Topic G - Coordination & Response Flashcards
how do organisms respond to changes in their surroundings
Tropisms
what tropism detects light
phototropism
what tropism detects moisture ( water)
hydrotropism
what tropism detects gravity
geotropism
in what direction of growth do shoots grow ( 2 things )
- towards light = +ve phototropism
2. away from gravity = -ve geotropism
in what direction of growth do roots grow ( 2 things )
- towards moisture = +ve hydrotropism
2. towards gravity = +ve geotropism
what are the 5 steps to co-ordinated/ reflex arc response
- stimulus =change in enviroment
- Receptor= sensor organs (nerve ending)
- Co-ordinating centre = brain + spinal chord
- Effector = muscle
- Response = movement
what is homeostasis
maintenance of constant internal enviroment
what are examples of homeostasis
body water content
body temperature
what do plants respond to
stimuli = light, heat, moisture
what is auxin
plant hormone that controls growth
where is auxin produced
in the shoot tips
what does auxin increase and decrease
increases growth in shoots
decreases growth in roots
how does auxin work in response to light
auxin accumulates on the dark side= growth on that side= bend towards light
what are 2 parts of the central nervous system and what are they linked to and how
brain + spinal chord
link to sense organs by nerves
what does stimulation of receptors in sense organs do
sends electrical impulse along nerves into and out of central nervous system= rapid responses ( reflex)
- what do synapses do
2. what do neurotransmitters (chemicals ) do at the synapse
1.connect neurons (connection between 2 neurons =synapse)
- transfers nerve signals by diffusing across the gap
+ set of new a new electrical signal in the next neurone
describe process of reflex arc - removal of finger from a hot object
(CNS= central nervous system)
- stimulus = hot object
- receptors (skin) detect stimulus
- impulse sent along sensory neurone to the CNS
- in CNS impulses are passed along relay neurone (via a synapse)
- relay neurones relay impulse to a motor neurone
- impulse travels along motor neurone to the effector (muscle)
- muscle contracts + moves finger away from hot object
what is the eye and what does it do
receptor = major sense organ = detects light
how does the eye focus on distant objects
cilary muscles relax= suspensory ligament pulled tight= lens = less convex (flat) = refracts light by smaller amount
how does the eye focus on nearer objects
cilary muscles contract = smaller amount of space = suspensory ligament relax = lens = more convex (rounded) = refracts light by larger amount
function of iris
muscle which contracts or relax to change pupil size
how does eye react to bright light
circular muscles contract= radial muscles relax= pupil constricts( smaller )= lets less light in
how does eye react to dim/ no light
circular muscles relax = radial muscles contract = pupil dilates = lets more light in
