Class 10 — Chapter 6: Control and Coordination

6.1 Animals – Nervous System

Receptors: Specialised tips of nerve cells located in sense organs that detect environmental information, such as gustatory receptors for taste and olfactory receptors for smell.
Neuron: The structural and functional unit of the nervous system, consisting of the dendrite, cell body, and axon.
Transmission: Information acquired at the dendritic tip sets off a chemical reaction that creates an electrical impulse. This travels to the cell body, along the axon, and crosses the synapse (gap between neurons) using chemical signals to trigger a fresh impulse in the next neuron.

Reflex Action: A sudden, involuntary, and immediate response of the body to a stimulus without conscious thought.
Reflex Arc: The pathway of a reflex action where the sensory input nerve directly connects to the motor output nerve in the spinal cord for highly efficient, rapid response execution.

Central Nervous System (CNS): Composed of the brain and spinal cord, functioning as the main integrating and coordinating center of the body.
Peripheral Nervous System (PNS): Consists of cranial nerves arising from the brain and spinal nerves arising from the spinal cord to facilitate communication between the CNS and the rest of the body.
Fore-brain: The primary thinking region of the brain, containing specialized areas for hearing, smell, sight, and association areas that interpret and integrate sensory information.
Mid-brain and Hind-brain: Responsible for controlling involuntary actions.
Medulla: A hind-brain structure that controls involuntary functions such as blood pressure, salivation, and vomiting.
Cerebellum: A part of the hind-brain responsible for maintaining the posture, balance, and precision of voluntary movements.

Tissue Protection: The delicate brain is enclosed in a fluid-filled balloon for shock absorption inside a bony box (skull), while the spinal cord is protected by the vertebral column.
Muscular Action: Upon receiving a nervous electrical impulse, muscle cells change their shape by altering the arrangement of specialized proteins, causing them to contract or shorten.

6.2 Coordination in Plants

Immediate Response: Growth-independent movement in response to touch, as seen in the sensitive plant (Mimosa pudica).
Mechanism: Plants use electro-chemical means to convey touch information cell-to-cell. Shape change is achieved by altering the amount of water inside cells, leading to swelling or shrinking.

Tropic Movements: Directional growth movements in plants in response to external environmental stimuli.
Phototropism: Movement in response to light, where shoots grow towards light (positive) and roots grow away from it (negative).
Geotropism: Movement in response to gravity, with roots growing downwards and shoots growing upwards.
Hydrotropism: Directional growth response to water.
Chemotropism: Directional growth response to chemical substances, such as the growth of pollen tubes towards ovules.
Auxin: A plant growth hormone synthesized at the shoot tip that helps cells grow longer, diffusing to the shady side to cause the plant to bend towards light.
Gibberellins: Plant hormones that assist in stem elongation and growth.
Cytokinins: Plant hormones that promote active cell division, found in higher concentrations in fruits and seeds.
Abscisic Acid: A plant hormone that inhibits growth and is responsible for effects like the wilting of leaves.

6.3 Hormones in Animals

Hormones: Chemical messengers secreted by glands of the endocrine system that coordinate growth, metabolism, and development.
Adrenaline: Secreted directly into the blood by the adrenal glands during emergency situations, increasing heart rate, breathing rate, and blood supply to skeletal muscles.
Thyroxin: Secreted by the thyroid gland to regulate carbohydrate, protein, and fat metabolism. It requires iodine for synthesis, and its deficiency leads to goitre (swollen neck).
Growth Hormone: Secreted by the pituitary gland to regulate bodily growth and development. Deficiency leads to dwarfism.
Testosterone & Oestrogen: Sex hormones secreted by the testes and ovaries respectively, causing body changes associated with puberty.
Insulin: Produced by the pancreas to regulate blood sugar levels. Deficiency causes diabetes.
Feedback Mechanisms: Regulatory processes that monitor and control the timing and amount of hormone release based on internal levels (e.g., insulin secretion decreasing as blood sugar falls).

Science: Class 10 — Chapter 6: Control and Coordination