Control and Coordination

Overview

• Living organisms respond to stimuli for protection.
• Nervous and hormonal systems are key to producing responses.

Nervous System

Nerve Cells (Neurons)

• Neurons are the basic units of the nervous system.
• Parts of a neuron:
  • Cell body
  • Nucleus
  • Dendrites
  • Axon
  • Nerve endings
• Specialized tips (receptors) in sense organs detect stimuli and convert them into electrical impulses.
  • Olfactory receptors: detect smell
  • Gustatory receptors: detect taste

Nerve Conduction

• Neurons collect impulses via dendrites and pass them through nerve endings.
• Gap between nerve endings and dendrites is called synapse.
• Electrical impulses convert to chemical signals at nerve terminals, crossing the synapse to stimulate other neurons.

Types of Neurons

• Sensory neurons: Carry information from sense organs to the brain/spinal cord.
• Motor neurons: Carry information from the brain/spinal cord to muscles/glands.

Response Pathways

• Long Pathway:

  1. Stimulus → spinal cord → brain
  2. Response generated in the brain → back to spinal cord → muscles.

• Short Pathway (Reflex Action):

  • A quicker reaction that passes through the spinal cord without brain involvement.
  • Components of a reflex arc:
    • Receptors
    • Sensory neurons
    • Relay neurons
    • Motor neurons
    • Effectors

Structure of the Nervous System

Central Nervous System (CNS)

• Comprises brain and spinal cord.

Peripheral Nervous System (PNS)

• Comprises nerves.

Brain Protection

• Protected by three layers called meninges.
• Cerebrospinal fluid cushions the brain.
• The outer cranium is a hard bone structure protecting the brain.

Functions of the Brain

• Main functions include:
  • Thinking
  • Decision making
  • Storing information
  • Producing emotions
  • Controlling body functions
    • Voluntary functions: under conscious control (e.g., writing, talking).
    • Involuntary actions: not under conscious control (e.g., digestion, heartbeat).

Parts of the Brain

Forebrain

• Responsible for thought processes, sensory impulses, analysis, and decision making.
• Controls hunger and fullness sensations.

Midbrain

• Controls visual and auditory reflexes and eye movements.

Hindbrain

• Comprises:
  • Pons: sleep and breathing control
  • Medulla Oblongata: heart rate, breathing, blood pressure
  • Cerebellum: coordination of voluntary movements, posture, and balance.

Plant Coordination

Plant Responses to Stimuli

• Plants respond to environmental stimuli (sunlight, water, etc.) through movement.
• Tropic Movements: directional movements caused by stimuli. Types include:
  • Phototropism: movement towards light
  • Geotropism: movement towards soil
  • Hydrotropism: movement towards water
  • Thigmotropism: movement in response to touch
  • Chemotropism: movement towards chemicals

Phytohormones

• Special chemical compounds that cause tropic movements.
• Major Phytohormones:
  • Auxins: stimulate cell elongation
  • Gibberellins: promote stem/root elongation
  • Cytokinins: promote cell division
  • Abscisic Acid: growth inhibitor
  • Ethylene: stimulates fruit ripening

Hormones in Animals

Endocrine System

• Comprises glands that secrete hormones (e.g., pituitary, thyroid, adrenal).
• Hormones control functions like growth and reproduction.

Functions of Hormones

• Hormones are secreted in small quantities and travel through the bloodstream, acting on target tissues.
• Example: Adrenaline secretion during stress increases glucose and oxygen supply to muscles.

Importance of Iodized Salt

• Iodine is essential for producing thyroxine in the thyroid gland, which regulates metabolism.
• Lack of iodine can cause goiter.

Growth Hormone

• Secreted by the pituitary gland, controls body growth.
• Deficiency leads to dwarfism, while excess can cause gigantism.

Male and Female Sex Hormones

• Testosterone: male hormone for secondary sexual characteristics.
• Estrogen: female hormone for secondary sexual characteristics.

Diabetes Management

• High blood sugar leads to insulin secretion.
• Insulin regulates blood sugar; malfunction leads to diabetes, requiring dietary adjustments.

Diagrams

• Instructions provided for drawing human brain, reflex arc, and endocrine system.

Conclusion

• Encouragement to like, share, and subscribe for more educational content.