Unformatted text preview: Unit 6 - Reception & Integration: The Nervous System
1. Describe the origin of the insect nervous system.
2. Identify the major structures of the insect nervous system and describe their function.
3. Compare and contrast the physical structure and functions of compound eyes and
4. Differentiate between the two types of simple eyes.
5. Describe the four types of Mechanical receptors insects possess. Introduction
Do insects have noses? Why or why not?
No, They have receptors on their antenna and other parts of their body to pick up scents. Briefly describe how insects smell beginning with chemical molecules binding to
Their olfactory neurons are within their antennae, mouthparts or even their legs. When a female moth sends out a chemical to attract a mate,
t he male moth picks up the chemicalmolecules with his antennae, where his
olfactory neurons are located. These neurons ﬁ re a message to his brain which interprets the signal and stimulates neurons that
cause the male to ﬂ y, migrating towards the female's scent. Male moths usually have very large antennae and these
antennae have small projections on the sides you can see where they can pick up of lots and lots of scent. Nervous System Development
Which embryonic layer gives rise to the nervous system?
Define ganglion: ectoderm a dividing cell that will develop into neurons or glia. neuroblasts ﬁrst developed into a mass of nerve Which pair of ganglia fuse to form the supraesophageal ganglion? ﬁrst 3 What forms the ventral nerve cord? fourth through sixth pairs fuse to form the subesophageal ganglion.
The remaining ganglion pairs fuse and form the ventral nerve cord. If an insect is highly specialized what kind of ganglia fusion takes place?
all the ganglia will fuse to form one large mass in the head and prothorax Nervous System Functions
Label diagram 1:
Diagram 1 medial
ocellus deutocerebellum corpus
allatum tritocerebellum subesophageal
ganglion Describe the functions of the following nervous system structures:
Supraesophageal ganglion (which three structures make up this part of the brain?):
protocerebrum, the deutocerebrum and the tritocerebrum. Protocerebrum: receives and processes nerve signals from the insect's eyes
then interprets the message and sends a response Deutocerebrum:
receives impulses from the antenna, interprets the message and controls the movement of the antenna Tritocerebrum: receives input from the labium nerves, subesophageal ganglion and assists in
controlling the digestive, circulatory, and endocrine systems Subesophageal ganglion:
coordinates and controls the maxilla, mandibles and the labium—all parts of the mouth. Corpora allata:
an endocrine gland which generates juvenile hormone; as such, it plays a crucial role in metamorphosis. Neurons
Fill in the following definitions.
neuron: s erve as information highways within the insect ʼs body and they may be unipolar with one end,
bipolar with two or multipolar with many ends. perikaryon (cell body): contains the nucleus and the typical cellular organelles is called the soma
dendrite: The long, thin cytoplasmic extension that conducts the nerve impulse
When a nerve impulse reaches the synapse, it releases a chemical messenger. This is called a
neurotransmitter and this chemical messenger defuses across the gap,
the synapse, and triggers a new impulse in the next dendrite of one or more connecting neurons. region of information input Eyes
List the two simple eye types: ocelli and stemmata What is the function of the lens in all eye types? focusing light Where are the color pigments located? rhabdoms
What happens when light rays hit these color pigments?
a chemical reaction which ﬁ res neurons surrounding the rhabdoms. Impulses pass down the axon and are sent to the
protocerebrum. There they are processed and the insect accomplishes vision. Do ocelli form clear images?
do not form clear images, but are most likely used to detect
changes in light, such as when a shadow is cast by an approaching predator. Define pigment cells:
surround the outer rim of the rhabdom cluster. shield surrounding structures from the piercing light rays. How are stemmata different than ocelli? structurally an intermediate between the ocelli and the more complex compound eyes. They have a corneal lens, but only have one rhabdom.
You only see stemmata on caterpillars and the larva of other holometabolous insects.usually located in a small cluster on the side of the
insect's head, but provide the insect with very limited images of the world. lost during metamorphosis and replaced by the adult compound eye. Define ommatidium: compound eyes have several facets, each with their own lens. Each facet is called an ommatidium. What two structures focus light onto the rhabdom in an ommatidium? corneal lens and crystalline cone What type of image does a compound eye form?
Each ommatidium forms a portion of the image, creating a multifaceted picture in the brain. As you increase the number of ommatidia, what happens to the resolution?
more ommatidium an eye has, the higher the image resolution, so the clearer the picture is How is an ocellus different than a compound eye, or rather how is an ocellus different
than one ommatidium? see table Receptors
What is chemoreception? ability to sense molecules through taste and smell. What are chemoreceptors?
Receptors that detect chemical molecules in the surrounding air, such as olfactory receptors in a mothʼs antenna How do flies taste their food? through their feet Describe a sensillum:
Insects smell by capturing small molecules of scent ﬂ oating in the air. These molecules enter a sensillum, through tiny pores.
two classes of sensilla: uniporus and multiporous. Inside the sensilla, the molecules attachto receptor molecules embedded
in the dendrite membranes of sensory nerve cells. Each molecule embedded in the dendrite is designed to receive or sense
the presence of a speciﬁ c typeof odor or molecule.It's kind of like a lock and key system: speciﬁ c smells ﬁ t into a speciﬁ c lobe on a dendrite. What is a mechanoreceptor? how insects use receptors to detect movement What is a trichoid sensillum?
Describe how an insect detects movement.
hair-like setae that have a single dendrite attached at their base. When these sensilla are
brushed, the movement of the hairis immediately sensed by the ﬁ ring of a neuron. That ﬁ ring transmits an impulse to
the rest of the nervoussystem. These trichoid sensilla are not only used to sense what's passing by the insect ʼs body but they're also used to
sense the relative position of an insect ʼs appendages. ...
View Full Document
- Summer '08
- Ventral nerve cord, compound eyes, insect ʼs body, Mechanical receptors insects, subesophageal ganglion