LAST QUIZ

• Plant hormones are chemical messengers that regulate sensory responses of plants to external stimuli
• Plant hormones, together with water and other metabolites, are usually transported to different plant tissues through the vascular bundles
• Cell-to-cell transport of hormones is possible through the plasmodesmata
• Types of Plant Hormones:

  • Auxin: controls cell elongation in stems and leaves as induced by light exposure and in roots as a response to gravity
  • Cytokinins: mainly responsible for the regulation of cell division
  • Gibberellins: responsible for shoot elongation, seed germination, and fruit and flower maturation
  • Abscisic Acid (ABA): primary hormone for stress response and stomatal closure
  • Ethylene: responsible for promoting fruit ripening, flower wilting, and leaf fall
• Phototropism refers to the movement of plant parts toward or away from a light source
• Gravitropism refers to the movement of plant parts as a response to gravity
• Seed Germination: Upon exposure to light, light-sensitive proteins signal the production of the enzyme amylase that breaks down the starch in the seed to produce simple sugars
• Stomatal Movement: Light-sensitive proteins that detect blue light cause stomata to open to allow gas exchange for photosynthesis to occur; Abscisic acid triggers stomatal closure to prevent excessive water loss
• Thigmotropism refers to the movement of plants in response to a touch stimulus
• Despite pathways that lead to stomatal closure at night, the small gap between guard cells can still allow small molecules such as gases to pass through
• Stimuli are factors that trigger responses in organisms
• Initiation of responses is best demonstrated by human sensory systems
• Plant hormones are chemical messengers released by tissues in trace or small quantities
• Plant hormones can be transported into distant targets via vascular tissues
• No special glands produce plant hormones as they can be synthesized by any plant cell or tissue
• Plant hormones influence various biological processes such as growth, development, and flowering
• Auxins play a role in plant growth, cell expansion, and inducing cell division in various plant tissues
• Cytokinins play a role in cell division, differentiation, aging, and the maintenance of meristems
• Gibberellins promote growth, elongation of plant stems, stimulate flower development, and leaf senescence
• Ethylene plays a role in the ripening of fruits, growth, aging of plants, and initiating responses against stress
• Common plant stimuli include light, gravity, touch, and water
• Submerged aquatic plants rely more on blue photoreceptors due to the penetration of blue light in water
• Forest floor plants rely more on red photoreceptors due to the presence of red light in less shaded areas
• Light-dependent responses in plants refer to development and growth influenced by light presence, type, or intensity
• Photomorphogenesis refers to altered growth in plants grown in the dark, making them slender and white
• Photoperiodism is when plants use light to track time and produce flowers based on day length
• Phototropism is the orientation of plants towards a light source, which can be positive or negative
• Gravitropism refers to the directional response of plant parts to gravity
• Glial cells are supporting cells of the nervous system that do not conduct or transmit nerve impulses but address important requirements of neurons
• Types of glial cells include:

  • Astrocytes: form the brain structure and support the metabolic needs of neurons
  • Microglia: immune cells that help fight invading pathogens in the nervous system
  • Schwann Cells: produce myelin, a lipid-rich substance that insulates axons for faster signal transmission
• Sea jellies have the simplest nervous system, the nerve net, sufficient to control their motor functions
• Sensory neurons, also called afferent neurons, are found in sensory structures that detect stimuli and relay information into the central nervous system for processing
• Types of sensory receptors and their functions:

  • Nociceptors: detect pain stimuli
  • Mechanoreceptors: detect mechanical stimuli like sound waves and tactile sensations
  • Photoreceptors: detect light presence, absence, wavelengths, and intensities
  • Chemoreceptors: detect chemicals in air and food
  • Osmoreceptors: sense changes in substance concentration or osmotic pressure
  • Thermoreceptors: sense specific temperatures or temperature changes
• Effector organs, like muscle tissues and glands, respond to signals from the central nervous system by triggering muscle contractions or gland secretions
• Examples of effector organs and their responses to stimuli:

  • Muscle tissues: voluntary or involuntary contractions for movement
  • Glands: secrete substances in response to nervous control, can be enzymes or hormones
• The human nervous system is highly similar to the nervous system of other mammals
• Among vertebrates, mammals have the most complex nervous systems
• Divisions of the Nervous System:

  • Central and peripheral divisions
  • Classification based on control: somatic nervous system and autonomic nervous system
• The somatic nervous system controls the activities of skeletal muscles
• Neurons extend from the spinal cord to the muscles, allowing voluntary and involuntary nervous control of these muscles