Neurons, Hormones, and Nervous System Function

Posted on Mar 29, 2025 in Biology

Synapses and Neurotransmitters

Synapses are connections between neurons that transmit nerve impulses. A neurotransmitter is a chemical substance that produces the nerve impulse across the synapse.

Neuron Structure

Neurons possess filamentous extensions that facilitate connections with other neurons and organs throughout our body. We distinguish two main parts:

  • Soma: Contains the nucleus and the main part of the cytoplasm.
  • Extensions: There are two types:
    • Dendrites: Short and highly branched extensions through which neurons interconnect with one another.
    • Axon: A long, typically unbranched prolongation. The axon is often protected by myelin, a white substance that wraps around it. The collection of axons and myelin forms nerve fibers, which are grouped into bundles to form nerves.

Nervous System Organic Disorders

These are physical alterations of the nervous system organs. They can be a consequence of:

  • Trauma (Hits): Can cause irreversible damage to the brain or spinal cord.
  • Obstruction (e.g., Stroke): Causes lesions due to the death of neurons from lack of blood supply.
  • Infectious Diseases: Such as meningitis, which affect the central nervous system.
  • Degenerative Diseases: Such as Alzheimer’s disease.

Functional Nervous System Disorders

Disorders like anxiety or depression are alterations in the functioning of the nervous system, often without structural damage.

Understanding Glands

Glands are organs formed by specialized cells designed to produce and secrete substances. There are two main types:

  • Endocrine Glands: Such as the pituitary or thyroid, which manufacture hormones and release them directly into the blood.
  • Exocrine Glands: Such as sweat or salivary glands, which release their secretions outside the organism or into the digestive tube. Therefore, they are not part of the endocrine system.

Mixed Glands

In addition to hormones, these glands produce other substances. For example, the pancreas secretes pancreatic juice into the digestive tube and also secretes hormones (like insulin and glucagon) released into the blood.

The Endocrine System

The endocrine system is constituted by the collection of glands that secrete hormones into the blood. Principal components include:

  • Pituitary Gland

    • Growth Hormone (Somatotropin, STH): Stimulates the growth of our organism.
    • Thyroid-Stimulating Hormone (Thyrotropin, TSH): Stimulates secretion by the thyroid gland.
    • Adrenocorticotropic Hormone (ACTH): Stimulates secretion by the adrenal glands.
    • Gonadotropins (FSH and LH): Regulate the activity of the sexual glands.
    • Prolactin (Lactotrophin, LTH): Stimulates milk secretion in women.

  • Thyroid Gland

    • Thyroxine: Stimulates cellular chemical activity (metabolism).

  • Adrenal Glands

    • Adrenaline: Stimulates heart rate and respiratory rate.
    • Cortisone: Stimulates glucose synthesis and fat breakdown.

  • Pancreas

    • Insulin: Stimulates processes that decrease the amount of glucose in the blood.
    • Glucagon: Stimulates processes that increase the amount of glucose in the blood.

  • Testes

    • Testosterone: Regulates the function of male sexual organs.

  • Ovaries

    • Progesterone and Estradiol: Regulate the development and functions of female sexual organs and prepare the organism for a possible pregnancy.

Hormone Characteristics

  • Specific: Each hormone acts on specific cells, called target cells, which respond to its presence.
  • Highly Effective: A minimal amount of hormone is sufficient to perform its function.
  • Controlled Production: An excess or deficit in the amount of hormone can cause diseases.

Pituitary Gland Action Mechanism

The pituitary gland operates via a feedback mechanism:

  1. The pituitary produces tropic hormones.
  2. These hormones travel through the blood to the corresponding target gland.
  3. They activate hormone production in the target gland.
  4. A high concentration of the target gland’s hormone in the blood inhibits the pituitary’s activity.
  5. The pituitary reduces or stops producing the tropic hormone.
  6. This slows down hormone production by the target gland.

Understanding Drugs and Their Effects

Drugs are toxic substances that produce dependence and build tolerance.

  • Toxicity: All drugs affect health and alter many of our organs.
  • Dependence: The need felt by the user to consume the drug to avoid the discomfort caused by its absence (withdrawal).
    • Withdrawal Syndrome: Physical and psychological suffering due to the lack of the drug.
  • Tolerance: The need to increase the dose of the drug consumed to achieve the same effect.

Types of Drugs

  • Depressants: (e.g., tranquilizers) Act on the central nervous system. Can cause loss of balance. Habitual consumption triggers serious alterations in the organism.
  • Narcotics: (e.g., morphine) Eliminate pain and cause drowsiness and stupor. They are very harmful and create dependence that is very difficult to overcome.
  • Stimulants: (e.g., cocaine) Stimulate the central nervous system and create a sensation of euphoria. They are very dangerous and can cause cardiac arrests. They create psychological dependence and tolerance.
  • Hallucinogens: (e.g., LSD) Produce hallucinations. Habitual consumption carries the risk of personality disorders, depression, and mental illness.