Notes Class 10 Science Chapter 6 Control and Coordination

Notes For All Chapters Science Class 10 CBSE

1. Introduction

Living organisms show movements as a response to changes in the environment.

Movements can be:

• Growth-based (e.g., seed germination)
• Non-growth-based (e.g., cat running, humans reacting to stimuli)

Controlled movement ensures appropriate response to specific environmental changes.

Control and coordination in organisms are essential for:

• Receiving information
• Processing it
• Responding correctly

2. Control and Coordination in Animals

2.1 Nervous System

Control and coordination in animals are performed by nervous and muscular tissues.

Receptors in sense organs detect stimuli:

• Gustatory receptors – taste
• Olfactory receptors – smell

Detected information becomes electrical impulses in neurons.

Neuron Structure and Function

Neuron: basic unit of the nervous system.

Parts:

• Dendrites: receive information
• Cell body: processes impulse
• Axon: transmits impulse

Synapse: junction between two neurons where impulses pass chemically.

Network of neurons forms the nervous tissue, transmitting information rapidly.

3. Reflex Actions

Reflex action: Sudden, automatic response to a stimulus without conscious thought.

Controlled by a reflex arc – pathway involving:

• Sensory neuron → Spinal cord → Motor neuron → Effector

Reflex arc allows rapid responses by bypassing the brain for immediate action.

Reflexes evolved for survival as the brain’s thinking process is slower.

4. Human Brain

• Brain and spinal cord form the Central Nervous System (CNS).
• CNS + peripheral nervous system coordinate body activities.

Parts of the Brain:

1. Fore-brain:

• Main thinking part
• Sensory areas: receive and interpret signals
• Motor areas: control voluntary actions
• Hypothalamus: hunger, thirst, emotions

2. Mid-brain:

• Controls certain reflexes
• Coordinates sensory information

3. Hind-brain:

• Medulla: controls involuntary activities (e.g., heartbeat, vomiting)
• Cerebellum: maintains posture, balance, and precision of voluntary actions

5. Protection of Brain and Spinal Cord

Brain protected by:

• Cranium (bony skull)
• Cerebrospinal fluid (CSF): shock absorber

Spinal cord protected by vertebral column.

6. Nervous System and Muscle Action

Muscle contraction: Final step of coordinated action.

Nerve impulse → Muscle cell → Special proteins change shape → Muscle shortens → Movement.

Types of muscles:

• Voluntary: under conscious control
• Involuntary: not under conscious control

7. Coordination in Plants

• Plants lack nervous and muscle tissues but still respond to stimuli.

Types of Plant Movements

1. Immediate Response (non-growth):

• E.g., Mimosa pudica leaves fold when touched.
• Communication: cell-to-cell via chemical signals.
• Movement: changes in water content in cells (swelling/shrinking).

2. Growth-based Movement:

Directional movement due to growth – tropisms.

Examples:

• Phototropism: shoot bends towards light
• Geotropism: roots grow towards gravity
• Hydrotropism: roots grow towards water
• Chemotropism: pollen tube grows towards ovule

8. Plant Hormones

Plants use chemical messengers (hormones) for control and coordination.

Major plant hormones:

Auxins: elongation of cells, phototropism

Gibberellins: stem growth

Cytokinins: promote cell division

Abscisic acid: inhibits growth, causes leaf fall and wilting

9. Hormones in Animals

Hormones: Chemical messengers secreted by endocrine glands into the blood.

Control various body activities like metabolism, growth, reproduction, etc.

Adrenaline – Fight or Flight Hormone

Secreted by adrenal glands.

Prepares body for emergencies by:

• Increasing heartbeat and breathing
• Diverting blood to skeletal muscles
• Reducing blood flow to skin and digestive system

10. Major Animal Hormones and Their Functions

11. Hormonal Regulation and Feedback Mechanism

Hormone release is controlled by feedback mechanisms.

Example:

• High blood sugar → pancreas secretes insulin → blood sugar drops → insulin secretion reduces.