Understanding the Anatomy and Function of the Nervous System

Choroid: is black and is the iris diaphragm that determines the color of the pupil. The retina is the innermost layer, which contains photoreceptors. The axons of these neurons form the optic nerve, which leads to the two types of photoreceptors in the brain. There are rods, which are involved in vision when the light intensity is low, and cones, which are responsible for vision in high light intensity.

MECHANISM OF VISION: Light enters the pupil, hits the lens, and the retina forms an image that is equal to the real one but inverted. It is here where the image is converted into nerve signals that travel through the optic nerve to the brain, where we recognize the image.

ANATOMY OF THE NERVOUS SYSTEM

The nervous system consists of the central nervous system and the peripheral nervous system.

1. Receivers

These are a set of specialized cells that perceive stimuli. The receptors can be classified according to the type of stimulus:

• Thermoreceptors: detect changes in temperature.
• Chemoreceptors: sensitive to chemicals.
• Mechanoreceptors: perceive pressure.
• Photoreceptors: sensitive to light.

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Internal receptors: detect changes in the internal environment of the organism, while external receptors: provide information about the surrounding environment (the five senses).

2.1 Touch

The sense of touch is in the skin, which detects sensations through thermoreceptors and mechanoreceptors.

2.2 Smell

The sense of smell resides at the top of the nasal cavity. Neurons in the olfactory nerve carry information to the olfactory area of the cerebral cortex.

2.3 Taste

Taste detects chemicals in food through receptors located on the tongue. There are four different types of chemoreceptors that react to chemicals, resulting in the four basic tastes: sour, bitter, salty, and sweet. The distribution of these receptors on the tongue is arranged in areas where one type dominates others. The stimulation of these receptors is very important for digestion, as it causes the production of gastric juices.

The taste of food is detected through different senses: smell and taste. The tongue detects the four basic tastes, while smell captures volatile substances released from food during chewing. The central nervous system receives all this information, including the taste of food.

2.4 Hearing

The ear consists of the following parts:

• Outer ear: consists of the pinna and ear canal that ends in the tympanic membrane.
• Middle ear: formed by a chain of ossicles and the Eustachian tube.
• Inner ear: in contact with the middle ear through the oval window, possessing a very complex structure, consisting of a coiled tube, known as the cochlea.