Response and Regulation
Information is fed to the brain constantly by a system of sense organs scattered around the body. Sense organs are groups of special cells called receptor cells, which can detect changes, either internally or externally.
These changes are called stimuli. They include; light, chemicals, sound, touch and temperature.
Each group of receptor cells responds to specific stimuli.
Ears detect both sound and balance, as they contain two types of receptor cells.
The information from the sense organs travels to the brain and spinal cord (central nervous system) along nerve cells (neurones).
The CNS controls the body. Information travels as electrical signals along nerves.
Some nerves take information to the CNS from sense organs. Some take information from CNS to muscles. Time taken between stimulus and response is the reaction time.
Growth movements called tropisms. Several different kinds:
- Phototropism - growth in response to light. Shoots grow towards light (positive)
Roots grow away from light (negative)
- Gravitropism - growth in response to gravity. Roots grow towards (positive)
Shoots grow away (negative)
No nerves. Controlled by chemicals called hormones. Produced in response to a stimulus. Travel to part of plant where response is needed
Nerves control quick responses. Hormones…