1. ANATOMY AND PHYSIOLOGY O F THE CENTRAL NERVOUS SYSTEM
3
will indicate if the graded threshold was of sufficient amplitude to discharge the neuron resulting in an action potential or spike (excitation),
or the postsynaptic membrane may become hyperpolarized owing to
axonal discharge ( inhibition) so that subsequent information will not
generate an action potential. The interaction or the balance of inhibitory
and excitatory information converging on a neuron makes up the sum
total of the postsynaptic neuronal membrane characteristics. This synaptic function with all its parts may well be the anatomical area that transforms a digital input into an analog system. The information, then, is
passed from the periphery into the central nervous system and to diflerent integrative areas within the central nervous system itself. The sum
total of the behavior of the animal then can be summarized by the
integrative area which is established by the anatomical connections of the
nervous system and the response of the neurons to the encoded messages.
There have been many experimental methods and designs developed
to ascertain the integrative function of various portions of the nervous
system of fish. Deficit function work has been carried out by removing
parts of the nervous system in order to locate portions of the brain which
are responsible for special integrative action. For the most part behavioral end points have been used in this type of experimentation.
That is, following lesion, animals have been placed in certain behavioral
situations to ascertain the animal's performance before and after the
loss of a particular area. Stimulation of portions of the nervous system
also has been utilized to ascertain the function of specific neural centers.
Electrical stimulation can elicit specific behavioral patterns. In addition,
electrophysiological recording from the various neural elements involved
in integration has yielded valuable information on the characteristics of
processing of neuronal information. These types of studies have demonstrated interactions of the various neural centers within the nervous
system proper and the interaction of the nervous system with the periphery ( central control of periphery). The neuroanatomical relationships
of the various centers in the central nervous system have been advanccd
by the use of modern techniqucs such as the use of specific stains for
the degeneration of neural pathways and the utilization of radioactive
tracers for the study of axoplasmic flow. In addition, electron microscopy
has revealed several unusual features of the fish nervous system.
The study of the integrative function of the central nervous system
of fish is aided by one of the most remarkable features of the system
which is its ability to regenerate. Thus, one can remove an area in the
fish central ncrvous system and have the area reconstituted. This characteristic of the central nervous system makes the fish an elegant experimental animal for the study of central nervous system function. Parts of
3
will indicate if the graded threshold was of sufficient amplitude to discharge the neuron resulting in an action potential or spike (excitation),
or the postsynaptic membrane may become hyperpolarized owing to
axonal discharge ( inhibition) so that subsequent information will not
generate an action potential. The interaction or the balance of inhibitory
and excitatory information converging on a neuron makes up the sum
total of the postsynaptic neuronal membrane characteristics. This synaptic function with all its parts may well be the anatomical area that transforms a digital input into an analog system. The information, then, is
passed from the periphery into the central nervous system and to diflerent integrative areas within the central nervous system itself. The sum
total of the behavior of the animal then can be summarized by the
integrative area which is established by the anatomical connections of the
nervous system and the response of the neurons to the encoded messages.
There have been many experimental methods and designs developed
to ascertain the integrative function of various portions of the nervous
system of fish. Deficit function work has been carried out by removing
parts of the nervous system in order to locate portions of the brain which
are responsible for special integrative action. For the most part behavioral end points have been used in this type of experimentation.
That is, following lesion, animals have been placed in certain behavioral
situations to ascertain the animal's performance before and after the
loss of a particular area. Stimulation of portions of the nervous system
also has been utilized to ascertain the function of specific neural centers.
Electrical stimulation can elicit specific behavioral patterns. In addition,
electrophysiological recording from the various neural elements involved
in integration has yielded valuable information on the characteristics of
processing of neuronal information. These types of studies have demonstrated interactions of the various neural centers within the nervous
system proper and the interaction of the nervous system with the periphery ( central control of periphery). The neuroanatomical relationships
of the various centers in the central nervous system have been advanccd
by the use of modern techniqucs such as the use of specific stains for
the degeneration of neural pathways and the utilization of radioactive
tracers for the study of axoplasmic flow. In addition, electron microscopy
has revealed several unusual features of the fish nervous system.
The study of the integrative function of the central nervous system
of fish is aided by one of the most remarkable features of the system
which is its ability to regenerate. Thus, one can remove an area in the
fish central ncrvous system and have the area reconstituted. This characteristic of the central nervous system makes the fish an elegant experimental animal for the study of central nervous system function. Parts of