Key Concepts in Animal Sensory and Coordination Systems and Plant Hormones

Sensory and Coordinating Systems of Animals

  • Basic Requirements for Survival
    • Organisms must respond to stimuli to survive, requiring:
    • Sensory receptors to detect stimuli
    • Motor effectors to respond
    • The nervous system links sensory and motor receptors.

Nervous System

  • Definition
    • Controls and coordinates actions and reactions, facilitating physiological processes.
  • Components
    • Brain: Command center
    • Spinal Cord and Nerves: Relay system
  • Simpler Organisms
    • Sponges lack a nervous system.
    • Cnidarians have a nerve net with minimal coordination.
    • Free-living flatworms possess nerve cords and a primitive brain (ganglionic system).
    • Earthworms have a central nervous system connecting all body parts.
Neurons
  • Definition
    • Primary structural and functional elements of the nervous system.
  • Key Functions
    • Receive information
    • Transmit electrical impulses
    • Influence other neurons or effectors
  • Parts of a Neuron
    • Cell Body
    • Dendrites: Transmit impulses to the cell body
    • Axons: Transmit impulses away from the cell body
Types of Neurons
  • Sensory (Afferent) Neurons
    • Carry information from periphery receptors to the CNS for interpretation.
    • Two types:
    • Somatic Sensory Neurons: Monitor external environment
    • Visceral Sensory Neurons: Monitor internal organ conditions
  • Motor (Efferent) Neurons
    • Relay information from the CNS to body effectors (muscles/glands).
    • Includes:
    • Somatic Nervous System: Conscious control over skeletal muscles
    • Autonomic Nervous System: No conscious control, regulates involuntary effectors (smooth muscle, cardiac muscle, glands).
Interneurons
  • Connect sensory neurons to motor neurons
Neurosecretory Neurons
  • Central role in neuroendocrine interactions, channeling afferent stimuli that control effector organs.

Parts of the Nervous System of Vertebrates

Central Nervous System (CNS)
  • Components
    • Brain: Processes information and decides on body responses.
    • Spinal Cord: Contains cerebrospinal fluid (CSF), gray matter (cell bodies, short fibers), and white matter (long fiber tracts).
    • Functional Structure:
    • Dorsal Side: Handles sensory information
    • Ventral Side: Handles motor information
Brain Classification
  • Three Main Parts:
    1. Brainstem: Involuntary actions (heartbeat, breathing)
    • Parts:
      • Midbrain: Auditory and visual processing
      • Pons: Sensory information communication
      • Medulla Oblongata: Vital function control
    1. Cerebellum: Coordinates muscle movements for smooth motion
    2. Cerebrum: Largest brain part, divided into hemispheres with various sensory and cognitive functions
    • Lobes:
      • Frontal Lobe: Memory, movement
      • Temporal Lobe: Auditory info
      • Parietal Lobe: Sensory info
      • Occipital Lobe: Visual information
Peripheral Nervous System (PNS)
  • Controls muscle movement and autonomic functions
  • Comprises cranial and spinal nerves.
  • Sensory Organs:
    • Touch Sensation: Skin's sensory nerve endings detect environmental stimuli.
    • Gustation: Taste buds identify five primary tastes (sweet, salty, sour, bitter, umami).
    • Olfaction: Nose's olfactory neuroepithelium detects odors.

Plant Hormones and Their Functions

  • Plant growth is regulated by hormones, which can stimulate or inhibit growth. Unlike animals, plant hormones are produced in non-specific tissues.
  • Types of Plant Hormones:
    • Auxins: Stimulate growth; involved in light response (phototropism).
    • Cytokinins: Promote cell division; play a role in lateral bud formation and leaf health.
    • Gibberellic Acid: Important for stem elongation; affects seed germination.
    • Abscisic Acid: Involved in dormancy and stress response.
    • Ethylene: Induces fruit ripening and affects flower development.
    • Brassinosteroids: Similar to animal hormones, assist in growth and development.
    • Oligosaccharins: Affect plant defense responses and growth.

Sensory System of Plants

  • Plants respond to stimuli more slowly and simply than animals, lacking specialized receptors.
  • Stimulus: External and internal changes prompting plant response.
Plant Responses to Environmental Factors
  • Light: Critical for photosynthesis; influences germination, flowering, etc.
  • Phytomorphogenesis: Plant's growth adjustment to light.
  • Phototropism: Directional growth response towards light source (young shoots).
  • Gravitropism: Root growth towards gravitational pull (positive), stem growth away (negative).
  • Thigmotropism: Growth response to contact (e.g., tendril curling).
Seed Dormancy and Abscission
  • Seed Dormancy: Protective measure ensuring seeds do not germinate until conditions are optimal.
  • Abscission: Leaf drop to conserve water and energy; hormonal control (abscisic acid).
Mendel’s Laws of Inheritance
  • Conducted experiments with garden peas to discover genetic inheritance laws.
  • Observed dominant and recessive traits, leading to understanding appearances in offspring.
  • Punnett Square: Tool for predicting offspring traits from parental genetic combinations.
Key Terms

  • Phenotype: Physical traits expressed in an individual.

  • Genotype: The genetic makeup determining trait expression.

  • Homozygous: Same alleles in a gene; Heterozygous: Different alleles.

  • Codominance: Both dominant traits expressed; Incomplete Dominance: Blending of traits.

  • Analyzing Pedigrees: Can determine inheritance patterns across generations, using symbols to represent traits and carriers in a family tree structure.