Stimuli and Response Flashcards
Why do plants use growth factors?
To respond to changes in their environment to increase their chance of survival e.g. towards light to increase the rate of photosynthesis
What is a tropism?
The response of a plant to a directional stimulus
How do plants respond to changes in their environment?
Growth factors because they dont have circulatory systems or nervous systems
What do auxins (e.g. IAA) do?
Cause cell elongation in shoots
What do gibberellins do?
Cause flowering and germination
Where are growth factors made?
In root and shoot tips
How do growth factors move short distances?
By active transport and diffusion
How do growth factors move long distances?
In the phloem
How does IAA cause phototropism?
IAA moves to the shaded side of the root or the shoot causing: - Shoots: Cells to elongate and grow towards light - Roots: (IAA inhibits cell growth) roots to grow away from light
How does IAA cause gravitropism?
IAA moves to the underside of the root or the shoot causing: - Shoots: Cells to elongate and grow against gravity - Roots: (IAA inhibits cell growth) roots to grow with gravity
What are taxes and kineses?
Simple responses that keep mobile organisms in favourable environments
What are taxes?
Mobile organisms move towards or away from a directional stimulus
What are kineses?
Mobile organisms change their movement in response to a non-directional stimulus
Which stimulus’s cause a taxes?
- Predators- Water loss- Heat
How do unfavourable conditions cause a kinesis?
- Move more/faster - Turn more- Allows them to move to a new area
How do favourable conditions cause a kinesis?
- Move less/slower- Turn less- Allows them to remain in a favourable area
What is a reflex?
A rapid response to a stimulus without conscious or deliberate control
What is the reflex arc?
- Stimulus - Receptor- Sensory neurone- Relay neurone in CNS- Motor neurone- Effector- Response
What are the advantages of reflexes?
- Help avoid damage- Very fast- Unconscious - Doesn’t need to learnt
What are pacinian corpuscles?
They detect pressure, touch and vibrations in the skin
What happens when pacinian corpuscles are stimulated?
- Pressure causes the lamellae to stretch and deform- Stretch mediated sodium ion channels open- Sodium ions diffuse into the neurone- The more sodium ions, the greater the stimulus - Causes depolarisation of the neurone (generator potential)- If threshold is reached then an action potential is initiated
How is light seen by the human eye?
- Light is focused on the retina by the lens- Light is absorbed by the pigments in photoreceptors - Causes sodium ion channels to open (how many depends on the strength) (generator potential)- If threshold met then action potential generated and transmitted along the bipolar neurone to the optic nerve where it is transmitted to the brain
What are the two photoreceptors in the eye?
Cone and rod cells
Rod cells…
- Detect monochromatic pigments - Are sensitive to low light- Have low visual acuity- Are mostly in peripheral parts of retina- Cannot differentiate the position of light but get an action potential at lower light because many rod cells are joined to one bipolar neurone
Cone cells…
- Detect trichromatic pigments - Allow us to see colour vision- Are less sensitive to low light - Have higher visual acuity - Each cone has its own bipolar neurone so position of light can be differentiated but a stronger stimulus is required to reach threshold
What is the role of the pulmonary artery?
Carries deoxygenated blood from right ventricle to the lungs
What is the role of the vena cava?
Carries deoxygenated blood from body to the right atria
What is the role of the aorta?
Carries oxygenated blood from left ventricle to body
What is the role of the pulmonary vein?
Carries oxygenated blood from lungs to left atria
What is the role of the semilunar valves?
Open when pressure in ventricles is greater than in blood vessels
What is the role of the atrioventricular valves?
Open when pressure in atria is greater than ventricles
What is the role of the SAN?
Initiates heart beat
What is the role of the AVN?
Delays the impulse, allowing atria to contract before the ventricles
What is the role of the bundle of His?
Carries the impulse to the Purkyne fibres
What is the role of the non-conductive tissue?
Stops impulse from SAN reaching ventricles
How is heart rate controlled?
- SAN initiates heart beat- Sends an electrical impulse across atria - Causes atria to contract - Non-conductive tissue prevents nerve impulses reaching the ventricles - Impulse arrives at AVN- AVN delays the impulse to allow atria to contract and empty before the ventricles contract- AVN sends impulse down the impulse down the bundle of His to the Purkyne fibres- Causes ventricles to contract from the base up
How is the left ventricle different to the right ventricle?
- Highest blood pressure- Most cardiac muscle- Contracts with greatest force- Pumps blood to whole body
What happens to the atria during atrial systole?
They are contracted and at high pressure
What happens to the ventricles during atrial systole?
They are relaxed and at low pressure
What happens to the atrioventricular valves during atrial systole?
Open
What happens to the semilunar valves during atrial systole?
Closed
What happens to the atria during ventricular systole?
They are relaxed and at low pressure
What happens to the ventricles during ventricular systole?
They are contracted and at high pressure
What happens to the atrioventricular valves during ventricular systole?
Closed
What happens to the semilunar valves during ventricular systole?
Open
What happens to the atria during diastole?
They are relaxed and at low filling pressure
What happens to the ventricles during diastole?
They are relaxed and at low lower pressure
What happens to the atrioventricular valves during diastole?
Open
What happens to the semilunar valves during diastole?
Closed
What do chemoreceptors detect?
- Changes in blood oxygen conc- Changes in blood carbon dioxide conc - Changes in pH
What do baroreceptors detect?
- Changes in blood pressure
What happens when a chemoreceptor detects high blood oxygen conc, low blood carbon dioxide conc or high pH?
1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the parasympathetic nervous system3 - Parasympathetic nervous system secretes acetylcholine4 - Acetylcholine is detected by the SAN5 - Heart rate slows down
What happens when a chemoreceptor detects low blood oxygen conc, high blood carbon dioxide conc or low pH?
1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the sympathetic nervous system3 - Parasympathetic nervous system secretes noradrenaline4 - Noradrenaline is detected by the SAN5 - Heart rate speeds up
What happens when baroreceptors detect high blood pressure?
1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the parasympathetic nervous system3 - Parasympathetic nervous system secretes acetylcholine4 - Acetylcholine is detected by the SAN5 - Heart rate slows down
What happens when baroreceptors detect low blood pressure?
1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the sympathetic nervous system3 - Parasympathetic nervous system secretes noradrenaline4 - Noradrenaline is detected by the SAN5 - Heart rate speeds up
What neurotransmitter is secreted by the parasympathetic nervous system?
Acetylcholine
What neurotransmitter is secreted by the sympathetic nervous system?
Noradrenaline
