Untitled Quiz

Insect movement is powered by their muscular system.
Muscles are made up of contractile units called myosin filaments, which are striated fibers.
Striated fibers are made up of actin and myosin filaments and have multiple nerve endings from a single axon.
Fibers are also called myofibrils and are found in a matrix of multinucleated cytoplasm.
Myofibrils are surrounded by mitochondria which contain enzymes for the oxidation process that releases free energy for muscle reaction.

Myosin filaments are made of protein and have long coiled chains of polypeptides.
They have lateral projections that interlink with actin filaments during contraction.
Myosin filaments form a cross-bridge, double helix structure.

Muscles act in antagonistic pairs, meaning if there is a flexor, there is an extensor.
Muscles convert chemical energy into mechanical work and heat.

There are four main types of insect muscles, categorized based on the arrangement and number of myofilaments, nuclei, and how the fibers are embedded in connective tissue.

Found in honeybee larvae.
Fibrils are slightly differentiated and enclosed in a thick layer of superficial plasma.
Nuclei are found within the plasma layer.

Found in direct flight muscles.
Nuclei are located centrally in a column and surrounded by alternating rows of mitochondria and fibrils.
High number of mitochondria indicate a higher energy requirement.

Have a large diameter and are surrounded by sarcolemma.
Mitochondria and sarcoplasm are found between fibrils.
Nuclei are peripheral.
Found in indirect flight muscles of highly efficient fliers.
Located along the dorsum (back) of the thorax.
Contain a large number of mitochondria, indicating high energy use during flight.
High in cytochrome C and glycogen, well tracheated, and ventilated.

Visceral muscles:
- Occur in circular, longitudinal, or oblique bands around the digestive tract.
- Produce peristaltic movements to move food and waste through the gut.
- Specialized muscles associated with the spiracles.
- Others cause peristalsis or contractile movements of the heart.
Segmental muscles:
- Series of bands that connect body segments.
- Longitudinal bands connect tergites and sternites in the abdomen.
- Oblique muscles on each side of the body connect tergites to sternites of the same segment.
- In the thorax, large cord-like bands move legs and wings.
Appendage muscles:
- Movable appendages have muscles either inside or attached to them.
- Muscles in the body move the whole appendage.
- Segmental muscles move parts of the appendage.

Walking:
- Basic mode of locomotion for insects on land.
- Adult insects use a tripod manner (three legs on the ground supported by the other three raised).
- Alternation of pushing tripods results in a slightly zigzag forward motion.
- Some insects use single-leg movements for slow walking.
- Praying mantises use their first pair of legs for capturing prey, not walking.
Crawling:
- Basic mode of locomotion for worm-shaped immatures (larvae).
- Longitudinal and dorsoventral muscles oppose each other in each segment, creating a wave of contraction down the body.
- Fleshy prolegs on the abdominal segments anchor the abdomen, preventing slipping backward.
- Loopers crawl by bringing their prolegs forward and anchoring them, creating a loop in the abdomen.
Flying:
- Only adults can fly, except for mayflies, which exhibit weak flights before sexual maturity.
- Muscles in the thorax are involved in flight:
  - Indirect flight muscles attached to tergites and sternites.
  - Direct flight muscles attached to wing bases.

Primitive insects, like dragonflies and cockroaches, have flight muscles that contract directly with the wings.
More evolved insects, like bees and flies, have indirect flight muscles that are attached to the thorax instead of the wings.
Indirect flight muscles generate a force that changes the shape of the thorax, which rotates the wings.

Direct flight muscles:
- Attached directly to the wing bases.
- Contract to move the wings up and down.
Indirect flight muscles:
- Attached to the tergites and sternites of the thorax.
- Contract and relax rhythmically, changing the shape of the thorax and indirectly moving the wings.
The action of the indirect flight muscles is crucial for efficient flapping flight.

Asynchronous muscles:
- Contract and relax multiple times for each nerve impulse, allowing for rapid wing movements.
Synchronous muscles:
- Contract and relax only once per nerve impulse, allowing for slower wing movements.

Wing size and shape are crucial for flight efficiency.
Wing venation (pattern of veins) contributes to wing rigidity and stability.
Aeroelasticity (the ability of wings to deform and recover) enhances flight efficiency.
Flight muscles are highly efficient and require large amounts of energy.

Hovering:
- Flies hover in the air by rapidly beating their wings.
- Involves precise control of wing movements and body orientation.
Gliding:
- Some birds and insects can glide in the air with minimal effort.
- Relies on air currents and wing shape.
Soaring:
- Larger birds and some large insects can soar on thermals (rising columns of warm air).
- Requires precise control of wing position and body posture.