Overview: Control & Coordination - 2 - Class 10 PDF Download

Spinal Cord:

• Protected by vertebral column within a canal in each vertebra.
• Conducts sensory and motor impulses.
• Center for reflex activities.

Human Spinal Chord

Reflex Action:

• Nerve-mediated, automatic response without brain involvement.
• Pathway: Reflex arc.
• Role in preventing overinvolvement of the brain.

Nervous System and Muscles:

• Muscles contract due to contractile proteins (actin and myosin).
• Neurotransmitters sensitize muscle fibers' chemoreceptor sites.
• Proteins change shape during muscle contraction.

Plants and Coordination:

Lack a nervous system and muscles. Exhibit coordinated movements via plant growth regulators (hormones).

Plant Growth Hormones:

1. Auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
2. Auxin response to light causes stem bending.
3. Gibberellins promote growth.
4. Cytokinin promotes cell division.
5. Ethylene induces ripening.
6. Abscisic acid inhibits growth.

Tropisms:

• Tropism is stimulus-oriented plant movement.
• Types: phototropism (light), hydrotropism (water), geotropism (gravity), thigmotropism (contact), and chemotropism (chemicals).

Roots and Shoots:

• Roots are positively geotropic and negatively phototropic.
• Shoots are positively phototropic and negatively geotropic.

Nastic Movements:

• Non-directional, growth-independent movements.
• E.g., folding of sensitive plant leaves.
• Due to changes in turgor pressure.

Chemical Coordination (Animals):

Apart from nervous coordination, chemical coordination via hormones. Hormones secreted by endocrine glands. Hormones act on specific target organs. Feedback mechanism regulates hormone secretion.

Endocrine Glands (in Humans):

Pituitary, pineal, hypothalamus, thyroid, parathyroid, thymus, pancreas, adrenal, testis (males), and ovary (females).

Feedback Mechanism:

• Regulatory mechanism based on substance levels.
• E.g., insulin regulation of blood glucose.
• Presence of excess glucose stimulates insulin secretion.

Adrenaline:

• Secreted in response to fear, anger, joy, cold, and stress.
• Target organs: heart and arteries.
• Increases blood supply to heart and muscles, constricts arterioles.

Thyroxine:

• Secreted by thyroid.
• Regulates carbohydrate, fat, and protein metabolism.
• Requires iodine.

Growth Hormone (GH):

• Secreted by anterior pituitary.
• Over-secretion causes gigantism; under-secretion results in dwarfism.

Sex Hormones:

• Testosterone (males) and estrogen (females) from testis and ovary.
• Responsible for puberty-related body changes.

Hypothalamus:

• Regulates hormone release via specific "release factors."
• Controls growth hormone release.
  
  Table : Some important hormones and their functions