Neurotransmission and treatments for depression Flashcards
Communication in the brain
What are different cells of the nervous system?
Neurons and Glial cells
What percentage of the volume do Glial cells make up of the CNS?
50%
What function do the Glial cells have in the CNS?
Maintenance of synapses through the production of myelin and provide nourishment for the neurons
What are the three major structures of the Neuron?
Cell body, Dendrites, Myelin sheath
What is in the Neuron cell body?
Contains all of the organelles which maintain the cell, includes the nucleus (contains all of the genetic material)
What is the function of the cell body?
Relays signals down to the axon
What is the structure of dendrite?
Thin, bushy like structures, specialised projections that can receive signals from neighbouring neurons
What are the functions of the dendrites?
Receiving signals from neighbouring neurons and relaying information into the cell body
What is the structure of the myelin sheath?
80% lipids (fats) and 20% proteins
What is the function of the myelin sheath?
Insulating the neurons so that electrical signals are not lost
What makes the myelin sheath?
Oligodendrocytes in the CNS
What does gray matter mostly consist of?
Neuronal cell bodies
What does white matter mostly consist of?
myelinated axons
Where are neuronal cell bodies most abundant?
Cerebrum, brain stem and cerebellum
What percentage of the brain volume does the cerebellum make up?
10%
What is special about the cerebellum?
It contains more neurons than the rest of the brain put together
Where is gray matter usually found?
Gray matter is usually found surrounding white matter in the external areas of the brain
What does the term nuclei refer to?
The regions of gray matter that are located in deeper regions of the brain
In the cerebrum and cerebellum where is white matter more likely to be found?
Predominantly found in deeper areas
What are other gray matter structures?
Basal ganglia
In what is the basal ganglia embedded in?
In white matter
In which case is the gray matter is embedded into the white matter?
In the spinal cord <3
Are neuron electrically excitable?
Yes
What concentration of ions differ from the inside the cells?
Sodium (NA+) and potassium (K+)
Which elements start off outside the cell?
Sodium
What causes the ions to continuously move down the concentration gradient?
The concentration differences cause ions to continuously move down the concentration gradient through ion channels that are high permeable
Which ion is the channel highly permeable to?
Potassium (K+)
If the movement stops with the inside of the cell what will be the resting potential of the cell?
-70mV
What is an action potential?
A short term change in the electrical potential that travels along a cell it releases the neurotransmitter into the synaptic cleft
What is the resting potential?
Is what happens when a neurons is at rest
What is an action potential is caused by?
Different ions crossing the neuron membrane resulting in the neuron sending information down the axon, away from the cell body
What is an action potential?
An explosion of electrical activity that is created by a depolarising current
How many steps can the formation of action potential be divided into?
five steps
What are the 5 steps involved in making an action potential
1) A stimulus from a sensory cell or another neuron causes the target cell to depolarise toward the threshold potential
2) If the threshold of excitation is reached, all sodium channels open and the membrane depolarise
3) At the peak action potassium channels open and K+ begins to leave the cell, at the same time sodium channels close
4) The membrane becomes hyperpolarized as potassium ions continue to leave the cells. The hyperpolarised membrane is in a refractory period and cannot fire
5) The potassium channels close and the sodium transporters restores the resting potential
What is the All or nothing principal?
If the neurons do not reach this critical threshold level then non action potential will fire
What does it mean when there are no big or small action potential?
It means that that action potential can only happen when the meet a certain threshold of excitation thus all action potentials are the same
What are the components of the structure of the synapse?
Synapse and axon terminals, and dendrites
Describe synaptic transmission
The neurotransmitters diffuse out of the synaptic vesicles and into the synaptic gap, the neurotransmitter usually have a summination of either -1/+1 which means they either have an excitatory or inhibitory effect. They then bind to the specialised receptor site where they are reabsorbed and resused
What is spatial summination?
Adds together all inputs received at the same time
What is temporal summination?
Adds together the inputs in the same place but slightly different times
What is a signal termination?
The synaptic cleft is cleared
How is the synaptic cleft cleared?
Neurotransmitter may be broken down my an enzyme, may be sucked back into the pre-synapse or simply diffused, could also be mopped up by glial cells
What is a neurotransmitter?
A chemical messenger that transmits signals from a neuron to a target cell across the synapse
What are the potential targets for neurotransmitters?
