4
JERALD J. BERNSTEIN
the central nervous system can be removed and be reconstituted often
with the return of normal function.
Recent findings have shown that removal of particular portions of
the brain of fish results in specific losses in behavioral patterns and perception. This has been a major finding since at one time it was thought
the removal of a particular portion of the brain did not result in deficits
in specific sensory, motor, or behavioral patterns, such as reproductive
behavior, because of the loss of particular areas of the brain.
It is the integrative function within the central nervous system to
which this chapter is devoted. Unfortunately, the wealth of information
which has been written on the subject far exceeds the space available.
II. ULTRASTRUCTURE
The central nervous system of vertebrates contains neurons and nonneuronal elements consisting of neuroglia, endothelia, ependyma, and
pericytes of blood vessel walls. In general the ultrastructure of neurons
of the fish central nervous system is similar to that of neurons found in
all vertebrates (Palay et al., 1962). The nerve cells have a rather large
nucleus with a distinct nucleolus. The nucleus is surrounded by a porous
double membrane. The inner membrane is the denser of the two, and
the outer membrane is continuous with the membranes of the extensive
vacuolar system within the cytoplasm of the cell (endoplasmic
reticulum).
Cytoplasm of the typical neuron perikaryon contains laminae of
ergastoplasm (rough endoplasmic reticulum, i.e., endoplasmic reticulum
lined by ribosomes) with free ribosomes interposed between the laminae.
In light microscopy this organelle stains with basic dyes and is the
characteristic Nissl body. Nissl bodies are not found as frequently in
fish neurons as in mammalian neurons. Therefore, as can be expected,
the bulk of the ribosomes are free in the cytoplasm. The Golgi apparatus
is a complex specialization of the endoplasmic reticulum and is comprised
of stacked cisternae and vesicles of smooth endoplasmic reticulum.
Organelles such as mitochondria are more or less evenly distributed in
the cytoplasm. Lysosomes may be present and are bound by a single
membrane. Mitochondria in fish are double membrane bound and often
contain tubular cristae. In addition, the cytoplasm of the perikaryon of
the neuron contains neurofilaments and often neurotubules.
Primary dendrites are similar in ultrastructure to the perikaryon with
rough endoplasmic reticulum that may extend into the basal regions of
JERALD J. BERNSTEIN
the central nervous system can be removed and be reconstituted often
with the return of normal function.
Recent findings have shown that removal of particular portions of
the brain of fish results in specific losses in behavioral patterns and perception. This has been a major finding since at one time it was thought
the removal of a particular portion of the brain did not result in deficits
in specific sensory, motor, or behavioral patterns, such as reproductive
behavior, because of the loss of particular areas of the brain.
It is the integrative function within the central nervous system to
which this chapter is devoted. Unfortunately, the wealth of information
which has been written on the subject far exceeds the space available.
II. ULTRASTRUCTURE
The central nervous system of vertebrates contains neurons and nonneuronal elements consisting of neuroglia, endothelia, ependyma, and
pericytes of blood vessel walls. In general the ultrastructure of neurons
of the fish central nervous system is similar to that of neurons found in
all vertebrates (Palay et al., 1962). The nerve cells have a rather large
nucleus with a distinct nucleolus. The nucleus is surrounded by a porous
double membrane. The inner membrane is the denser of the two, and
the outer membrane is continuous with the membranes of the extensive
vacuolar system within the cytoplasm of the cell (endoplasmic
reticulum).
Cytoplasm of the typical neuron perikaryon contains laminae of
ergastoplasm (rough endoplasmic reticulum, i.e., endoplasmic reticulum
lined by ribosomes) with free ribosomes interposed between the laminae.
In light microscopy this organelle stains with basic dyes and is the
characteristic Nissl body. Nissl bodies are not found as frequently in
fish neurons as in mammalian neurons. Therefore, as can be expected,
the bulk of the ribosomes are free in the cytoplasm. The Golgi apparatus
is a complex specialization of the endoplasmic reticulum and is comprised
of stacked cisternae and vesicles of smooth endoplasmic reticulum.
Organelles such as mitochondria are more or less evenly distributed in
the cytoplasm. Lysosomes may be present and are bound by a single
membrane. Mitochondria in fish are double membrane bound and often
contain tubular cristae. In addition, the cytoplasm of the perikaryon of
the neuron contains neurofilaments and often neurotubules.
Primary dendrites are similar in ultrastructure to the perikaryon with
rough endoplasmic reticulum that may extend into the basal regions of