Morphology of Insect Sensilla Flashcards
What are sense cells?
interface between the environment and the insects CNS
- present on surface of insect
Why can’t insect sensilla be too specific?
have very few compared to mammals
How can a specific response be generated from sensilla of insects?
if many separate sensilla respond
What are the different types of sensilla? (surface)
- olfaction
- vision
- mechanoreceptors
- gustation
What are primary sense cells (Neurons)?
they receive the stimulus and transmit a message (electrical impulse) to the CNS
What are two broad categories of primary sense cells?
- Type 1 Neurons
- Type 2 Neurons
What are some functional types of type 1 neurons?
- mechanoreceptors (include sound receptors)
- light receptors (eyes, oceli)
- chemoreceptors (olfaction, gustation)
What are type 1 neurons?
receptors associated with cuticle, derived from a single epidermal cell
- have hair
What are type 2 neurons? what are they functionally alike?
receptors not associated with integument. Don’t have hair. are internal. x cuticular element
- proprioreceptors
what are proprioreceptors?
receptors that respond to deformations and stresses (eg: stretch receptors)
What do type 1 neurons sense?
touch, vibration, pressure, air currents, water currents, cutaneous tension
What is the trichogen of type 1 neurons?
the inner sheath cell which produces the hair in trichoid sensilla
What is the tormogen of type 1 neurons?
the outer sheath cell. in chemosensilla produces the fluid that bathes the dendrites
What is the Neurilemma of type 1 neurons?
thecogene cell which ensheathes the nerve cell
- play a nutritive role for the nerve cell
What is the sensory cell of type 1 neurons?
a neuron
What are the neuron of mechanoreceptors like? how many are there?
mechanoreceptor sensilla contains a single neuron.
dendrites of the neuron may be fused to form a cuticular filament
How many neurons do chemoreceptors usually have?
chemoreceptors usually contain more than one neuron.
How are mechonoreceptors on the integument categorized?
by their morphology
What are the two types of mechanoreceptor?
- trichodea
2. Campaniform sensilla
What are trichodea?
sensory hairs with scolopale affixed to the base of a hair
Where are trichodea found in the highest concentrations?
the tarsi, antennae, mouthparts and cerci
What are two types of trichodea?
- long fine hairs - habituate rapidly
2. short, stiff hairs or pegs - habituate slowly
What do long, fine hairs of the trichodea respond to?
subtle stimuli such as wind, gravity, posture.
What do short, stiff hairs or pegs of the trichodea respond to?
direct deflection (touch)
What are campaniform sensilla?
mechanoreceptors which terminate in a dome-shaped plate of cuticle.
- neuron determines the degree of arching of the domed cap
Where are campaniform sensilla found in greatest concentration?
leg bases, wing bases and antennae
What do campaniform sensilla respond to?
- pressure changes
- body orientation
- location of legs, wings, antennae
What are two types of internal proprioreceptors?
- chordotonal sensilla
2. Stretch receptors
What are chordontonal sensilla?
similar to trichodea but no cuticular component. usually exists as an organ
- a strand of nervous tissue stretched between two points (of cuticle)
What are chordontonal sensilla triggered by?
triggered internally by pressure changes eg:
- how much air in trachea
- how much hemolymph in body cavity
What do chordontonal sensilla measure?
differences in length between the two points
What are stretch receptors?
multipolar neurons (multiple dendrites) attached to a modified muscle or connective cell.
What do stretch receptors respond to?
differences in stretch
eg: between intersegmental membranes
What are three types of sound receptors?
- johnston’s organ
- tympanal organ
- Subgenual organs
What is the johnston’s organ?
a group of chordotonal sensilla in the pedicel (socket) of antennae
What is the tympanal membrane/organ?
consists of a membrane stretched over a tracheal air sac ( enlarged spiracle) to produce a drum. Sound waves vibrate the membrane to which chordotonal sensilla respond
What are subgenual organs?
chordotonal sensilla in the tibiae of many insects. Detect vibrations in the substrate
What are tympanal membranes/organs used for?
- mate location
- defense
What are chemosensory hairs?
receptors which usually have a single pore at the tip of the trichodeum. olfactory hairs are multiporous however
Where are chemosensory hairs found?
the legs, external labellum, and internal labellum
How many neurons does each chemosensory hair contain? what the the neurons used for?
5
- 2 different salt sensitivity cells
- 1 sugar cell
- 1 water cell
- mechanoreceptor
Why is the varied times to habituation important in chemosensilla?
the brain received a continued flow of information - retains sensitivity without fatiguing the individual receptors
