Biomedical Engineering Reference
In-Depth Information
d n 4 t 3 n g | 2
n 3 .
Figure 5.14
Illustration of selective properties of a resonant neuron (d) in comparison
with the frequency response of electronic components: (a) resistor;
(b) resistor in parallel with a capacitor and an oscillatory circuit formed
by a resistor; and (c) a capacitor and an inductance in parallel. The input
is a complex signal containing a range of frequencies, while the output is
analyzed using the Fast Fourier Method. 30
(Reprinted by kind permission of Elsevier BV.)
receptors. NMDA is a water-soluble synthetic substance that is not normally
found in biological tissue. First synthesized in the 1960s, NMDA is an excitocin
which has applications in behavioral neuroscience research. Researchers apply
NMDA to specific regions of an animal brain or spinal cord and subsequently
test for aberrant behavior. If behavior is compromised, it suggests that the
destroyed tissue was part of a brain region that made an important
contribution to the normal expression of that particular behavior. The cation
pore of the NMDA receptor allows the diffusion of both Ca 21 and Na 1 ,
although these processes are blocked by the presence of Mg 21 . When the
membrane is strongly depolarized, Mg 21 is cleared away and Ca 21 and Na 1
are allowed to diffuse through the membrane. As a result of the Ca 21 influx,
intracellular Ca 21 or Mg 21 activates a Ca 21 -dependent K 1 current that
eventually hyperpolarizes the membrane when there is a su cient build-up of
 
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