Neurophysiology Flashcards
What was Luigi Galvani know for?
First appreciating that electricity is the primary force of our behaviour, explaining our fast reaction, as shown with his experiments on frogs
What did Giovanni Aldini show?
That the whole nervous system communicates with electricity. He showed this by stimulating all muscles with cut nerve.
Where is information integrated?
The dendrites
Which type of potential is maintained at the same magnitude along the axon?
Action potential
What happens to synaptic potential as it goes along?
It diminishes
Where does signal summation occur?
At the cell body
When will a neuron pass on the action potential?
If it reaches the threshold potential (-50mv)
What is the threshold potential?
The minimum depolarisation required to initiate a nerve impulse, passing on the action potential (-50mv)
What are gap junctions?
purely electrical synapses that allow electrical charge to cross directly between specialised channels (~10% of synapses)
Where is an action potential generated?
At the axon initial segment/axon hillock
Which type of neurite has the biophysical mechanisms to generate action potential?
Axons
What type of mechanism is used to generate an action potential?
Voltage-dependent
What does an intracellular recording measure?
The difference in current flow inside the neuron compared to a reference electrode outside, away from the neuron (differential recording)
What does an oscilloscope do?
Tracks changes in potential difference over time
What is resting membrane potential?
Approximately -65mv (more negative inside the neuron than outside)
What is depolarisation?
The rapid rise in membrane potential initiated by an action potential, which, at its peak, become greater than outside of the membrane (around 30mv)
What does an intracellular recording measure during depolarisation?
The flow of positively charged ions into the neuron, toward the electrode
What is an extracellular recording?
A method of recording electrical activity whereby the recording electrode is placed outside of but very close to the neuron to measure an extracellular spike, with a reference electrode placed far away.
What does an extracellular recording measure?
The flow of positively charged ions away from the electrode, into the membrane
What is the purpose of the reference electrode in am extracellular recording?
To remove background electrical noise/events in the recording area
What is the role of the phospholipid bilayer?
A barrier maintaining the compartment of the cell, helping to keep things from going in and out
Why is water good at breaking down compounds/salts such as NaCl?
Because it is polar molecule
What are membrane channels made of?
Multiple trans-membrane proteins forming a pore
What are the three main types of membrane channels?
- Simple leak channels
- Ligand gated channels
- Voltage gated channels
What are leak channels?
A channel which is constantly open
What is a ligand gated channel?
A channel which is opened when a substance binds to it (receptors that form the basis of neurotransmission)
What is voltage gated channel?
A channel which opens when the voltage changes across the membrane, changing the structure of the proteins
Which type of channel is important for the generation of an action potential?
Voltage gated channels
Which type of channel is important for neurotransmission?
Ligand gated channel
What is the most common (and important) ion pump?
The sodium-potassium ATPase pump
What does the sodium potassium pump do?
It transports 3 Na+ ions out of the cell and brings in 2 K+ ions
Why is the sodium potassium pump important?
To reestablish the resting membrane potential and ion gradients/balance needed to generate another action potential
At rest, which ions are more concentrated in the extracellular space than inside the neuron?
Sodium (Na+), Chloride (Cl-), and Calcium (Ca2+)
At rest, which ions are more concentrated inside the neuron than outside?
Potassium (K+) and organic anions (A-)
What is the main ion involved in maintaining the negative membrane potential inside of a neuron?
Organic anions that are too big to cross the membrane
What are the two forced involved in the movement of ions across the membrane?
Diffusion and electrostatic force
Why is the net diffusion on K+ more limited than Na+?
Because the direction of the two forces oppose each other (it wants to diffuse out of the cell where there is less K+ but it’s positive nature is electrostatically attracted to the intracellular space where it is relatively more negatively charged)
Why do Na+ ions flood into the cell when given the opportunity?
Because they are under the dual aligned pressure of electrostatic force and diffusion.
What is an intracellular sharps recording?
An incredibly fine glass pipette is filled with a solution of charged particles and pierces the phosholipid membrane to record electrical events
What did John Eccles find?
That, using the sharps method, you can record the excitatory post-synaptic potential (a relatively slow electrical event) by stimulating presynaptic axons
What is an EPSP?
An Excitatory Post-Synaptic Potential, the result of the opening on sodium channels and the influx of Na+ ions
What type of receptor do nicotine, muscarine, and belladonna all act on?
Cholinergic receptors
What are the two types of receptor involved in cholinergic transmission and where does this typically occur?
The nicotinic receptors and the muscarinic receptors at the neuromuscular junction.
What type of channel is the nicotinic receptor?
Ligand gated ion channel - allows Na+ ions in when acetylcholine binds
Which type of receptor mediates fast cholinergic transmission?
The nicotinic receptor (an ionotrophic receptor)
What type of receptor is the muscarinic receptor?
A metabotropic/G-protein-coupled receptor
Which type of receptor mediates slower cholinergic transmission?
Muscarinic receptors
What does nicotine do to cholinergic transmission?
It binds directly to the nicotinic receptor, acting as an agonist
How do muscarinic/G-protein receptors work?
They are attached to several proteins inside of the membrane which are released when the receptor changes shape due to acetylcholine binding, causing a cascade of the processes such as the opening of channels
What are the three main receptors involved in glutamate transmission?
- AMPA receptor
- NMDA receptor
- Kainate receptor
Which receptor carries the majority of the synaptic current for fast excitatory (glutamate) transmission?
The AMPA receptor
What is the NMDA receptor?
A voltage-dependent ionotrophic receptor involved in glutamate transmission, neuroplasticity, and learning.
What is required for the activation of the NMDA receptor?
The presence of glutamate AND the depolarisation of the cell
What is the major excitatory neurotransmitter in the brain?
Glutamate
