Home / IB DP Biology- C2.2 Neural signaling – IB Style Questions For SL Paper 2

IB DP Biology- C2.2 Neural signaling - IB Style Questions For SL Paper 2 - FA 2025

IBDP Biology Paper 2 - All Chapters

Question

Neurons are highly specialized cells with structures that support their role in transmitting signals. The diagram below shows a neuron forming a connection with a muscle cell.
(a) State whether this neuron is insulated, and justify your answer.
(b) Identify two cellular features that neurons share with prokaryotic cells.
(c) Explain the process by which neurotransmitters leave the presynaptic membrane.

Most-appropriate topic codes (CED):

• TOPIC C2.2: Neural signalling — parts (a), (c)
• TOPIC A2.2: Cell structure — part (b)
▶️ Answer/Explanation
Detailed solution

(a)
Yes. The neuron is insulated because the axon is covered by a myelin sheath, formed by Schwann cells in the diagram.

(b)
Two shared structures:
1. Ribosomes
2. Plasma membrane (phospholipid bilayer)
(Other acceptable examples: cytoplasm, DNA)

(c)
When an action potential reaches the presynaptic terminal, the membrane depolarizes and voltage-gated \(\text{Ca}^{2+}\) channels open. The influx of calcium ions triggers synaptic vesicles carrying neurotransmitters to move toward and fuse with the presynaptic membrane. The neurotransmitters are then released into the synaptic cleft via exocytosis.

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