Control and Coordination (Class 10): Notes और MCQ Practice

आसान भाषा में

हमारी body में external stimuli (जैसे गर्म छूना या रोशनी) के खिलाफ सही response generate करना ही Control and Coordination है। Animals में यह काम Nervous System (electric signals) और Endocrine System (hormones) मिलकर संभालते हैं, जबकि Plants में nervous system नहीं होता, इसलिए वे केवल Chemical Coordination (Plant Hormones) और movements पर depend करते हैं।

Important Points & Definitions

• Neuron Pathway: Dendrite (stimulus detect) → Cell Body → Axon → Nerve Ending → Synapse (gap जहाँ electric impulse, chemical signal में बदलती है)।
• Reflex Arc: Sudden involuntary action का quick route:

Receptor → Sensory Neuron → Spinal Cord (Relay Neuron) → Motor Neuron → Effector (Muscle)।

• Human Brain:
• Forebrain (Cerebrum): Thinking, memory, reasoning और voluntary control।
• Hindbrain:
• Cerebellum: Body posture, balance और precision (e.g., riding a bicycle)।
• Medulla: Involuntary actions (BP, salivation, vomiting)।
• Pons: Respiration rate control।
• Plant Hormones (Phytohormones):
• Auxin: Shoot tip पर बनता है, cell elongation और phototropism में help करता है।
• Gibberellin & Cytokinin: Stem growth और rapid cell division (fruits/seeds)।
• Abscisic Acid (ABA): Growth inhibitor, wilting of leaves (stress hormone)।
• Animal Hormones:
• Thyroxin (Thyroid): Carbohydrate/fat metabolism (Iodine जरूरी है, कमी से Goitre)।
• Insulin (Pancreas): Blood sugar regulation (कमी से Diabetes)।
• Adrenaline (Adrenal): Emergency / Fight or Flight hormone।

2 Memory Tricks

1. Cerebellum = Cycle Balance: 'C' for Cerebellum, 'C' for Coordination and Cycle riding balance (body posture maintain करता है)।
2. Plant Growth: A vs A: Auxin = Aage badhana (Growth/Shoot tip), जबकि Abscisic Acid = Alarm/Stop (Growth रोकना/पत्तियां गिराना)।

2 Common Board Exam Mistakes

1. Synapse Signal Flow: Axon के अंदर signal Electrical होता है, लेकिन Synapse cross करते वक्त यह Chemical रूप में जाता है। इसे electrical मत लिखना।
2. Reflex Action Center: Reflex arc का direct connection Spinal Cord से होता है, Brain से नहीं (Brain तक सिर्फ information बाद में पहुंचती है)।

Control and Coordination

1. Chapter in Short

All living organisms respond to changes in their environment (stimuli) to survive. This chapter explores how living beings detect these signals and produce appropriate responses.

• In Animals: Coordination is carried out by two systems working together:

1. Nervous System: Fast, electrical signaling using specialized cells called neurons.
2. Endocrine System: Chemical signaling using chemical messengers called hormones.

• In Plants: Since plants lack nervous tissue and muscles, they coordinate entirely through chemical signals (phytohormones), resulting in movements such as bending toward light or folding leaves.

2. Key Concepts Explained Simply

A. The Nervous System (Animals)

1. The Neuron (Nerve Cell): The functional unit of the nervous system.

• Dendrite: Receives information/stimulus from receptors.
• Cell Body (Cyton): Processes the impulse.
• Axon: Long fiber that carries the impulse away from the cell body.
• Nerve Ending: Releases chemicals to trigger the next neuron.
• Everyday Example: Think of a relay race. The runner takes the baton (dendrite), runs down the track (axon), and hands it over to the next runner at the end line (synapse).

1. The Synapse: The tiny gap between the nerve ending of one neuron and the dendrite of the next. Electrical signals cannot jump this gap, so they are converted into chemical signals (neurotransmitters) that diffuse across and start a fresh electrical impulse in the next neuron.

1. Reflex Action and Reflex Arc:

• Reflex Action: An extremely fast, automatic, and involuntary response to a stimulus that does not require conscious thinking by the brain (e.g., pulling your hand away immediately when you touch a burning hot pan).
• Reflex Arc: The pathway taken by nerve impulses in a reflex action:

Receptor (Skin) → Sensory Neuron → Spinal Cord (Relay Neuron) → Motor Neuron → Effector (Muscle)

1. The Human Brain:

• Forebrain: Main thinking region. Includes the Cerebrum. Controls voluntary actions, sensory interpretation (sight, hearing, smell), memory, hunger, and emotions.
• Midbrain: Controls certain involuntary actions and visual/auditory reflex movements of head and neck.
• Hindbrain:
• Cerebellum: Controls posture, balance, and precision of voluntary movements (e.g., walking in a straight line, riding a bicycle).
• Medulla: Controls involuntary vital functions (blood pressure, salivation, vomiting, heartbeat).
• Pons: Regulates respiration.
• Protection: The brain is protected inside a bony box called the cranium (skull) and surrounded by shock-absorbing fluid called cerebrospinal fluid (CSF). The spinal cord is protected inside the vertebral column (backbone).

B. Coordination in Plants

Plants do not have a nervous system, but they show two types of movements:

1. Movement Independent of Growth (Nastic Movement):

• Immediate, non-directional response.
• Example: Drooping of Mimosa pudica ("Touch-me-not" or Chhui-mui) leaves upon touching. The plant changes leaf shape by changing the amount of water in cells (turgor changes).

