Control and Coordination

Q1. A student accidentally touches a hot stove in the kitchen. Her hand pulls back immediately without her consciously thinking about it. Which of the following best explains why this response is faster than a response involving conscious thought?

• A. The reflex arc bypasses the brain by using a direct pathway through the spinal cord, reducing the time needed for response ✓
• B. The hand muscles contract automatically because they are not controlled by the nervous system
• C. Conscious thought is slower because the brain is located far from the spinal cord
• D. Heat energy directly triggers muscle contraction without involving nerve impulses

Answer: A — Reflex arcs use a short pathway through the spinal cord that doesn't require input from the brain, making them much faster than conscious responses; option B incorrectly suggests muscles aren't nervous-system controlled, and D falsely claims muscles contract without nerve impulses.

Q2. During a biology practical, a student observes that when she blocks her nose and eats a piece of apple, she cannot distinguish its taste properly, but when she releases her nose, the taste becomes clear. Which concept from the nervous system best explains this observation?

• A. Gustatory receptors alone cannot detect all components of taste; olfactory receptors in the nose contribute significantly to the perception of flavor ✓
• B. The taste buds in the mouth are connected directly to the brain, while smell receptors bypass the brain
• C. Blocking the nose prevents saliva from reaching taste buds, so taste receptors cannot function
• D. The tongue and nose use different types of neurons that do not communicate with each other

Answer: A — Taste and smell together create the perception of flavor; blocking the nose prevents olfactory input, reducing flavor perception despite gustatory receptors still functioning, while option C incorrectly suggests saliva access is blocked.

Q3. A gardener observes that his sunflower plant bends toward the sunlight over the course of several days. Which statement correctly describes the control mechanism involved in this movement?

• A. This is a growth response controlled by plant hormones that redistribute due to light direction, not a rapid nervous response like in animals ✓
• B. The plant's roots detect light and send electrical impulses to the stem to make it bend
• C. The sunflower has a nervous system similar to animals that allows it to consciously turn toward light
• D. Light directly causes the cells on the shaded side to contract, bending the plant toward sunlight

Answer: A — Plant movements toward light are slow, growth-based responses mediated by hormones, not rapid nerve-impulse responses; option B incorrectly assigns light detection to roots, and C falsely claims plants have animal-like nervous systems.

Q4. Assertion (A): When a person's hand touches a hot object, the hand is pulled away before the person consciously feels pain. Reason (R): The reflex arc allows a rapid response because sensory and motor neurons communicate directly through the spinal cord without involving the brain. Choose the correct option:

• A. Both A and R are true and R is the correct explanation of A ✓
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer: A — The reflex arc does involve the spinal cord as a relay point between sensory and motor neurons, bypassing the brain and allowing faster withdrawal than conscious pain perception; both statements are scientifically accurate and causally related.

Q5. A doctor shines a bright light into a patient's eye and observes that the pupil constricts immediately. Which type of neuron is primarily responsible for detecting the light stimulus in this reflex?

• A. Sensory receptors (photoreceptors) in the retina of the eye ✓
• B. Motor neurons in the iris muscle of the eye
• C. Interneurons located in the spinal cord
• D. Gustatory receptors in the cornea of the eye

Answer: A — Photoreceptors in the retina detect light stimulus and initiate the reflex arc; motor neurons cause the response (pupil constriction) but do not detect the stimulus, and gustatory receptors detect taste, not light.

Q6. Assertion (A): Electrical impulses in neurons travel from the dendrite through the cell body and along the axon in a single direction. Reason (R): Synapses contain vesicles that release neurotransmitters only from the axon terminal to the next cell. Choose the correct option:

• A. Both A and R are true and R is the correct explanation of A ✓
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer: A — The one-way transmission at synapses (neurotransmitter release from presynaptic axon terminal) ensures impulses travel directionally through neurons; both statements are true and the structural feature of synapses explains the directional flow.

Q7. In a laboratory experiment, a student stimulates a frog's leg nerve with an electrical impulse and observes that the leg muscle contracts. If the same electrical impulse is applied directly to the muscle tissue (bypassing the nerve), what would be the most likely outcome?

• A. The muscle would not contract because muscles require nerve signals to interpret stimuli
• B. The muscle would still contract because muscle cells can respond directly to electrical stimulation ✓
• C. The muscle would contract only if the stimulus is stronger than normal nerve impulses
• D. The muscle would contract, but the response would be slower than when stimulated through the nerve

Answer: B — Muscle cells respond directly to electrical impulses; stimulating muscle directly bypasses the nerve but the muscle still contracts because it can respond to electrical signals independently, making option A incorrect.

Q8. Assertion (A): In a reflex arc, the sensory neuron synapse directly with the motor neuron through an interneuron located in the spinal cord. Reason (R): This arrangement allows the reflex action to occur without sending information to the brain, thereby reducing response time. Choose the correct option:

• A. Both A and R are true and R is the correct explanation of A ✓
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer: A — The reflex arc involves sensory-interneuron-motor connections in the spinal cord, enabling rapid responses without brain involvement; the structural arrangement directly explains why reflex actions are faster than conscious responses.

Q9. A student observes that when she chews gum, saliva is produced automatically. Which of the following best explains this response?

• A. Mechanoreceptors in the mouth detect chewing and trigger a reflex that stimulates salivary glands via the nervous system ✓
• B. The muscles in the mouth directly secrete saliva without any nervous system involvement
• C. The brain consciously decides to produce saliva whenever chewing is detected
• D. Saliva is produced by the teeth grinding together, not by the nervous system

Answer: A — Salivary reflex is triggered by sensory receptors detecting mechanical stimulation (chewing), which activate the nervous system to stimulate salivary glands; option B incorrectly excludes nervous system involvement, and C falsely claims the response is conscious.

Q10. In an experiment, when a student's patellar tendon (just below the kneecap) is tapped with a small hammer, the leg kicks involuntarily. If the student's spinal cord were damaged at the level of the lower back, which of the following would most likely occur?

• A. The knee-jerk reflex would still occur because the reflex arc can function through the local spinal cord segment, even if higher connections are damaged ✓
• B. The knee-jerk reflex would be absent because the brain must be involved in all reflex actions
• C. The knee-jerk reflex would occur but would be slower because signals must now travel through alternative neural pathways
• D. The knee-jerk reflex would not occur because the hammer tap would not generate enough force to stimulate receptors

Answer: A — The knee-jerk reflex involves a local reflex arc in the spinal cord that operates independently of the brain; damage to higher spinal levels does not affect the reflex because it doesn't require brain involvement, making option B incorrect.