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IB MYP Integrated Sciences e-Assessment : Nervous system Exam Style Practice Questions - New Syllabus

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Question : Human Body Systems [8 marks]

The human body consists of several organ systems working together to maintain homeostasis.

Question a [1 mark] – Cells: Systems

List the four main body systems that work together during physical exercise:

▶️ Answer/Explanation

Detailed Answer:

The four primary systems that coordinate during exercise are:

  1. Muscular System – Contracts skeletal muscles to produce movement
  2. Respiratory System – Increases oxygen intake and carbon dioxide removal through faster breathing
  3. Cardiovascular System – Accelerates heart rate to deliver more oxygenated blood to muscles
  4. Nervous System – Coordinates muscle contractions and regulates breathing/heart rate

Key Interactions:

  • Nervous system stimulates muscles to contract
  • Increased muscle activity raises oxygen demand
  • Respiratory system responds by increasing ventilation rate
  • Cardiovascular system increases cardiac output to meet demand

Common Mistakes: Students often include the digestive system, which actually slows down during exercise as blood is diverted to muscles.

Question b [2 marks] – Cells: Tissues and Organs

Complete the table by matching each organ with its correct system and primary function:

OrganSystemFunction
Heart
Alveoli
▶️ Answer/Explanation

Detailed Answer:

OrganSystemFunction
HeartCardiovascular System
  • Primary: Acts as a muscular pump to circulate blood
  • Mechanism: Contracts rhythmically (≈72 bpm at rest)
  • Pathway: Right side pumps to lungs, left side to body
AlveoliRespiratory System
  • Primary: Site of gas exchange in lungs
  • Mechanism: Oxygen diffuses into blood, CO2 diffuses out
  • Structure: Tiny air sacs with large surface area (≈70m2)

Key Concepts:

  • Heart: Must emphasize pumping action – accept “circulates blood” but not “transports oxygen” alone
  • Alveoli: Must mention gas exchange – accept “oxygen absorption” but not just “breathing”

Marking Guidance: Award 1 mark for correct system identification (0.5 each) and 1 mark for accurate function description (0.5 each).

Question c [4 marks] – Interaction with Environment: Nervous System

Describe the pathway of a reflex arc when touching a hot surface:

1.
2.
3.
4.
▶️ Answer/Explanation

Detailed Answer:

  1. Stimulus Detection (1 mark):
    • Thermoreceptors in skin detect dangerous heat (>45°C)
    • Nociceptors (pain receptors) may also activate
    • Receptors convert thermal energy to electrical nerve impulses
  2. Sensory Transmission (1 mark):
    • Sensory neurons carry action potentials to spinal cord
    • Via dorsal root ganglion (unipolar neurons)
    • Myelinated fibers allow rapid transmission (≈120 m/s)
  3. Processing (1 mark):
    • Synapse occurs in spinal cord gray matter
    • Interneurons relay signal to motor neurons
    • May involve withdrawal reflex (polysynaptic arc)
  4. Motor Response (1 mark):
    • Motor neurons activate skeletal muscles (e.g., biceps)
    • Simultaneous inhibition of antagonistic muscles (triceps)
    • Response occurs in ≈50ms (before pain perception)

Diagram Reference:

[Reflex Arc Diagram: Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector]

Marking Scheme:

  • 1 mark per correct stage with key terminology
  • Deduct 0.5 if “brain” is incorrectly included as essential
  • Accept “withdrawal reflex” as alternative description

Question d [1 mark] – Interaction with Environment: Nervous System

Explain one survival advantage of the fight-or-flight response:

 
▶️ Answer/Explanation

Detailed Answer:

The fight-or-flight response provides critical survival advantages through:

  1. Physiological Enhancement:
    • Adrenal medulla releases epinephrine (adrenaline)
    • Heart rate increases from ≈72 to ≈180 bpm
    • Bronchodilation improves oxygen intake by 40-60%
    • Blood glucose levels rise by 75-100%
  2. Threat Response Optimization:
    • Blood diverted from digestion to skeletal muscles
    • Pupils dilate to improve visual acuity
    • Pain perception temporarily reduced
  3. Evolutionary Advantage:
    • Enabled ancestors to escape predators
    • Modern equivalent: Reacting to vehicles/dangers
    • Short-term activation prevents tissue damage

Acceptable Responses (1 mark each):

  • “Increases physical strength/speed to escape danger”
  • “Prioritizes oxygen/blood flow to essential organs”
  • “Provides immediate energy for emergency actions”

Common Misconceptions: Do not accept “makes you brave” or vague answers about “staying safe”. Must describe physiological changes.

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