Insect Nervous System Overview

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Questions and Answers

What role do the thoracic ganglia play in an insect's nervous system?

They facilitate gaseous exchange.

They manage olfactory learning and memory.

They control sensory integration.

They govern the locomotor organs and innervate muscles. (correct)

Which part of the insect's nervous system is mainly involved in olfactory learning and memory?

Mushroom body (correct)

Abdominal ganglia

Ventral nerve cord

Thoracic ganglia

What are spiracles in an insect's body primarily used for?

Locomotive control

Gaseous exchange (correct)

Muscle innervation

Nervous signal transmission

What characterizes the abdominal ganglia in the ventral nerve cord?

They are variable in number. Signup and view all the answers

What additional function is performed by the meso- and meta-thoracic ganglia compared to the first three thoracic ganglia?

Regulating wing movements. Signup and view all the answers

What is the primary function of the plasmatocyte in the blood?

Aids in phagocytosis Signup and view all the answers

Which phase of the heart's function involves the expansion of the heart?

Diastole Signup and view all the answers

What is the role of incurrent ostia in the heart?

Facilitate the entry of blood into the heart Signup and view all the answers

What is a characteristic of the cystocyte?

Obscures the nucleus with cytoplasmic inclusions Signup and view all the answers

What happens during the systole phase of the heart?

Blood is pumped into the aorta Signup and view all the answers

How does haemolymph function as a lubricant?

Keeps internal cells moist Signup and view all the answers

Which type of haemocyte is described as having a distinct fat droplet?

Adipo haemocytes Signup and view all the answers

What is the primary mechanical action of the heart for blood circulation?

Contraction and relaxation Signup and view all the answers

What is the most common mechanism of sound production in the Pentatomoid groups?

Rubbing a file on the ventral surface by a scraper on the legs Signup and view all the answers

In which group of insects is sound commonly produced by vibration of a membrane driven by muscles?

Homoptera Signup and view all the answers

What is a unique feature of sound production observed in Acherontia (Lepidoptera)?

Stridulation through air stream via proboscis Signup and view all the answers

What describes the type of circulatory system present in insects?

Blood flows through the body cavity known as haemocoel Signup and view all the answers

What does the dorsal sinus contain in the circulatory system of insects?

Heart Signup and view all the answers

Which substance is found between the sternum and the ventral diaphragm in the insect circulatory system?

Ventral or perineural sinus Signup and view all the answers

The return of the tymbal muscle to its normal position is primarily due to what feature?

Elasticity of the surrounding cuticle Signup and view all the answers

What phenomenon describes the presence of three sinuses in an insect's haemocoel?

Circulatory separation mechanism Signup and view all the answers

What surrounds each ganglion and provides mechanical support for the nervous system in insects?

Neural lamella Signup and view all the answers

What is the primary function of glial cells associated with individual nerves in the insect nervous system?

Support and repair of neurons Signup and view all the answers

Which segment of the insect nervous system consists of the brain and segmental ganglia?

Central Nervous System Signup and view all the answers

What region of a ganglion contains the axons and dendrites of interneurons and motor neurons?

Neuropil Signup and view all the answers

What anatomical structure acts as a brain-blood barrier in the insect nervous system?

Perineurium Signup and view all the answers

Where does nutrient and excretion provision occur within the insect ganglia?

By diffusion through the sheath of the ganglia Signup and view all the answers

What is the primary function of the tracheal system in insects?

To transport oxygen Signup and view all the answers

Which type of nervous system in insects is primarily responsible for involuntary functions?

Visceral Nervous System Signup and view all the answers

What is the first ganglion in the insect's central nervous system called?

Subesophageal ganglion Signup and view all the answers

Which structures connect the longitudinal tracheae between the two sides of an insect's body?

Transverse commissures Signup and view all the answers

Where does the head of an insect receive oxygen from in the tracheal system?

From spiracle 1 Signup and view all the answers

What differentiates the tracheal system in Apterygota compared to most other insects?

Unconnected tracheal tufts Signup and view all the answers

Which part of an insect's body is primarily supplied by the dorsal trunks?

Heart and dorsal muscles Signup and view all the answers

What is the function of the constricted connecting tubes in some insects' tracheal systems?

To isolate the tracheal system of the head Signup and view all the answers

Which structures in the tracheal system are responsible for delivering oxygen to the central nervous system?

Ventral trunks or transverse commissures Signup and view all the answers

What is the role of the tracheoles in the insect tracheal system?

To run to the individual cells for oxygen delivery Signup and view all the answers

What is the primary function of the Stomatogastric nerve system (SNS)?

Regulate food uptake and transport Signup and view all the answers

Which part of the insect nervous system is known as the major association center?

Brain Signup and view all the answers

Which ganglia are primarily involved in the control of food passage through the gut and crop emptying?

Frontal and hypocerebral ganglia Signup and view all the answers

What structure is associated with higher-order sensory integration and learning in insects?

Mushroom body Signup and view all the answers

How is the peripheral nerve system (PNS) characterized in insects?

Consists of all sensory neurons Signup and view all the answers

What is the relationship between the optic lobes and eye size in insects?

Optic lobes develop proportionally to eye size Signup and view all the answers

What type of neurons are part of the peripheral nerve system (PNS)?

