Nervous System Senses and Endocrine Functions Explained

Function and Response Relationship

Allows beings to perceive changes in the external or internal cause of responses. This process consists of:

• Perception of the stimulus
• Analysis of the information
• Production of a response

The Sense of Sight (Vision)

Through this sense, we perceive shapes, colors, sizes, and distances. The organ is the eye. To work, light enters the eye through the pupil, which is controlled by the iris. From there, it reaches the lens, which acts like a focusing mechanism, projecting the image onto the retina. The retina contains photoreceptors called rods and cones. These translate the light into a nerve impulse that passes through the optic nerve to the brain.

The Sense of Hearing (Audition)

Through this sense, we perceive the intensity, duration, and timbre of sounds. Operation: Sound enters the ear canal and vibrates the eardrum. The vibration is transmitted to the ossicles, which stimulate the cochlea (snail). The cochlea contains mechanoreceptors that send an auditory nerve impulse to the brain.

Endocrine Gland Functions

Pituitary Gland

Located below the hypothalamus. It secretes growth hormone and prolactin.

Thyroid and Parathyroid

The thyroid is at the base of the neck near the trachea and secretes thyroxine. The parathyroid glands are located below the thyroid and secrete parathyroid hormone.

Pancreas

A gland located in the waist area (left side) that secretes insulin and glucagon.

Adrenal Glands

These glands sit on top of the kidneys and secrete cortisol and adrenaline.

Gonads

• Ovaries: Secrete estrogens and progesterone.
• Testicles: Secrete testosterone.

Diabetes Mellitus

A disease caused by a malfunction of the pancreas, resulting in insufficient insulin production. It is characterized by high glycosuria, hyperglycemia, continuous thirst, fatigue, hunger, and weight loss. Diagnosis is done through urine analysis; in severe cases, it can cause blindness.

Nervous Tissue Components

Neurons

Neurons are nerve cords that transmit nerve impulses. They are distinguished by:

• Neuronal Body (Soma): Contains the nucleus and most organelles.
• Dendrites: Branches that connect other neurons to the soma.
• Axon: A prolongation of the neuron that transmits nerve impulses away from the soma.

Synapse

The area where neurons communicate. It involves the presynaptic neuron, the postsynaptic neuron, and the synaptic space.

Functions of the Skeleton

• Supports the body and maintains posture.
• Provides protection for vital organs.
• Acts as the passive component of motion.
• Deposits mineral salts (e.g., calcium).

About Hormones

Hormones are molecules produced by a gland that travel through the blood to reach the target organ where they exert their function. Hormones are specific, required in small amounts, and their production is tightly controlled.