Sensory Receptors and Sense Organs: A Detailed Look

Posted on Feb 22, 2025 in Biology

Sensory Receptors

Sensory receptors are responsible for perceiving and receiving stimuli, which they convert into nerve impulses.

Photoreceptors: Detect light stimuli and are located in the eye. They respond to dim or bright light and produce black and white vision or color images.
Mechanoreceptors: Stimulated by mechanical changes such as pressure, contact, or sound waves. Several receptors in the skin, muscles, and joints, including auditory receptors, are included.
Chemoreceptors: Respond to chemical changes. Taste and smell receptors are included.
Thermoreceptors: Detect temperature changes. Some skin receptors are included.

Internal Receptors: Located in the internal organs, they collect information about them and analyze the condition of the body.
External Receptors: Located on the surface of the body and are responsible for collecting information about the external environment.

The eye is the organ where sight is located. It’s a complex structure that receives light and carries it to the photoreceptors.

Lens: Transparent, elastic, and biconvex organ attached to the inner wall of the eyeball. It separates two chambers:
- Anterior chamber: Filled with aqueous humor.
- Posterior chamber: Contains vitreous humor.
Optic nerve: Nerve cell extensions that communicate with rods and cones.
Blind spot: The exit of the nerve endings; there are no photoreceptor cells.
Retina: Innermost layer of the ocular globe; contains rods (detect visible light) and cones (perceive color).
Choroid: Second layer of the ocular globe; it is black, but its iris can be colored. In the center of the iris is the pupil.
Sclera: Outermost layer of the ocular globe. It is white and transparent. It forms the cornea.
Fovea: Area of the retina that offers the best visibility.

The ears are the sensory organs located inside the cavities of the temporal bones.

The Outer Ear: Formed by the pinna and auditory canal, which penetrates the bone and has an elastic membrane called the eardrum.
The Middle Ear: A cavity in the temporal bone that starts at the eardrum and reaches the oval window and the round window. It contains three small bones: the hammer, anvil, and stirrup.
The Inner Ear: The deepest section, formed by the membranous labyrinth and bony labyrinth. The membranous labyrinth has several sections, including the cochlea and the vestibular system.

The skin is an organ that has sensory receptors that perceive very diverse stimuli through touch.

Melanocytes: Cells that contain melanin, which protects the body from solar radiation.
Adipose Tissue: Layer of fat cells located in the deepest part of the skin, used to absorb impact, protect the body from cold, and act as an energy reserve.
Sweat Glands: Secrete sweat, cool the body surface, and remove certain waste substances.
Hair: Covers the entire body surface, protecting us against the cold.
Sebaceous Glands: Secrete substances that lubricate the skin and hair.

Taste allows us to detect chemical substances from foods as they dissolve in our saliva.

Sweet, salty, bitter, sour, and umami.

Our sense of smell allows us to perceive gas molecules that reach our nose.