Neurotransmitters & (basic) Psychopharamcology Flashcards
The study of the effects of drugs on the nervous system and on behaviour
This is known as…?
Psychopharmacology
What is Psychopharmacology?
The study of the effects of drugs on the nervous system and on behaviour
Why is it important to study Psychopharmacology?
- Our brain develops a good protective system (blood-brain barrier)
- BBB does not allow some substances to enter the brain
- Studying Psychopharmacology tells us that drugs are able to cross the BBB to affect the CNS
Drugs are able to cross the BBB to affect the CNS
How is this possible?
- There are some substances that can cross the BBB through active transport (because they are lipid soluble)
- The membrane of BBB is made of lipids and if a substance can be dissolved in lipids, it has greater potential of crossing BBB
Define drug effects
The changes a drug produces in an animal’s physiological processes and behavior. In the nervous system, most drugs affect synaptic transmission.
The changes a drug produces in an animal’s physiological processes and behaviour. In the nervous system, most drugs affect synaptic transmission.
This is known as…?
Drug effects
What are the 2 types of drugs?
1) Antagonist
2) Agonist
A drug that opposes or inhibits the effects of a particular neurotransmitter on the postsynaptic cell.
What type of drug is this?
Antagonist
A drug that facilitates the effects of a particular neurotransmitter on the postsynaptic cell.
What type of drug is this?
Agonist
What is an agonist drug?
A drug that facilitates the effects of a particular neurotransmitter on the postsynaptic cell.
Simply - A drug that imitate/pretend to be neurotransmitters that bind with receptors in the brain to increase the effects of neurotransmitters
What is an antagonist drug?
A drug that opposes or inhibits the effects of a particular neurotransmitter on the postsynaptic cell.
Simply = A drug that blocks neurotransmitters from doing what they usually do (stop the effect or action of neurotransmitters)
What are sites of action?
The locations at which molecules of drugs bind with the molecules located on or in cells of the body
This affects some biochemical processes of the cells
The locations at which molecules of drugs bind with the molecules located on or in cells of the body
This is known as…?
Sites of action
What are the 4 main sites of action?
1) Production of neurotransmitters in presynaptic cell
2) Storage and release of neurotransmitters
3) Effects on receptors on postsynaptic cell
4) Effects on reuptake
Which drug increases the release of neurotransmitters?
a. Antagonist
b. Agonist
b. Agonist
Which drug blocks the storage of neurotransmitters?
a. Antagonist
b. Agonist
a. Antagonist
The most important and most complex site of action of drugs in the nervous system is …?
On receptors (both presynaptic and postsynaptic)
What happens when drugs are in our system at the same time as when neurotransmitters are supposed to bind with the receptors?
Once a neurotransmitter has been released, it must stimulate the postsynaptic receptors.
Some drugs bind with these receptors, just as the neurotransmitter does (they steal the place of neurotransmitters by mimicking their behaviour and binding with the receptors)
Once a drug has bound with the receptor, it can serve as either …… or ………
An agonist or an antagonist
Which drug facilitates transmission?
a. Antagonist
b. Agonist
b. Agonist
Which drug blocks transmission?
a. Antagonist
b. Agonist
a. Antagonist
What are the 2 types of drug binding?
1) Competitive binding (or direct agonist/antagonist)
2) Indirect binding (or indirect agonist/antagonist)
What happens in competitive binding (or direct agonist/antagonist)?
Drug molecules bind with and activate receptors
This drug mimics the effects of a neurotransmitter
What are the 4 steps to competitive binding (or direct agonist/antagonist)?
1) Drug travels from presynaptic cell
2) Drug binds to receptor on postsynaptic cell
3) If drug is an Agonist, it keeps the postsynaptic site/ion channel open all the time
4) If drug is an Antagonist, it keeps the postsynaptic site/ion channel closed all the time
In competitive binding (or direct agonist/antagonist), what happens if the drug is an antagonist?
It keeps the postsynaptic site/ion channel closed all the time
Less ions flow in the cell which stops neurotransmission
In competitive binding (or direct agonist/antagonist), what happens if the drug is an agonist?
It keeps the postsynaptic site/ion channel open all the time
More ions flow in the cell which stops neurotransmission
When drug molecules are similar to neurotransmitters, they’re in direct competition to bind with a receptor in the postsynaptic cell
What type of binding is this?
Competitive binding (or direct agonist/antagonist)
What happens in indirect binding?
