Unit 6 Flashcards
responding to changes in environment
define stimulus
detectable change in internal or external environment of an organism
define receptors
cells which detect a stimulus
what is the importance of being able to respond to stimuli
increases chance of survival and reproduction
name the tropism for light in plants
phototropism
name the tropism for gravity in plants
gravitropism (geo-)
what is IAA (indoleacetic acid)
a type of auxin and growth factor which elongates cells or inhibits it
why is phototropism important
required for the light dependant reaction in photosynthesis
describe what happens when light is on one side of the shoot
IAA diffuses to the shaded side, theres a greater con. of IAA there. cells elongate and the shoot moves toward the lighter side (positive phototropism)
in the roots IAA inhibits cell elongation, describe what happens when light is on one side of the root
IAA diffuses to the shaded side, theres a greater con. of IAA there. cell growth is inhibited and the root turns away from the light (negative phototropism)
what is the importance of root moving downwards
plants anchor into the ground and can reach more water sources, needed in the light dependant reaction of photosynthesis
describe gravitropism in the shoots
IAA diffuses in the direction of gravity and the lower cells elongate, the shoot moves vertically up
if the plant is on its side and the shoots turn upwards this would be called
negative gravitropism
if the plant was on its side describe what would happen at the roots
IAA would diffuse downwards with gravity, inhibiting elongation. the upper side of the roots would grow and the shoot would turn downward (positive gravitropism)
define reflex
a rapid, automatic response to protect the animal from danger
give the three neurones of the reflex arc in order
sensory neurone, relay neurone, motor neurone
define taxes
the entire organism moves its whole body away from an unfavourable or toward a favourable stimuli
define kinesis
an organism changes the speed of movement or rate it changes direction
give three examples of conditions of an environment
light, moisture, chemicals (pH)
what is the purpose of kinesis
to move in order to find favourable conditions
what kind or receptors a pacinian corpuscles and describe structure
pressure receptors, a sensory neurone ending at the centre of connective tissue (lamellae) in layers separated by gel
describe what happens to pacinian corpuscles when pressure is applied
- stretch-mediated sodium channels deform allowing Na+ ions to enter. if enough sodium ions diffuse into the axon an generator potential may be established
- if exceeds threshold an action potential may form
name the two photoreceptors in the retina
rods and cones
rods allow you to see in black and white in very low light intensity. what pigment do they contain
rhodopsin
what happens to rhodopsin in light
the pigment breaks down
rod cell provide a low visual acuity. what does this mean
many rod cells are connected to one neurone (spatial summation) so light sources are more difficult to distinguish
cones process in colour. what pigment do they have
iodopsin (red green blue)
in what conditions is iodopsin broken down
high light intensity
what kind of summation do cone cells have
temporal summation - only one cone cell per neurone
what kind of visual acuity do cones have
high visual acuity (can distinguish wavelengths)
where are rod cells
mainly outside the fovea
where are cone cells and why
mainly in the fovea (closes to light, receives higher light intensity)
the cardiac muscle (heart) is myogenic. what is meant by that
contracts on its own accord
where is the sinoatrial node (SAN) found
the right atrium
where is the Atrioventricular node (AVN) found
in the right atrium, near the border of the right and left ventricle
where is the bundle of His (conducting tissue) found
runs through the septum of the heart
where are the Purkyne fibers found
along the walls of the ventricles
describe how the cardiac muscle is pumped
- SAN releases a wave of depolarisation causing the atria to contract
- then AVN then releases another wave of depolarisation
- this travels down the bundle of His and Purkyne fibers causing the ventricles to contract
- cells repolarise and the cardiac muscles relax
theres a short delay before the AVN’s wave of depolarisation. how is this helpful
allows the atria to fully pump out the blood into the ventricles
in which direction to the ventricles contract and why
apex up which forces all of the blood out
describe the sympathetic nervous system
activate fight or flight response such as increasing heartrate
describe the parasympathetic nervous system
part of your autonomic nervous system, slows heart rate
which receptors detect high and low blood pressure
baroreceptors
what happens once high blood pressure is detected by baroreceptors
- impulse is sent from the medulla alone the parasympathetic neurones to the SAN
- neurotransmitter acetylcholine is released
- heart rate slows down and blood pressure decreases
what happens once low blood pressure is detected by baroreceptors
- impulse is sent from the medulla alone the sympathetic neurones to the SAN
- neurotransmitter noradrenaline is released
- heart rate gets faster and blood pressure increases
what kind of receptors respond to low/high O2/CO2
chemoreceptors - CO2 + H2O -> carbonic acid and lactic acid from anaerobic respiration effect pH
what happens once low O2/ high CO2 (pH) is detected by chemoreceptors
- impulse is sent from the medulla alone the parasympathetic neurones to the SAN
- neurotransmitter acetylcholine is released
- heart rate slows, CO2 decease and O2 increases
what happens once high O2/ low CO2 (pH) is detected by chemoreceptors
- impulse is sent from the medulla alone the sympathetic neurones to the SAN
- neurotransmitter noradrenaline is released
- heart rate rises, O2 decease and CO2 increases
what happens if blood pressure remains too high
damage to the walls of the arteries
what happens if blood pressure remains too low
insufficient blood supply to respiring cells:
- not enough O2 for aerobic respiration (anarobic + lactic acid bulid up) low pH = denatures enzymes
- no removal of waste - CO2 and H2O caused the production of carbonic acid low pH = denatures enzymes
describe dendrites
carry action potentials to surrounding cells
describe the axon
conductive, long fibre that carries the nervous impulse along the neurone
describe the structure of a Schwann cell
cell that wraps around the axon
