synapse and networks Flashcards
What is the input zone
where neurons collec adn integrate information, either from the environment or from other cells
what is the integration zone
where the decision to produce a neural signal is made
what is the conduction zone
where informaiton can be transmitted over great distances
what is the output zone
where the neuron transfers inforamiton to other cells
Where are leak channels and ion pumps
entire neural membrane
where are voltage-gated channels
axonal hillock (integration zone) and the axon (conduction zone)
where are voltage-gated Ca2+ channels?
axon terminals (output zone)
where are ligand-gated channels?
dendrites adn soma (input zone)
Where are voltage-gated ion channels common?
bacteria, viruses, plants and fungi
What did Camillo Golgi (1853-1934) do?
historical silver stainings of neurons
What did Santiago Ramon y Cajal (1853-1934) do?
the father of neuroscience’, brilliant neuroanatomist and artist who drew the microscopic structures of brains
Who shared the nobel prize for medicine and physiology in 1906
camillo Golgi and Ramon y Cajal
What is the neuron doctorin?
Brains are composed of separate neurons and other cells
2) Cells are independent
3) Neurons are polarised cells
4) Information is transmitted from cell to cell across tiny gaps (synapses)
At a synapse, where are signals transmitted to?
another neuron or to tissues
What is an electric synapse?
gap junctions connect the cytoplasm of two neurons
How big is the gap between membrane?
20-40nm
What is fast action?
Commanding escape responses (crayfish, fish)
What is synchronised activity?
Inhibitory neurons in mammalian brain, eye-moving muscles
Although slower, nearly all synapses are _____
chemical
What is resting potential
membrane potential when the neuron is at rest
When is it depolarisation
graded potential before reaching threshold.
when the neuron is excited (received signal)
Where are action potentials generated
in the integration zone if depolarisation reaches threshold. Signal transmission inside neuron
What are some frequently found synapses?
axo-dendric, axo-somatic, axo-axonic
What is golgi?
impregnated pyramidal cell in hippocampal area CA1, showing the soma and apical and basal dendrites
What is the signal transformation fo the presynaptic neuron during synaptic transmission?
depolarisation of the axon terminal membrane opens Ca2+ channels and Ca2+ ions enter the terminal because the intracellular concentration is lower.
The increase in Ca2+ concentration stimulates the release of neurotransmitter that is stored in vesicles. When these vesicles fuse with presynaptic membrane the neurotransmitter diffuses into the synaptic cleft.
what is the signal transforamtion of the post-synaptic neuron
The neurotransmitter either crosses the synaptic cleft and interacts with ionotropic receptors that are embedded in the membrane of the dendrite or soma (typically) of the postsynaptic neuron…
OR
Or the neurotransmitter crosses the synaptic cleft and interacts with metabotropic receptors
When do ligand-gated ion channels open?
when bound by neurotransmitter molecules
when does the problem of signal loss arise?
when transmission distances are longer
why are the neural membrane exposed at the nodes of ranvier?
for ion conductance through voltage-gated channels
what is saltatory conduction
Because the myelin insulation offers considerable resistance to the flow of ionic currents across the membrane, the action potential jumps from node to node.
Most neurons in the mammalian nervous system are…
short, unmyelinated
When and which signal is picked up by a neuron depends on the:
- type of neurotransmitter
- duration of neurotransmitter release
Example of transmitters at excitatory synapses
glutamate, aspartate, nAch
examples of transmitters at inhibitory synapses?
GABA, glycine, acetylcholine
What is temporal summation?
If the neurotransmitter is released for longer time into the synaptic cleft, then the postsynaptic potential is stronger
What is spatial summation
If postsynaptic potentials arrive together in the integration zone, they are summed up
what are spiking neurons?
if the membrane at the integration zone is depolarised above threshold an action potential will be generated
The more excitatory input arrives, the ____ the output signal
stronger
the more inhibitory input arrives, the _____ the output signal
weaker
Spatial and temporal summation at the synapses determine the strength of the signal when?
when it is passed on from one neuron to the next
What do feedback loops provide
direct or indirect input influencing signals and thus information
How do neurons communicate?
via electric signals
What are ionotropic receptors
ligand-gated ion channels
what are metabotropic receptors
coupled to G-protein
Saltatory conduction of singals in…
myelinised neurons
• Temporal and spatial summation of postsynaptic potentials in the integration zone determine what?
strength of the signal
