CONTROL AND COORDINATION NOTES CLASS 10

Chapter: Control and Coordination (Class 10 - Biology)

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🔍 Introduction

All living organisms respond to stimuli such as light, heat, gravity, chemicals, etc. This ability to detect and respond to changes in the environment is called control and coordination.

• In animals, control and coordination are provided by:

  • Nervous system

  • Endocrine system (hormones)

• In plants, it is achieved through:

  • Hormones (plant growth regulators)

  • Tropisms (movement towards/away from stimulus)

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🧠 Control and Coordination in Animals

1. Nervous System in Humans

It consists of:

• Central Nervous System (CNS): Brain + Spinal Cord

• Peripheral Nervous System (PNS): Nerves arising from brain and spinal cord

• Autonomic Nervous System (ANS): Involuntary control (heartbeat, digestion)

2. Structure of a Neuron (Nerve Cell)

• Dendrites: Receive signals

• Cell body (cyton): Contains nucleus

• Axon: Transmits impulse away from the cell body

• Axon terminal: Transfers impulse to next cell through synapse

🔁 Nerve Impulse Transmission:

1. Dendrites receive signal.

2. Signal reaches cell body.

3. Moves down the axon.

4. Reaches axon terminal.

5. Neurotransmitters released at synapse.

6. Next neuron is stimulated.

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3. Types of Neurons

Type	Function
Sensory Neuron	Carries impulses from sense organs to CNS
Motor Neuron	Carries impulses from CNS to muscles
Interneuron	Connects sensory and motor neurons

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4. Human Brain (Main Control Centre)

🧠 Protected by:

• Skull (bone)

• Meninges (membranes)

• Cerebrospinal fluid (shock absorber)

🧩 Parts of the Brain:

Part	Function
Cerebrum	Largest part, intelligence, memory, voluntary actions
Cerebellum	Balance and coordination of movement
Medulla oblongata	Involuntary actions like heartbeat, breathing
Midbrain	Relays information from eyes and ears
Hypothalamus	Hunger, thirst, temperature regulation
Pituitary gland	Master gland, controls other endocrine glands

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5. Reflex Action

• Definition: An automatic, quick response to a stimulus without conscious control.

• Example: Pulling hand back from a hot object.

Reflex Arc Pathway:
Stimulus → Receptor → Sensory neuron → Spinal cord (interneuron) → Motor neuron → Effector (muscle)

👉 In reflexes, the brain is not involved directly; spinal cord handles it for speed.

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🧪 Coordination by Hormones (Endocrine System)

• Hormones: Chemical messengers secreted by endocrine glands into blood, affecting target organs.

Important Human Endocrine Glands:

Gland	Hormone(s)	Function
Pituitary (master gland)	Growth hormone, TSH, FSH etc.	Controls other glands
Thyroid	Thyroxine	Controls metabolism
Parathyroid	Parathormone	Calcium balance
Adrenal (above kidneys)	Adrenaline	Fight or flight, increases heart rate
Pancreas (mixed gland)	Insulin, Glucagon	Controls blood sugar
Testes (males)	Testosterone	Male sex characteristics
Ovaries (females)	Estrogen, Progesterone	Female sex characteristics, menstrual cycle

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🌱 Control and Coordination in Plants

Unlike animals, plants do not have nervous systems or muscles, but they still respond to stimuli.

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1. Plant Movements

a. Tropic Movements (Directional growth towards or away from a stimulus):

Type	Stimulus	Example
Phototropism	Light	Stem bends towards light
Geotropism	Gravity	Roots grow downward
Hydrotropism	Water	Roots grow towards water
Thigmotropism	Touch	Tendrils coil around support
Chemotropism	Chemicals	Pollen tube grows toward ovule

• Positive Tropism: Growth towards stimulus

• Negative Tropism: Growth away from stimulus

b. Nastic Movements (Non-directional, in response to stimuli):

• Touch-sensitive plants (e.g., Mimosa pudica) fold leaves on touch

• Movement not related to direction of stimulus

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2. Plant Hormones (Phytohormones)

Hormone	Function
Auxins	Cell elongation, phototropism
Gibberellins	Stem elongation, seed germination
Cytokinins	Cell division, delays aging
Abscisic acid	Inhibits growth, promotes dormancy, stress hormone
Ethylene	Ripening of fruits

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⚖️ Differences Between Nervous and Endocrine System

Nervous System	Endocrine System
Uses electrical impulses.	Uses hormones (chemical)
Fast response	Slower response
Short-lived effect	Long-lasting effect
Involves neurons	Involves glands

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🔚 Summary

• Animals use nervous and endocrine systems for coordination.

• Neurons transmit signals; reflex actions are quick and involuntary.

• The brain controls and processes responses.

• Plants coordinate via hormones and directional movements (tropisms).

• Hormones play a vital role in regulating various activities in both plants and animals.