1.1 The LETTER that represents the central nervous system is B.

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Here are the answers to your questions about the reflex arc and nervous system injuries:

3.1.1 The LETTER that represents the central nervous system is B.

3.1.2

The sharp nail acts as a stimulus, which is detected by receptors (pain/pressure receptors) in the skin of the foot.
These receptors generate a nerve impulse that is transmitted along the sensory neuron (A) to the spinal cord.
In the spinal cord, the sensory neuron synapses with an interneuron (B), which then synapses with a motor neuron (C).
The motor neuron (C) transmits the nerve impulse from the spinal cord to the effector (D), which is a muscle in the foot/leg.
The effector muscle contracts, causing the foot to be immediately withdrawn from the nail.
Simultaneously, the impulse travels up the spinal cord to the brain, resulting in the sensation of pain.

3.1.3
- a) The patient can feel the scraping but cannot move his feet: C
- b) The patient cannot feel the scraping, but is able to move his feet: A
- c) The patient can neither feel the scraping nor move his feet: B
- d) The patient cannot feel the scraping or move his upper and lower limbs: B

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