CBSE Class 10 Science Chapter 6: Control and Coordination – Comprehensive Notes

Introduction

Control and coordination are essential functions in living organisms that enable them to respond to stimuli. In animals, the nervous system and endocrine system work together to regulate body activities, while plants rely on chemical coordination through hormones. The nervous system transmits signals rapidly using neurons, whereas hormones provide slow and long-lasting effects. This chapter explores the mechanisms of control and coordination in animals and plants, detailing nervous control, reflex actions, the role of hormones, and movement responses in plants, ensuring survival and adaptation.

Key Terms of the Chapter

Term	Definition
Stimulus	A change in the environment that triggers a response.
Neuron	The structural and functional unit of the nervous system that transmits nerve impulses.
Reflex Action	An automatic and rapid response to a stimulus without conscious control.
Synapse	The junction between two neurons where nerve impulses are transmitted.
Endocrine Gland	A gland that releases hormones directly into the bloodstream.
Hormones	Chemical messengers secreted by endocrine glands that regulate body functions.
Tropism	Directional movement of plants in response to stimuli.
Phototropism	Growth movement of plants toward or away from light.
Geotropism	Growth movement of plants in response to gravity.
Hydrotropism	Movement of plant roots toward a water source.
Chemotropism	Movement of plants in response to chemicals (e.g., pollen tube growth towards ovules).
Homeostasis	The maintenance of a stable internal environment in an organism.

Control and Coordination in Animals

1. Nervous System in Humans

The nervous system in humans consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, responsible for processing information and generating responses. The PNS consists of nerves that connect the CNS to different body parts. It controls voluntary and involuntary actions and helps in maintaining homeostasis. The nervous system transmits electrical signals through neurons, ensuring quick responses. It plays a crucial role in learning, memory, and reflex actions.

Components of the Nervous System

Part	Function
Brain	Controls thinking, memory, emotions, and voluntary actions.
Spinal Cord	Acts as a relay center between the brain and body, controls reflexes.
Nerves	Transmit signals between the CNS and body organs.

Here’s a tabular comparison of the Central Nervous System (CNS) and Peripheral Nervous System (PNS):

Aspect	Central Nervous System (CNS)	Peripheral Nervous System (PNS)
Components	Brain and spinal cord.	Cranial nerves, spinal nerves, ganglia, and nerve fibers.
Function	Processes, integrates, and coordinates sensory/motor data; control center.	Transmits sensory/motor signals between CNS and body.
Location	Protected within the skull and vertebral column.	Outside the skull and spine; extends throughout the body.
Protection	Bone (skull, vertebrae), meninges, and cerebrospinal fluid (CSF).	Connective tissue sheaths (endoneurium, perineurium, epineurium).
Regeneration Capacity	Limited regeneration due to inhibitory environment.	Better regeneration aided by Schwann cells.
Neuron Repair	Rarely repairs damage.	Can repair axons if cell body is intact.
Divisions	No subdivisions; organized into brain regions/spinal cord.	Divided into somatic (voluntary) and autonomic (involuntary; sympathetic/parasympathetic).
Examples	Cerebrum, cerebellum, brainstem, spinal cord.	Sciatic nerve, vagus nerve, sensory receptors in skin.

Key Differences:

Role: CNS is the command center, while PNS acts as a communication network.
Protection: CNS has robust structural protection (bone, meninges, CSF), whereas PNS relies on connective tissue.
Recovery: PNS nerves can regenerate more effectively than CNS neurons.
Structure: CNS contains nuclei and tracts; PNS comprises nerves and ganglia.

2. Structure and Function of Neuron

A neuron is the basic unit of the nervous system, specialized to transmit nerve impulses. It consists of three parts:

Dendrites – Receive signals from other neurons or sensory receptors.
Cell body – Contains the nucleus and processes information.
Axon – Carries electrical impulses away from the cell body.

At the end of an axon, the impulse is transmitted to another neuron or muscle through a synapse, using neurotransmitters like acetylcholine.

