Year 9 MYP Homeostasis Notes (copy)

Year 9 MYP Homeostasis

Inquiry Questions

  • Factual: What conditions are regulated by body systems?
  • Conceptual: How do systems work together to respond to change?
  • Debatable: When body systems fail, who should decide how medical information and resources are allocated?

Cell and System Basics

  • Cells: Smallest living structures capable of self-maintenance.
  • Tissues: Formed when cells of the same type work together.
  • Organs: Composed of different types of tissues working together (e.g., stomach, lungs).
  • Systems: Organs collaborating towards common goals (excretion, digestion, respiration).
  • Organism: Multitude of systems working together to form a living being.

Key Terms

  • Cell: Basic unit of life.
  • Tissue: Group of similar cells performing a specific function.
  • Organ: A structure made of tissues working together.
  • System: Group of organs working collectively.

The Nervous System

  • Neurons: Nerve cells that transmit impulses rapidly.
  • Neuroglial Cells: Support cells in the nervous system.

Types of Receptors and Stimuli

  • Sense Organs: Detect stimuli from the environment (light, sound, touch, taste, smell).
  • Receptor Types:
    • Photoreceptors: Detect light (e.g., rods and cones in the eye).
    • Mechanoreceptors: Detect touch, pressure, and sound.
    • Thermoreceptors: Sense variations in temperature.
    • Chemoreceptors: Respond to chemical stimuli (e.g., taste and smell).
    • Pain Receptors: Detect harmful stimuli, indicating danger or injury.

Homeostasis

  • Definition: The process of maintaining a stable internal environment despite external changes.
  • Examples of Regulated Conditions: Water balance, temperature, energy, oxygen, and waste levels.
  • Importance: Body functions optimally when internal conditions are stable.
  • Responding to Stimuli: Essential for homeostasis; systems must detect and respond appropriately.

Stimulus-Response Model

  • Components:
    • Stimulus: Change in the environment (internal/external).
    • Receptor: Detects the change.
    • Control Centre: Regulates the output to adjust for changes.
    • Effector: Organs, glands, or tissues executing the adjustments.
    • Response: Outcome from the adjustments made.

Feedback Mechanisms

  • Negative Feedback: Opposes change to return to normal (e.g., regulating body temperature).
  • Positive Feedback: Amplifies change until an endpoint is reached (e.g., childbirth, blood clotting).

The Nervous System's Structure

  • Central Nervous System (CNS): Comprises the brain and spinal cord.
  • Peripheral Nervous System (PNS): Neurons that carry messages to and from the CNS.
  • Neuron Structure:
    • Dendrites: Receive signals from other neurons.
    • Cell Body: Contains nucleus and integrates signals.
    • Axon: Transmits impulses away from the cell body.
    • Myelin Sheath: Insulates axon for faster signal transmission.
    • Synapse: Junction where signals are passed between neurons.

Neural Impulses

  • Process: Electrical impulses generated by ion movement.
  • Neurotransmitters: Chemicals released at synapse to relay messages
    to the next neuron.

Types of Neurons

  • Sensory Neurons: Relay sensory information from the PNS to the CNS.
  • Interneurons: Connect sensory and motor neurons within the CNS.
  • Motor Neurons: Carry messages from the CNS to effectors (muscles and glands).

Reflex Actions

  • Reflex Arc: Pathway for reflex actions that bypasses the brain, allowing for quick responses to stimuli.
  • Process: Involves a sensory neuron, interneuron (in spinal cord), and motor neuron.

Conclusion

  • Reflective Practices: Metacognition about the lesson—consider connections with prior knowledge and challenges faced while learning.