Lecture Notes: Control and Coordination in Animals and Plants

Introduction

• Organisms respond to stimuli to protect themselves from danger.
• Stimulus and Response Examples:
  • Cold Weather: Stimulus -> Shivering: Response
  • Sunlight: Stimulus -> Plant bending: Response
  • Ice Cream: Stimulus -> Mouthwatering: Response

Systems Involved in Response to Stimuli

• Nervous and Hormonal Systems
  • Detect and respond to stimuli

Nervous System

• Comprised of neurons (nerve cells)
• Neuron Structure: Cell body, nucleus, dendrites, axon, nerve endings
• Types of Neurons:
  • Sensory neurons: Carry information from sense organs to brain/spinal cord
  • Motor neurons: Carry responses from brain/spinal cord to muscles/glands

Nerve Impulse Transmission

• Electrical impulses are converted to chemical signals across synapses (gaps between neurons)
• Pathways:
  • Long Pathway: Involves brain processing
  • Short Pathway: Reflex actions processed in spinal cord

Reflex Actions

• Reflex Arc Components:
  • Receptors, sensory neurons, relay neurons, motor neurons, effectors

Central and Peripheral Nervous System

• Central Nervous System: Brain and spinal cord
• Peripheral Nervous System: Nerves

Brain Functions

• Protected by: Meninges and cerebrospinal fluid
• Parts of the Brain:
  • Forebrain: Sensory processing and decision-making
  • Midbrain: Visual and auditory reflexes
  • Hindbrain: Involuntary functions (heart rate, breathing)

Coordination in Plants

• Plants respond to stimuli through growth or cell shape changes
• Tropic Movements: Responses to environmental stimuli
  • Types:
    • Phototropism: Towards light
    • Geotropism: Towards soil
    • Hydrotropism: Towards water
    • Thigmotropism: Towards touch
    • Chemotropism: Towards chemicals

Plant Hormones

• Auxin: Cell elongation and tropic movements
• Gibberellins: Stem and root elongation
• Cytokinins: Promote cell division
• Abscisic Acid: Growth inhibitor
• Ethylene: Stimulates fruit ripening

Hormonal Control in Animals

• Endocrine System: Composed of glands secreting hormones
• Key Hormones:
  • Adrenaline: Rapid response in fight or flight situations
  • Thyroxin: Metabolism control
  • Growth Hormone: Body growth
  • Testosterone: Male secondary sexual characteristics
  • Estrogen: Female secondary sexual characteristics
• Diabetes: Insulin regulation of blood sugar levels

Conclusion

• Control and coordination are achieved through a complex interaction of nervous and hormonal systems in animals, while plants rely on growth and chemical signals for responses.