neurotransmission SAQ

neurotransmission

the process of transferring information from one neuron to another at a synapse

An electrical impulse travels down the axon (body) of the neuron. When it reaches an axonal terminal a neurotransmitter is released that then crosses the synaptic gap to the next neuron. Neurotransmitters are stored in a neuron's terminal buttons. After crossing the synapse, the neurotransmitter fits into receptor sites on the post-synaptic cell, like a key in a lock.

After a neurotransmitter has signalled an electrical impulse in the post-synaptic cell, some types are 'cleaned up' by transporter molecules released by the pre-synaptic neuron (reuptake) and they are reabsorbed, re-entering the pre-synaptic cell to be reused. In some cases, neurotransmitters are broken down (degradation)

neurotransmitters

chemical messengers that cross the synaptic gaps between neurons, transmitting information from one neuron to another in the brain and body

reuptake

After a neurotransmitter has signalled an electrical impulse in the post-synaptic cell, some types are 'cleaned up' by transporter molecules released by the pre-synaptic neuron; process by which neurotransmitters are taken back into the synaptic vesicles

excitatory vs inhibitory

excitatory: neurotransmitters that increase the likelihood of a neuron firing, as they excite or stimulate the post-synaptic neuron to fire (ex. Acetylcholine)

inhibitory: neurotransmitters that 'turn off' a neuron or decrease the likelihood of a neuron firing bcz they serve to inhibit or prevent the post-synaptic receiving neuron from firing (ex. GABA (calming effect))

agonist vs. antagonist

agonist: a chemical or drug that enhances the action of a neurotransmitter (can be drug or neurotransmitter, or hormone) -- does this by mimicking the neurotransmitter itself and binding to the receptor site of the post-synaptic neuron

antagonist: chemicals or drugs that block the receptor site on the post-synaptic neuron and do not allow the neurotransmitter to do its job

acetylcholine (ACh)

a neurotransmitter which has been linked to synaptic plasticity in the hippocampus, an agonist for AcH receptor sites

plays an important role in learning, muscle movement, and STM in the cholinergic system (Shinoe et al. (2005))

cholinergic system

a system of nerve cells that use AcH in transmitting nerve signals for the function of memory and higher cognitive functioning

dopamine

a neurotransmitter, one of those chemicals that is responsible for transmitting signals between the nerve cells (neurons) of the brain, an antagonist for AcH

one of the best-described roles for VTA dopamine neurons is in learning about rewards -- become activated when something good happens unexpectedly, such as the sudden availability of food

scopolamine

blocks acetylcholine receptors

Antonova et al (2011)

Aim: ?

Participants & design: 20 healthy male adults, w/mean age of 28 yrs; a double-blind procedure was used and participants were randomly allocated to one of two conditions where they were injected w/ Scopolamine or a placebo

Procedure: They were then put into an fMRI where they were scanned while playing the "Arena task" (a complex VR game in which the researchers are observing how well the participants are able to create spatial memories). The goal is for the participants to navigate around an "arena" with the goal of reaching a pole. After they have learned where the pole is located, the screen would go blank for 30 secs. During this time, the participants were told to actively rehearse how to get to the pole in the arena. When the arena reappeared, the participant was now at a new starting point in the arena. The participants would have to use their spatial memory to determine how to get to the location of the pole.

The procedure was repeated three to four weeks later, each participant received the other treatment.

Results: when participants were injected with scopolamine, they demonstrated a significant reduction in the activation of the hippocampus compared to when they received a placebo

Conclusion: blocking acetylcholine receptors in the brain can affect spatial memory tasks in humans; acetylcholine could play a key role in the encoding of spatial memories in humans, as well as in rats

link back to neurotransmission SAQ (conclusion)

Because ACH receptors were blocked by the agonist scopolamine and the participants performed worse in the spatial memory tasks, it is possible that that the agonist acetylcholine enhances the activation of the hippocampus and can play a key role in the transmission of neurons and info, and in the encoding of spatial memories in humans

link back to agonist SAQ (conclusion)

Because in the scopolamine condition the ACH receptor sites were blocked and the participants showed reduced activation in the hippocampus, this shows how on the other hand the agonist ACH can enhance the activation of the hippocampus and can play a key role in the encoding of spatial memories in humans.

link back to antagonist SAQ (conclusion)

In the scopolamine condition, this antagonist blocked the acetylcholine receptor sites, reducing the activation of the hippocampus compared to when the participants received a placebo. From these results, it appears that acetylcholine could play a key role in the encoding of spatial memories in humans

link back to excitatory/inhibitory neurotransmitter SAQ (conclusion)

In conclusion, the study showed that in the placebo condition, ACH was binding to excitatory synapses that led to the creation of spatial memories, whereas in the Scopalomine condition, these receptor sites were blocked so ACH could not bind to the site and cause the action potential to fire, resulting in the decrease of spatial awareness

neurotransmission SAQ outline

describe neurotransmission in great detail

identify acetylcholine as a neurotransmitter and its function in memory formation

define acetylcholine - as both an agonist and excitatory neurotransmitter

outline Antonova et al (2011)

link

agonist SAQ outline

describe agonist in reference to neurotransmission

describe neurotransmission in great detail

identify acetylcholine as an agonist for ACH Receptor sites

describe the function of acetylcholine in memory formation

outline Antonova et al (2011)

link

antagonist SAQ outline

define antagonist in reference to neurotransmission

describe neurotransmission in great detail

identify Scopolamine as an antagonist and define its function in relation to acetylcholine

outline Antonova et al (2011)

link

excitatory/inhibitory neurotransmitter SAQ outline

define excitatory neurotransmitters

describe neurotransmission in great detail

identify acetylcholine as both an agonist and excitatory neurotransmitter and describe its function in memory formation

outline Antonova et al (2011)

link