fundamental concepts Flashcards
What is resting membrane potential?
-Underpins the ability of neurons to generate signals and to communicate
-its an example of something called “electrical excitability”
-because the neuron is in an unstable state, upon a trigger that stored up energy is released and its the release of that energy that is the signal (action potential)
What is electrical excitability?
when a neuron is not active energy is being is being expended (spent or used up) to maintain an unstable state
What is action potential?
Triggered signals within a neuron that are electrical in nature
-Depends on the RMP
What is happening within the resting membrane potential?
-the RMP depends upon the fact that the cell membrane of a neuron is a lipid bilayer
(two layers of fatty molecules) charged molecules don’t tend to pass through however it is leaky
-This membrane creates a barrier between the inside of a neuron and the outside of the neuron
What are the 3 forces acting on the distribution of ions across the cell membrane?
Electrostatic pressure
Transporter
Diffusion
Describe electrostatic pressure
-same charged ions repel each other and differently charged ions attract each other
-Positively charged ions will typically want to move into an area that is more negatively charged
Describe Transporter
- moves specific ions
-Uses energy (a substantial proportion of the energy consumed by the brain is in maintaining the RMP)
Diffusion
Irrespective of the charge those ions will tend to want to move from areas of their high concentration to areas of low concentration
Summarise the forces at work in relation to sodium
-There is a greater concentration of sodium outside than inside, so there is a diffusion gradient inducing sodium to want to go back into the cell
-The outside of the neuron is more positive than the inside and so there is electrostatic pressure as well pushing sodium inside
-While the cell membrane has a barrier it is slightly leaky and so some of the sodium can get through the membrane
-The transporter pushes it back out
What is the structure of a synapse?
-made up of a presynaptic and postsynaptic terminal.
-The presynaptic terminal is at the end of an axon and is the place where the electrical signal (the action potential) is converted into a chemical signal (neurotransmitter release)
What is neural integration?
-Each post synaptic neuron may receive inputs from many different pre synaptic neurons
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What is the difference between ESPS and IPSPS
PSPs are called excitatory (or EPSPs) if they increase the likelihood of a postsynaptic action potential occurring, and inhibitory (or IPSPs) if they decrease this likelihood.
What are Ligands also referred to as
Neurotransmitter
What is the binding site
place on receptor where the ligand interacts
What are the two main concepts of binding the ligand to the receptor
Selective binding
Affinity
Describe selective binding
-Only specific ligands will fit in a binding site
Due to the 3D shape of the receptor
-But some drugs bind to more than one receptor type
Describe Affinity
-Essentially how well a ligand binds to a receptor
-High affinity means that receptors are saturated (completely bound) = a small amount of ligand binds to almost all the receptors
What are the two types of receptor?
Ionotropic receptor
metabotropic receptor
Describe the Ionotropic receptor
-Receptor is “directly coupled” to an ion channel
-Essentially true to say “the receptor is an ion channel”
Ligand binds = Ion channel opens
Describe the Metabotropic receptor
-Ligand binds to receptor
-Changes 3D shape of receptor
-This activates a G-protein that connects to the receptor inside the neuron
-activating an intracellular signalling cascade
(Can alter ionotropic receptors to make them more or less excitable
Can alter protein synthesis)
What are the two broad types of neurotransmitter
Amino acid derivatives
Monoamines
What are the 3 main neurotransmitters within Amino acid derivatives
Glutamate
GABA
Glycine (technically an amino acid)
What are the 4 main components of glutamate
-Derived from glutamic acid
-Most abundant neurotransmitter
-Excitatory
-Binds to at least 8 different receptors, both ionotropic and metabotropic (including NMDA and AMPA receptors)
What are the 3 main components of GABA
-Made from glutamate
-Most abundant inhibitory neurotransmitter
-Binds to both ionotropic and metabotropic GABA receptors
