Introduction to Neurones, Nerve Conduction and Synaptic Transmission Flashcards
What is the soma?
The cell body
What is the function of the soma?
It is the metabolic area, it interprets the excitatory and inhibitory signals to produce a net signal.
Which organelles does the soma contain?
Nucleus, mitochondria, Ribosomes and endoplasmic reticulum (RER)
What is the function of dendrites?
The receive input from other neurones and convey graded l electrical signals passively to the soma
What is the function of the axon hillock?
The site of initiation of all or none action potential
Why is the axon hillock area highly excitable?
It contains a high concentration of voltage gated sodium channels
What is the function of the axon?
Conducts output signals (Action potentials) to other neurones or cells and mediates transport of materials between soma and presynaptic terminal.
What is a synapse?
A point of chemical communication between neurones.
Neurones can be classified by shape, name them (4)
Unipolar
Pseudounipolar
Bipolar
Multipolar
What is the difference between Golgi 1 and 2 axons
Golgi 1- Long
Golgi 2- Short
Describe action potential generation
Depolarisation Threshold reached (~-60mV) Voltage activated Na channels open Na influx Depolarisation of cell Voltage activated K channels open K efflux Repolarisation
Why can passive signals not be transmitted for long distances?
The nerve cell membrane is leaky, and hence some of the current is lost across this (Leaky hose analogy)
What is the length constant?
The distance it takes for voltage to reach 37% of its original value (Denoted Lambda)
How does a passive neuronal signal diminish with distance
Exponentially
Which 2 factors are distance travelled by current determined by?
Resistance of the membrane
Axial resistance of axoplasm
How are length constant and current distance related?
The longer the length constant, the greater the distance spread
What is the water pipe analogy?
The greater the diameter of an axon, the less the internal resistance and the faster a signal can be conducted.
How is conduction distance increased in the human body?
Myelin sheath
Increases membrane resistance and therefore conduction loss
Increases length constant
Further transmission
Where are Schwann cells found and how do they wrap around axon?
PNS- Several layers wrap around axon
Where are oligodendrocytes found and how do they wrap around axons?
CNS- One wraps around many axons
What is saltatory conduction?
Current jumps from one excited node of ranvier to the next, as opposed to a continuous flow.
Synapses are classed morpholigcally, name them from most to least common (3)
Axodendritic
Axosomatic
Axoaxonic
What is the most frequent excitatory transmitter in the CNS?
Glutamate
What are the most frequent inhibitory transmitters in the CNS?
GABAa
Glycine
How does glutamate work?
Activates postsynaptic, cation selective, ionotropic receptore–> depolarisation + excitatory response
How do GABAa and Glycine work
Activates postsynaptic anion selective ionotropic receptors–>hyperpolarisation + inhibitory response
Describe spatial summation
Many inputs converge upon a neurone to determine it’s output
Describe temporal summation
A single input modulates output by variation in action potential frequency of that input
All transmitters can activate metabotropic GPC receptors except 1, which is it?
Glycine
Which transmitters activate Ionotropic ligand gated receptors
Glutamate GABA Glycine 5HT Acetylcholine
