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