Human Health: Disorders and Nervous System Functions

Common Health Disorders

Sensory Organ Issues

• Eyes:
  • Short-sightedness (Myopia): Eyeball too long. Images focus in front of the retina.
  • Long-sightedness: Images focus behind the retina.
  • Cataracts: The crystalline lens loses transparency until it becomes opaque.
  • Conjunctivitis: Inflammation in the conjunctiva.
  • Astigmatism: Irregularly shaped cornea; objects appear distorted or blurred.
• Skin:
  • Psoriasis: Skin patches covered with silver scales.
  • Urticaria: Allergic reaction, often to food or medicine.
• Ear:
  • Otitis: Acute inflammation.
  • Deafness: Hearing loss.
• Nasal Cavity:
  • Rhinitis: Inflammation in the nasal respiratory membrane, often caused by allergies.

Mental Health Conditions

• Phobias: An anxiety disorder due to a persistent, irrational fear (e.g., fear of confined spaces).
• Dementia: A disease characterized by declining brain function (problems with memory, language, etc.).
• Schizophrenia: A brain disorder appearing in adolescence or adulthood; symptoms include hallucinations and drastic changes in behavior.
• Mental and Behavioral Problems due to Drug Use: Lack of motivation, changes in behavior, depression, addiction, etc.

Drugs and Health Effects

Stimulants, depressants, and mind-altering substances affect the body:

• Tolerance: A person becomes less sensitive to a substance and requires more to achieve the same effect.
• Dependence: After a period of repeated use, absence of the substance produces withdrawal symptoms.

Promoting Healthy Habits

To maintain well-being:

• Eat a healthy diet.
• Avoid harmful substances.
• Schedule routine examinations (check-ups).
• Maintain good hygiene and avoid injuries (focusing on eyes, ears, skin, and mouth).

Nervous System Structure and Function

The nervous system detects and interprets external and internal stimuli, produces necessary responses for the body to function, and transmits them to the effectors. It controls the internal environment (homeostasis) and enables the body to interact with the environment.

Components of the Nervous System

Cell Types

Two types of cells exist:

• Neurons: Generate and transmit impulses. Parts include the cell body, dendrite, and axon.
• Glial Cells: Surround the neurons, providing support and protection; they get nutrients directly from the blood for the neurons.

Neuron Subtypes

• Sensory Neurons: Send information from receptors to the CNS.
• Motor Neurons: Send responses from the CNS to effectors.
• Relay Neurons: Connect sensory and motor neurons.

Glial Cell Subtypes

• Astrocytes: Star-shaped; transport nutrients to neurons.
• Microglia: Remove cellular waste and protect against microbes.
• Oligodendrocytes: Produce myelin, which covers some axons, helping nerve impulses travel faster.
• Schwann Cells: Produce myelin; help transmission, but only cover one axon each.

Transmission of Nerve Impulses

• Neurons transmit information as electric signals.
• Impulses travel along the neuron, always exiting from the axon terminal.
• Transmission of information between neurons occurs at the synapses.