Neurotransmission

Question 1

What are the Parts of a Neuron?

Answer 1

1. Dendrites
2. Axon
3. Myelin Sheath
4. Nucleus
5. Stoma [cell body]
6. Schwann cell
7. Node of Ranvier
8. Axon terminal

Question 2

Excitatory and Inhibitory Receptors / Synapses

Answer 2

Excitatory: increases the likelihood of a neuron firing by depolarizing the neuron. [acetylcholine]
Inhibitory: decrease the likelihood of a neuron firing by hyperpolarizing the neuron. [GABA]

Question 3

Antagonists and Agonists

Answer 3

Antagonist: block the receptor site and do not allow the neurotransmitter to do its job [no action potential is sent]. Ex. scopolamine is an antagonist for ACh.
Agonist: a substance that mimics the actions of a neurotransmitter or hormone to produce a response when it binds to a specific receptor in the brain.

Question 4

What are the two types of agonists?

Answer 4

Endogenous agonists -> biological neurotransmitters [ex. acetylcholine is an agonist for ACh receptor sites]

Exogenous agonists -> drugs [ex. nicotine is an agonist for ACh receptor sites]

Question 5

Describe the role of Neurotransmitters

Answer 5

• The body’s natural chemical messengers [transmit information from one neuron to another]
• Cross the synapse and bind to receptor sites
• Once a message has been passed on, a neurotransmitter is either broken down by an enzyme or reabsorbed by terminal buttons (reuptake)

Question 6

Name four Neurotransmitters and their function

Answer 6

Question 7

Background for the Antonova study

Answer 7

• Scopolamine is an antagonist [blocks acetylcholine receptor sites]
• This decreases the availability of acetylcholine, which assists in encoding of memories and learning

Question 8

What is the aim of Antonova [2011]

Answer 8

To determine how blocking the acetylcholine receptors with scopolamine affects spatial memory

Question 9

Describe the method of Antonova [2011]

Answer 9

• [Participants were initially trained in the game to ensure comfort with the joystick and understanding of the rules]
• Participants were injected with either Scopolamine or a placebo 70 - 90 minutes before taking part in the experimental task.
• Participants underwent fMRI scans while playing a complex virtual reality game called the “Arena task.”
• The game involved navigating around an arena to reach a pole, [ability to create spacial memories]
• After learning the pole’s location, the screen went blank for 30 seconds, during which participants actively rehearsed the route to the pole.
• Upon the screen’s reappearance, participants started from a new point and had to find it again.
  Brain activity was measured for six trials during the experiment.
• Participants returned 3-4 weeks later for a repeated measures design, undergoing the opposite treatment from the initial study.

Question 10

Describe the Design of Antonova [2011]

Answer 10

• 20 male adults [mean age of 28]
• Double-blind
• Random allocation
• Repeated measures
• Use of a placebo [control]
• Counter-balanced

Question 11

Describe the Results of Antonova [2011]

Answer 11

Short: it appears that acetylcholine could play a key role in the encoding of spatial memories in humans.

Explained:
The researchers found that when participants were injected with scopolamine, they demonstrated a significant reduction in the activation of the hippocampus compared to when they received a placebo. It appears that acetylcholine could play a key role in the encoding of spatial memories in humans, as well as in rats.
Note: Although there was a higher rate of error in the scopolamine group, it was not a significant difference. The difference in the activity in the hippocampus, however, is significant.

Question 12

Evaluate Antonova [2011]

Answer 12

Advantages [issues this study avoids and how]:
Practice effect → Repeated measures design
Participant variability → Counter-balanced
Researcher bias → double-blind
Extraneous variables → highly controlled
Replicable → Reliability can be checked

Limitations [problems with this study’s method]:
Internal validity → Stress [due to injections and fMRI] could influence hippocampus activity
Sample size → Small sample might not be representative
Ecological validity → performed in a lab
Sampling bias [androcentric] → all participants were male

Question 13

What are the Implications of Antonova [2011]

Answer 13

• Acetylcholine-producing cells in the basal forebrain are damaged in the early stages of Alzheimer’s disease,
• May contribute to the memory impairments [early symptoms]
• Alzheimer’s drugs, are agonists to Ach, meaning that they increase the effectiveness of acetylcholine in the brain.