Overview: Control & Coordination | Science Class 10 PDF Download

"Control and Coordination" refers to the physiological processes that allow organisms, including humans, to respond to changes in their environment, maintain internal balance, and carry out various activities in a coordinated manner.

Nervous System

The nervous system comprises sense organs, nerves, and neurons that form a network that conducts information via electrical impulses throughout the body.

The human nervous system consists of three divisions: central nervous system (CNS), peripheral nervous system (PNS) and autonomic nervous system (ANS).

• The brain and spinal cord constitute the central nervous system (CNS). The nerves arising from the brain (cranial nerves) and nerves arising from the spinal cord (spinal nerves) constitute the peripheral nervous system.
• The nerve cell or neuron is the structural and functional unit of the nervous system.

• Effectors are muscles, glands, tissues or cells which act in response to a stimulus received by the nervous system.

The Human Brain

• The human brain is protected by a bony skull, also called the cranium. Internal to the skull, it is covered from the outside by three membranes called meninges. In between the meninges, there is a fluid called cerebrospinal fluid. Beneath the membranes, the brain is subdivided into three major parts, namely the forebrain, midbrain and hindbrain.

• Fore-brain is the main thinking part of the brain. It has different regions or areas, such as:
  (i) Sensory area - It receives sensory impulses from various receptors.
  (ii) Auditory area - It is concerned with hearing.
  (iii) Olfactory area - It is concerned with the smell.
  (iv) Gustatory area - It is concerned with taste.
  (v) Optic area - It is concerned with sight.
  (vi) Association area - This area interprets various sensory information and makes a decision on how to respond.
  (vii) Motor area - Decisions made by association area are passed on to this area, which controls the movement of voluntary muscles.
• The midbrain comprises four lobes. The actions of involuntary muscles are controlled by the mid-brain and hind-brain.
• Hind-Brain (Components): Cerebellum, pons varolii, and medulla oblongata. The cerebellum coordinates a muscular activity and maintains body equilibrium. The medulla controls involuntary actions like blood pressure, salivation, and vomiting.

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Spinal Cord

• Protected by a vertebral column within a canal in each vertebra.
• Conducts sensory and motor impulses.
• Centre 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 fibres' chemoreceptor sites.
• Proteins change shape during muscle contraction.

Coordination in Plants

Lack of 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 in Animals

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

Endocrine Glands (in Humans):

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

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Feedback Mechanism:

• Regulatory mechanism based on substance levels.
• E.g., insulin regulation of blood glucose.
• The 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 constrict arterioles.

Thyroxine

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

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Growth Hormone (GH):

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

Sex Hormones:

• Testosterone (males) and estrogen (females) from the 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