Interaction: Stimulus and Response in Living Things

The Interaction in Living Things

The interaction functions are those enabling a living being to receive information from the outside to the inside, and respond to it. A stimulus is a change in the environment surrounding a body or inside it.

There are two types of responses:

• Static: There is no movement.
• Dynamic or taxis: Movement occurs in response to a stimulus.

The Interaction in Plants

• Tropism: Movements related to plant growth or its parts. They are slow and irreversible responses.
• Nasties: Rapid and temporary changes in certain parts of the plant.
• Photoperiodism: Responses due to changes in illumination that occur throughout the seasons.

The Relationship in Animals (1)

Many animals have developed sophisticated sensory organs that detect specific stimuli, complex nervous systems of chemical coordination, and effectors that execute responses.

Types of Receptors:

• According to their location, they can be: external and internal.
• According to the type of stimulus, they may be:
  • Photoreceptors: Capture light stimuli.
  • Chemoreceptors: Are stimulated by chemical substances.
  • Mechanoreceptors: Respond to mechanical stimuli (pain, touch, etc.).
  • Thermoreceptors: Discriminate between heat and cold.
  • Electroreceptors: Detect electrical energy.

The Relationship in Animals (2)

Hormonal or Endocrine System

The hormonal system controls and regulates the response, and the hormones are produced in endocrine glands. In invertebrates, the hormonal system is underdeveloped. In insects, it is involved in growth, molting, and metamorphosis. In vertebrates, it is well-developed and controls many functions.

Nervous System

The nervous system regulates the activities of the body through neurons, which are the type of cells responsible for processing and transmitting information. This is done by nerves and nerve centers, which are organs that receive information from the receptors and produce the appropriate response.

Effectors

• The secretion of substances: In this case, the effector cells are gland cells, which are responsible for secreting different types of substances, such as hormones.
• Movement: In this case, the effectors are muscle cells that make muscles contract to produce movement. In some invertebrates, the contraction of muscles results in movements by means of crawling on land and transport in aquatic environments. Arthropods have powerful muscles that rely on the exoskeleton of jointed legs and wings.

In vertebrates, muscles attach to bones via tendons.