Science Chapter 6 Hindi - Class 10 Haryana Board Science

Control and Coordination in Living Organisms

Control and coordination refer to the processes by which living organisms regulate and harmonize various activities within their bodies. In animals, this is achieved through the nervous system and endocrine (hormonal) system, while in plants, coordination is managed primarily by hormones. Both voluntary and involuntary actions are coordinated to maintain internal balance and respond to environmental changes.

Meaning and Importance of Control and Coordination

Control is the regulation of various activities in the body, ensuring that all processes occur in a coordinated and orderly manner. Coordination is the harmonious functioning of different…

Control and Coordination in Living Organisms

Control and coordination refer to the processes by which living organisms regulate and harmonize various activities within their bodies. In animals, this is achieved through the nervous system and endocrine (hormonal) system, while in plants, coordination is managed primarily by hormones. Both voluntary and involuntary actions are coordinated to maintain internal balance and respond to environmental changes.

Meaning and Importance of Control and Coordination

Control is the regulation of various activities in the body, ensuring that all processes occur in a coordinated and orderly manner. Coordination is the harmonious functioning of different organs and systems to achieve a common purpose. These mechanisms are essential for survival, allowing organisms to respond appropriately to internal and external stimuli.

• Stimulus (Uddyapeen): Any change in the environment that elicits a response from an organism.
• Response (Anukriya): The action or reaction of an organism to a stimulus.
• Examples: Touching a hot object and withdrawing the hand, blinking in response to bright light.

Nervous System in Animals

The nervous system in animals is responsible for rapid transmission of information and coordination of body activities. It consists of specialized cells called neurons, which transmit electrical impulses.

• Main components: Brain, spinal cord (merurajju), and nerves.
• Neuron: The structural and functional unit of the nervous system, consisting of dendrites (dhrumika), cell body (koshika kaya), axon (tantrika aksha), and synaptic knobs (synaptic gundiyan).
• Synapse (Antargathan): The gap between two neurons where chemical signals are transmitted.
• Types of actions:
  • Voluntary (Aichhik): Actions under conscious control, e.g., moving limbs.
  • Involuntary (Anaichhik): Actions not under conscious control, e.g., heartbeat, breathing.
  • Reflex (Prativart): Quick, automatic responses to stimuli, e.g., withdrawing hand from heat.

Reflex Actions and Reflex Arc

Reflex actions are immediate, involuntary responses to specific stimuli, designed to protect the body from harm. The pathway followed by nerve impulses during a reflex action is called the reflex arc.

• Pathway:
  1. Sensory organ detects stimulus.
  2. Sensory neuron transmits impulse to spinal cord.
  3. Relay neuron (sahayak/sahacharya) in spinal cord processes the impulse.
  4. Motor neuron carries impulse to effector organ (muscle).
  5. Effector organ produces response.
• Key points:
  • Reflex actions are managed by the spinal cord, not the brain.
  • Information is sent to the brain after the response for awareness.

Human Brain: Structure and Functions

The human brain is the main coordinating center, protected by the skull (kapal) and surrounded by three membranes (meninges): dura mater (dridh tanika), arachnoid, and pia mater (mrid tanika). It is divided into three main parts:

• Forebrain (Agra Mastishk):
  • Cerebrum (Pramastishk): Largest part, responsible for thinking, memory, intelligence, and voluntary actions.
  • Thalamus: Relays sensory information.
• Midbrain (Madhya Mastishk): Connects forebrain and hindbrain, controls involuntary actions like pupil size and some reflexes.
• Hindbrain (Pashch Mastishk):
  • Cerebellum (Anumastishk): Maintains posture and balance, coordinates voluntary movements.
  • Medulla Oblongata (Medulla): Controls involuntary actions like heartbeat, breathing, sneezing, coughing.
  • Pons: Relays messages between different parts of the brain, helps regulate breathing and sleep cycles.

