Unformatted text preview: n depends on the summation of synaptic
potentials which spread passively to the neuron’s trigger zone.
– Up to 10,000 different presynaptic endings on a motoneuron
• In order to analyze neuronal integration at the cell level, we need
– passive properties of the postsynaptic cell (temporal / spatial
– synaptic inputs (excitatory / inhibitory?)
• highest excitatory postsynaptic potentials (EPSPs) are 0.2 - 0.4 mV in
• EPSPs are countered by inhibitory postsynaptic potentials (IPSPs) of
other cells… – there is location, size, shape, proximity of synergistic and
25 KNES 462 ©FK ‘08 all of that is leading up to the AP Signal Integration V receiving the input is graded but the action potetnial is all or nothing To fire
Not to fire id the stimuoi is too weak then there is no aciton potetnial at all. • this choice between competing alternatives also
reflects a fundamental activity of the brain! simular to the computer precessses aslo based on a binary code. 26 KNES 462 ©FK ‘08 THE AO --leaded to release of nuerotransmitters Signal Conduction I
• Action potentials (APs) are
– AP amplitude can be up to 110
– Duration: ~ 1 ms.
– Unlike input potentials, APs do not
decay as they travel down the
– AP signaling very stereotyped all simular
– Frequency coding of information!
27 ﬁring frequency
KNES 462 ©FK ‘08 the myalin sheet is interupted byt hte nodes of ranier---the action potetnialhelps it jump the ap 3 KNES 462 Signal Conduction II
• APs carried into the CNS by sensory neurons
often indistinguishable from APs carried out
• Intensity of sensation or speed of movement
are determined by frequency of APs;
• Duration of sensation or movement determined
by period over which APs are generated.
• Meaning of signal is determined entirely by the
neural pathway activated by that stimulus!
28 KNES 462 ©FK ‘08 Signal Output I
• Output takes place via synapses:
– electrical s.: also found in other body cells,...
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- Winter '13