Notes on Control and Coordination

  • Control and Coordination

    • Stimuli: Changes in the environment that organisms respond to.
    • Response: Reaction of an organism to a stimulus.
    • Coordination: The collaboration of body parts to respond to stimuli.

  • Coordination in Animals

    • Systems:
    • Endocrine System: Hormonal control.
    • Nervous System: Involves the central nervous system (CNS) and peripheral nervous system (PNS).
      • Central Nervous System: Composed of the brain and spinal cord.
      • Peripheral Nervous System: Includes cranial and spinal nerves.

  • Receptors and Effectors

    • Receptors: Cells/organs detecting stimuli (e.g. photoreceptors, thermoreceptors).
    • Examples:
      • Eyes: Detect light.
      • Nose: Detect smell.
      • Tongue: Detect taste.
    • Effectors: Muscles/glands responding to stimuli.

  • Neurons

    • Definition: Structural and functional unit of nervous system.
    • Components:
    • Dendrites, cell body, axon, nerve endings.
    • Function: Carry messages as electrical impulses.

  • Synapse

    • Definition: Gap between neurons for impulse transmission.
    • Process:
    • Electrical impulse generates a chemical signal for next neuron.
    • Neurotransmitters: Chemicals facilitating transmission.

  • Reflex Actions

    • Definition: Sudden, quick, involuntary movements controlled by spinal cord, not directly by the brain.
    • Types of Actions:
    • Voluntary: Controlled actions (e.g., walking).
    • Involuntary: Uncontrolled actions (e.g., heartbeat).

  • Brain Functions

    • CNS Components:
    • Brain: Main coordinating center.
    • Spinal Cord: Protected by vertebrae.
    • Parts of the Brain:
    • Cerebellum: Balance and coordination.
    • Medulla: Controls involuntary actions (e.g., heartbeat).

  • Hormones in Animals

    • Hormones: Chemical messengers.
    • Key Hormones and Functions:
    • Growth Hormone: Regulates growth and development.
    • Thyroxine: Regulates metabolism (iodine deficiency leads to goitre).
    • Testosterone and Oestrogen: Secondary sexual characteristics.
    • Insulin: Regulates blood sugar levels (deficiency causes diabetes).

  • Coordination in Plants

    • Types of Movement:
    • Tropic Movement: Directional growth in response to stimulus (e.g., phototropism).
    • Nastic Movement: Non-directional growth (e.g., sensitive plant leaves fold).

  • Plant Hormones

    • Auxins: Promote cell elongation.
    • Cytokinins: Promote cell division.
    • Gibberellins: Stimulate stem growth.
    • Abscisic Acid: Stress hormone causing wilting.