Answer: [Description: Arc shape connecting skin to spinal cord and back to muscle].
Analysis: Why withdrawal before pain?
Answer: The reflex arc is local to the spinal cord for speed. The message to the brain (pain perception) travels through a longer path and takes slightly more time.
Damaged motor neuron?
Answer: The person will feel the pain (sensory works) but will not be able to move the hand (effector fails).
Case Study 2:
Elderly person with Parkinson's (lack of Dopamine).
6. What is a "Synapse"?
Answer: The microscopic gap between the axon terminal of one neuron and the dendrite of the next.
Role of neurotransmitters.
Answer: They are chemicals (like Acetylcholine or Dopamine) released from vesicles that diffuse across the synapse to transmit the impulse to the next neuron.
Creating: Analogy.
Answer: Like a relay race where the baton (neurotransmitter) is handed from one runner to the next at the exchange zone (synapse).
Critical Thinking: Why one direction?
Answer: Vesicles containing neurotransmitters are only present at the axon terminals, and receptors are only present on the dendrites.
Resting vs Action Potential.
Answer: Resting: Neuron is not conducting (-70mV). Action: Reversal of polarity (+30mV) during conduction of an impulse.
Answer: (a) Both A and R are true and R is the correct explanation.
Assertion (A): Medulla Oblongata is vital.
Reason (R): It controls involuntary activities.
Answer: (a) Both A and R are true and R is the correct explanation.
Assertion (A): Rod cells responsible for dim light vision.
Reason (R): They contain Rhodopsin.
Answer: (a) Both A and R are true and R is the correct explanation.
Assertion (A): Blind spot is area of best vision.
Reason (R): It has maximum Cones.
Answer: (d) A is false but R is true (in definition of fovea, but for blind spot, both are false). Correct Answer: (d) A is false. (Blind spot has no photoreceptors).
Answer: Cerebrum: Large, memory/intellect, outer grey. Cerebellum: Small, balance/coordination, outer grey with tree-like white inside.
Visualisation: Neuron diagram.
Answer: [Description: Star-shaped cyton with a long tail]. Myelin sheath acts as insulation and increases speed of impulse (Saltatory conduction).
Application: Dizziness after spinning.
Answer: The fluid (endolymph) in the semicircular canals continues to move due to inertia even after the head stops, sending false signals to the brain.
Creating: Anosmia effect on taste.
Answer: Flavor is a combination of smell and taste. Without smell, food tastes bland and complex flavors cannot be distinguished.
Analysis: "All-or-None" law.
Answer: A stimulus must reach a threshold to trigger an impulse. Once triggered, the impulse always has the same strength regardless of the stimulus intensity.
Designing: Color Blindness test.
Answer: Use Ishihara plates (dots of different colors forming numbers).