Response To Stimuli Flashcards
What is an effector
A range of different cells, tissue , organs or organ system that carry out a response
What is a stimuli
Detectable change in the internal or external environment
What is a receptor
Cells or organs that detect specific stimuli
What is Kineses
Non directional random response to an unpleasant stimuli
Changes speed of movement and rate of change of direction
More unpleasant the stimuli the more changes of direction
What is a coordinator
An intermediary between a receptor and an effector which formulates a suitable response to a stimuli
What is taxis
A simple response whose direction is determined by the direction of the stimulus
What is taxis
A simple response whose direction is determined by the direction of the stimulus
Move towards stimulus is positive taxis
Move away from stimulus is negative taxis
Why do organisms respond to a stimulus
More chance of finding and staying in favourable conditions so increasing chance of survival so greater chance of successful reproduction
So greater chance if beneficial alleles being passed on to the next generation
What is a tropisum
Plant growth in response to directional stimulus
Posssitve - towards
Negative - away from stimulus
What type of tropisums are involved in plant shoot growth
Positive phototropism - plants grow towards the sun
Negative geotropisum
What type of tropisum are involved in plant root growth
Positive geotropisum - to root the plant and stop it falling over
Negative phototropism
Positive hydro tropisum - for water in light dependant reaction
What do plant growth factors do
Cause cells to elongate
Describe auxin production. Phototropism
Auxins produced in the tip diffuse down the tip
Light causes it to move to the shaded side and concentration is greater on the shaded side
Attaches to receptors on the cell membrane
Releasing H+ions to decrease pH breaking bonds in the micro fibrils in the cellulose wall so they stretch easier
Shaded region grow faster and shoot bends towards the light
Describe geotropisum in the root
Auxins produced in the tip diffuse down the root
Gravity causes them to move to the bottom of the root
Concentration is higher at the bottom of the root
They attach to receptors on cell membrane
Lower side grows slower
Top side grows faster and roots bend towards the centre of the earth
Why didn’t the shoot grow so much after the tip had been cut off and then replaced
Replacing the cut off tip limits the growth because the phloem is damaged and hormones are unable to flow easily
If the was cut off and replaced with agar jelly soaked in the tip why did the shoot still grow
Because chemicals from the tip and moved into the agar jelly
This proves chemicals are responsible for growth
If an agar jelly soaked in the tip Is placed in the shoot at an angle why does the shoot still curve in the dark
The part with the agar jelly has a higher concentration of auxins so it elongates faster causing the shoot to bend
What is a sensory neuron
Carries nervous impulses from receptor towards CNS
What is the voluntary nervous system
Carries nervous impulses to body muscles under concious control
What is a motor neuron
Carries nervous impulses away from CNS to effector
What is the CNS
Brain and spinal cord
What is the autonomic nervous system
Carries nervous impulses to glands , smooth muscles and cardiac muscles
What is peripheral nervous system
Made up from pairs of nerves from brain or spine
Describe the reflex arc
Stimuli - heat from an object
Receptor- temperature receptor generates nervous impulses
Sensory neuron - passes nerve impulses to spin
Intermediate neuron - links sensory neuron to motor neuron
Motor neuron- carries nerve impulses from spine to arm muscle
Effector - muscle is stimulated and contacts
Response - pulling hand away
What are the pacinian corpuscle
Transducers converting pressure energy into electro chemical energy
Produces a generator potential which is large enough to make an action potential
How do graded responses work in the pacinian corpscule
The greater the pressure the greater the frequency of impulses along the neurone
The shape changes causing stretch mediated sodium ion channels to open and sodium ions diffuse down their conc gradient
This creates a generator potential which if big enough makes an action potential
Describe the structure of the pacinian corpuscle
Sensory neuron covered in myelin sheath for insulation to reduce sensitivity
Layers of lamellla
What are rods
sensitive to low light intensity and can distinguish between light and dark in dim lights
They are so sensitive that they respond with only one photon
Rods do not do colour
What are cones
Sensitive to different wave lengths so can distinguish colour
Human eye had three types cones responding to either red blue or green light
Why do rods only let us see in black and white
Multiple rod cells connected to one bipolar cell so threshold is exceeded easier to break down pigment in lower light intensity
Why do cones allow us to look at colour but not in low light
Each cone cell has its own bipolar cell so generator doesn’t get high enough as easily so pigments don’t break down as easy
If adjacent cones are stimulated at the same time then because they have different bipolar cells they have separate impulses sent to the brain showing the colours
Why do cones allow us to look at colour but not in low light
Each cone cell has its own bipolar cell so generator doesn’t get high enough as easily so pigments don’t break down as easy
If adjacent cones are stimulated at the same time then because they have different bipolar cells they have separate impulses sent to the brain showing the colours
where are cones and rods distributed
cone cells are found at the fovea opposite the pupil because it recieves the most light intensity
rod cells are found at the perpheries of the retina where the light intensity is lowest
what is the sympathetic nervous system
stimulates effetcors and speeds up activity ( excersie / flight or fight )
what is the parasympathetic nervous system
inhibits effectors and slows down activtiy
conserve energy and replenish reserves
how does the heart beat
electrical waves are generated in and sent out from sinoatrial node
across atrium wall
atrium wall contracts
the atrioventricular septum is non conductivite to prevent it crossing to the ventricle
impulses are sent down the bundle of his to the purkinjie fibres
they spread from the apex up the ventricular walls
why is the delay in the heart beat important
allows the atria to finish contracting before the ventricles start making it more efficiant
