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QLDBiologyQuick questions
Unit 2: Maintaining the internal environment
Quick questions on Neurons, action potentials, synapses and reflex arcs (QCE Biology Unit 2)
7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is structure of a neuron?Show answer
A neuron is a specialised cell built for long-distance signalling.
What is the resting potential?Show answer
At rest, the inside of the neuron is around 70 mV more negative than the outside.
What is the action potential?Show answer
If a stimulus depolarises the membrane past the threshold (around minus 55 mV), an action potential is triggered. The response is all-or-nothing: once threshold is crossed, the action potential goes ahead at full size; below threshold, nothing happens.
What is the reflex arc?Show answer
A reflex arc is the neural pathway responsible for a reflex: a rapid, involuntary response to a specific stimulus. The classic example is the patellar (knee-jerk) reflex.
What is q1?Show answer
Describe the sequence of events from stimulus to response in a knee-jerk reflex, naming each component of the reflex arc. [4 marks]
What is q2?Show answer
A neuron at rest has a membrane potential of minus 70 mV. After stimulation, the trace rises to plus 35 mV, then falls below minus 70 mV before stabilising. Identify the ions responsible for each phase and explain the temporary undershoot.
What is q3?Show answer
Refer to synaptic transmission. (a) Describe how an action potential at the presynaptic terminal releases neurotransmitter. (b) Explain how the postsynaptic membrane depolarises.
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