Notes on Control and Coordination in Biological Systems

CONTROL AND COORDINATION

RESPONDING TO STIMULI

GENERAL CONCEPTS
  • Organisms continuously respond to environmental changes.
  • Stimuli: Information from the environment causing a response (e.g., heat from the sun).
  • Receptors: Specialized cells that collect stimuli and send information to the Central Nervous System (CNS).
RECEPTORS AND STIMULI
  • Receptors convert environmental energy into a form interpretable by the brain.
  • Sense organs contain receptors specialized for different types of stimuli:
    • Photoreceptors: Detect light (found in eyes).
    • Chemoreceptors: Detect chemicals (found in taste buds and nose).
    • Mechanoreceptors: Detect movement and pressure (found in skin).
    • Nociceptors: Detect pain (found in skin).
    • Thermoreceptors: Detect temperature (found in skin).
TYPES OF RECEPTORS

  • Sight:

    • Name: Photoreceptors
    • Location: Eye
    • Stimulus: Light

  • Taste:

    • Name: Chemoreceptors
    • Location: Tongue
    • Stimulus: Chemicals in food

  • Smell:

    • Name: Chemoreceptors
    • Location: Nose
    • Stimulus: Chemicals in air

  • Hearing:

    • Name: Mechanoreceptors
    • Location: Ear
    • Stimulus: Movement of air particles

  • Touch/Pressure:

    • Name: Mechanoreceptors
    • Location: Skin
    • Stimulus: Pressure from solid objects or water depth

  • Pain:

    • Name: Nociceptors
    • Location: Skin
    • Stimulus: Sharp objects, burns, skin damage

  • Temperature:

    • Name: Thermoreceptors
    • Location: Skin
    • Stimuli: Hot and Cold
SENSORY PROCESSING

  • Olfactory Receptors:

    • Detect olfactory stimulates through air molecules dissolved in mucus, sending messages via the olfactory nerve to the brain.

  • Touch Sensation:

    • Skin contains various receptors (pain, mechanoreceptors) detecting sharpness, temperature increases/decreases.
VISION
  • Photoreceptors have two types:
    • Cones (Colour and sharp vision, located in retina).
    • Rods (Night vision and peripheral vision, located in retina).
GUSTATION (TASTE)
  • Taste Process:
    • Tongue’s taste buds respond to dissolved chemicals from food.
    • Each bud can sense all flavors.
    • Approximately 10,000 taste receptors exist in the mouth.
NEURONS (Nerve Cells)
  • The nervous system comprises neurons which transmit information via electrical impulses:
    • Cell Body: Houses the nucleus.
    • Dendrites: Receives messages.
    • Axon: Sends impulses away from the cell body.
    • Myelin Sheath: Insulates axon, speeding up impulses.
TYPES OF NEURONS
  • Sensory Neurons: Conduct messages from senses to CNS.
  • Interneurons: Connect sensory and motor neurons in CNS.
  • Motor Neurons: Send signals from CNS to muscles/glands.
SYNAPSES AND TRANSMISSION
  • Neurons do not touch; they transmit signals through synapses.
  • Neurotransmitters: Chemicals that carry signals across synapses, converting electrical signals to chemical and back.
NERVOUS SYSTEM STRUCTURE
  • Two main parts:
    • Central Nervous System (CNS): Brain and spinal cord.
    • Peripheral Nervous System (PNS): Nerves throughout the body.
BRAIN FUNCTION
  • Cerebrum: Conscious thought and voluntary movement.
  • Cerebellum: Balance and coordination.
  • Brain Stem: Controls vital body functions like heartbeat and breathing.
  • The brain is divided into lobes, each responsible for specific functions (e.g., frontal lobe for reasoning, parietal lobe for sensations).
SPINAL CORD AND INJURIES
  • Spinal cord injury disrupts signal transmission, leading to conditions like quadriplegia or paraplegia depending on severity and location.
  • Slipped Disc: A protruding disc can compress spinal nerves, causing pain or numbness.
ENDORCRINE SYSTEM
  • Comprises glands secreting hormones, controlling body functions over more extended periods.
    • Regulates growth, repair, reproduction, digestion, and homeostasis.
HOMEOSTASIS
  • The process of maintaining a stable internal environment despite external changes (e.g., temperature and water balance).
  • Involves feedback mechanisms:
    • Negative Feedback: Reverses changes in the body (e.g., temperature regulation).
    • Positive Feedback: Accelerates changes (less common, can be life-threatening).
BLOOD GLUCOSE REGULATION
  • Involves hormonal control (
    • Insulin lowers blood glucose levels.
    • Glucagon raises blood glucose levels).
WATER REGULATION
  • Controlled by the hypothalamus and pituitary gland through anti-diuretic hormone (ADH).
    • Low water levels signal the release of ADH, increasing water reabsorption by kidneys.
    • High water levels result in decreased ADH release, leading to diluted urine.