coordination and respone Flashcards
what is a stimulus
any change in the internal or external environment
what are receptors
receptors detect stimuli, receptors in the sense organs are a group of cells that detect external stimuli
what are effectors
effectors are cells that bring about a response to a stimuli, include muscle cells and cells found in glands
how do receptors communicate with effectors
via the nervous system or hormonal system
3 type sof neurone
sensory
relay
motor
what happens when receptors detect a stimulus
they send electrical impulses along sensory neurones to the CNS, the CNS then sends electrical impulses to an effector along a motor neurone, the effector then responds accordingly
why is the CNS able to bring about very rapid responses
neurones transit information using high speed electrical impulses
what is the connection between 2 neurones called
synapse
how is the nerve signal transferred across a synapse
neurotransmitters diffuse across the gap, setting off a new electrical signal in the next neurone
what is the purpose of reflexes
to prevent injury
what is a reflex arc
the route taken by the information in a reflex from receptor to effector
explain the reflex arc of touching a hot object
stimulus (hot object) is detected by receptors, sending an impulse along a sensory neurone to the CNS
the sensory neurone passes on the message to a relay neurone which relays the impulse to a motor neurone
impulse travels along the motor neurone to the effector (muscle)
the muscle (effector) then contracts and moves your hand away from the object
block diagram for reflex arc
stimulus
receptor
sensory neurone
CNS
motor neurone
effector
response
what is the conjunctiva
lubricates and protects the surface of the eye
what is the sclera
tough outer layer that protects the eye
what is the cornea
refracts light into the eye
what is the iris
controls the diameter of the pupil
what is the lens
focuses light onto the retina
what is the retina
light-sensitive part, covered in light receptors called cones and rods
what do rods receive
light
what do cones receive
colour
what is the optic nerve
carries impulses from the receptors to the brain
what happens to the iris in bright light
circular muscle contracts to make the pupil smaller
what happens to the iris in dim light
radial muscles contract making the pupil bigger
what is accommodation
focusing light onto the retina by changing the shape of the lens
what happens when the eye looks at distant objects
ciliary muscles relax
suspensory ligaments contract
lens goes thin
light is refracted by a smaller amount
what happens when the eye looks at distant objects
ciliary muscles contract
suspensory ligaments slacken
lens goes more curved
light is refracted by a greater amount
what are hormones
chemical messengers sent in the blood
hormone properties
travel slowly and have long lasting effects
source of adrenaline
adrenal glands
source of insulin
pancreas
source of testosterone
testes
source of progesterone
ovaries
source of oestrogen
ovaries
source of ADH
pituitary gland
source of FSH
pituitary gland
source of LH
pituitary gland
roles of adrenaline
readies body for fight or flight response
role of insulin
helps control the blood sugar level
role of testosterone
main male sex hormone
role of progesterone
supports pregnancy
role of oestrogen
man female sex hormone
role of ADH
controls water content
role of FSH
female sex hormone
role of LH
female sex hormone
effects of adrenaline
increases heart rate, blood flow to muscles and blood sugar level
effects of insulin
stimulates the liver to turn glucose into glycogen for storage
effects of testosterone
promotes male secondary sexual characteristics
effects of progesterone
maintains lining of the uterus
effects of oestrogen
controls menstrual cycle and promotes female secondary sexual characteristics
effects of ADH
increases permeability of collecting duct in nephrons
effects of FSH
causes an egg to mature in an ovary, stimulates ovaries to produce oestrogen
effects of LH
stimulates the release of an egg from an ovary
differences between nerves and hormones
nerves = fast, short time, precise area
hormones = slow, long time, general way
what is homeostasis
maintenance of a constant internal environment
what conditions does homeostasis keep balanced
water content
body temperature
what is the ideal body temperature
37 degrees
why do you sweat when hot
sweat evaporates from the skin’s surface transfers energy from your skin to the environment
what is vasodilation
blood vessels close to the surface widen, allowing more blood to flow near to the surface transferring energy to the surroundings
what happens to hairs when your hot
hairs lie flat
what is vasoconstriction
blood vessels near to the surface of the skin constrict meaning less blood flows near the surface so less energy is transferred to the surroundings
why do you shiver when cold
increases rate of respiration, transferring more energy to warm the body
what happens to hairs when you are cold
hairs stand on end to trap an insulating layer of air helping to keep you warm
why do smaller organisms lose or gain body heart easily
they ahem a bigger surface area to volume ratio
what is auxin
plant hormones which control growth at the tips of shoots and roots
what is the difference between auxin in shoots and in roots
auxin promotes growth in shoots and inhibits growth in the roots
shoot phototropism
positively phototrophic (grow towards the light)
how does auxin make shoots grow towards the light
shoot tip accumulates more auxin on the shaded side, making the cells grow faster on the shaded side causing it to bend towards the light
shoot geotropism
negatively geotropic (grow away from gravity)
how does auxin make a shoot grow away from gravity
when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip with more auxin on the lower side. this causes the lower side to grow faster bending the shoot upwards
roots geotropism
positively geotropic, grow towards gravity
why does auxin make roots grow towards gravity
more auxin on the lower side, it inhibits growth, meaning the cells on top elongate faster bending the root downwards
roots phototropism
negatively phototrophic, grow away from light
why does auxin make roots grow away from light
more auxin on the shaded side, inhibiting cell elongation and bending the root downwards.
why do underground roots grow downwards
positive geotropism, as they are not exposed to the light