Structure of Neuron

Part	Function
Dendrites	Receive signals from other neurons.
Cell Body	Processes signals and contains the nucleus.
Axon	Conducts impulses away from the neuron.
Synapse	Transfers signals to the next neuron or muscle.

3. Reflex Action and Reflex Arc

A reflex action is an automatic, involuntary, and rapid response to a stimulus without conscious thought, like withdrawing a hand from a hot object. The reflex arc is the pathway followed by nerve impulses during a reflex action. It includes:

Receptor (skin) – Detects the stimulus.
Sensory neuron – Carries the impulse to the spinal cord.
Interneuron (spinal cord) – Processes the signal.
Motor neuron – Sends response to muscles.
Effector (muscles) – Performs the action.

Example of Reflex Actions

Stimulus	Response
Touching a hot object	Withdrawing the hand.
Sudden bright light	Pupil contracts.
Knee-jerk test	Leg moves forward.

Hormonal Coordination in Animals (Endocrine System)

The endocrine system consists of glands that secrete hormones directly into the bloodstream. Unlike the nervous system, it controls slow and long-term processes like growth, metabolism, and reproduction.

Major endocrine glands include:

Pituitary gland – Master gland controlling other glands.
Thyroid gland – Produces thyroxine for metabolism regulation.
Adrenal gland – Releases adrenaline for emergency responses.
Pancreas – Produces insulin to regulate blood sugar.
Ovaries/Testes – Produce sex hormones.

Gland	Hormone	Function
Pituitary	Growth Hormone	Regulates body growth.
Thyroid	Thyroxine	Controls metabolism.
Adrenal	Adrenaline	Prepares body for emergencies.
Pancreas	Insulin	Regulates blood sugar.

Human Brain

The brain is the control center of the body, protected by the skull and cerebrospinal fluid. It has three regions:

Forebrain:
- Cerebrum: Controls voluntary actions, memory, and reasoning.
- Thalamus: Relays sensory signals.
- Hypothalamus: Regulates hunger, thirst, and temperature.
Midbrain: Processes visual and auditory data.
Hindbrain:
- Cerebellum: Maintains balance and posture.
- Medulla: Controls involuntary actions (e.g., breathing).

Example: Solving a math problem involves the cerebrum

Control and Coordination in Plants

1. Plant Hormones

Plants lack a nervous system but coordinate functions using plant hormones (phytohormones). These include:

Auxins – Promote cell elongation and phototropism.
Gibberellins – Stimulate stem elongation and seed germination.
Cytokinins – Promote cell division and delay aging.
Abscisic Acid – Inhibits growth, induces dormancy.
Ethylene – Accelerates fruit ripening.

Hormone	Function
Auxins	Growth in shoot, root development.
Gibberellins	Increases plant height, seed germination.
Cytokinins	Delays leaf aging, promotes cell division.

2. Tropic Movements in Plants

Plants exhibit tropic movements, which are directional growth responses to external stimuli:

Phototropism – Growth towards light (e.g., Sunflower bending towards sunlight).
Geotropism – Roots grow downward (positive geotropism), stems grow upward (negative geotropism).
Hydrotropism – Roots grow toward water (e.g., root movement toward underground water sources).
Chemotropism – Growth due to chemicals (e.g., pollen tube growth towards ovule).
Thigmotropism – Response to touch (e.g., tendrils wrapping around objects).

Type of Tropism	Stimulus	Example
Phototropism	Light	Sunflower bending toward the sun.
Geotropism	Gravity	Roots growing downward.

Conclusion

Control and coordination in living organisms ensure proper functioning and survival. While the nervous system and endocrine system regulate responses in animals, plants rely on hormonal coordination and tropic movements. Understanding these mechanisms helps us appreciate the complexity of life processes and their role in adaptation and survival.

These comprehensive notes ensure detailed coverage of each concept with examples, tables, and a logical flow of information.