Protection of Brain and Spinal Cord

The brain is protected by the skull and three layers of membranes. The spinal cord is protected by the vertebral column (kasheruki dand). Both are cushioned by cerebrospinal fluid, which absorbs shocks and prevents injury.

• Key protective structures:
  • Skull (kapal) for the brain.
  • Vertebral column for the spinal cord.
  • Meninges: dura mater, arachnoid, pia mater.
  • Cerebrospinal fluid (CSF) acts as a shock absorber.

Limitations of Nervous Coordination and Need for Hormonal Control

Nervous coordination is limited to cells connected by nerves and is rapid but short-lived. Not all body parts are connected by nerves, and plants lack a nervous system. Therefore, chemical coordination through hormones is necessary for long-term and widespread regulation.

• Hormones: Chemical messengers produced by endocrine glands, transported via blood to target organs.
• Endocrine glands: Ductless glands that release hormones directly into the bloodstream.

Plant Movements and Plant Hormones

Plants coordinate their activities using hormones and show two main types of movements:

• Nastic Movements (Anukunchan Gati): Growth-independent, immediate responses to stimuli, direction of response is predetermined (e.g., folding of Mimosa pudica leaves on touch).
• Tropic Movements (Anuvartani Gati): Growth-dependent, direction of movement depends on the direction of the stimulus (e.g., bending of plant towards light).

Key plant hormones:

• Auxin: Promotes cell elongation, found in shoot and root tips, responsible for phototropism and gravitropism.
• Gibberellin: Promotes stem elongation, found between nodes, used to induce flowering and seedless fruit.
• Cytokinin: Promotes cell division, found in fruits and seeds, reduces dormancy.
• Abscisic Acid (Abscisic Amle): Inhibits growth, closes stomata during water stress, helps plants survive adverse conditions.
• Ethylene: Gaseous hormone, promotes fruit ripening.

Animal Hormones and Endocrine Glands

Animals use hormones for chemical coordination, produced by various endocrine glands located throughout the body.

• Pituitary gland (Piyush Granthi): Master gland, controls other endocrine glands, located in the brain.
• Hypothalamus: Controls pituitary gland.
• Thyroid gland: Produces thyroxine, regulates metabolism of fats, carbohydrates, and proteins.
• Adrenal gland: Produces adrenaline, prepares body for emergency (fight or flight), increases heart rate and blood flow to muscles.
• Pancreas: Produces insulin (lowers blood sugar) and glucagon (raises blood sugar).
• Testes (male): Produce testosterone, responsible for male secondary sexual characteristics.
• Ovaries (female): Produce estrogen and progesterone, responsible for female secondary sexual characteristics.

Feedback Mechanism in Hormonal Control

The secretion of hormones is regulated by feedback mechanisms to maintain balance and prevent excess or deficiency.

• Example: Blood sugar regulation by insulin and glucagon.
• If hormone levels are too high or too low, feedback signals adjust secretion to restore normal levels.

Differences Between Nervous and Hormonal Coordination

Nervous coordination uses electrical impulses, is rapid, and targets specific organs. Hormonal coordination uses chemical messengers, is slower, and affects multiple organs.

• Nervous system: Fast, short-lived, specific.
• Hormonal system: Slow, long-lasting, widespread.

Disorders and Clinical Relevance

• Iodine deficiency: Leads to goiter due to insufficient thyroxine production; doctors recommend iodized salt.
• Diabetes (Madhumeh): Caused by insufficient insulin production; treated with insulin injections.
• Damage to neurons: Irreversible, leading to conditions like paralysis.

Key Exam Points

• Stimulus and response definitions and examples.
• Structure and function of neuron, synapse, and reflex arc.
• Parts and functions of the human brain and spinal cord.
• Protection mechanisms for brain and spinal cord.
• Types of plant movements and their hormonal control.
• Major plant and animal hormones, their sources, and functions.
• Feedback mechanism in hormonal regulation.
• Differences between nervous and hormonal coordination.
• Clinical importance of hormones (e.g., iodine in diet, insulin in diabetes).