Describe Hygroreceptors, phonoreceptor, Tactilereceptors, Thermoreceptors, and propioreceptors
Hygroreceptors:
Hygroreceptors
(Hygro=moist) detect the water content of air. For example some insects have
hygroreceptors that can detect small changes in the ambient relative humidity.
This sense enables them to seek environments with a specific humidity or to
modify their physiology or behaviour with respect to the ambient humidity to
control the opening or closing of spiracles.
Zoologists have
identified a variety of hygrosensory structures on the antennae, pulps, under
side of body and near the spiracles of insects.
Phonoreceptors:
Phonoreceptors
(Phone=voice + receptor) that respond to sound have been demonstrated only in
insects, arachnids and centipedes although other invertebrates seem to respond
to sound induced vibrations of the substratum. For example, crickets,
grasshoppers and cicados possess phonoreceptors called tympanic or tympanal
organs. This organ consists of a flexible tympanum that covers an internal sac
that allows the tympanum to vibrate when sound waves strike it. Sensory neurons
attached to tympanum are stimulated and produce a generator potential.
Proprioreceptor:
Proprioreceptors (Propricus=one’s self + receptors) commonly
called “stretch receptors” are internal sense organs that respond to
mechanically induced changes caused by stretching, compression, bending or
tension. These receptors give an annual information about the movement of its
body parts and their position relative to each other.
Proprioreceptors
have been most thoroughly studied in arthropods where they are associated with
appendage, joints and body extensor muscles. In these animals the sensory neurons
involved in proprioreception are associated with and attached to some part of
the body that is stretched. These parts may be specialized muscle cells,
elastic connective tissue fibres or various membranes that span joints. As
these structures change shape, sensory nerve endings of the attached nerves
distort accordingly and initiate a generator potential.
Tactilereceptors:
Tactile or touch
receptors are generally derived from modification of epithelial cells
associated with sensory neurons. Most tactile receptors of animals involve
projection from the body surface e.g. various bristles, spines, setae and
tubercles. When an animal contracts an object in the environemtn these
receptors are mechanically deformed. These deformations activate the receptor
which in turn activates underlying sensory neurons initiating a generator potential.
Most tactile receptors are also sensitive to mechanically induced vibrations
propagated through water or a solid substrate.
Tube dwelling
polychaetes bear receptors that allow them to retract quickly into their tubes
in response to movements in their surroundings. Web building spiders have
tactile receptors that can sense struggling prey in webs through vibrations of
the web threads.
Thermoreceptors:
Thermorecepetors
(Thermo=heat + receptors) respond to temperature changes. Some invertebrates can
directly sense differences in environmental temperatures.
Protozoa
paramecium collects in areas where water temperature is moderate and it avoids
temperature extremes. Heat sensing mechanism draws Leeches and ticks to warm
blooded hosts. Certain insects, some crustaceans and horse shoe crab (limulus)
can also sense thermal variations.
Comments
Post a Comment