The Human Nervous System
Overzicht
Touch something scalding and your arm is already moving before you have decided anything. You did not choose it, you could not have stopped it, and the pain arrives afterwards like a report filed late. That tiny gap between the injury and the feeling is the most revealing thing your body does all day, because it shows that a decision was taken somewhere other than in your thoughts.
This lesson follows a single signal from the skin of a fingertip to the muscle that pulls the hand clear. You will meet the three kinds of neurone and learn which direction each one carries traffic, see what actually crosses the tiny gap between one nerve cell and the next, take apart a pain-withdrawal reflex step by step, and finish by measuring a reaction time and judging whether the measurement can be trusted. By the end you will be able to take any piece of behaviour an examiner puts in front of you, however unfamiliar the animal or the situation, and lay it out as stimulus, receptor, coordinator, effector, response.
Doelstellingen
- The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
- Information from receptors passes along cells (neurones) as impulses to the central nervous system (CNS). The CNS is the brain and spinal cord. The brain coordinates the response.
- Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurones.
- In a simple reflex action such as a pain-withdrawal reflex: impulses from a receptor pass along a sensory neurone to the CNS; at a junction (synapse) between a sensory neurone and a relay neurone in the CNS, a chemical is released that causes an impulse to be sent along a relay neurone; a chemical is then released at the synapse between a relay neurone and motor neurone in the CNS, causing impulses to be sent along a motor neurone to the effector; the effector is either a muscle or a gland: a muscle responds by contracting and a gland responds by releasing (secreting) chemical substances.
- Effectors include muscles and glands. Students should be able, when provided with appropriate information, to analyse a particular given example of behaviour in terms of: stimulus → receptor → coordinator → effector → response
Mindmap
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Lesevaluatie
Gefeliciteerd met het voltooien van de les op The Human Nervous System. Nu je de sleutelconcepten en ideeën, het is tijd om uw kennis op de proef te stellen. Deze sectie biedt een verscheidenheid aan oefeningen vragen die bedoeld zijn om uw begrip te vergroten en u te helpen uw begrip van de stof te peilen.
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- Which two structures make up the central nervous system? A. The brain and the nerves B. The brain and the spinal cord C. The spinal cord and the nerves D. The receptors and the effectors Answer: B
- Which type of neurone carries impulses from the central nervous system to a muscle? A. Sensory neurone B. Relay neurone C. Motor neurone D. Receptor neurone Answer: C
- What crosses the gap at a synapse? A. An electrical impulse B. A chemical C. A nerve fibre D. A red blood cell Answer: B
- Which of the following is an effector? A. A pain receptor in the skin B. A relay neurone in the spinal cord C. A salivary gland D. The retina of the eye Answer: C
- Impulses travel 1.5 m along a reflex pathway at an average speed of 50 m/s. What is the reaction time? A. 0.003 s B. 0.03 s C. 0.3 s D. 33 s Answer: B
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