Nerves and Synapses Flashcards
What are the main regions of a neuron?
Cell body, dendrites, axon and axon terminal.
How many neurons are there in the human nervous system?
More than 10^11
What characteristic allows the nervous system to process information?
Neurons are arranged in neural networks.
What are the three types of neurons?
Afferent, inter and efferent.
What is the function of interneurons?
To integrate and store information
What is the standard membrane potential at rest?
-70mV
What causes the membrane potential?
Differences in ion distribution across the membrane and differences in permeability to ions.
What causes the membrane potential to be negative at rest?
Potassium ions leaving the cells.
What is responsible for the membrane potential?
Sodium and potassium ion receptors
How are the inactivation and activation gate arranged at rest?
Inactivation gates open, activation gates closed so no ions can move.
What does the activation potential result in?
A hyper shoot where the potential is less than the resting potential.
How do invertebrates increase action potential speed?
By increasing fibre diameter
What do vertebrate nervous systems use to increase action potential speed?
Myelination and saltatory conduction.
What cells carry out myelination?
Schwann cells
What are Nodes of Ranvier?
Gaps between areas of the axon surrounded by Schwann cells.
What is saltatory conduction?
The action potential jumps from one node of Ranvier to the next.
How does myelination increase speed?
It reduces the need for opening and closing channels.
Where do neurons communicate with each other?
At synapses
What are released at synapses?
Neurotransmitters
What is a graded potential?
A small change in membrane potential either positive or negative.
When will a graded potential become an action potential?
When depolarisation exceeds the threshold at the axon hillock.
What causes a graded potential?
Release of a neurotransmitter.
What is the inhibitory action at the post synaptic cell?
Hyperpolarisation
What does spatial summation add up?
Simultaneous influences of simultaneous synapses at different sites on the post synaptic cell.
What does temporal summation add up?
Post-synaptic potentials generated at the same time in rapid sequence.
What is convergence of input?
When once cell is influenced by many others.
What is divergence of output?
When one cell influences many others.
What is the benefit of electrical signals?
They are faster than chemical signals.
What is the benefit of chemical signalling?
It allows more control.
