Nervous and Endocrine Systems: Functions and Interconnections

The Nervous System

Consisting of two types of cells:

• Neurons: consist of neuronal bodies, Dendrites (extensions where the nerve impulse enters the body), and axons.
• Glia (or Neuroglia): Made by the supporting structure of the nervous system, they collaborate in nutrition and feeding of neurons.

Nervous System Division

Central Nervous System (CNS), peripheral nervous system, autonomic (or vegetative) nervous system.

Central Nervous System

Comprising:

• Brain: Located in the skull, it consists of an internal gray substance and an external white substance. Surrounded by 3 membranes called meninges: Piamater, Arachnoid, Dura mater.

Parts:

• Cerebrum: Divided into hemispheres (left and right), weighing between 1200 and 1600g. It includes frontal, parietal, occipital, and temporal lobes. It controls the senses.
• Cerebellum: Weighing 140g, located in the rear lower skull, consisting of a central body called the vermis and central lobules. It coordinates movements.
• Medulla Oblongata: Consists of numerous bundles of fibers that connect the cerebrum with the cerebellum and spinal cord.
• Spinal Cord: Travels inside the spinal column to the meninges of the brain. Function: The white matter conducts nerve impulses through the elaboration of reflexes that will be processed by the gray matter.

Peripheral Nervous System

Classified depending on where the nerves emerge:

• Cranial Nerves: 12 pairs.
• Spinal Nerves: 31 pairs.

According to the direction of nerve impulses:

• Sensory Nerves: Carry nerve impulses from receptors to the CNS (e.g., a pinprick).
• Motor Nerves: Carry impulses from the CNS to effectors (e.g., moving an arm).
• Mixed Nerves: Carry impulses in both directions.

Within these are nervous ganglia: accumulations of neuronal bodies that might receive or generate nerve impulses.

Autonomic (or Vegetative) Nervous System

Types:

• Sympathetic: Formed by a series of ganglia and nerves from the medulla, it controls the functioning of internal organs and is activated in emergency situations or during severe exertion.
• Parasympathetic: Major nerves originating from the brain, the most important being the vagus nerve. Its functions are opposed to the sympathetic system, promoting recovery (e.g., contraction of the pupil, muscle relaxation).

Reflex Action vs. Voluntary Act

• Reflex Action: Occurs when the response is elaborated in the spinal cord. It is a very fast and unconscious response.
• Voluntary Act: Occurs when the response is elaborated in the cerebrum. In this case, there is conscious awareness of the response.

Functions of the Nervous System

Connects sensory receptors to effector organs and nerve centers, conducting nerve impulses to integrate sensory stimuli.

The Endocrine System

Made up of glands and hormones, it acts as a communication network that responds to stimuli by releasing hormones: chemicals that endocrine glands release into the bloodstream. Functions:

• Regulates basic instincts and emotions.
• Helps produce energy.
• Controls body temperature.
• Stimulates growth.
• Develops sexual tissues.
• Helps repair damaged tissues.

Endocrine Organs

• Adrenal Glands:
  • Adrenal Cortex:
    • Aldosterone: Regulates the balance of minerals and water in the body, maintaining sodium and potassium balance.
    • Cortisol: Produces energy, regulates the conversion of carbohydrates to glucose, reduces inflammation, and directs energy reserves to the liver.
  • Adrenal Medulla:
    • Adrenaline: Activates metabolism and prepares the body for great effort by releasing glucose into the blood. Increases blood pressure.
• Hypothalamus: Small groups of nerve cells located in the cerebrum. Integrates appropriate responses to stimuli. Regulates hunger, thirst, sleep, and insomnia. Regulates the functions of the pituitary gland.
• Ovaries: Produce estrogens, which develop secondary sexual characteristics. Progesterone: Develops mammary cells and prepares the uterus for ovulation.
• Testicles: Produce androgens. Testosterone: Develops sexual characteristics.
• Pancreas: Insulin: Regulates the amount of glucose (sugar) in the blood, promoting its storage in the liver as glycogen.
• Thyroid: Activates metabolism and influences intellectual growth.
• Parathyroid: Parathyroid hormone: Regulates the metabolism of calcium and phosphorus.

Physical Activity and Hormones

• Catecholamines (Adrenaline, Noradrenaline): Prepare the body for exertion and increase in concentration.
• Insulin: During physical activity, insulin levels decrease, regulating blood sugar. Glucocorticoids and glucagon are involved.
• Glucocorticoids and Glucagon: Mobilize sugar and transport it in the blood for use as energy by muscles.
• Testosterone: Anabolic protein hormone: training initially slows its production. After 30-90 minutes, it increases slightly before stopping.
• Cortisol: Increases with resistance training, especially in the afternoon. Appears when there is stress.
• Growth Hormone (GH): Helps the recovery process of our body.