B1.2.1 The Nervous system Flashcards
What does the nervous system enables humans to do?
To react to their surroundings and coordinate their behaviour.
What are receptors?
- Cells that detect stimuli (changes in the environment).
- convert information to impulses (send impulses to the CNS along sensory neurones)
Where about in the body are receptors found?
in the:
eyes, ears, tongue, nose and skin
What are receptors in the eye sensitive to?
Light
What are receptors in the ear sensitive to?
- Sound
- Changes in position and enable us to keep our balance
What are receptors on the tongue and in the nose sensitive to?
Chemicals and let us taste and smell
What are receptors in the skin sensitive to? (4 marks)
Touch, pressure, pain and to temperature changes
What do light receptor cells have in common with most other animal cells? (3 marks)
They have a nucleus, cytoplasm and cell membrane
What are the key point about reflex actions compared to voluntary actions?
Reflex actions are automatic and rapid.
They often involve only the sensory, relay and motor neurones.
Outline the sequence of events in a simple reflex action. (4 marks)
- impulses from a receptor pass along a sensory neurone to the central nervous system
- at a junction (synapse) between neurones in the central nervous system, a chemical is released that causes an impulse in the next neurone.
- This continues until the motor neurone is reached and stimulated.
- the effector (either a muscle or a gland) responds by contracting or by releasing (secreting) chemical substances
What is a gland?
An organ in the human body that produces and releases chemical substances
What are impulses?
Electrical signal carried along the neurones
What is a motor neurone?
Neurone that carries impulses from the central nervous system to the effector organs
What is a sensory neurone?
Neurone that carries impulses from the sense organs to the central nervous system
What is a stimuli?
A change in the environment
