Information Processing Flashcards by Cosima von U

Pathway of information in neurons

Dendrites: intake of information
Nucleus: information processing
Axon: transport/ conduction of information
Presynaptic terminal: information transfer

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Synapses

weakening/strengthening and integration of signals
electrical
chemical

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Electrical Synapses

Gap junction
No transmitter, controlled by charge
Close membranes, connected by ion pipe
Synchronization of cells with same function
Reciprocal, without delay, no processing

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Chemical

Neurotransmitter to synaptic cleft, only one direction

Slower, but complex signal processing

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Structure of chemical synapses

Presynaptic terminal (Mitochondria, Vesicles with neurotransmitter, sending neuron)
Synaptic cleft
Subsynaptic membrane as part of postsynaptic membrane (receptors)

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Transfer at chemical synpase

AP coming in at presynaptic terminal -> dumping of neurotransmitter in synaptic cleft
NT reaching receptor -> change of permeability -> potential shift
Amount of transmitter binding if inhibiting or exciting

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Principles of neurotransmitter

Short distance, only between two cells via dendrites

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Vesicles

From Golgi-apparatus -> fusion with cell membrane -> into synaptic cleft
Main and co-transmitters

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Calcium Ions

Release of neurotransmitters only if enough CA2+ in extracellular fluid
AP -> new membrane potential at presynaptic terminal -> CA2+ channels opening -> CA2+ coming in -> if enough intracellular fluid fusion of vesicles and cell membrane

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Receptors and ligands

Change in shape when binding
One to many, many to one affinity
Medicines similar sjape

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Ligand-gated ion channels

Direct, type I, building own ion channel
Conformation change to open by NT
Selective, fast (sensory and motor system)

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Metabotropic receptors

slower, but more variable
Indirect, type II
G Protein attached to Membran protein on inside -> NT binding with protein -> open channels

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Auto receptors

Presynaptic membrane

Feedback (own transmitter release)

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Chemical characteristics of NT

Monoamines
Amino Acids
Peptides

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Acetycholin

Excitatory transmitter in PNS

important in motor function, vegetative system, glands

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Glutamate

most important NT in brain, stimulate for learning

GABA

most important inhibiting NT in brain

4 conditions from thousands of incoming signals

Neutralisation
Hyperpolarisation
Depolarisation
Depolarisation until AP+ threshold exceeded

Tetanic potentation

Tetanic stimulation: fast, repetitive at nerve/muscle cell
Potentiation: Over-proportional increase of effect at postsynapse
Posttetanic petentiation: effect lasting longer than stimulation

Depression mechanism

Presynaptic depression: Decrease of subsynaptic reaction -> lass vesicle -> repetitive stimulation
Receptor desensitisation: when constantly high concentration of neurotransmitters -> receptor resistant/ no effect

Divergence

Many target cells aroused by one neuron (fine and gross motors skills, motor units redundance)

Convergence

Many terminals at dendrite

Presynaptic inhibition

While AP: CI- channels open-> neutralisation of CA2+

Before AP: Hyperpolarisation so depolarisation is difficu

Descending Inhibition

Cushioning pain

Onward Inhibition

by an interneuron (inhibition of antagonist muscle)

Backward inhibition

inhibition of neuron that aroused inhibiting one

Lateral Inhibition

Inhibition of neighbouring neurons -> higher contrast

Membrane Potential

Different concentration in intra-extracellular fuid Intra = - (KA+, A-, Na+, Cl-) Extra = + (Na+, Cl-) Different sorts of ions and different ions concentration

Membrane permeability

Membran potential not possible if cell membrane permeable for every ion -> ion channel High permeability for K+, Cl- low for NA+

Electrochemical gradient

Potential: From same charged to negative charged (Na+ via sodium-potassium) Concentration Gradient: Diffusion (osmotic pressre)

Ion transport

Active: Using ATP, sodium potassium pump Passive: No ATP, free diffusion, feasible diffusio Alongside Membrane (Passive/Active Conduction)

Passive/Active Conduction

Passive: (depolarisation, short distances, very fast, but loosing) Active: (AP by nerve impulse, long distances, self-reinforcing, all or non law)

Refractory Phase

Absolute: During Depolarisation (impossible to trigger another AP) Relative: (during late repolarisation and hyperpolarisation, stronger stimulus the more frequent AP's)

Node of Ranvier

Solution for electrical isolation | Saltatory Conduction