B9.2 sense organs, 9.3 Hormones Flashcards
what is a cornea
a transparent coating on the front of the eye- protects the eye and refracts light as it enters the eye
what is a pupil
a central hole in the iris- allows light to enter the eye
what is an iris
a coloured ring of muscle tissue- alters the size of the pupil
what is a lens
a transparent biconvex lens- refracts and focuses light clearly on the retina
what is a ciliary muscle
a ring of muscle tissue-alters lens thickness by contracting or relaxing
what is a suspensory ligament
a ligament tissue- connects the ciliary muscle to the lens
what is an optic nerve
a nervous tissue- carries nerve impulses to the brain
what does circular and radial muscles do?
circular muscles contract to make the pupil smaller and the radial muscle contracts to make the pupil bigger
what happens when the ciliary muscle contracts?
the lens gets thicker and the suspensory ligament slackens
what happens to the lens when it has to focus nearby object?
the lens get thicker as it has to refract light
how do we correct short sightedness?
wear a concave lens so the focus point is on the retina
what does rods and cones do in eyes?
rods- see low light levels
cones- see different colours
what are hormones
chemical messengers
where are hormones made?
in endocrine glands
what is homeostasis
the maintenance of a constant internal environment.
