survival + response Flashcards
describe pathway by which organism responds to environment
- stimulus
- receptor
- coordinator
- effector
- muscle
define stimulus
detectable change in environment
causing response
explain importance of reflex arc
rapid - only 3 neurones + few synapses
autonomic - doesntt involve passage to brain
protects from harm
define taxis
directional movement
organism moves towards/away stimulus
explain example of how woodlice show tactic response to light
-move away from light
keeps concealed from predators in daylight
-moves towards damp conditions
reduces water loss
improves chance of survival
define kinesis
non-directional movement
by organsims
who change speed of movement/rate of direction change
in response to non-directional stimulus
example of how woodlice show kinetic response to humidity
move faster/change direction more often when drier
increases chance of moving to area with higher humidity
less water loss
improves chance for survival
define tropism
growth of a part of plant in response to stimulus
2 types of tropisms?
positive - growth towards stimulus
negative - growth away from stimulus
what are growth factors in plants
plant responses to external stimuli involve growth factors
growth factors move from growing regions to other tissues
in roots IAA…
inhibits cell elongation
in shoots IAA…
promotes cell elongation
how does IAA cause phototropism in shoots
- cells in tip produce IAA
- IAA transported down shoot
- IAA conc increases on shaded side
- promotes cell elongation
- shoot bends towards light
how does IAA cause gravitropism in roots
- cells in tip produce IAA
- IAA transported down shoot
- IAA conc increases on lower side of root
how does the pacinican corpuscle produce a generator effect
- mechanical stimulus -pressure deforms lamellae+ deform stretch-mediated sodium ion channel
- sodium ion channels open + sodium ions diffuse into sensory neurone
- greater pressure causes more channels to open + more sodium ions to enter
- causes depolarisation, leading to generator potential
where are rods found
more at periphery of retina
absent in fovea
how many pigments- rod
one type of rod
containing one pigment
how are rod cells connected to bipolar
multiple connect to one bipolar neurone
what is the photoreceptor in rod cells called
rhodopsin
how sensitive are rod cells to light
very sensitive
do rod cells have high or low visual acuity
low
rod cells dected
black and white
cone cells are found at
concentrated at fovea
fewer at periohery of retina
how many pigments - cone
3 pgiment
blue
red
green
photoreceptor in cone cells
iodopsin
how are cone cells connected to bipolar
each cone cell
attached to its own bipolar neurone
how sensitve are cone cells to light
less sensitve
require bright light
do cone cells have high or low visual acuity
high
cone cells detect
colour
why is a single impulse generated in rod cells
many rod cells joined to the same bipolar
source of light cannot be distinguished between rod cells
why is an impulse more liekly to be generated for rod cells
each rod cell simulation = sub-threshold
cells conncected - spatial summation
so threshold more likely met
why is generator potential often not exceeded for cones
each cone cell has own bipolar sensory neurone
high light intensity needed to produce greater impulse
why do cones have higher visual acutiy
one cone cell to one neurone
so source of light can be distinguished
why do rods have lower visual acuiity
many rods connected to bipolar
many neurones generate one impulse
so source of light cannot be distunished
