Behind the iris is a lens which changes shape in order to focus the image.
.Retina is the internal layer.It contains two types of photoreceptors rods ( don't perceive colors) and cones (perceive colors)
.The auxiliary structures are eyebrows, eyelids, eye lashes, eye muscles and lacrimal glands.
how our eyes work: sight
light reaches cornea, which directs it towards the pupil.The pupil opens or closes depending on the intensity of the light.The light then travels through the lens, which focuses it onto the retina. In the retina, photoreceptor cells generate nerve impulses which they then send through the optic nerve to the brain (occipital lobe)
3 nervous coordination
nervous coordination is the coordination carried out by the nervous system.This system is made up of nerve tissue whose cells, called neurons, are capable of transmitting information through nerve impulses
.Cell body: contains the nucleus and other organelles
.Dendrites: short, branch-like projections
.The axon: longer projection.Ends in branches which widens at the tip and are called axon terminals
axons are protected by a while substance called myelin.Axons of various neurons sometimes group to form nerves.
3.2 transmitting a nerve impulse
neurons are connected to each other.The place where one neuron connects to another is called a synapse.
a nerve impulse is like an electrical current transmitted along the neuron membrane and then on to other neurons through synapses.
.Neuron that transmit: transmitter neuron
.Neuron that receive: receptor neuron
nerve impulse transmission across a synapse
1 the transmitted nerve impulse reaches theendofits axon