A drug that attaches to a binding site on a receptor and facilitates the action of the receptor
It does not interfere with the binding site of the principal neurotransmitter.
What are the 4 steps to indirect binding?
1) Drug travels from presynaptic cell
2) Drug binds to a similar neuromodulation binding site as the neurotransmitter but does not take it’s place (happens on postsynaptic cell)
3) If drug is an Agonist, it keeps the postsynaptic site/ion channel open all the time
4) If drug is an Antagonist, it keeps the postsynaptic site/ion channel closed all the time
Drug molecules attach to other sites whilst neurotransmitters attach to their usual site
What type of binding is this?
Indirect binding
Some drug molecules do not resemble/imitate neurotransmitters and they find binding site alternatives instead of competing for the same binding site as the neurotransmitters
What type of binding is this?
Indirect binding
In indirect binding, what happens if the drug is an agonist?
It keeps the postsynaptic site/ion channel open all the time
More ions flow in the cell which stops neurotransmission
In indirect binding, what happens if the drug is an antagonist?
It keeps the postsynaptic site/ion channel closed all the time
Less ions flow in the cell which stops neurotransmission
Define reuptake and destruction of neurotransmitters
The process of termination of the postsynaptic potential by:
1) Molecules of the neurotransmitter are taken back into the terminal button through the process of reuptake
2) They are destroyed by an enzyme.
What happens in the process of reuptake and destruction of neurotransmitters when drug molecules are present?
1) The drug molecules attach to the transporter molecules that are responsible for reuptake and inactivate them, thus blocking reuptake (preventing neurotransmitters from leaving synaptic cleft)
2) In the second case the drug bind with the enzyme that normally destroys the neurotransmitter and prevents the enzymes from working (preventing neurotransmitters from being destroyed)
Both types of drugs prolong the presence of the neurotransmitter in the synaptic cleft (more neurotransmitters remain in the cleft and causes more stimulation of postsynaptic cell by default)
Do they serve as…?
a. Agonist
b. Antagonist
a. Agonist
An inert substance given to an organism in lieu of a physiologically active drug; used experimentally to control for the effects of mere administration of a drug
This is known as…?
Placebo
Define placebo
An inert substance given to an organism in lieu of a physiologically active drug; used experimentally to control for the effects of mere administration of a drug (usually sugar pill)
Simply = A substance that you’re told should produce some kind of effects but in actuality, it is completely harmless/has no specific physiological effect
When experimenters want to investigate the behavioral effects of drugs in humans, they must use control groups whose members receive placebos, or they cannot be sure that the behavioral effects they observe were caused by specific effects of the drug.
This is known as…?
Placebo effects
Where people can feel worse after an intervention that should have no ill effects
This is known as…?
Nocebo effect
For example:
Doctors say a red pill reduces migraines. So when you consume the red pill, you report that your migraine has been reduced, even though there’s no actual drug in the red pill
What effect is this?
Placebo effect
For example:
Doctors say a red pill reduces migraines but it also has nausea side effects. So when you consume the red pill, you report feeling sick and wanting to vomit
What effect is this?
Nocebo effect
Define the nocebo effect
Where people can feel worse after being told an intervention (that should have no ill effects) has negative sideeffects
What do including placebo and nocebo substances tell us about the way people behave?
Tells us that telling people different things can change the results of the experiment
In the brain, most synaptic communication is accomplished by two neurotransmitters
What are they?
1) With excitatory effects(glutamate)
2) With inhibitory effects (GABA in the CNS or glycine-spinal cord)
Neurons receive excitatory input from …?
Glutamate-secreting terminal buttons
Neurons receive inhibitory input from…?
Neurons that secrete either GABA or glycine
Neurons that secrete either GABA or glycine give out…?
a. Excitatory input
b. Inhibitory input
b. Inhibitory input
Glutamate-secreting terminal buttons give out…?
a. Excitatory input
b. Inhibitory input
a. Excitatory input
Other than glutamate and GABA, what do other neurotransmitters do?
They have modulating effects rather than information-transmitting effects.
The release of neurotransmitters other than glutamate and GABA tends to activate or inhibit ….?
Entire circuits of neurons that are involved in particular brain functions.
Is acetylcholine excitatory or inhibitory or both?
Both
Is norepinephrine excitatory or inhibitory or both?
Excitatory
Is dopamine excitatory or inhibitory or both?
Both
Is glutamate excitatory or inhibitory or both?
Excitatory
Is serotonin excitatory or inhibitory or both?
Both
Is GABA excitatory or inhibitory or both?
