Human Nervous System and Sensory Functions Explained

Central Nervous System

The brain is divided into two hemispheres and contains convolutions. It controls all voluntary movement.

Cerebellum: Divided into two hemispheres, it controls and coordinates voluntary muscle movements, ensuring accuracy and maintaining equilibrium.

Medulla Oblongata: Connects the brain to the spinal cord and is responsible for controlling pulmonary ventilation and cardiac rates.

Spinal Cord: Located inside the vertebral column and surrounded by meninges. It is formed by a nervous cord with two main functions: communication and the elaboration of responses.

Peripheral Nervous System

Cranial Nerves: There are 12 pairs that originate from the encephalon and travel to various parts of the body.

Spinal Nerves: There are 31 pairs that emerge from the spinal cord and reach all parts of the body.

Nervous System Cells

There are two main types of cells:

• Neurons: Cells whose main characteristic is the excitability of their plasma membrane. They specialize in receiving stimuli and conducting nerve impulses between themselves or with other cell types, such as muscle fibers.
• Glial Cells: Also known as neuroglia. In addition to supporting neurons, they are active in cerebral information processing.

The Five Senses

Smell

This is the least developed sense, yet we can distinguish 10,000 different odors. Molecules penetrate the external nostrils and dissolve in the overlying mucus, where they are detected by olfactory cells that send a stimulus to the olfactory nerve.

Taste

On the surface of the tongue, there are chemoreceptor taste cells that capture different flavors. These cells are located within structures called taste buds, which are found in the bumps on the tongue.

Hearing

Beyond hearing, this sense maintains equilibrium. It captures vibrations that penetrate the ear pinna, travel through the external canal, and cause the eardrum to vibrate.

Vision

The eye works like a camera. The outermost part, the cornea, directs light toward the pupil.

Touch

The skin contains a large capacity of receptors distributed throughout the body, categorized by the sensations they capture:

• Thermoreceptors: Capture exterior temperatures (heat or cold).
• Nociceptors: Respond to attacks or damage to the skin.
• Mechanoreceptors: Detect changes in pressure on the skin.

Common Diseases

• Myopia: Affects distance vision; corrected with lenses.
• Cataracts: An opaque layer develops on the crystalline lens.
• Vertigo: Dizziness due to strong alterations in equilibrium.
• Hypoacusis: The diminution or loss of hearing.