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
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- describe the features of the endocrine system with reference to the hormones ADH, glucagon and insulin (see 14.1.8, 14.1.9 and 14.1.10)
- compare the features of the nervous system and the endocrine system
- describe the structure and function of a sensory neurone and a motor neurone and state that intermediate neurones connect sensory neurones and motor neurones
- outline the role of sensory receptor cells in detecting stimuli and stimulating the transmission of impulses in sensory neurones
- describe the sequence of events that results in an action potential in a sensory neurone, using a chemoreceptor cell in a human taste bud as an example
- describe and explain changes to the membrane potential of neurones, including: • how the resting potential is maintained • the events that occur during an action potential • how the resting potential is restored during the refractory period
- describe and explain the rapid transmission of an impulse in a myelinated neurone with reference to saltatory conduction
- explain the importance of the refractory period in determining the frequency of impulses
- describe the structure of a cholinergic synapse and explain how it functions, including the role of calcium ions
- describe the roles of neuromuscular junctions, the T-tubule system and sarcoplasmic reticulum in stimulating contraction in striated muscle
- describe the ultrastructure of striated muscle with reference to sarcomere structure using electron micrographs and diagrams
- explain the sliding filament model of muscular contraction including the roles of troponin, tropomyosin, calcium ions and ATP
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.
- › Note that endorphins bind to specific receptors on the presynaptic knob to inhibit the release of neurotransmitters.
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.
Chemoreceptors bind to specific molecules in food. This causes a change in membrane permeability, leading to influx of Na+ ions, depolarising the membrane. If depolarization reaches threshold, voltage-gated Na+ channels open, initiating an action potential.
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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