Study Guide: Biology - Coordination and Response (Chapter 10)

Syllabus Coverage: Comprehensive overview of physiological control mechanisms, integrating nervous and hormonal principles. Format Goal: Quick-reference summary; distill concepts for rapid tutor/student review. Syllabus Note: Covers core topics. Topics marked (E) denote detailed focus typically reserved for Extended grades (e.g., full endocrine pathway analysis).

Overview: Coordination Principles

Coordination ensures organism survival. Requires communication systems to detect stimulus and initiate response.

  • Detection: Stimulus received by Receptors.
  • Processing: Signal processed in the Central Nervous System (CNS) or Endocrine system.
  • Response: Action initiated by Effectors.

System 1: Nervous Coordination (Fast Response)

Mechanism: Electrical impulse transmission via neurons. Very rapid response time. Pathway (Reflex Arc): Receptor $\rightarrow$ Sensory Neuron $\rightarrow$ CNS $\rightarrow$ Motor Neuron $\rightarrow$ Effector.

  • Neuron Action Potential: Electrical charge (depolarisation/repolarisation) moves along axon in directional flow.
  • Synapse Gap: Chemical transmission. Neurotransmitters cross gap to excite or inhibit next neuron.
  • Key Concept: Reflexes: Automatic, immediate protective actions. CNS intercepts signal quickly.

System 2: Hormonal Coordination (Slow/Long-Term Response)

Mechanism: Chemical messengers (Hormones) travel via blood. Regulates long-term balance and processes. Slower action, but sustained effect.

  • Feedback Loop: Primary control structure. All major systems rely on Negative Feedback to return the body to a set point (homeostasis). -Example: High blood sugar $\rightarrow$ Pancreas releases Insulin $\rightarrow$ Lowers blood sugar back to normal range._

Critical Systems

  1. Blood Glucose Homeostasis:

    • Hormones Involved: Insulin, Glucagon, GLP-2 (Released by pancreatic Islets of Langerhans).
    • Low Sugar Scenario ($\downarrow$ Glu): Hypothalamus detects low glucose $\rightarrow$ release of Glucagon and potentially $GLP-2$; stimulates liver to break down stored glycogen (glycogenolysis) and synthesize glucose (gluconeogenesis) $\rightarrow \uparrow$ blood glucose.
    • High Sugar Scenario ($\uparrow$ Glu): Pancreas detects high glucose $\rightarrow$ releases Insulin $\rightarrow$ facilitates uptake of glucose by body cells; liver converts excess glucose into glycogen storage $\rightarrow \downarrow$ blood glucose. (Core/Extended)

  2. Thermo-regulation:

    • Process: Maintaining stable core temperature. Fluctuation destabilizes homeostasis. Hypothalamus acts as the primary monitoring center.
    • Cooling Mechanism: Sweating and vasodilation (blood vessels near skin surface expand, releasing heat).
    • Warming Mechanism: Shivering/Vasoconstriction (reducing blood flow to outer skin layers to conserve heat). (Core)/(E)

  3. Stress Response:

    • Input: Danger/Stress.
    • Immediate Action: Adrenaline release rapidly (increased rate, heart rate) (Core).
    • Sustained Action: Cortisol release maintains response over long period (E).

Plant Coordination & Responses

Lacks nervous system; uses chemical signals and structural changes.

  1. Tropisms: Directional growth responses to stimuli. (General concept - Core)
    • Phototropism: Growth toward light via differential auxin concentration. (Core)
    • Gravitropism: Reaction to gravity. (Core)
  2. Nastic Movements: Non-directional movement regardless of stimulus angle (e.g., leaf folding upon touch). (Core/Basic extension concept)

Synthesis & Comparison Table

Feature Nervous System Endocrine System Plant Trophes
Messenger Electrical/Chemical Impulse Chemical (Hormones) Chemical (Auxin)
Speed Very Fast Slow Growth Rate Dependent
Duration Brief/Immediate Long-Lasting Sustained Growth
Example Reflex Arc, Signal Transfer Blood Glucose Regulation Phototropism

(End of Study Guide)