Understanding Sensory Receptors and Their Functions in the Human Body

Sensory Receptors

Sensory receptors are responsible for perceiving information, which they convert into a nerve impulse.

Types of Sensory Receptors

Photoreceptors: they detect light stimuli and are located in the eye.

Mechanoreceptors: mechanical changes pressure, contact or sound waves. Skin, muscles and joints Auditory receptors

Chemoreceptors: they respond to chemical changes.

Thermoreceptors; they detect temperature changes.

According to Their Location

Internal receptors: they are located in the internal organs: hunger, thirst, body position, the need to urinate, among other things.

External receptors: they are located on the surface of the body and are responsible for collecting information about the external environment. They are stimulated by light, sound and changes in temperature.

The Eye

The eye is the organ, where the sense of sight is located. It is a complex structure that receives light and carries it to the area where the photoreceptors are located.
Photoreceptors located in the eye transform light stimuli into electrical impulses and transmit the information to the optic nerve, which carries it to the brain.

Anatomy of the Eye

Retina this is the innermost layer of the ocular globe it contains two types of photoreceptor cells: rods and cones.

Choroid this is the second layer iris (behind the cornea) it appears coloured in the centre of the iris there is an orifice, the pupil.

Sclera this is the outermost layer transparent, forming the cornea.

Blind spot: the nerve ending exits. there is no sight are no photoreceptor cells.

Fovea: this is the area of the retina that offers the best visibility. There is an abundance of cones here.

Optic nerve this a group of nerve cell extensions that communicate with rods and cones.

Eyebrows they divert sweat to protect the eye
Eyelids: protect the ocular globe covered by the conjunctiva
Eyelashes: diffuse light
Ocular muscles: they move the ocular globe up, to direct our sight to the object that we want to see
Lacrimal glands: they secrete tears which keep the frontal part of the eye humid in order to avoid dryness. They also contain a substance that kills bacteria.

How the Eye Works

Ocular globe is to allow light to stimulate cones. Cones and rods will produce a nervous impulse that will be carried to the brain by the optic nerve.

Regulation of light intensity: The pupil intervenes in this mechanism of light regulation, opening and closing according to light conditions.

Focusing on Images: In order not to see blurred images, the object needs to be focused properly, by modifying the lens: it flattens in order to focus on objects that are far away and widens in order to see objects that are near.

The Ear

The ear: perceive two types of stimuli in two different areas sounds, and changes of body posture (balance).

Anatomy of the Ear

The outer ear: this is formed by the pinna (the visible ear) and auditory canal which penetrates an elastic membrane at the end called the eardrum. In this duct there are glands that secrete protective wax.

The middle ear: three small bones the hammer, anvil and stirrup.

The inner ear: membranous labyrinth, two labyrinths there is a fluid, perilymph, endolymph: cochlea, detects sounds. vestibular system, is responsible for spatial awareness and balance. The vestibular system is composed of three semicircular canals and two vesicles: the utricle and saccule.

Hearing Mechanism

Vibrations in molecules found in the air or any other object produce sound waves.

The last bone, the stirrup, transfers the vibration to the oval window causing the perilymph to vibrate. As a consequence certain cells (located inside the cochlea, forming the organ of Corti) are stimulated. A nervous impulse is created which travels through the nerve to the brain where the information is interpreted.

Balance Mechanism

Knowledge of the body’s position: Inside the utricle and saccule there are sensory cells that have cilia covered by a gelatinous mass containing small mineral particles.

Detecting Movement: Walk, run, and dance without falling. It occurs in the semicircular canals.

When we move, our ears and head move too. The endolymph remains static for a few moments due to inertia. The cells are covered in a gelatinous mass and have cilia, which bend. This generates a nerve impulse that reaches the brain.

The Skin

Is an organ that has sensory receptors that perceive very diverse stimuli through touch.

The shape and texture that objects have
Pressure occurring as a result of strong tactile sensation
Heat and cold

Pain receptors which are just free nerve endings, the other touch receptors are located in dermal corpuscles. encapsulated endings.

In addition to sensory receptors, the skin has other structures responsible for other functions:
Melanocytes these are cells that contain a dark pigment (melanin) that protects the body from solar radiation.

Adipose tissue: protect the body from cold temperatures and act as an energy reserve.

Sweat glands: secrete sweat, cooling the body surface when necessary and removing certain waste substances.

Hair: to protect us against the cold.

Sebaceous glands: lubricate the skin and hair.


Taste allows us to detect chemical substances from foods as they dissolve in our saliva. The sensations produced are the different tastes.
Basic tastes: sweet, salty, acidic (bitter), sour and umami.
Taste receptors are cells that group in taste buds, which are located inside the mouth, especially on the tongue.


Our sense of smell allows us to perceive gas molecules that reach our nose.
In the interior of the nasal passages, there is an area called the olfactory epithelium where the olfactory receptor cells group, forming the olfactory bulb.


The muscles are responsible for changing the position of bones and creating movement.


Bones contain calcium salts that makes them hard and tough. They are formed of bone tissue, which can be of two types: spongy bone that has cavities and compact bone that has no internal spaces.

Long bones: these are long and contain spongy. support and move the body.

Short bones: rounded spongy none. the vertebrae and the wrist bones

Flat bone: plate-shape. Two layers of compact bone tissue. Skull bone and shoulder blade.


The skeleton also has cartilage, a structure which isn’t as hard as bone because it doesn’t contain calcium salts. Cartilage is located in the ears, the front part of the nose and in between the vertebrae; it also forms the skeleton of embryos.


  • Fixed: these stop the movement of bones.
  • Mobile: these allow bones to move.
  • Semi-mobile: these only allow limited movement of the bones.

Functions of Bones:

  • Anchor the muscles
  • Support
  • Protect
  • Calcium reserve
  • Blood cells are created.