Sensory neurons exclusively Signup and view all the answers

Which of the following accurately describes the structure and components of the Central Nervous System (CNS) in insects?

Includes brain and ventral nerve cord with many ganglia Signup and view all the answers

Study Notes

Brain

Proto-, deuto- and tritocerebrum are part of the insect brain
The mushroom body is the center for higher-order sensory integration and learning
The mushroom body receives information mainly from the olfactory (antennal lobe)
Hymenoptera (ants, bees, wasps, etc.) mushroom bodies also receive information from the optic lobe
The mushroom body is involved in olfactory learning and memory, place memory, associative memory, and motor control

Ventral Nerve Cord

It is a series of ganglia lying on the floor of the thorax and abdomen
The ganglia are united by a pair of connectives
Thoracic ganglia are situated one in each of the thoracic segments
The function of the thoracic ganglia is to control the locomotor organs
Thoracic ganglia supply a pair of nerves to general muscles and a pair of nerves to leg muscles
Meso- and meta-thoracic ganglia control movements of wings
Abdominal ganglia are variable in number, with their number differing between insect species

Plasmotocyte

Plasmotocytes are a type of hemocyte
They are responsible for phagocytosis, which is the ingestion of foreign particles and cellular debris
Plasmotocytes help to fight off infections and maintain tissue homeostasis

Tracheal System

The tracheal system is responsible for gaseous exchange in insects
It consists of a network of tracheae, which are internal tubes that carry oxygen to the tissues and remove carbon dioxide
Tracheae open to the outside through spiracles, which are segmental pores
The tracheal system allows for efficient gas exchange, even in small insects
The tracheal system is found in different parts of the insect's body

Stridulation in Insects

Heteroptera commonly stridulate using files and scrapers on the ventral or dorsal surfaces of the body
- Pentatomoid groups exhibit 15 different stridulation methods
- Reduvioidea stridulate with a file between the front coxae and the tip of the rostrum
Coleoptera often use elytra for stridulation
Lepidoptera can create sound by rubbing veins on the wings together

Sound Production by Vibrating Membranes

Homoptera, Heteroptera (Pentatomidae), and Lepidoptera (Arctiidae) use vibrating membranes to produce sound
Cicada (male) tymbal muscle contracts, pulling on the tymbal to produce a click
- Relaxation of the tymbal muscle returns it to its normal position, creating a second click
- Large air sacs amplify sound

Sound Production by Pulsed Air Streams

Acherontia (Lepidoptera) is the only known insect to use a pulsed air stream for stridulation
- Dilation of the pharynx creates a vibration in the epipharynx, generating a pulsed air stream

Insect Circulatory System

Open circulatory system in insects
- Blood flows through the body cavity (haemocoel)
- Haemocoel divided into three sinuses by diaphragms

Haemocoel Sinuses

Dorsal or Pericardial Sinus: Contains the heart
Ventral or Perineural Sinus: Contains the nerve cord
Visceral Sinus: Lies between the dorsal and ventral diaphragms

Haemocyte Types

Prohaemocyte: Smallest cell with a large nucleus
Plasmatocyte (Phagocyte): Aids in phagocytosis
Granular Hemocyte: Contains numerous cytoplasmic inclusions
Spherule Cell: Cytoplasmic inclusions obscure the nucleus, involved in blood coagulation and plasma precipitation
Cystocyte (Coagulocyte):
Oenocytoids: Large cells with an eccentric nucleus
Adipo Haemocyte: Round or avoid with fat droplets
Podocyte: Large, flattened cells with protoplasmic projections
Vermiform Cells: Rare, long, thread-like cells

Blood Circulation

Heart: A pulsatile organ that drives blood circulation
- Circulation is generally anti-clockwise, from the posterior end to the anterior end
- Diastole: Heart expansion, increasing heart volume and decreasing pericardial sinus area, allowing blood to enter the heart
- Systole: Heart contraction, pushing blood forward into the aorta
  - Blood then enters the head and flows back to bathe visceral organs and the neural cord
- Diastasis: Short period of rest between diastole and systole

Functions of Haemolymph

Lubricant: Keeps internal cells moist and facilitates movement of internal organs
Hydraulic Medium: Hydrostatic pressure supports various functions, including distribution of tracheoles

Insect Respiratory System

Tracheal system: A network of tubes that deliver oxygen to tissues
- Tracheoles: Terminal branches of the tracheal system that end blindly or anastomose
  - Located within the tissues
- Spiracles: Openings on the body surface that connect to the tracheal system
- Longitudinal Trunks: Major tracheal branches that run the length of the body
  - Connect to each other through transverse commissures
- Branches: Extend to various tissues and give rise to tracheoles
Arrangement of Tracheal System:
- Heart and dorsal muscles supplied by branches from dorsal trunks
- Alimentary canal, gonads, legs, and wings supplied by lateral trunks
- Central nervous system supplied by ventral trunks or transverse commissures
- Head supplied by branches from spiracle 1
- Dorsal branch to antennae, eyes, and brain
- Ventral branch to mouthparts and muscles
Some insects have constricted connecting tubes, isolating the tracheal system of the head to ensure oxygen supply to the brain and sense organs.