,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"fc8e4265-33c0-4f8b-886c-33899080c3ba","label":null,"content":"Describe the pathway of the electrical impulses from the pain receptor in the foot to the effector muscle.\n\nIn your answer, you should:\n* name neurones P, Q, and R\n* describe the sequence of events along the reflex arc, including how information is passed between neurones.","markscheme":"- Identifies Neurone P as the sensory neurone, Neurone Q as the relay neurone, and Neurone R as the motor neurone B1\n- Describes that a stimulus (the sharp pin) is detected by receptors in the skin which generate an electrical impulse B1\n- Describes the impulse travelling along Neurone P (sensory neurone) to the spinal cord (central nervous system) M1\n- Explains that at the synapse between Neurone P and Neurone Q, a chemical neurotransmitter diffuses across the gap to trigger an impulse in Neurone Q M1\n- Describes the impulse travelling through Neurone Q (relay neurone) and crossing a second synapse to Neurone R (motor neurone) A1\n- Describes the impulse travelling along Neurone R to the effector (leg muscle), causing it to contract and lift the foot A1","marks":6,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"reflex_arc_pathway","label":"Trace the reflex arc","steps":[{"type":"text","order":0,"title":"Name the neurones","content":"First use the positions in the supplied diagram. **Neurone P** carries information from the receptor *towards* the spinal cord, so it is the **sensory neurone**. **Neurone Q**, entirely in the spinal cord, is the **relay neurone**. **Neurone R** carries information from the spinal cord to the muscle, so it is the **motor neurone**.\n\nThis identification earns the first **B1** mark.","highlights":[{"text":"* name neurones P, Q, and R","location":"specification"}]},{"type":"text","order":1,"title":"Start at the receptor","content":"The sharp pin is the **stimulus** (a change detected by the body). Pain receptors in the skin of the foot detect it and generate an electrical impulse.\n\nState both the receptor and the electrical impulse for the second **B1** mark.","highlights":[{"text":"a rapid reflex action occurs to lift the foot away.","location":"specification"}]},{"type":"text","order":3,"title":"Reach the spinal cord","content":"The impulse travels along neurone P, the sensory neurone, into the spinal cord. The spinal cord is part of the **central nervous system**.\n\nFollowing the impulse from P to the spinal cord earns **M1**.","highlights":[{"text":"describe the sequence of events along the reflex arc","location":"specification"}]},{"type":"text","order":4,"title":"Explain the first synapse","content":"There is a tiny gap, called a **synapse**, between P and Q. The electrical impulse causes a chemical called a **neurotransmitter** to be released. It diffuses across the synapse and triggers a new electrical impulse in neurone Q.\n\nDo not write that the electrical impulse itself jumps the gap: the chemical transmitter is needed for the **M1** mark.","highlights":[{"text":"including how information is passed between neurones.","location":"specification"}]},{"type":"text","order":5,"title":"Pass through the relay","content":"The new impulse travels along Q, the relay neurone, through the spinal cord. It then crosses the second synapse to R, the motor neurone, by the same neurotransmitter process.\n\nMentioning Q and the second synapse earns **A1**.","highlights":[{"text":"including how information is passed between neurones.","location":"specification"}]},{"type":"text","order":6,"title":"Cause the response","content":"Finally, the impulse travels along R, the motor neurone, to the effector: the leg muscle. The muscle contracts, lifting the foot away from the pin.\n\nThis final link from motor neurone to response earns the last **A1** mark. A complete answer therefore follows the route in order and names the chemical transfer at each synapse.","highlights":[{"text":"to the eff

The brain and the nervous system

Question 4

The brain and the nervous system Questions

The brain and the nervous system

Question 4

The brain and the nervous system Questions