6.1 (14) - Response to Stimuli Flashcards
What is a stimulus?
A change in the internal or external environment
What is a receptor?
Cells that detect a stimulus
What is a tropism?
What is phototropism?
The growth of a plant in response to light
What is gravitropism?
The growth of a plant in response to gravity
What
A simple response of an organism whose direction is determined by the direction of the stimulus
What is a positive taxis?
Moving towards a favourable stimulus
What is a negative taxis?
Moving away from an unfavourable stimulus
What is a kinesis?
Simple response where speed and rate of change of direction will change in response to a stimulus, NOT direction
Random
Related to intensity of stimulus
What is positive phototropism?
Plant shoots grow towards light
What is negative phototropism?
Plant roots grow away from light
What is positive gravitropism?
Plant roots grow towards gravity
What is negative gravitropism
Plant shoots grow away from gravity
What is IAA?
A type of auxin (plant growth factor)
What does IAA do?
- Promotes growth in shoots
- Inhibits growth of roots
- Promotes plasticity of cell walls by actively transporting hydrogen ions from cytoplasm to the spaces in cell walls
Describe how IAA causes phototropism in shoots and roots
1) IAA produced by cells in the tip of the shoot/root
2) Light causes IAA to accumulate on the shaded side of the plant
3) IAA accumulation on the shaded side of the shoot promotes elongation of cells on shaded side = bending towards light (positive phototropism)
4) IAA accumulation on the shaded side of roots inhibits growth of cells on shaded side = bending away from light (negative phototropism)
Describe how IAA causes gravitropism in shoots and roots
1) IAA produced by cells in the tip of the shoot/root
2) Gravity causes IAA to accumulate on the lower side of the shoot/root
3) IAA build up on the lower side on the roots and inhibits elongation of the lower side = bending of the plant downwards (positive gravitropism)
4) IAA builds up on the lower side on the shoto and promotes elongation of cells on the lower side = bening of the plant upwards (negative gravitropism)
What is the central nervous system made up of?
Brain and spinal cord
What is the peripheral nervous system made up of?
Nerves found outside of the brain and spinal cord
What is a sensory neuron?
Carries nerve impulses from a receptor to the coordinator
What is a relay neuron?
Connects a sensory neuron to a motor neuron
What is a motor neuron?
Carries nerve impulses from the coordinator to the effector
What is a synapse?
A gap between 2 neurons
What are the components of a reflex arc?
Stimulus > receptor > sensory neuron > relay neuron > motor neuron > effector > response
What is the order of the nervous system?
Nervous system > Peripheral NS
Central NS
PNS > Autonomic NS
Somatic NS
ANS > Sympathetic NS
Parasympathetic NS
Describe a reflex action
- Automatic, rapid responses that don’t involve conscious areas of the brain
- Consist of 3 neurons
- Protective responses that occur in response to certain stimuli
What are the divisions of the peripheral NS?
Autonomic and somatic NS
What are the divisions of the autonomic NS?
Sympathetic and parasympathetic NS
Describe the sympathetic NS
- Stimulates effectors and speeds up activity
- Controls responses to stressful situations
- Heightens our awareness
Describe the parasympathetic NS
- Inhibits effectors and slows down activities
- Controls activities in normal and restful conditions
- Conserves energy and replenishes the body’s reserves
