Reponses Flashcards
Taxes + positive and negative
An organism will move body towards a favourable stimulus / away from an unfavourable stimulus
Positive taxes = organism moves towards a stimulus
Negative taxes = organism moves away from stimulus
Kinesis
What increases kinesis response
What decreases kinesis response
Organism changes speed of movement and the rate it changes direction
Moves from area with beneficial stimuli to area with harmful stimuli it’s kinesis response = INCREASE RATE IT CHANGES DIRECTION to return to favourable conditions quickly
If surrounded by neg stimuli = rate of turning decreases (keep moving straight - increases chances of finding new location with favourable cond)
What are the pacinian corpuscles
Respond to pressure changes
Deep in our skin (fingers +feet)
Consists of a single sensory neuron wrapped with layers of connective tissue with (separated by) viscous gel
Contain channel proteins in plasma membrane - allow ion transportation
Membranes surrounding sensory neurones have stretch mediated sodium channels - open up + allow NA to enter neurone when stretched and deformed
Inside ong sensory neurone becomes closer to positive (goes from -70 to -55 = reached threshold)
= ACTION POTENTIAL
Pacinian corpuscles at rest and with generated potential
At rest stretched mediated sodium channels of membrane are too narrow to allow NA to pass along
Nothing is deformed
Pressure applied:
Pressure pushed down on sensory neurone = deformed plasma membrane
Stretch mediated NA channels widen = NA ions diffuse in
= more positive ions inside than outisde
Enough positive ions = exceeds threshold
= generated action potential
=RESPONSE
Rod cells
Cannot distinguish different wavelengths of light = images are BLACK AND WHITE
Used to detect light of VERY LOW intensity
Pigment in rod cells (rhodopsin) must be broken down to generate potential.
(There’s enough energy in low light)
Once threshold is exceeded a generator potential is created by bipolar cells
Much greater chance threshold is exceeded as a number of rod cells are connected to a single bipolar cell = SUMMATION
GIVE LOW VISUAL ACUITY - two dots close together cannot be resolved
Many rod cells linked to single bipolar - light received by rods sharing same neurone = simple impulses , brain can’t distinguish between separate sources of light
What must be broken for a generator potential to be set (rod cells)
Rhodopsin (pigment)
how does having high density of cones allow for organism to see in detail
high visual acuity
each cone is connected to a singular neurone
send separate impulses to the brain
how does having high density of rod cells allow owls to see in the dark
high visual sensitivity
several rods connected by neurone/ bipolar cell
spatial summation to overcome/ reach threshold