1. Movement Dependent on Growth (Tropic Movement / Tropism):

• Directional growth movements in response to an external stimulus:
• Phototropism: Response to light (Shoots bend toward light; roots bend away).
• Geotropism: Response to gravity (Shoots grow upward; roots grow downward).
• Hydrotropism: Response to water (Roots grow toward moisture).
• Chemotropism: Response to chemical stimuli (Growth of pollen tube down the style toward an ovule during fertilization).

1. Plant Hormones (Phytohormones):

• Auxin: Promotes cell elongation; responsible for phototropism (accumulates on the shaded side of shoots).
• Gibberellins: Promotes stem growth and seed germination.
• Cytokinins: Promotes cell division; present in high concentration in fruits and seeds.
• Abscisic Acid (ABA): Growth inhibitor; causes wilting and falling of leaves, and seed dormancy.

C. Hormones in Animals (Endocrine System)

Endocrine glands release hormones directly into the bloodstream without ducts to reach target organs.

Endocrine Gland — Hormone — Key Function

Pituitary (Master gland) — Growth Hormone (GH) — Regulates growth and development. Deficiency causes dwarfism; excess causes gigantism.

Thyroid — Thyroxin — Regulates carbohydrate, protein, and fat metabolism. Requires iodine.

Pancreas — Insulin — Regulates blood glucose levels (converts excess glucose to glycogen).

Adrenal — Adrenaline — Prepares the body for emergencies ("Fight or Flight"): increases heart rate, breathing, and blood supply to muscles.

Testes (Males) — Testosterone — Development of male secondary sexual characteristics and sperm production.

Ovaries (Females) — Estrogen / Progesterone — Development of female secondary sexual characteristics and menstrual cycle regulation.

• Feedback Mechanism: The timing and amount of hormone released are controlled by regulatory feedback loops. For example, when blood sugar levels rise, pancreatic cells detect it and secrete more insulin. As blood sugar falls back to normal, insulin production decreases.

3. Important Definitions, Facts, and Rules

• Stimulus: Any change in the environment to which an organism responds.
• Receptors: Specialized sensory nerve ends (e.g., Photoreceptors for light, Phonoreceptors for sound, Olfactory for smell, Gustatory for taste).
• Synapse: The functional microscopic gap between the axon terminal of one neuron and the dendrite of the next.
• Reflex Arc: The structural and functional neural pathway that mediates a reflex action.
• Tropic Movement: Directional growth movement toward or away from a stimulus.
• Feedback Mechanism: A self-regulating biological mechanism in which the output of a system regulates its own activity (e.g., insulin secretion).
• Goitre: Swollen neck caused by thyroxin deficiency due to lack of iodine in the diet.

4. Solved Board-Style Questions

Question 1

Trace the path of a nerve impulse in a reflex action when a person accidentally touches a hot object.

Answer:

1. Receptor: Heat is detected by thermo-receptors in the skin.
2. Sensory Neuron: Transmits the electrical impulse to the spinal cord.
3. Relay Neuron (in Spinal Cord): Interprets the impulse and transfers it to a motor neuron.
4. Motor Neuron: Transmits the command from the spinal cord to the muscle.
5. Effector (Muscle in Arm): Muscles contract, pulling the hand away immediately.

$\text{Receptor (Skin)} \rightarrow \text{Sensory Neuron} \rightarrow \text{Relay Neuron (Spinal Cord)} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector (Muscle)}$

(Plain text: Receptor (Skin) → Sensory Neuron → Relay Neuron (Spinal Cord) → Motor Neuron → Effector (Muscle))

Question 2

How does auxin cause a shoot to bend towards light?

Answer:

• Auxin is synthesized at the shoot tip.
• When light shines from one side of the plant, auxin diffuses toward the shaded side of the shoot.
• Higher concentration of auxin stimulates cells to grow longer on the shaded side compared to the illuminated side.
• This uneven growth causes the stem to bend toward the source of light (positive phototropism).

Question 3

Compare the Nervous System and the Endocrine System.

Answer:

• Nervous System:
• Information travels as electrical impulses along neurons.
• Rapid and immediate response.
• Reaches only specific cells connected by nerves.
• Effects are short-lived.
• Endocrine System:
• Information travels as chemical messengers (hormones) through the bloodstream.
• Relatively slow response.
• Reaches all target tissues throughout the body via blood.
• Effects are generally longer-lasting.

Question 4

Why is the use of iodized salt recommended in our diet?

Answer:

• Iodine is necessary for the thyroid gland to synthesize the hormone thyroxin.
• Thyroxin regulates carbohydrate, protein, and fat metabolism in the body to ensure optimal growth.
• If iodine is deficient in the diet, thyroxin cannot be produced in sufficient amounts, leading to an enlargement of the thyroid gland in the neck, a condition called goitre.

5. Common Mistakes and Quick Revision Points

• Mistake: Thinking that the brain is not involved in reflexes at all.
• Correction: While the spinal cord executes the reflex immediately to save time, the information about the event is also relayed to the brain simultaneously for processing.
• Mistake: Confusing the functions of Cerebrum and Cerebellum.
• Correction: Cerebrum = thinking, intelligence, senses, voluntary decisions. Cerebellum = body balance, posture, precision of physical movements (walking, cycling).
• Mistake: Confusing direction of impulse in a neuron.
• Correction: Always unidirectional: Dendrite → Cell Body → Axon → Axon Terminal.
• Mistake: Writing that Mimosa pudica movement is due to growth.
• Correction: It is a non-growth (nastic) movement caused by the movement of water out of cells (turgor changes).
• Quick Revision Checklist:
• Plant growth promoters: Auxin, Gibberellin, Cytokinin.
• Plant growth inhibitor: Abscisic Acid (ABA).
• Pancreas secretes: Insulin (lowers blood sugar).
• Adrenal glands secrete: Adrenaline (emergency response).
• Pituitary gland: Master gland located at the base of the brain.