Human Health: Diseases, Immunity, and Prevention

Understanding Health & Disease

Health initiatives are often geared toward reducing exposure to various factors that are carcinogens, such as alcohol, tobacco, and diet. Recent years have spawned a new area of scientific knowledge: epigenetics, which studies the influence of the environment on gene expression.

Mental Health Conditions

Some diseases of the nervous system are due to malfunctioning neurons or injuries provoked by varied causes, such as high blood pressure, strokes, or lack of blood supply. The most important mental health challenges include:

• Depression

  Characterized by deep sadness and an incapacity to lead a normal life.

• Schizophrenia

  A disease that can present from adolescence, provoking serious personality disorders and disconnecting individuals from the outside world.

• Dementia

  A progressive loss of intellectual functions that individuals experience. Two types are recognized:

  • Senile Dementia: Typically affects individuals aged 80 and above.
  • Presenile Dementia: Usually appears around age 50.

Neurodegenerative Disorders

These are progressive conditions that affect the nervous system.

• Alzheimer's Disease

  An incurable, progressive degenerative disease that affects the brain and approximately 5% of the population aged 75 and above. It leads to memory loss and changes in cognitive behavior.

• Parkinson's Disease

  Affects persons of advanced age, deteriorating the neurons that control involuntary muscle movement. Symptoms include tremors in the hands and feet. Parkinson's disease occurs when neurons in a specific area known as the substantia nigra die.

Allergies & Autoimmune Conditions

These conditions involve the immune system reacting inappropriately.

• Allergies

  Alterations provoked by hypersensitivity to substances in the environment, such as pollen or animal hair.

• Autoimmune Diseases

  Caused by a failure of the immune system, where immune cells produce antibodies against the body's own tissues, leading to diseases such as severe multiple sclerosis.

The Human Immune System

The immune system is responsible for defending our body against the invasion by antigens (e.g., germs, foreign organisms). Antibodies are proteins that counteract antigens. Immunity refers to the body's capacity to defend itself against foreign substances and pathogens. These defenses are grouped into two types:

1. Nonspecific Immunity

   The most important components are:

   • Entry barriers (e.g., skin, mucous membranes)
   • Inflammation
   • The complement system
   • Natural Killer (NK) cells

2. Specific Immunity

   This is based on the body's ability to respond to each specific pathogen, capable of bypassing nonspecific defenses and penetrating inside. B cells and T lymphocytes are responsible for specific immunity.

Vaccines & Immunity Types

Immunity occurs because the body produces specific memory lymphocytes against antigens it has previously encountered. Immunity can be active or passive:

• Active Immunity

  Occurs when the body produces its own antibodies against an antigen after being in contact with it.

• Passive Immunity

  In cases of infections where the body cannot be expected to produce its own antibodies quickly, it is necessary to provide them, often manufactured by another organism (e.g., through antitoxins or maternal antibodies).