scans
• track dopamine transporter activity in humans during a cocaine induced high
• more cocaine occupying dopamine receptors = more intense high
• good spatial resolution
• however invasive and cannot isolate brain areas

Question 26

weakness PEE
- opposing study

Answer 26

• Li et al
• ex heroin addicts shown drug related images and neutral images during fMRI
• ethical concerns
• can detect small changes but effected by movement