Neurons, another type of cell such as muscle or gland cells
Where are neurotransmitters held?
Synaptic vesicles of the pre-synaptic cell
What a Ligand Gated Ion Channels?
A simplistic gated transmitter site
How does the gated mechanism work in the Ligand Gated Channel?
The ion binds to the specialised receptor sites and then the gated channel opens up which induces ion fluxes
What is the G protein coupled receptor?
The neurotransmitter binds to the receptor site which cause the the G protein to release and trigger gate open and trigger the release of enzymes
What is the difference between the ion gated channel and the G protein receptor?
Ion gated is a lot simpler mechanism than g protein
What is another difference between Ion gated channel and Metabotropic receptors?
Metabotropic receptors are less direct so their reactions are slower.
What are the two types of neurotransmitters?
Inhibitory and Excitatory
What is an inhibitory neurotransmitter?
They have an inhibitory effect on the neuron and decrease the likelihood that the neuron will fire an action potential
What is an excitatory neurotransmitters?
They have an excitatory effect on the neurons. This means that they increase the likelihood that the neuron will neurons will fire an action potential.
List the excitatory neurotransmitters?
Glutamate, Acetylcholine, Histamine, Dopamine, Norepinephrine, Epinephrine
List the inhibitory neurotransmitters?
Gamma-Aminobutyric acid, Serotonin, Dopamine
List the neuromodulators
Dopamine, Serotonin, Acetylcholine, Histamine, Norepinephrine
What is the chief neurotransmitter of the parasympathetic nervous system?
Acetylcholine
What the neurotransmitter Acetylcholine responsible for?
Plays a role in memory, learning, attention, arousal and involuntary muscle movement
What medical condition is associated with low levels of Acetylcholine?
Alzheimer’s disease
What is the function of Acetylcholine?
Helps send messages between nerve cells
Why is it important to have a higher concentration of Acetylcholine?
Leads to better communication in the brain
What medications can ease symptoms of Alzheimer’s disease for a while?
Donepezil, rivastigmine and galantamine
How do Donepezil, rivastigmine and galantamine ease symptoms of Alzheimer’s disease?
Prevent the enzyme called acetylcholinesterase from breaking down acetylcholine
Where are amino acid neurotransmitters common?
In the central nervous system
What are the amino acid neurotransmitters?
Glycine, glutamate and GABA
What is Glutamate?
The most abundant excitatory neurotransmitter
Is glutamate limited to binding to a specific receptor?
No it can bind to a range of different receptor sites
What does glutamate have implication on?
Learning and memory
What does any dysfunction in the glutamate neurotransmitter have an effect on?
Propose to play a role in schizophrenia
Which is the most abundant inhibitory neurotransmitter?
GABA
What neurotransmitter is Glycine?
A co-agonist
What is an agonist?
A substance that mimics the actions of neurotransmitter or hormone to produce the same response from the target receptor
Examples of Monoamines
catecholamines, epinephrine, norepinephrine, dopamine, Indolamine
What function does catecholamines have?
Helps the body respond to stress and prepare the body for flight or flight reactions
What function does epinephrine have?
It is both a neurotransmitter and a hormone. As a neurotransmitter it aids communication in the brain. As a hormone it aids the function of the adrenal gland.
What other monoamine functions as both a hormone and neurotransmitter?
Norepinephrine
What function does norepinephrine have as a neurotransmitter?
Plays a role in the sleep- wake cycle, helping you wake up, increasing attention and focus on preforming a task and in memory storage.
What function does dopamine have?
It is important in executive function, motor control, motivation, reinforcement and reward
What is the function of Indolamines
Helps with sleeping, eating and digestion
What are the three treatment methods for Depression?
Tricyclics, MAOIs, SSRI’s
Why are tricyclic and SSRI’s considered similar treatment methods?
Because they both block the reuptake of serotonin how tricyclics also block the reuptake of norepinephrine
What gives MAOI’s it s anti-depressant effect?
It prevents the enzyme called monoamine oxidase is involved in removing the neurotransmitters norepinephrine, serotonin and dopamine which means there is a greater concentration of these neurotransmitters in the brain.
What are condition associated with lower concentrations of dopamine?
Parkinson’s Disease, restless leg syndrome, Depression, Schizophrenia, ADHD
