Sensory Receptors and the Human Body: Functions and Systems
What is the Mission of Sensory Receptors?
They are responsible for receiving and transmitting information from outside the nervous system.
What is the Mission of the Effectors?
Effectors are responsible for carrying out the response developed by nerve centers. The response may be secretory or motor.
Sensory Receptor Types
What sensory receptor types are known?
- Photoreceptors: They detect light stimuli and are located in the eyes.
- Mechanoreceptors: These are stimulated by mechanical changes, pressure, contact, and sound waves. Included in this group are several receptors in the skin, muscles, and joints, as well as the auditory receptors.
- Chemoreceptors: They capture information from chemical changes. The receptors of taste and smell belong to this group.
- Thermoreceptors: These are stimulated by temperature changes, such as some receptors in the skin.
Sense Organs
How Does the Eyeball Work?
The eyeball carries out two processes:
- Regulating the intensity of light: Too much light can damage the photoreceptor cells, and too little light prevents visual processing. This process involves the pupil, which opens or closes depending on the intensity of light due to the contraction or relaxation of muscles located in the iris.
- Focusing images: Objects should focus on the retina. This modification is done with the thickness of the lens, which flattens or bulges depending on whether objects are near or far. The image formed on the retina is inverted, but the brain interprets it correctly. Human vision is stereoscopic, thanks to the images obtained by the two eyes overlapping in the same brain area, providing a sense of space.
How is Audition Produced?
Sound waves are produced by vibrations of air molecules or objects. When these waves reach the eardrum, it vibrates and transmits the vibrations to the ossicles. The last ossicle (stapes) transmits the vibration to the oval window. This, in turn, causes the vibration of the perilymph of the inner ear and, consequently, the excitement of certain cells in the interior of the cochlea, which is the organ of Corti. This generates a nerve current that travels to the brain, where the information is interpreted.
How Does Balance Work in the Ear?
The knowledge of body position occurs in the utricle and saccule. In these structures, there are sensory cells provided with cilia and covered with a gelatinous mass that contains small mineral particles. When the head position changes, these particles cause a change in the position of the cilia, generating a nerve impulse that is conducted by nerves to the cerebellum. The detection of movement is done in the semicircular canals. When we move, the endolymph moves, causing a relative motion between it and certain cells of the vestibular apparatus. These cells have a gelatinous mass that bends the cilia, generating a nerve current that is transmitted to the cerebellum.
What is Touch? What Kind of Feelings Does it Include?
Touch consists of sensory receptors in the skin that capture a wide range of stimuli. It includes feelings of the appearance and texture of objects, pressure, heat, high or low temperatures, and pain.
What are Taste and Smell?
Taste is the sense that can capture the information of chemical compounds from food. Smell is the detection of gaseous molecules that reach the nose.
Effector Organs: Locomotor System
What is the Mission of the Musculoskeletal System?
Its mission is to move our body.
What Two Systems Comprise the Locomotor System?
It is constituted by muscles and bones.
What is the Mission of the Muscular System?
Its mission is to lead to changes in the position of the bones, causing movement.
How are Muscles Formed? How is Muscle Contraction Produced?
Muscles consist of muscle groups, which in turn are composed of elongated muscle cells. All are covered by protective sheaths. These sheaths meet and are wrapped by tendons, which are the point of union between muscles and bones. Muscle contraction is a shortening and thickening process. This requires:
- A nervous connection. The order from a motor center is called a motor endplate, similar to a synapse, and releases neurotransmitters that cause muscle contraction.
- Energy production in muscle cells for contraction, obtained from cellular respiration.
What is the Mission of the Skeletal System?
It allows the attachment of muscles, supports the body, protects important organs, stores calcium, and produces blood cells.
How are Bones Formed?
Bones are composed of bone tissue that may be spongy (with cavities, giving it a characteristic appearance) or compact (with no interior spaces). They have solid calcium salts that give them strength, as well as living tissue.
What are Joints? What Types are Known?
Joints are the points of union between bones. They can be fixed, mobile, or semi-mobile.
Diseases
- Conjunctivitis: Inflammation of the conjunctiva of the eye due to an infection or allergy, causing itching, tearing, and redness.
- Cataracts: The lens becomes opaque and does not let light through. It appears in the elderly.
- Color Blindness: A congenital disease in which the affected person cannot distinguish some colors.
- Deafness: The lack of hearing due to injury to the cochlea or the auditory nerve, difficulties in the transmission of sound vibrations, etc.
- Arthritis: Inflammation of joints, causing pain and swelling. The joints become hot, lose mobility, and can become deformed. It may be due to infection or unknown causes.
- Gout: A very painful joint inflammation accompanied by redness and swelling.
- Osteoporosis: A reduction in bone mass, making fractures more likely.