Cellular Neurophysiology Flashcards
What is the organisation of the Neural Cell Membrane?
Channels allow ions in and out of neuron
Channels can be open or closed
What are the ion pumps?
In the channels, pumps push or pull ions inside or outside of the neuron
What is the excitation threshold?
Neuron needs to be pushed so they reach the excitation threshold so the action potential can happen
What are neurotransmitters?
Gap between axon and dendrite, the gap is called a synapse
Axon sends signal to dendrite via chemical messengers, called neuron transmitters
Dendrite receive neurotransmitters, becomes an electrical signal, which begins action potential
What are glial cells?
Provide support to neurons
Regulate blood flow
Supply nutrients to neurons
Guide development
Guide neural migration and produce chemicals to stop it
they communicate with other glial cells but on a slower basis as it’s chemical
What are ligand gated ion channels?
Type of postsynaptic receptor
Binds with neurontransmitter
Ion-channel which open to allow ions to pass through the membrane
Leads to either depolarization or hyperpolarization
What are voltage gated ion channels?
In response to voltage (e.g. whether a cell is depolarized.)
Sodium channel and Potassium channel
What is ATP?
Adenosine Triphosphate
Inside the cell
Attach to pump, release one phosphate to the channel which releases energy for the pump to work
What is ADP?
Adenosine Diphosphate
The Adenosine Triphosphate after it’s lost one of its phosphates
di- 2 phosphates
tri- 3 phosphates
What is a H gate?
Channels are always open
H-gate inactivates (‘‘closes’’) the channel. This is a block that is put in the way of the channel. Only happens for sodium channels
What are myelin sheaths?
Myelin sheath speeds up communication between neurons
It surrounds the axon
Node of Ranvier: spaces between the myelin sheaths, it isn’t surrounded by the myelin sheath
What triggers channels to open?
Channels are activated by different type of neurotransmitters, e.g. key and lock, there needs to be a match to open the channel
If the neurotransmitter doesn’t fit the channel stays closed
Neurotransmitters bind to sites on the receptive neuron
What are presynaptic and postsynaptic cells?
Neurotransmitters are in the synaptic vesicles, which is in the presynaptic cell, released into the synapse, neurotransmitters are activated in the channels, the channels are located in the postsynaptic cell
Neurotransmitters are chemical signals
What is stage 1 in action potentials?
To reach equilibrium, sodium channels allow ions inside the neuron, these are chemically activated
Outside (sodium) is positively charged, inside (potassium) negatively charged, so outside positively charged ions are going inside the neuron
What happens in stage 2 (depolarizing) action potentials?
Excitation
Overshooting happens: more ions than needed are sent inside the neuron
Voltage increases
Majority of sodium is now inside the neuron
What happens in stage 3 (repolarization) action potentials?
At this point, potassium channels open so sodium channels close, electrically activated, negatively charged potassium ions are let into the cell, and positively charged ions are let out
Voltage decreases
Undershoot also happens here: Now sodium ions are mostly inside, while potassium ions are outside
What happens in stage 5 (the refractory period) in action potentials?
Neuron can’t be excited anymore during this period, neuron needs to go back to the resting potential to reach another action potential
What happens in an electrical transmission?
No gap between the synaptic cells
Gap junctions: neuron membranes touch
Both neurons are isopotential, meaning electrical changes in one neuron are instantaneously reflected in the other neuron
What is stage 4 (hyperpolarization) in action potentials?
Inhibition
The potential is negative because there are too many potassium ions
The potential is more negative than the resting state and the threshold which is required for triggering action potentials
Why are electrical synapses useful?
When information needs to be conducted more quickly, chemical signals are slower
What are spines in dendrites?
Knob at the end of the dendrite where the inputs are received from other neurons
What is a resting potential?
More negatively charged on the inside, positively charged on the outside
Not actively signalling
What is saltatory conduction?
Action potential jumps from one Node of Ranvier to the next Node of Ranvier
What are axons?
Long projection from the cell body
Longest are motor neurons
