Biology - Receptors, Impulses, and the Structure of the Eye

Vocabulary practice flashcards covering sensory stimuli reception, electrical impulses in neurons, external protective eye structures, and the anatomy and functions of the layers of the eye.

Sensory Receptors

Specialised cells or nerve endings through which stimuli are recognised by the body.

Receptor Potential

Electrical impulses produced in sensory receptors in response to external and internal stimuli.

Action Potential

Electrical impulses formed in neurons associated with receptors when receptor potential reaches a higher concentration, travelling through the neuron as nerve impulses.

Illustration 3.1: Action Potential in Neuron

Diagram illustrating how receptor potential generated in skin receptors forms an action potential that travels along a neuron.

Eye Muscles

Muscles associated with the eye that facilitate the movement of the eyeball.

Conjunctiva

The membrane covering the anterior part of the eye, including the eyelids except the cornea, which protects the eye, keeps it moist and lubricated, and prevents dust, germs, and other particles from entering.

Lacrimal Glands

Glands located towards the upper part of the eyelids that produce tears.

Tears

Fluid produced by the lacrimal glands that is essential for keeping the surface of the eye moist, providing nutrients, and eliminating waste materials.

Lysozyme

Enzymes present in tears that help protect the eye from infections.

Sclera

The outer layer of the eye that provides firmness and protection.

Cornea

The transparent anterior part of the eye that allows light to enter.

Choroid

The middle layer of the eye that provides oxygen and nutrients to the inner layer of the retina and regulates temperature.

Ciliary Muscles

Muscles in the eye that adjust the curvature of the lens.

Iris

The part of the eye containing two types of muscles that regulate pupil size according to light intensity, as well as the pigment melanin.

Melanin (in Iris)

A pigment that gives the iris its characteristic colour and absorbs ultraviolet rays.

Convex Lens (of the Eye)

A lens that forms a small, real, and inverted image of an object on the retina.

Retina

The inner layer of the eye containing photoreceptor cells where the image is formed.

Rod Cells

Photoreceptor cells in the retina that recognise objects in dim light and in shades of black and white.

Cone Cells

Photoreceptor cells in the retina that provide vision in intense light and assist in recognizing colours.

Bipolar Cell Layer

A retinal layer consisting of on-bipolar cells and off-bipolar cells that transmits impulses from photoreceptors to ganglion cells.

Ganglion Cell Layer

A layer of cells in the retina that transmits impulses from bipolar cells to the optic nerve.