Control and Coordination is one of the important chapters in SSLC Science. In this chapter, students learn about the nervous system in animals, reflex action, coordination in plants, plant hormones and animal hormones. This article is prepared based on the uploaded LBA document.
Learning Points
This chapter mainly includes:
- Animals – Nervous system
- Reflex action and reflex arc
- Coordination in plants
- Hormones in plants and their functions
- Hormones in animals and their functions
Control and Coordination
The process by which living organisms control body activities and respond to stimuli is called Control and Coordination.
This process helps organisms to:
- Respond to environmental changes
- Maintain body balance
- Coordinate body activities
Nervous System in Animals
The nervous system controls and coordinates all activities in animals.
It consists of:
- Brain
- Spinal cord
- Nerves
The nervous system receives information, processes it and sends responses.
Neuron – Structural Unit of Nervous System
Neuron is the structural and functional unit of nervous tissue.
Parts of Neuron
- Dendrite
- Cell body
- Axon
- Nerve ending
Path of Nerve Impulse
Dendrite → Cell body → Axon → Nerve ending
This pathway helps in transmission of nerve impulses.
Synapse
The gap between two neurons is called Synapse.
It helps transmission of chemical signals from one neuron to another neuron.
Human Brain
The brain is the control centre of the body.
Human brain has three major parts:
Cerebrum
Functions:
- Thinking
- Memory
- Voluntary actions
- Intelligence
The cerebrum controls voluntary actions.
Cerebellum
Functions:
- Maintains body posture
- Controls balance
- Accuracy of voluntary actions
Activities such as riding bicycles and writing are controlled by cerebellum.
Medulla Oblongata
Functions:
- Controls involuntary actions
- Regulates heartbeat
- Controls breathing
Reflex Action
Reflex action is an immediate automatic response to a stimulus without thinking.
Example:
Pulling back hand when touching a hot or sharp object.
Reflex Arc
The pathway followed during reflex action is called Reflex Arc.
Sequence:
Receptor → Sensory neuron → Spinal cord → Relay neuron → Motor neuron → Effector
Reflex actions are controlled by the spinal cord.
Coordination in Plants
Plants also show coordination through growth movements called Tropisms.
Phototropism
Growth movement of plants towards light.
Example:
Stem bends towards light.
The hormone responsible is Auxin.
Geotropism
Movement in response to gravity.
Examples:
- Roots show positive geotropism
- Stem shows negative geotropism
Roots grow downward into soil.
Hydrotropism
Growth movement towards water.
Roots move towards the water source.
Chemotropism
Movement in response to chemicals.
Example:
Movement of the pollen tube towards the ovary.
Thigmotropism
Movement due to touch.
Example:
Tendrils of climbers coil around support.
Plant Hormones
Plant hormones control growth and development.
Auxin
Functions:
- Promotes stem elongation
- Controls phototropism
- Helps growth of roots and shoots
Cytokinin
Functions:
- Promotes cell division
- Delays ageing of leaves
Gibberellin
Functions:
- Promotes plant growth
- Increases stem length
Abscisic Acid
Functions:
- Inhibits plant growth
- Causes wilting and dormancy
Hormones in Animals
Hormones are chemical messengers secreted by endocrine glands.
Thyroxine
Secreted by: Thyroid gland
Functions:
- Controls metabolism of carbohydrates, proteins and fats
- Maintains body growth and development
Iodine is necessary for production of thyroxine. Deficiency causes goitre.
Insulin
Secreted by: Pancreas
Function:
Controls blood sugar level.
Adrenaline
Function:
Prepares the body to face emergency situations.
Effects:
- Increases heartbeat
- Increases breathing rate
- Increases blood supply to muscles
This is called “fight or flight response”.
Estrogen
Function:
Controls menstrual cycle and development of female secondary sexual characters.
Reflex Action vs Voluntary Action
| Reflex Action | Voluntary Action |
|---|---|
| Automatic response | Controlled consciously |
| Controlled by spinal cord | Controlled by cerebrum |
| Faster response | Comparatively slower |
Important Exam Questions
One Mark Questions
- What is neuron?
- What is reflex action?
- What is geotropism?
- Which hormone inhibits plant growth?
Two Mark Questions
- Write functions of cerebellum and medulla.
- Differentiate endocrine system and nervous system.
- Explain the role of adrenaline.
Three and Four Mark Questions
- Explain reflex arc.
- Explain coordination in plants.
- Explain phototropism.
- Explain functions of hormones.
These questions are repeatedly asked in examinations.
Preparation Tips for Students
- Learn diagram of neuron and human brain
- Practice reflex arc sequence
- Study plant hormones carefully
- Learn differences between reflex and voluntary actions
- Revise tropic movements and hormones regularly
Conclusion
“Control and Coordination” is an important chapter in SSLC Science. Students can score good marks by understanding the nervous system, reflex actions, tropisms and hormones clearly. Regular practice of diagrams and concepts will improve examination performance.
