Action Potentials And Synaptic Signalling Flashcards
What are graded potentials?
Graded potentials allow communication over short distances only whereas action potentials are both long and short
Also a small deviation from resting potential makes it either hyperpolarised or depolarised
Where are graded potentials found?
Occur most often in the dendrites and cell body of a neuron and produced by ligand or mechanically gated channels
Allows multiple signal inputs
What is an action potential?
Sequence of depolarisation and repolarisation
Which occur in the axon and nerve terminals
Produced by voltage gated ions
How can conduction velocity be increased?
By increasing the diameter of the nerve fibre which reduces resistance
Myelination - forcing current to pass further along the axon
Olivodendrocytes vs Schwann cells? What are they specific to?
Oligodendrocytes are specific to the CNS myelinate multiple axons
Schwann cells myelinate single axons in PNS
What is myelination?
Myelination is a multilayered lipid and protein covering called the myelin sheath and produced by Schwann cells/ oligodendrocytes
What do myelin sheaths do?
The sheath electrically insulates the axon and has gaps between each one called nodes of ranvier
What is saltatory conduction?
Nerve impulse conduction in which the impulse jumps from node to node
What is a synapse?
Is the function junction between one neuron and another or an effector like a muscle/gland
What are the two types of synapses?
Electrical synapses - gap junctions that line up directly and release ions
Chemical synapses - one way street from presynaptic cell to a postsynaptic cell and either cause excitatory or inhibitory graded potential.
Where can you find electrical synapses?
Found in several areas of the brain and NS
Important in the heart
Very fast as less gap between them and the effector
What does the neurotransmitter binding cause in chemical synapses?
Binding of neurtransitter causes change to membrane potential of target cell
If large enough this leads to cell firing an action potential and neurotransmitter either broken down by enzymes or pumped back into nerve terminals
