grey matter Flashcards
describe the role of sodium ions in the functioning of a mammalian rod cell
sodium ions pumped out of the rod cell
in the light sodium ions do not move back into rod cell
in the dark sodium ions can move back into the rod cell
in the light the rod cell is hyper polarised
in the dark the rod cell is depolarised
other affects of IAA
alters pH of cell wall
makes cellulose cell wall more plastic
effect on transcription
cells in the tip of the oat coleoptile release IAA
explain how the IAA affects the growth of the coleoptile
IAA diffuses from the tip of the coleoptile
can be taken up by cells in the zone of elongation
causes cells to elongate
leads to lowering of the pH in the cellulose cell wall
causes the coleoptile to grow towards the light/ increase in height
give one example of a growth response of a plant that is affected by phytochrome
seed germination
flowering
explain the effect of increasing light intensity on the current produced by a rod cell
decreases current
rhodopsin is broken down/ opsin is released
more opsin binds to channel proteins in outer segment
sodium voltage gated channels close
stopping the influx of sodium ions/ making the membrane impermeable to sodium ions
describe the role of IAA in the phototropic response of plants
produced in the tip of the shoot
accumulates on the dark side of the shoot
stimulates cell elongation
causing shoot to grow towards the light source
the non protein part of the light absorbing pigment in the rod cells of the retina is called
retinal
explain the electrical changes in an axon that allow nerve impulses to be detected
potential difference across axon changes (from -70 to +40)
due to increased permeability to Na+/ Na+ channels open
Na+ move into the axon/ cause depolarisation
followed by an increased permeability to K+/ K+ channels open
K+ move out of the axon/ cause re polarisation of the membrane
give 3 similarities between IAA and animal hormones
chemicals
produced in cells
move away from production site
long term effect
involved in gene activation
give the name of the light absorbing part of rhodopsin
retinal
the cell that links a rod cell to a sensory neurone is
a bipolar neurone
describe the roles of the circular and radial muscles in pupil dilation
muscles work antagonistically
circular muscle relaxes
radial muscle contracts
describe the role of dendrites in a neurone
form synapses/ connections w other neurones
integrate/ receive impulses from other neurones
involved in summation
propagate a signal/ initiate an action potential to the cell body/ axon
describe how ions and neurotransmitter molecules are involved in the transmission of an impulse
Ca2+ enter presynaptic neurone so vesicles w neurotransmitter can move towards/ fuse w presynaptic membrane
neurotransmitter molecules diffuse along synapse
neurotransmitter binds w receptors on postsynaptic membrane
Na+ diffuse into post synaptic cell leading to a depolarisation/ action potential
similarities between sensory and motor neurone structure
both have:
axon
cell body containing nucleus
dendrites at one end of neurone and terminal branches at other end
difference between sensory and motor neurone structure
motor neurone cell body is at one end of the axon
sensory neurone cell body is located along the axon
describe the post synaptic receptor’s role in synaptic transmission
neurotransmitter attaches to it
Na+ enter post synaptic neurone
depolarising it
Explain why a myelinated axon conducts impulses faster than a non myelinated axon
Action potential/ depolarisation only occurs at nodes
Nerve impulse jumps from node to node/ salta Tory conduction
Action potential/ impulse doesn’t travel along whole length
Explain how a lower temperature can effect the speed of an action potential
Slower diffusion/ movement down conc grad
Of ions/ K+/ Na+
