A reflex arc: rapid automatic coordination
הוצג| English | משמעות |
|---|---|
| sensory neurone/ˈsensəri ˈnjuːrəʊn/ | נוירון רגשי |
| synapse/ˈsɪnæps/ | סינפסה |
What would explain this observation?
- A hand can withdraw from a harmful stimulus before a person consciously decides to move it. The response follows a coordinated nerve pathway.
Build the model
- The nervous system enables responses to surroundings and coordinates behaviour.
- Receptors detect a stimulus and information travels as electrical impulses along neurones to the central nervous system, the brain and spinal cord.
- A response passes to an effector such as a muscle, which contracts, or a gland, which secretes.
- sensory neurone 感觉神经元: A neurone carrying information from receptors towards the CNS.
- synapse 突触: The junction across which a signal passes between neurones.
Which sequence is correct for the simplified reflex pathway?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
The simplified pathway runs receptor to sensory neurone to relay neurone to motor neurone to effector - detection inward, response outward. The other orders run backwards or mix in structures that carry no impulses.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- A reflex pathway includes a sensory neurone carrying information from a receptor, a relay neurone in the CNS and a motor neurone carrying information to an effector.
- At a synapse a chemical messenger crosses the small junction between neurones and triggers a new electrical impulse in the next cell.
- Reflexes are automatic and rapid and do not involve the conscious part of the brain, helping protect the body from harm.
In the lab: Arrange a labelled reflex-arc model in the correct order and explain the direction of information at each connection. Compare automatic reflexes with deliberate choices without testing pain or injury. Use supplied timing tables to interpret responses; do not claim that a stimulus physically travels as an object through the nerve.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: fictional pathway stages take 8, 3 and 11 ms in a supplied model.
- Total model time = 8+3+11 = 22 ms, or 0.022 s.
- This sums the stated delays only.
- It is not a universal human reflex time and does not include any omitted receptor or muscle delay.
Your turn: Supplied model delays are 9, 4 and 13 ms. Calculate their total.
Supplied model delays are 9, 4 and 13 ms. Calculate their total.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 26 ms. Known: model delays 9, 4 and 13 ms. Total = 9 + 4 + 13 = 26 ms. This sums the stated stage delays only; it is not a universal human reflex time.
Check the conclusion and its limits
- A reflex does involve the nervous system even though it is not a conscious choice.
- The sensory neurone leads towards the CNS; the motor neurone leads towards an effector.
- A synapse is a junction, not a whole sensory cell or a blood vessel.
Not true: A reflex cannot involve the spinal cord because it is not conscious. Reflexes are fast BECAUSE they bypass conscious processing - the spinal cord coordinates them directly. Not being conscious is the point, not a disqualification.
- The nervous system enables responses to surroundings and coordinates behaviour.
- A reflex pathway includes a sensory neurone carrying information from a receptor, a relay neurone in the CNS and a motor neurone carrying information to an effector.
- Watch for: A reflex does involve the nervous system even though it is not a conscious choice.
A reflex cannot involve the spinal cord because it is not conscious.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Reflexes are fast BECAUSE they bypass conscious processing - the spinal cord coordinates them directly. Not being conscious is the point, not a disqualification.
A neurone carrying information from receptors towards the CNS: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
sensory neurone means A neurone carrying information from receptors towards the CNS.