Reponses

Question 1

Taxes + positive and negative

Answer 1

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

Question 2

Kinesis
What increases kinesis response
What decreases kinesis response

Answer 2

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)

Question 3

What are the pacinian corpuscles

Answer 3

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

Question 4

Pacinian corpuscles at rest and with generated potential

Answer 4

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

Question 5

Rod cells

Answer 5

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

Question 6

What must be broken for a generator potential to be set (rod cells)

Answer 6

Rhodopsin (pigment)

Question 7

how does having high density of cones allow for organism to see in detail

Answer 7

high visual acuity
each cone is connected to a singular neurone
send separate impulses to the brain

Question 8

how does having high density of rod cells allow owls to see in the dark

Answer 8

high visual sensitivity
several rods connected by neurone/ bipolar cell
spatial summation to overcome/ reach threshold