Module 3 - The Business of Being an Insect II Flashcards
What does a nervous system do?
Detects, transmits, and interprets info from the outside world
What are one of the reasons that insects have become such a successful and diverse group?
Sophistication of their nervous system gives them a keen awareness of the external environment
What is a neuron?
The foundation of the nervous system. It is a special type of cell which receives info from the external enviro and sends info to tissues
What are the 3 key parts of the neuron?
- Dendrite
- receives info from enviro or other neurons - Cell body
- signal transmitted through the cell body, this is where the nucleus is found - Axon
- signal continues along from the cell body along the axon towards another neuron or a target cell tissue
In what form do neurons transmit information?
Electrical impulses btw other neurons or to and from cells and tissues. Impulses travel in waves mediated by the electrochemical gradient neurons maintain across their cell membranes.
What is the action potential of a neuron?
Wave-like change in membrane potential along the neuron
What are the 3 roles neurons can perform in the transmission of info within the nervous system?
- Sensory neurons
- sense info from the external enviro and pass it along to the CNS - Motor neurons
- transmit signals from the CNS to the muscles - Interneurons
- create a ‘bridge’ btw any two or more neurons so that info can pass btw cells quickly and efficiently
What is the space between the axon of the transmitting neuron and the dendrite of the receiving neuron?
a SYNAPSE sometimes called a synaptic cleft
Within the synapse, what are the chemical messengers that pass the signal between neurons or between a neuron and a target tissue?
Neurotransmitters
- can either excite or inhibit the transmission of a signal
What is an important excitatory neurotransmitter in insects? What does it affect?
Acetylcholine
- an organic chemical released by neurons that stimulates other neurons
- affects muscular movement, learning, and memory
What are the two components of the nervous system?
- Peripheral NS
- neurons housed in sensory receptors throughout the body which detect and transmit signals from stimuli in the surrounding enviro - Central CS
- brain and ventral nerve cord
What are neurons that pick up external stimuli found distributed across the insect body called?
Sensory receptors
- antennae, compound eyes, and mouthparts all contain an abundance
What is the trichoid sensillum?
A common sensory receptor found in insects
- has a single hair-like structure called a seta that is associated with one or more neurons
- modified for mechanoreception or chemoreception
What is ‘mechanoreception’?
When the seta of the trichoid sensillum is stimulated by movement, an AP is generated in the neuron within the sensillum, which is transmitted to the CNS. This allows mechanoreceptors to inform insects about physical cues from the enviro.
What is chemoreception?
The ability to perceive chemical stimuli. Many critical decisions are dependent upon chemoreception. Chemosensitive sensilla have one or more tiny pores along the seta that allow molecules of liquids and gases to enter. The chemical compounds dissolve in a fluid contained within the seta and then bind to receptors on the sensory neuron, which transmits a signal to the CNS.
What are the 2 types of trichoid sensilla that can detect chemical stimuli?
- olfactory chemoreceptors
- contact chemoreceptors
Where is the nerve cord in insects?
lies along the ventral side of the body
What does the CNS do?
Receives signals from the PNS and controls behaviour
Within the CNS, nerve cells are bundled into interconnected masses called what?
Ganglia
- located along the length of the ventral nerve cord and joined by connectives
What is the insect brain comprised of?
3 distinct pairs of ganglia within the head
What do mushroom bodies in the anterior brain allow for?
some capacity for memory retention and learning in insects, especially from olfactory cues.
- well developed in social insects which require complex communication
What do the second pair of ganglia in the insect brain receive signals fom?
Receive signals mainly from the receptors on the antennae.
- olfactory signals are process here, and interneurons transmit these signals to higher brain centres to influence subsequent behaviour
What does the third part of the brain receive information from?
Directly from the labrum and foregut, and from the rest of the body.
What is the subesophageal ganglion?
Found posterior to the brain, they are a fourth pair of ganglia. This acts as a bridge between the insect brain and the rest of the CNS. It also connects with the muscles that control the movement of the insect mouthparts.
What does the nervous system rely on to communicate complex information?
Hormones and neurohormones
How are hormones different than neurotransmitters?
Hormones move through the insect body via the hemolymph, rather than directly between neruons in the nervous system.
Where are insect hormones and neurohormones produced and released?
By a special type of neuron called a NEUROSECRETORY CELL
- located throughout nervous system but there is a greater concentration in the brain
What are neurohormones?
Hormones produced by neurosecretory cells that promote further hormone production in other non-neural tissues, such as the endocrine glands
What are ecdysteroids and juvenile hormone examples of?
Hormones regulated by neurohormones
- ecdysteroids play a major role in the process of molting
- neurohormones produced and released by the corpora cardiaca stimulate the production and release of exdysteroids by the prothoracic glands
- JH is produced directly by the corpora allata
What do insecticides target?
the insect nervous system of pest species; without a functioning nervous system an insect cannot survive
What are 2 groups of neurotoxic intesticides?
- axonic poison
- synaptic poisons
What does the neurotoxic insecticide, axonic poison do?
Inhibits the ability of a neuron to transmit an AP along the axon
- insects will exhibit tremors and have a general loss of control of motor fxns
What is a well-known axonic poison?
DDT
What does the neurotoxic insecticide, synaptic poison, do?
They affect the synapses btw neurons within the nervous system of the affect insect. Synaptic poisons cause rapid
nerve firing in neurons
- cause uncontrollable tremors, restlessness, paralysis, death
- many target acetylcholine or the enzyme that break it down since it is the most abundant
Insects exhibit internal fertilization, when does this occur?
Occurs when the sperm and egg unite inside the body of the female, which requires that the individuals find each other and interact
- ensures a high rate of fertilization
- evolved in response to a terrestrial lifestyle where external conditions are too harsh for gamete survival
What is multimodal communication? When it is used?
Step 1 of reproduction is finding a partner. Communication between sexes occurs in a variety of ways and many use multiple types of cues in multimodal communication
- visual, auditory, pheromones (most common)
What is a pheromone?
A chemical signal that when received alters the behaviour or physiology of conspecifics
- many insects signal their mating availability with sex pheromones; female often releases pheromones and male locates her but for bumblebees it is the opposite
What allows individuals of the same species to communicate amidst other chemical cues in the enviro?
Chemical composition of pheromones is very species specific