Human Nervous system
Stimulus:
- Changes in an organism´s environment
- Sensed by receptors and the organism respond using effectors
Need for fast and efficient communication system between receptors and effectors
Coordination: The way in which receptors pick up stimuli, and then pass information on to effectors
By nerves
By hormones
Neurones: - Special cells that make the HNS. ---Structure adapted to be able to carry out messages quickly
Central Nervous system: - Made up of the brain and the spinal cord. - Coordinate the messages travelling through the nervous system.
Peripheral nervous system: Made up of nerves and receptors
Reflex action: Reactions that you do not need to think about it.- Useful: The message gets from the receptor to the effector as quickly as possible. - Involuntary actions
Reflex arc: The pathway along which the nerve impulse passes.
Coordination and response in plants: - Respond to stimuli by changing their rate or direction of growth.
Tropisms: Growth response by a plant
Growth towards a stimulus is said to be a positive response
Growth away a stimulus is said to be negative
Important stimuli for plants
Light
Gravity
Important for plants that its rots and shoots grow in an appropiate direction
Plant Hormones
Sensitive region is the tip of the shoot, where the receptor is.
The part just below the tip of the shoot is the one which responds to the stimulus, and where the effector is.
Auxin: Diffuses downwards from the tip, into the rest of the shoot. It makes the cells just behind the tip get longer so they could grow faster.