Simply CBSE

Control and Coordination — Class 10 Science

Understand how nervous system and hormones work together to control and coordinate body functions in animals and plants.

In this chapter, you will learn

  • —Understand the structure and function of nervous system (CNS and PNS)
  • —Learn about neurons and how they transmit signals
  • —Understand reflex arc and reflex actions
  • —Study brain structure and functions of different regions
  • —Learn about spinal cord and its role in reflex and communication
  • —Understand hormones and endocrine system
  • —Study feedback mechanisms and homeostasis
  • —Learn about plant hormones and their effects on growth

The Nervous System - Structure and Organization

The nervous system is the body's communication network that receives stimuli, processes information, and sends responses. It has two main divisions: the Central Nervous System (CNS) and Peripheral Nervous System (PNS).

Organization of Nervous System Central Nervous System (CNS) Brain Spinal Cord Processes information Peripheral Nervous System (PNS) Somatic Nerves Autonomic Nerves Carries signals to/from CNS

Central Nervous System (CNS):

  • Brain: Enclosed in skull, controls all voluntary and involuntary functions, processes sensory info
  • Spinal Cord: In vertebral column, transmits signals between brain and body, controls reflex actions

Peripheral Nervous System (PNS):

  • Somatic nervous system: Controls voluntary (conscious) movements and carries sensory info
  • Autonomic nervous system: Controls involuntary functions (heart beat, digestion, breathing) without conscious effort

Exam Tip

Remember CNS = Brain + Spinal Cord (control center). PNS = Nerves carrying signals in both directions. Spinal cord relays signals AND controls reflexes.

Common Mistake

Students think spinal cord only relays signals. It also DIRECTLY controls reflex actions without brain involvement!

Neurons - The Building Blocks of Nervous System

Neurons (nerve cells) are the basic structural and functional units of the nervous system. They transmit electrical and chemical signals throughout the body.

Neuron Structure Dendrites Nucleus Cell Body Axon Axon Terminals Signal: Dendrites → Cell Body → Axon → Terminals

Neuron Parts and Functions:

  • Dendrites: Branch-like structures that receive signals from other neurons
  • Cell body: Contains nucleus, controls metabolic activities of neuron
  • Axon: Long extension that transmits signals away from cell body
  • Axon terminals: Endings that form synapses with next neuron or organ
  • Synapse: Gap between neurons where chemical transmission occurs

Types of Neurons:

  • Sensory neurons: Carry signals from receptors (eyes, ears, skin) to CNS
  • Motor neurons: Carry signals from CNS to effectors (muscles, glands)
  • Interneurons: Connect sensory and motor neurons, process information in CNS

Exam Tip

Know neuron structure and signal transmission: Dendrites receive → Cell body processes → Axon transmits → Terminals release. Three neuron types for reflex arc.

Common Mistake

Students confuse the direction of signal. Remember: Dendrites RECEIVE, Axon SENDS. Signal goes: Dendrite → Cell body → Axon → Terminal.

Reflex Arc and Reflex Actions

A reflex action is an automatic, rapid response to a stimulus that occurs without conscious thought. It's controlled by the spinal cord, not the brain.

Reflex Arc - Path of Nerve Impulse 1 Stimulus (Touch) Sensory Spinal Cord Motor 6 Response (Hand pulls back) 2 3,4,5 6 Reflex Arc Steps 1. Stimulus: Touch detected by receptor (skin) 2. Sensory neuron: Carries signal from receptor to spinal cord 3. Synapse: Chemical transmission in spinal cord 4. Interneuron: Processes signal in spinal cord 5. Motor neuron: Carries signal from spinal cord to muscle 6. Response: Muscle contracts, hand pulls back (all happens in milliseconds!)

Characteristics of Reflex Actions:

  • Automatic: Occurs without conscious thought or brain involvement
  • Rapid: Happens in milliseconds - much faster than voluntary actions
  • Protective: Protects body from harm (e.g., pulling hand from hot surface)
  • Spinal cord controls: Decision made at spinal cord level, brain informed later
  • Examples: Blinking, pulling hand from hot object, knee-jerk reflex

Exam Tip

Reflex arc has 5 components: Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector. Brain is NOT involved in the reflex - it just gets informed!

Common Mistake

Students think brain controls reflexes. WRONG! Reflex arc bypasses brain - spinal cord makes the decision. That's why it's so fast!

Brain Structure and Functions

The brain is the main control center that processes information, controls behavior, and maintains body functions. It has three main regions with different functions.

