12.1 - Coordination and Response

Components of Coordination

• Sensitivity: The ability to detect changes in the environment and respond to the changes.
• Stimulus: A change that stimulates a response.
• Receptor: A special sensory cell that detects a stimulus and converts it into a nerve impulse.
• Integration centre: The brain translates nerve impulses and coordinates an appropriate response.
• Effector: The part of the body that responds; examples are muscles and glands.
• Response: The way an organism reacts after detecting a stimulus.

Pathway: stimulus → receptor → sensory neurone → integration centre → motor neurone → effector → response.

External and Internal Stimuli

• External stimuli: Light, sound, smell, taste, surrounding temperature, pressure and touch.
• Internal stimuli: Changes in blood osmotic pressure, body temperature and blood sugar level.

Types of Sensory Receptors

• Chemoreceptor: Detects chemical substances.
• Mechanoreceptor: Detects touch and pressure stimuli.
• Photoreceptor: Detects light.
• Thermoreceptor: Detects changes in temperature.
• Baroreceptor: Detects changes in pressure.
• Nociceptor: Detects pain.

Necessity of Response

• A response to external stimuli enables humans and animals to adapt to environmental changes and survive.
• A response to internal stimuli returns changes in the internal environment to the normal range.