Human Sensory Receptors and Musculoskeletal System

Types of Sensory Receptors

According to their function, sensory receptors are classified as follows:

• Chemoreceptors: Sensitive to chemical stimuli.
• Mechanoreceptors: Sensitive to mechanical stimuli such as friction and pressure.
• Photoreceptors: Light-sensitive receptors.
• Thermoreceptors: Sensitive to temperature variations.
• Nociceptors: Sensitive to intense pressure and responsible for pain.

Anatomy of the Eye and Ear

The Pupil: It controls the amount of light entering the eye. It contracts when there is a lot of light and dilates in low light.

The Retina: The retina forms an inverted image that is smaller than the real object. This image is captured by the photoreceptors.

Eustachian Tube: It connects the ear to the airways.

Semicircular Canals: Their function is to maintain balance within the ear.

Common Sensory Disorders

• A) Cataracts (Eye): Clouding of the lens.
• B) Myopia (Eye): Difficulty focusing on distant objects, which appear blurred.
• C) Otitis (Hearing): Ear inflammation, sometimes accompanied by pus, which can be painless.
• D) Rhinitis (Nostrils): Inflammation of the nasal mucous membrane.
• E) Dermatitis (Skin): Allergic alteration of the skin characterized by the appearance of rashes, repeated spots, or blotches.

Classification of Joints

Joints are structures where adjacent bones meet, preventing their separation. The main types include:

• Stationary: These do not allow movement between bones, such as the bones of the skull.
• Semi-mobile: These join bones strongly but allow a small amount of movement. Between the joined bones are cartilage and ligaments that strengthen the joint (e.g., the vertebrae, where discs are located between each vertebra).
• Mobile (Synovial): These allow a wide variety of movements between the bones that form them. Their ends are coated with an articular capsule and cartilage. Between them is a bag of synovial fluid, which is a colorless, viscous liquid (e.g., knee, elbow, or shoulder).

Muscular and Spinal Health

Muscle Contractures: These consist of the involuntary and sustained contraction of a muscle. They occur when a muscle is required to work beyond what it can perform. They are frequent due to poor posture in the cervical, dorsal, and lumbar areas of the spinal column, which often causes pain.

Deformations of the Spinal Column

• Scoliosis: S-shaped deviation of the spine.
• Lordosis: Increased lumbar curvature.
• Kyphosis: Increased dorsal curvature.