Inhibitory
Is opioid excitatory or inhibitory or both?
Inhibitory
What are the 2 receptors of acetylcholine neurotransmitters?
Nicotine and Muscarinic
The primary neurotransmitter secreted by the efferent axons of the CNS
This is known as…?
Acetylcholine
What does the release of acetylcholine lead to?
The control of muscle contractions and muscle movements
The effects of acetylcholine are generally…?
a. Agonist
b. Antagonist
a. Agonist (facilitatory)
ACh is involved in regulating what type of sleep?
REM
Apart from REM sleep, what else does the release of ACh help with? List 3 more
- Dreaming (doroslateral pons)
- Perceptual learning (forebrain)
- Memory (hippocampus)
Where was ACh first found?
At the target of the parasympathetic branch of the ANS – outside of the CNS
Who first discovered ACh?
Otto Loewi
What did Otto Loewi do in his experiment involving frog hearts?
1) Otto Loewi stimulated the heart of a frog (vagus nerve) with electrical impulses and slowed the heartbeat
2) Loewi had the heart pump a small amount of nutrient solution (extracellular fluid around the heart)
3) When the fluid was transferred to another heart, it operated in a similar way (fluid caused the rate of the heart to slow down without it being stimulated)
What did Otto Loewi discover about the relationship between the chemical substance in our body and our organs?
Chemical substances convey nerve signals to organs
Believed = There was some chemical substance released by the vagus nerve that caused the first heart rate to slow down. The substance was acetylcholine.
Define Cholinergic Synapses
Synapses that have acetylcholine transmitters
Usually happens in any transsynaptic transmission
Synapses that have acetylcholine transmitters are called?
Cholinergic Synapses
What happens in stage 1 of a cholinergic synapse?
An action potential arrives at the presynaptic membrane.
Voltage-gated calcium channels in the presynaptic membrane open
Calcium ions enter the presynaptic neuron
What happens in stage 2 of a cholinergic synapse?
Calcium ions cause synaptic vesicles to fuse with the presynaptic membrane
This releases acetylcholine into the synaptic cleft
What happens in stage 3 of a cholinergic synapse?
Acetylcholine diffuses across the synaptic cleft and binds to specific neuroreceptor sites (either nicotinic or muscarinic) in the post-synaptic membrane
What happens in stage 4 of a cholinergic synapse?
Once acetylcholine binds with the receptors, sodium channels open
Sodium (excitatory) ions diffuse into the postsynaptic membrane
This causes depolarisation, which may initiate an action potential.
What happens in stage 5 of a cholinergic synapse?
Acetylcholinesterase (enzyme) breaks down acetylcholine in the synaptic cleft
The products diffuse back into the presynaptic neuron where acetylcholine is resynthesised using energy (ATP) from the mitochondria.
What stage of a cholinergic synapse does this occur in?
Calcium ions cause synaptic vesicles to fuse with the presynaptic membrane
This releases acetylcholine into the synaptic cleft
Stage 2
What stage of a cholinergic synapse does this occur in?
Once acetylcholine binds with the receptors, sodium channels open
Sodium (excitatory) ions diffuse into the postsynaptic membrane
This causes depolarisation, which may initiate an action potential.
Stage 4
What stage of a cholinergic synapse does this occur in?
Acetylcholine diffuses across the synaptic cleft and binds to specific neuroreceptor sites (either nicotinic or muscarinic) in the post-synaptic membrane
Stage 3
What stage of a cholinergic synapse does this occur in?
Acetylcholinesterase (enzyme) breaks down acetylcholine in the synaptic cleft
The products diffuse back into the presynaptic neuron where acetylcholine is resynthesised using energy (ATP) from the mitochondria.
Stage 5
What stage of a cholinergic synapse does this occur in?
An action potential arrives at the presynaptic membrane.
Voltage-gated calcium channels in the presynaptic membrane open
Calcium ions enter the presynaptic neuron
Stage 1
What are Neuromuscular Junctions?
A specialized synapse that bridges the motor neuron and the skeletal muscle fibre
It is crucial for the conversion of electrical impulses originating in the motor neuron to action potentials in the muscle fibre
What is the main effect of ACh outside of the CNS?
Muscle contraction
What is the process of muscular contractions due to ACh?
Same stages as cholinergic synapses, but the postsynaptic membrane is the muscle fibre membrane (Sarcolemma)
Depolarisation of the sarcolemma leads to …?
Contraction of muscle fibre