This chapter explains how living organisms control and coordinate their activities and responses to changes in the environment. It describes the two main systems of control in animals—the nervous system and the endocrine (hormonal) system—and explains how plants respond to stimuli without nerves or muscles. The chapter highlights how quick responses are managed through electrical impulses, while slow and long-lasting responses occur through chemical signals (hormones). Together, these systems help organisms survive, grow, and maintain balance within the body.
Key Points
Control and coordination help organisms respond properly to environmental changes.
Movement in living organisms is often a response to a stimulus.
In animals, control is achieved through the nervous system and hormones.
The nervous system uses electrical impulses for fast responses.
Receptors detect stimuli such as light, heat, sound, smell, and taste.
Neurons transmit impulses through dendrites, cell body, axon, and synapse.
Reflex actions are quick, automatic responses that do not involve thinking.
Reflex arcs are formed in the spinal cord for faster responses.
The brain is the main coordinating centre of the body.
The forebrain controls thinking and voluntary actions.
The midbrain and hindbrain control involuntary actions like breathing and heartbeat.
The cerebellum maintains posture, balance, and precision of movements.
The spinal cord protects reflex pathways and connects the brain to the body.
Muscles move by changing shape due to special contractile proteins.
Plants respond to stimuli through growth movements and non-growth movements.
Tropic movements in plants are directional growth responses to stimuli.
Phototropism, geotropism, hydrotropism, and chemotropism are types of tropisms.
Plant hormones like auxin, gibberellin, cytokinin, and abscisic acid regulate growth.
Animals use hormones for slow but widespread coordination.
Adrenaline prepares the body for emergency situations.
Thyroxin, growth hormone, insulin, testosterone, and oestrogen regulate growth and metabolism.
Feedback mechanisms control hormone levels in the body.
👉 👉Efficient control and coordination are essential for survival. By working together, the nervous system and hormonal system ensure proper responses, balanced growth, and internal stability. Understanding these systems helps us appreciate how the body and plants function in a highly organised and intelligent manner.