Lecture 18 - Cognition and Chemicals

Question 1

What is the aim and general overview of the lecture

Answer 1

Aim of lecture: to be able to answer questions such as:
What kinds of things do psychoactive drugs and medications do?
Is addiction physical or psychological?
What is the role of cognition in addiction?

Question 2

What are the key concepts in the lecture?

Answer 2

KEY CONCEPT 1: Information processing is all about neural communication

KEY CONCEPT 2: Drugs affect neurotransmission (this is where most drugs act)

KEY QUESTION: Is there a clear distinction between a
medical/physical problem and “its all in the mind”?

KEY CONCEPT 3: Networks learn: e.g. down-regulation.

We are talking mostly about the connection between neurons rather than the neuron itself.

Question 3

Parts of the neuron (or ‘brain cell’) we are interested in

Answer 3

Cell body, the axon (sends information), synapses (sends info) and dendrites (receives info)

Work on the principle of electrical potential

An action potential is also called depolarisation

Question 4

Why is it called a neurotransmitter

Answer 4

A neurotransmitter transmits info from one neuron to another

In the next neuron it triggers ions and changes the electrical potential in the next neuron.

Question 5

Key neurotransmitters in the brain

Answer 5

Glutamate: Excitatory; sensory input / motor output

GABA: Inhibitory:
(reduced in epilepsy; affected by many things, including alcohol)

Dopamine: “Modulatory”. Pleasure / reward.

Serotonin: “Modulatory”. General well being. (anti-depressants)

Adrenalin / nor-adrenalin: Body brain communication; flight/fight
Response

Drugs can affect the same system but not have the same cognitive effect and this can be why they have different effects

Question 6

How many neurons are in your brain? And Synapses?

Answer 6

10-100 billion neurones

~1000,000,000,000,000 synapses!
(each neuron has several thousand!)

Question 7

What can drugs do?

Answer 7

1. Synthesis: neurotransmitter is made
2. Storage: it gets put inside the cell and stored in synapses
3. Release: Action potential triggers the neurotransmitter to be released
4. Receptor interaction: After synaptic gap it binds to a receptor (ligand). Receptor lets positive charge into the post-synaptic neuron (if excitatory) if inhibitory it makes charge negative and prevents postsynaptic neuron from firing
5. Inactivation: After the neurotransmitter has carried its message, it is removed or neutralized to reset the synapse for the next signal.
6. Reuptake: Neurotransmitter can be pumped back up the synapse
7. Degradation: breakdown of neurotransmitters in the synaptic cleft by specific enzymes, effectively terminating their activity. This is one of the primary mechanisms of inactivation, ensuring that neurotransmitters do not continuously stimulate the postsynaptic neuron and allowing the synapse to reset for future signaling.

Question 8

General concepts in this

Answer 8

Agonist: Anything that enhances neurotransmission

Antagonist: Anything that reduces neurotransmission

The word refers to the neurotransmitter so a GAMA agonist (like benzodiazepene) helps GAMA to inhibit

Question 9

Some drugs and what they do

Answer 9

Alcohol: GABA agonist (+
complex non-specific effect
acting on many bodily tissues).

Anti-depressants: e.g. Prozac,
block reuptake of 5-HT / serotonin

Nicotine: Activates a class of acetyl choline receptors.
Activates sympathetic
nervous system.

Inhibition at neural level is not the same at behavioural level. Might inhibit behaviour but not be an inhibiter in neurotransmission.

Cocaine: Cocaine blocks
reuptake of dopamine into
synaptic terminals. Also
serotonin and noradrenalin.

Amphetamines: Also
dopamine, serotonin and
noradrenalin

Opiates: (heroin & morphine):
Opiate receptors in limbic
system led to discovery of
“endogenous” opiates
endorphins and enkaphalins

Question 10

How do opioids work in pain management

Answer 10

1. Substance P along with glutamate and other pain producing neurotransmitters produces depolarisation potential in pain neuron
2. Opioid peptides and opioid drugs open ligand gated K+ channels to decrease the intensity of depolarisation
3. Opioid receptors on sensory neurons when stimulated open Cl- ion channel and block Ca2+ ion channel to inhibit firing of sensory neuron

Question 11

Autoreceptors and neurotransmitters

Answer 11

Here’s How It Works:
Sending the Message:

A neuron releases neurotransmitters (the message) into a small gap called the synapse to pass it to the next neuron.
The Check-In (Autoreceptor):

Before releasing too much of the message, the neuron has a way to monitor itself: the autoreceptor.
These are special spots (like tiny antennas) on the sending neuron that detect how much neurotransmitter has been released.
Why It’s Important:

If the neuron releases too much neurotransmitter, the autoreceptors send a signal saying, “Whoa, slow down!”. It is going to shut itself down less quickly if more of the neurotransmitter is firing.

If there’s not enough, they let the neuron know it can keep sending.

This self-regulation part is thought to be more important in SSRIs than immediate action at the synapse as with SSRIs the effects are result of a build up over time

Answer 12

Opioid drugs comes in and inhibits GABA cells, this frees the cells up that GABA neuron was inhibiting

This means serotonin and dopamine can be more active which then affects the next cell

In the short term you get lots of reward signal. But if you stick this opioid in repeatedly, the GABA cells become less sensitive to the opioid, they are much more powerful GABA cells now and inhibit serotonin and dopamine cells a lot so cannot fire and get reward

So you have to put loads of opioid in in order for the GABA to respond and to get that reward signal.

Question 13

Is addiction physical or cognitive phenomenon

Answer 13

They are interrelated.

Question 14

Questions for this topic

Answer 14

1. What is the mind-staggering number of synaptic connections in your brain
   a) A trillion
   b) A million
   c) A billion
   d) A godzillion (AKA a quadrillion)
2. Neurons are basically…
   a) Adding machines that pool and sum up all the positive and negative inputs they receive
   b)multiplication machines that mulitply the amount of positive input by the negative inputs they
   receive
   c)Dividing machines that divide the positive inputs by the number of axons they have
   d) Why are you asking me about maths?
3. Which of the following do you need to become a neuroscientist
   a) An impressive moustache
   b) A severe expression
   c) A Y chromosome
   d) A quadrillion synapses (or the best part thereof)

Question 15

Answers

Answer 15

D
2 is A
The other is irrelevant

Question 16

Questions

Answer 16

4. A drug that INHIBITS neurotransmitter REUPTAKE is
   a) An inhibitor
   b) A depressant
   c) An antagonist
   d) An agonist
5. Alcohol is a GABA agonist (among other things)…which means it must
   a) Inhibit the action of GABA at synapses
   b) Enhance the action of GABA at synapses
   c) Enhance the reaction to GABA in receptors
   d) Enhance the reaction to ABBA in receptions
6. The most important thing Professor Dumbledore said to Harry (from the point of view of making use of
   the quote in a neuroscience lecture) was…
   a) Of course its not happening inside your head, Harry. Why should that mean that it’s real?
   b) Of course its not happening inside your head, Harry. You are a fictional character, innit.
   c) Of course its happening inside your head, Harry. Why should that mean that it’s not real?
   d) I think if you so desired, you’d be able to board a train.

Question 17

Answers

Answer 17

D
C
C