Human Biology: Drugs, Hormones, and Sensory Organs

Classification of Drugs and Their Effects

Nervous system drugs include various types of illegal substances:

• Stimulants: Cocaine and amphetamines.
• Depressants: Derived from opium, morphine, and heroin.
• Hallucinogens: Barbiturates, marijuana, toxic substances, LSD, and synthetic drugs.

Legal drugs include alcohol, caffeine, and tobacco.

Impact of Alcohol on the Body

Effects of alcohol: It causes damage and maladies to various organs. It affects the digestive system, leading to conditions such as cirrhosis, gastritis, cancer, and ulcers. It also causes obesity due to the calories produced by alcohol. In the nervous system, it leads to intellectual deterioration, memory loss, and addiction. Furthermore, it causes disorders in the reproductive tract, such as impotence and infertility.

The Endocrine and Hormonal System

The endocrine system, along with the nervous system, functions to coordinate and organize the body; it is hierarchically below the central nervous system. It consists of a series of glands distributed throughout the body that secrete hormones, which is why it is also called the hormonal system.

These endocrine glands release secretions inside the body (into the blood). Hormones are chemical substances (lipids or proteins) that travel through the blood. When they find a particular organ, they cause a specific effect. Hormones are related to specific target organs and not others.

Major Glands in the Human Body

• Pituitary Gland: Located at the base of the brain in a part named the hypothalamus; it controls other glands.
• Testes (male) and Ovaries (female).
• Adrenal Gland: Located on top of the kidneys.
• Thyroid Gland: Located in the neck around the windpipe.
• Pancreas.

Sensory Organs: Vision and Hearing

Common Vision Disorders

• Myopia: Occurs when the eye is longer than normal or the cornea is too curved.
• Hypermetropia: Occurs when the eye is shorter than normal or the cornea is very flat.
• Astigmatism: Occurs when the cornea does not have the same curvature in all directions.

Anatomy of the Ear

The ear is divided into several sections:

• External Ear: Includes the ear (collects sound waves) and the auditory canal (channels sound waves toward the eardrum).
• Middle Ear: Contains the tympanic membrane (transmits sound vibrations) and the chain of bones (conveys vibrations to the inner ear).
• Inner Ear: Contains the cochlea (snail), which is the organ of hearing containing receptors. It also includes the utricle and saccule.
• Semicircular Canals: This is where the organ of balance is located.
• Auditory Nerve: Formed by the axons of neurons from the cochlea; it leads auditory sensations to the brain.

Hormonal Imbalances and Diseases

Disruptions in hormone production can lead to various health conditions:

• Growth Hormone: Excess leads to gigantism; deficiency leads to dwarfism.
• Thyroxine: Deficiency can cause goiter, cretinism, or myxedema.
• Insulin: Deficiency leads to diabetes mellitus.
• Adrenal Hormone: Deficiency leads to Addison's disease (decreased response to stress).
• Vasopressin: Deficiency leads to diabetes insipidus.
• Sexual Hormones: Deficiency leads to infertility and a delay in the appearance of secondary sexual characteristics.