1. 1
   A student accidentally touches a hot saucepan with a finger and immediately pulls the hand away before feeling any pain. This rapid, automatic response is coordinated by the nervous system and involves a reflex arc passing through several types of neurone.

   (a)

   Which part of the nervous system consists of the brain and the spinal cord?

   [1 mark]

   • AThe peripheral nervous system
   • BThe central nervous system
   • CThe endocrine system
   • DThe autonomic system

   (b)

   In the reflex arc that withdraws the hand from the saucepan, which type of neurone carries the impulse from the receptor in the skin towards the central nervous system?

   [1 mark]

   • AMotor neurone
   • BRelay neurone
   • CSensory neurone
   • DEffector neurone

   (c)

   Name, in the correct order, the five components of the reflex arc involved in withdrawing the hand from the hot saucepan.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   At a synapse, neurotransmitter molecules stored in vesicles are released and diffuse across a small gap before binding to receptor proteins on the next neurone, generating a new impulse only in that neurone.

   (a)

   Along the reflex arc, an impulse must cross a junction between the sensory neurone and the relay neurone. What is this junction called?

   [1 mark]

   • AA synapse
   • BA ganglion
   • CAn axon terminal
   • DA dendrite

   (b)

   What ensures that impulses travel across a synapse in one direction only?

   [1 mark]

   • AImpulses are electrical rather than chemical at the synapse
   • BThe synaptic gap is filled with myelin
   • CMotor neurones are shorter than sensory neurones
   • DNeurotransmitter is only released from vesicles on one side of the gap

   (c)

   Describe the sequence of events that occurs at a synapse when an electrical impulse arrives from the first neurone.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A doctor is explaining to a patient how reflex actions and synapses protect the body, using the example of the withdrawal reflex and the structure of a synapse between two neurones.

   (a)

   A doctor explains that a reflex action allows the body to respond to a stimulus automatically, without the person needing to think about it. Describe why a reflex action is important for survival, and explain why it does not require conscious thought.

   [3 marks]

   (b)

   Describe the structure of a synapse, including the parts involved in transmitting an impulse from one neurone to the next.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Researchers compared reaction times for a reflex withdrawal response and a voluntary button-press response to a stimulus, finding the reflex was consistently faster, and investigated the role of synapses in both pathways.

   (a)

   Researchers compared how quickly volunteers could withdraw a hand from a painful stimulus (a reflex action) with how quickly they could press a button in response to seeing a light (a voluntary action requiring conscious decision). The reflex action was consistently faster. Explain, with reference to the structures and pathways involved, why the reflex withdrawal of the hand is faster than the voluntary button-press response.

   [6 marks]

   (b)

   The researchers also found that when a drug blocking receptor proteins at synapses was applied, both the reflex and the voluntary responses were abolished entirely. Explain the role of synapses in impulse transmission and why blocking receptor proteins would prevent both types of response.

   [6 marks]

   Total for question 4: 12 marks

End of questions