Coordination and Response Flashcards
what is a stimulus (stimuli)?
any change in the internal or external environment
what is the function of receptors ?
how do they communicate with effectors?
to detect stimuli
communicate with effectors via nervous system / hormonal system / both
what are effectors ?
give some examples
cells that bring about a response to the stimuli
examples - muscle cells contract and gland cells (like pancreas) secrete hormones
describe the Central nervous system (CNS)
made up of neurons (nerve cells)
consists of brain and spinal cord
coordinates the response to a stimuli
very rapid responses with fast electrical impulses
what are the sense organs ?
eyes, ears, nose, tongue, skin
what are reflexes ?
automatic responses to certain stimuli which help prevent injury
what is the reflex arc?
stimulus – receptor – sensory neuron – relay neuron – motor neuron – effector – response
what are the three main neurons ?
what are their functions?
sensory neuron - carry signals from receptors to spinal cord / brain
relay neuron - carry messages from one part of CNS to another
motor neuron - carry signals from CNS to effectors
what is the function of the conjunctiva ?
lubricates and protects surface of eye
what is the function of the cornea ?
refracts (eye) light into eye
is transparent and has no blood vessels so oxygen diffuses in from outer surface
what is the function of the iris?
controls diameter of pupil, therefore how much light enters the eye
what is the function of the lens?
focuses the light onto retina
what is the function of the retina ?
responsible for colour and bright light
uses light receptors called cones and rods
what is the function of the rod receptors ?
provide side vision and sight in dim light
what is the function of the cone receptors ?
provide coloured vision and sharp central vision
what is a synapse?
located in the CNS
gap between neurons which passes electrical messages or chemical signals
works with neurotransmitters
reaction time depends on how fast signals are passed
Depressants
slows brain activity / slow reaction time
examples - alcohol, solvents and temazepam
Stimulants
increases brain activity / faster reaction time
examples - nicotine, caffeine, ecstasy
what is the function of the optic nerve ?
carries impulses from the receptors (cones and rods) to the brain
Bright light, what happens to the eye?
pupils constrict, letting in less light to protect the eye
circular muscles contract
radial muscles relax
Dim light, what happens to the eye?
pupils dilate, letting in more light to see better
circular muscles relax
radial muscles contract
what is accommodation ?
changing the shape of the lens to see distant/near objects
what happens to the eye to look at distant objects…
ciliary muscles relax, allowing the suspensory ligaments to pull tight
this makes the lens go thin (less curved)
what happens to the eye to look at close objects…
ciliary muscles contract, slackening the suspensory ligaments
this makes the lens become fat (more curved)
why are some people long sighted ?
unable to focus on close objects as cornea or lens doesn’t bend light enough / eyeball is too short
near objects are brought into focus behind retina
why are some people short sighted ?
unable to focus on distant objects as cornea or lens bends light too much / eyeball is too long
distant objects are brought into focus in front retina
what are hormones ?
chemicals sent in the blood (carried in blood plasma)
slow message time
act for a long time and in a general area
ADH
source -
role -
effects -
ADH
source - pituitary gland (brain)
role - controls water content
effects - increases permeability of collecting ducts (kidney nephrons)
Adrenaline
source -
role -
effects -
Adrenaline
source - adrenal glands (on top of kidneys)
role - readies body for ‘fight or flight’ response
effects - increases heart rate, blood flow to muscles and blood sugar levels
Insulin
source -
role -
effects -
Insulin
source - pancreas
role - helps control blood sugar level
effects - stimulates liver to turn glucose into glycogen for storage
Testosterone
source -
role -
effects -
Testosterone
source - testes
role - main male sex hormone
effects - promotes male secondary characteristics e.g. facial hair
Progesterone
source -
role -
effects -
Progesterone
source - ovaries
role - supports pregnancy
effects - maintains lining of uterus
Oestrogen
source -
role -
effects -
Oestrogen
source - ovaries
role - main female sex hormone
effects - controls menstrual cycle and promotes secondary sexual characteristics e.g. widening hips
what are Nerves ?
very fast message time
act for a short time
act on a very precise area
define homoeostasis
control of constant internal conditions
what are the ways water is lost from the body
through the skin as sweat
via the lungs as breath
via the kidneys as urine
what is body temperature ?
how is it controlled?
37°C as this is the optimum temp for enzymes
brain is sensitive to blood temp and receives messages about the skin temp
CNS activates effectors to make body temp right
define thermoregulation
process that allows your body to keep at its core internal temperature
what happens to body when Too hot ?
sweating - evaporates, transferring heat to environment
distillation - blood vessels near surface widen, so more blood to flows, to radiate more heat to surroundings
hairs lie flat - lets heat escape
what happens to body when Too cold ?
hair stick up - trap air in
shiver - movement in muscles generate heat
vasoconstriction - blood vessels constrict so less heat radiates to surroundings
smaller organisms cool down…
why?
quicker
larger surface area to volume ratio so can lose / gain heat faster
larger organisms cool down…
why?
slower
smaller surface area to volume ratio so loses/gains heat slower
what are auxins?
how do they work?
plant hormones which controls growth at the tips of shoots / roots
diffuses backwards to stimulate cell elongation
promotes growth in tips, inhibits growth in roots
involved with geotropism and phototropism
describe positive phototropism
growth towards light caused by more auxin on shaded side so grows more that side, bending towards light
occurs in tips and maximises light for photosynthesis
describe negative phototropism
growth away from light
occurs usually in roots to prevent them drying out
describe negative geotropism
growth away from gravity, usually to find light
more auxin produced on lower side, pushing it upwards (occurs in tip)
describe when positive geotropism would be used
growth towards gravity usually in roots to find moisture
