Response to stimuli
- Created by: ggmonkey
- Created on: 22-11-16 10:16
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- Response to stimuli
- Plant growth factors - Tropisms
- Light
- IAA (an auxin) as positive tropism
- 1. Cells in the tip produce IAA.
- 2. IAA transported evenly through all parts of shoot.
- 3. Light causes IAA to move to dark side.
- 4. Larger concentration of IAA on shaded side.
- 5. Greater elongation on darker side, tip bends towards the light so get more light for photosynthesis.
- IAA (an auxin) as positive tropism
- Water
- Gravity
- IAA as a positive geotropism
- 1. Cells in the tip produce IAA.
- 2. IAA transported evenly through all parts of root.
- 3. Gravity pulls IAA to lower side.
- 4. Larger concentration of IAA on lower side.
- 5. Greater inhibition of cells on lower side so upper side elongates more and cells grow down.
- IAA as a positive geotropism
- Light
- Stimulus and response
- Taxes
- Direction determined by stimulus
- Positive taxis - Towards a favourable stimulus
- Single celled algae will move towards light as light is used in photosynthesis.
- Negative taxis - Away from an unfavourable stimulus
- Earthworms move away from light as this moves them into the soil where they will find food.
- Kineses
- Changes speed and rate of change in direction.
- Usually a response to humidity and temperature
- Woodlice rapidly move and change direction in dry conditions to try and find warm conditions.
- Taxes
- Reflex arc
- Stimulus - Receptor - Sensory - Relay - Motor - Effector - Response
- Receptors
- Pacinian Corpsucle
- Specific to a single stimulus
- Transducer - produces a generator potential
- Stretch mediated sodium channel
- 1. Pressure deforms channel so sodium ions can flow.
- 2. Membrane becomes depolarised producing the generator potential and in turn the impulse (action potential).
- Specific to a single stimulus
- Pacinian Corpsucle
- The eye
- Rod cells
- Can't distinguished different wavelengths
- One pigment - rhodopsin
- 1. Breaks down into opsin and retinal.
- 2. Cisretinal changes to transretinal.
- 3. This causes a stretch mediated sodium channel response.
- Convergence as more than one rod cell can be connected to one bipolar cell
- Threshold for generator potential
- Cone cells
- Have their own bipolar cell.
- Only respond to high light intensity as no threshold can be releases.
- Can distinguish between colours. 3 pigments - iodopsin
- Iodopsin breaks down to create a generator potential.
- Only cone cells in fovea in the macula
- Have their own bipolar cell.
- Rod cells
- Control of heart rate
- The autonomic nervous system
- The parasympathetic pathway
- Inhibits effectors and slows down activity
- Controls activity under normal resting conditions
- Cardioinhibitory centre
- The sympathetic pathway
- Stimulates effectors and speeds up activity
- In control when we excersise
- Fight or flight
- Cardioacceleroratory centre
- Example
- Increased muscular activity
- More carbon dioxide from respiration
- Blood pH lowered
- Chemoreceptors in the carotid arteries increaese frequency of impulses to medulla oblongata
- Cardioacceleratory centre increases frequency of impulses to the SA node.
- SA node increases heart rate.
- Cardioacceleratory centre increases frequency of impulses to the SA node.
- Chemoreceptors in the carotid arteries increaese frequency of impulses to medulla oblongata
- Blood pH lowered
- More carbon dioxide from respiration
- Increased muscular activity
- Chemoreceptors and pressure receptors in carotid artery and aorta.
- The sympathetic pathway
- Stimulates effectors and speeds up activity
- In control when we excersise
- Fight or flight
- Cardioacceleroratory centre
- Example
- Increased muscular activity
- More carbon dioxide from respiration
- Blood pH lowered
- Chemoreceptors in the carotid arteries increaese frequency of impulses to medulla oblongata
- Cardioacceleratory centre increases frequency of impulses to the SA node.
- SA node increases heart rate.
- Cardioacceleratory centre increases frequency of impulses to the SA node.
- Chemoreceptors in the carotid arteries increaese frequency of impulses to medulla oblongata
- Blood pH lowered
- More carbon dioxide from respiration
- Increased muscular activity
- Plant growth factors - Tropisms
- Antagonistic
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