Brain Regions and Functions Cerebrum Largest part • Conscious activities • Thinking, memory • Voluntary movements • Sensations Intelligence & Learning Cerebellum Below cerebrum • Body balance • Muscle coordination • Posture control • Fine movements Coordination & Balance Medulla Lower brain • Breathing • Heart beat • Blood pressure • Digestion Vital Functions Other Important Regions Hypothalamus: Controls hunger, thirst, body temperature, hormones via pituitary Midbrain & Pons: Relay stations for signals between brain regions Thalamus: Relays sensory information to cerebrum (except smell) Protection: Skull protects brain; cerebrospinal fluid cushions and nourishes it

Brain Functions Summary:

  • Receives and processes sensory information from all body parts
  • Controls voluntary and involuntary movements
  • Center for emotions, memory, learning, and thinking
  • Regulates vital functions (breathing, heart rate, digestion)
  • Produces and regulates hormones through hypothalamus-pituitary axis

Exam Tip

Remember three main brain regions: Cerebrum (thinking), Cerebellum (balance/coordination), Medulla (vital functions). Hypothalamus controls hormones!

Common Mistake

Students think medulla controls voluntary movements. WRONG! Cerebrum controls voluntary, medulla controls involuntary vital functions.

Hormones and Endocrine System

Hormones are chemical messengers secreted by endocrine glands that regulate body functions. Unlike nervous system (fast, short-lived), hormonal effects are slower but longer-lasting.

Endocrine Glands and Their Hormones Major Endocrine Glands Pituitary: Growth, FSH, LH (Master gland) Thyroid: Thyroxine (metabolism) Pancreas: Insulin (blood glucose) Adrenal: Adrenaline (fight/flight) Ovaries: Estrogen, Progesterone Testes: Testosterone Parathyroid: Calcium regulation Released into bloodstream Slow but long-lasting effects Hormone Effects Growth: Growth hormone from pituitary Metabolism: Thyroxine increases metabolic rate Blood glucose: Insulin lowers, glucagon raises Stress response: Adrenaline increases HR & BP Reproduction: FSH, LH, estrogen, testosterone Water balance: ADH controls urine production Calcium levels: Parathyroid hormone Regulation of vital functions Maintain homeostasis

Nervous System vs Hormonal System:

  • Nervous: Fast transmission, short-lived effects, precise location
  • Hormonal: Slower transmission, long-lasting effects, widespread action via bloodstream
  • Both: Work together for body regulation and homeostasis

Exam Tip

Know major glands and their hormones! Pituitary = growth, Thyroid = metabolism, Pancreas = blood glucose, Adrenal = stress response.

Common Mistake

Students think hormones act immediately like nervous system. Hormones are SLOWER but have LONGER-LASTING effects.

Plant Hormones and Growth Regulation

Plant hormones (or plant growth regulators) control growth, development, and responses to environment. Unlike animals, plants don't have a nervous system but use hormones for coordination.

Plant Hormones and Their Functions Auxins Promote cell elongation • Root bending (geotropism) • Apical dominance • Prevent abscission • Root development Primary at shoot apex Gibberellins Promote growth • Stem elongation • Seed germination • Flowering • Leaf expansion Promote elongation Cytokinins Cell division • Cell division • Bud formation • Delay senescence • Chloroplast form Promote cell division

Other Important Plant Hormones:

  • Ethylene: Ripening of fruits, dropping of leaves (abscission), aging
  • Abscisic acid: Stress response, stomatal closure during drought, inhibits growth

Plant Movements Controlled by Hormones:

  • Phototropism: Plant bends toward light (auxin causes bending away from light side)
  • Geotropism: Plant roots bend downward toward gravity (auxin concentration in roots)
  • Hydrotropism: Roots bend toward water source
  • Thigmotropism: Response to touch (climbing plants curl tendrils)

Exam Tip

Plant hormones: Auxins (elongation, geotropism), Gibberellins (stem growth, seed germination), Cytokinins (cell division). Know what each does!

Common Mistake

Students think plant hormones act like animal hormones. They do but in plant-specific ways - no nervous system, so hormone control is slower and more localized.

Chapter Summary

The nervous system comprises CNS (brain + spinal cord) and PNS (carries signals). Neurons transmit signals through dendrites → cell body → axon → terminals. Reflex arc shows spinal cord controls fast automatic responses without brain involvement: stimulus → sensory neuron → spinal cord → motor neuron → response. Brain has three regions: Cerebrum (thinking, voluntary movement), Cerebellum (balance, coordination), Medulla (vital functions like breathing). Hormones are chemical messengers secreted by endocrine glands (pituitary, thyroid, pancreas, adrenal, ovaries, testes) that regulate growth, metabolism, reproduction, and stress response - slower but longer-lasting than nerves. Plant hormones (auxins promote elongation, gibberellins promote growth, cytokinins promote cell division, ethylene controls ripening) regulate growth and responses to environment without nervous system. Nervous and hormonal systems work together maintaining homeostasis.

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