Morphology of Insect Sensilla

Question 1

What are sense cells?

Answer 1

interface between the environment and the insects CNS

- present on surface of insect

Question 2

Why can’t insect sensilla be too specific?

Answer 2

have very few compared to mammals

Question 3

How can a specific response be generated from sensilla of insects?

Answer 3

if many separate sensilla respond

Question 4

What are the different types of sensilla? (surface)

Answer 4

• olfaction
• vision
• mechanoreceptors
• gustation

Question 5

What are primary sense cells (Neurons)?

Answer 5

they receive the stimulus and transmit a message (electrical impulse) to the CNS

Question 6

What are two broad categories of primary sense cells?

Answer 6

• Type 1 Neurons

- Type 2 Neurons

Question 7

What are some functional types of type 1 neurons?

Answer 7

• mechanoreceptors (include sound receptors)
• light receptors (eyes, oceli)
• chemoreceptors (olfaction, gustation)

Question 8

What are type 1 neurons?

Answer 8

receptors associated with cuticle, derived from a single epidermal cell
- have hair

Question 9

What are type 2 neurons? what are they functionally alike?

Answer 9

receptors not associated with integument. Don’t have hair. are internal. x cuticular element
- proprioreceptors

Question 10

what are proprioreceptors?

Answer 10

receptors that respond to deformations and stresses (eg: stretch receptors)

Question 11

What do type 1 neurons sense?

Answer 11

touch, vibration, pressure, air currents, water currents, cutaneous tension

Question 12

What is the trichogen of type 1 neurons?

Answer 12

the inner sheath cell which produces the hair in trichoid sensilla

Question 13

What is the tormogen of type 1 neurons?

Answer 13

the outer sheath cell. in chemosensilla produces the fluid that bathes the dendrites

Question 14

What is the Neurilemma of type 1 neurons?

Answer 14

thecogene cell which ensheathes the nerve cell

- play a nutritive role for the nerve cell

Question 15

What is the sensory cell of type 1 neurons?

Answer 15

a neuron

Question 16

What are the neuron of mechanoreceptors like? how many are there?

Answer 16

mechanoreceptor sensilla contains a single neuron.

dendrites of the neuron may be fused to form a cuticular filament

Question 17

How many neurons do chemoreceptors usually have?

Answer 17

chemoreceptors usually contain more than one neuron.

Question 18

How are mechonoreceptors on the integument categorized?

Answer 18

by their morphology

Question 19

What are the two types of mechanoreceptor?

Answer 19

1. trichodea

2. Campaniform sensilla

Question 20

What are trichodea?

Answer 20

sensory hairs with scolopale affixed to the base of a hair

Question 21

Where are trichodea found in the highest concentrations?

Answer 21

the tarsi, antennae, mouthparts and cerci

Question 22

What are two types of trichodea?

Answer 22

1. long fine hairs - habituate rapidly

2. short, stiff hairs or pegs - habituate slowly

Question 23

What do long, fine hairs of the trichodea respond to?

Answer 23

subtle stimuli such as wind, gravity, posture.

Question 24

What do short, stiff hairs or pegs of the trichodea respond to?

Answer 24

direct deflection (touch)

Question 25

What are campaniform sensilla?

Answer 25

mechanoreceptors which terminate in a dome-shaped plate of cuticle.
- neuron determines the degree of arching of the domed cap

Question 26

Where are campaniform sensilla found in greatest concentration?

Answer 26

leg bases, wing bases and antennae

Question 27

What do campaniform sensilla respond to?

Answer 27

• pressure changes
• body orientation
• location of legs, wings, antennae

Question 28

What are two types of internal proprioreceptors?

Answer 28

1. chordotonal sensilla

2. Stretch receptors

Question 29

What are chordontonal sensilla?

Answer 29

similar to trichodea but no cuticular component. usually exists as an organ
- a strand of nervous tissue stretched between two points (of cuticle)

Question 30

What are chordontonal sensilla triggered by?

Answer 30

triggered internally by pressure changes eg:

• how much air in trachea
• how much hemolymph in body cavity

Question 31

What do chordontonal sensilla measure?

Answer 31

differences in length between the two points

Question 32

What are stretch receptors?

Answer 32

multipolar neurons (multiple dendrites) attached to a modified muscle or connective cell.

Question 33

What do stretch receptors respond to?

Answer 33

differences in stretch

eg: between intersegmental membranes

Question 34

What are three types of sound receptors?

Answer 34

1. johnston’s organ
2. tympanal organ
3. Subgenual organs

Question 35

What is the johnston’s organ?

Answer 35

a group of chordotonal sensilla in the pedicel (socket) of antennae

Question 36

What is the tympanal membrane/organ?

Answer 36

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

Question 37

What are subgenual organs?

Answer 37

chordotonal sensilla in the tibiae of many insects. Detect vibrations in the substrate

Question 38

What are tympanal membranes/organs used for?

Answer 38

• mate location

- defense

Question 39

What are chemosensory hairs?

Answer 39

receptors which usually have a single pore at the tip of the trichodeum. olfactory hairs are multiporous however

Question 40

Where are chemosensory hairs found?

Answer 40

the legs, external labellum, and internal labellum

Question 41

How many neurons does each chemosensory hair contain? what the the neurons used for?

Answer 41

5

• 2 different salt sensitivity cells
• 1 sugar cell
• 1 water cell
• mechanoreceptor

Question 42

Why is the varied times to habituation important in chemosensilla?

Answer 42

the brain received a continued flow of information - retains sensitivity without fatiguing the individual receptors