E4 Neurotransmitters and Synapsis

Question 1

Presynaptic neurons can…

Answer 1

excite (stimulate the next neurone to forward the message, increase permeability of the postsynaptic membrane to positive ions) neurones or inhibit (cause positive ions to move out of postsyn. cell, back into the cleft = depress) postsynaptic transmission

Question 2

E.4.2 Explain how decision-making in the CNS can result from the interaction between the activities of excitatory and inhibitory presynaptic neurons at synapses.

Answer 2

Excitatory neurostransmitters: generaytes A.P.. increase permeability of positive ions, causes Na in cleft to diffuse in POSTSyn. , depolarized, net positive charge, triggers next area – impulse conducted along neurone

Inhibitory neurotransmitters: inhibit action potential , causes hyper-polarization: inside of the neuron becomes more positive = harder to establish A.P
-when neurotran. binds to receptor causes Cl- to move through, or K+ to move out

neurone sums up the signal (receives many different signals) : if sum in excit, fire if inhib. does not fire
-summation of the messages is way decisions are made

Question 3

E.4.3 Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing postsynaptic transmission. Include ways in which synaptic transmission can be increased or decreased

Answer 3

Drugs: chemical substances that are ingested, injected, inhaled or put into the body in some other way, to cause a change in the functioning of the body.
Psychoactive drugs: affect the brain and personality.
- increase or decrease transmission or may mimic the action of neurotransmitters

can change synaptic transmission by:
.1. block a receptor for a neurotransmitter (drug has structure similar to neurotransmitter)
2. block release of neurotransmitters from the presynaptic membrane
3. enhance release of neurotransmitter
4. enhance transmission by mimicking a neurotransmitter (drug same shape = same effect but stronger cause doesn’t break down as easy)
5. block removal of neurotransmitter from the synapse, prolong the effect of the neurotransmitter

Question 4

E.4.4 List three examples of excitatory

Answer 4

1. nicotine,
2. cocaine
3. amphetamines

Question 5

three examples of inhibitory psychoactive drugs.

Answer 5

1. Benzodiazepines
2. alcohol
3. tetrahydrocannabinol (THC).

Question 6

5 Explain the effects of cocaine in terms of their action at synapses in the brain. Include the effects of these drugs on both mood and behaviour.

Answer 6

• Cocaine is an excitatory
• dopamine (makes us feel euphoria) initiates depolarization of post-synaptic membrane
• Dopamine is normally reabsorbed after it has initiated an impulse.
• Cocaine clogs dopamine transporters that reabsorb dopamine after synaptic transmission
• = dopamine build up in synaptic cleft, continues to stimulate post-synaptic membrane
• = cocaine is excitatory

Effect on mood and behaviour:

• Euphoria/increase energy, alertness and talkativeness,
• Decrease in food and sleep
• Large amounts = erratic and violent behaviour
• Later depression
• highly addictive: users after death had lower than normal levels of dopamine, suggesting that the body adapts to cocaine use by reducing secretion. This would explain cocaine-induced depression.

Question 7

5 Explain the effects of cocaine in terms of their action at synapses in the brain. Include the effects of these drugs on both mood and behaviour.

Answer 7

THC ( in marijuana)
• THC is inhibitory
• THC mimics anandamide.
• Anandamide is used to erase memories that are not needed.

Under Normal Conditions
Brain naturally releases neurotransmitter, GABA, which inhibits the release of dopamine
Dopamine is a neurotransmitter which gives us a feeling of euphoria.

Under THC
THC binds cannabinoid receptors. (where anandamide binds to stop the release of GABA)
hyperpolarizes the membrane and prevents the release of GABA (harder to break down than anadamide, stays for a long time)
No GABA= release of dopamine = feeling of euphoria
Effect on mood and behaviour
– Learning
– Coordination
– Problem-solving
– Short-term memory

Question 8

E.4.6 Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion.

Answer 8

• dopamine and addiction: [3 max]
  o substances with addictive potential stimulate the release of dopamine;
  o dopamine is a chemical in the brain that is associated with reward and pleasure;
  o substance use brings a flood of dopamine, which alters the chemistry of the brain;
• social and genetic: [4 max]
• genetic:
  o genetic link found for (cocaine/alcohol) addiction;
  o counter: difficult to prove / multifactorial;
• social:
  o alcohol/other drug problems among family members;
  o poor school performance;
  o poverty / family conflicts / chaos / stress;
  o having friends who drink/use other drugs;
  o not fitting in socially / being excluded because of race/ability/ethnicity/gender/age/sexual orientation / other factors;
  o if drug cheap, easy to get hold of= increase addiction