Control and coordination in mammals
Cambridge A-Level Biology (9700) · Unit 15: Control and coordination · 10 flashcards
Control and coordination in mammals is topic 15.1 in the Cambridge A-Level Biology (9700) syllabus , positioned in Unit 15 — Control and coordination , alongside Control and coordination in plants. In one line: Sensory neurones have a cell body located off to the side of the axon, a long dendron extending from the sensory receptor to the cell body, and a short axon carrying impulses to the central nervous system. Function is to transmit sensory information from receptors to CNS.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 10 flashcards — 1 definition and 9 key concepts — covering the precise wording mark schemes reward. Use the definition card to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Describe the structure of a sensory neurone, including the location and function of its key components
Sensory neurones have a cell body located off to the side of the axon, a long dendron extending from the sensory receptor to the cell body, and a short axon carrying impulses to the central nervous system. Function is to transmit sensory information from receptors to CNS.
What the Cambridge 9700 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Describe the endocrine system's features, using the hormones insulin, glucagon and ADH as reference points (see 14.1.8 to 14.1.10).
- Compare the nervous system's features with those of the endocrine system.
- Describe how sensory and motor neurones are structured and what they do, and state that intermediate neurones link sensory to motor neurones.
- Outline how sensory receptor cells detect stimuli and trigger impulses to be transmitted along sensory neurones.
- Describe, with a chemoreceptor cell from a taste bud in humans as the example, the series of events that leads to a sensory neurone producing an action potential.
- Describe and explain how a neurone's membrane potential changes, including: maintenance of the resting potential; the events of an action potential; restoration of the resting potential during the refractory period.
- Describe and explain how saltatory conduction lets impulses travel rapidly along myelinated neurones.
- Explain why the refractory period matters in setting how often impulses can be sent (their frequency).
- Describe how a cholinergic synapse is structured and explain how it works, including what calcium ions do.
- Describe how neuromuscular junctions, the sarcoplasmic reticulum and the T-tubule system each help to stimulate striated muscle to contract.
- Use diagrams and electron micrographs to describe the fine structure (ultrastructure) of striated muscle, focusing on how a sarcomere is built.
- Explain how muscles contract according to the sliding filament model, including the roles of tropomyosin, troponin, ATP and calcium ions.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9700 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in Control and coordination in mammals
- › Always include charge symbols (Na+ and K+) for ions. Referring to them as 'sodium and potassium' implies the metal atoms, not the ions.
- › Use the term 'saltatory conduction' to describe the 'increased speed of transmission' of the impulse; the action potential itself is not faster.
- › Use precise language: ions pass 'through' or 'across' a membrane, and it is the 'membrane' (not the whole neurone) that becomes depolarised.
Compare and contrast the nervous and endocrine systems in terms of speed, duration, and signal transmission.
The nervous system uses electrical impulses for rapid, short-duration responses, transmitted via neurons. The endocrine system uses hormones for slower, longer-duration responses, transmitted via the bloodstream.
Describe the structure of a sensory neurone, including the location and function of its key components.
Sensory neurones have a cell body located off to the side of the axon, a long dendron extending from the sensory receptor to the cell body, and a short axon carrying impulses to the central nervous system. Function is to transmit sensory information from receptors to CNS.
Outline the role of sensory receptor cells in initiating a nerve impulse.
Sensory receptor cells detect specific stimuli (
Describe the key steps involved in generating an action potential in a sensory neurone, using a chemoreceptor in a taste bud as an example.
Na⁺ from salty food diffuses into the chemoreceptor cell through Na⁺ channels, depolarising it (receptor potential). This opens voltage-gated Ca²⁺ channels, Ca²⁺ enters, and vesicles release neurotransmitter onto the sensory neurone. The neurotransmitter depolarises the sensory neurone, and if threshold is reached, an action potential is generated in it.
Explain how the resting potential of a neurone is maintained.
The resting potential is maintained by the sodium-potassium pump, which actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell. Additionally, the membrane is more permeable to K+ than Na+, resulting in a negative charge inside the cell.
Explain the role of voltage-gated ion channels in the generation of an action potential.
Voltage-gated Na+ channels open when the membrane potential reaches threshold, allowing Na+ to rush into the cell and cause rapid depolarization. Voltage-gated K+ channels then open, allowing K+ to flow out of the cell, causing repolarization.
Describe saltatory conduction and explain its advantages in impulse transmission.
Saltatory conduction is the 'jumping' of an action potential between Nodes of Ranvier in myelinated neurones. This increases the speed of impulse transmission significantly compared to unmyelinated neurones, as depolarization only occurs at the nodes.
Explain the importance of the refractory period following an action potential.
The refractory period ensures that action potentials travel in one direction only (down the axon). It also limits the frequency of action potentials, preventing continuous stimulation and allowing for discrete signal encoding.
Describe the sequence of events at a cholinergic synapse that leads to the transmission of a nerve impulse across the synaptic cleft.
Action potential arrives, voltage-gated Ca2+ channels open, Ca2+ influx triggers exocytosis of vesicles containing acetylcholine (ACh). ACh diffuses across the cleft, binds to receptors on the postsynaptic membrane, causing Na+ channels to open, leading to depolarization.
Explain the role of calcium ions in muscle contraction.
Calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin. This allows myosin heads to bind to actin, forming cross-bridges and initiating the sliding filament mechanism.
Review the material
Read full revision notes on Control and coordination in mammals — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 15 — Control and coordination
Control and coordination in mammals sits alongside these A-Level Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Control and coordination in mammals deck
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