Understanding the Human Nervous System and Sensory Organs

The Nervous System

Central Nervous System (CNS)

Brain

Located inside the head, the brain is divided into three regions:

• Cerebrum: Receives and interprets information from the sense organs. Language, memory, learning, and thinking are located here.
• Cerebellum: Plays an important role in motor control and motor learning. It acts in coordination and precision.
• Brain Stem: Joins the brain and spinal cord. It controls involuntary actions.

Spinal Cord

A long, thin tube running inside the backbone, the spinal cord transports information from the brain to the nerves and carries reflexes.

Protection of the CNS

• Hard: Bones protect the CNS. The brain is protected by the skull, and the spinal cord is protected by the backbone.
• Soft: Meninges, a system of membranes and liquid, surround and protect the CNS.

Peripheral Nervous System (PNS)

The PNS consists of nerves that connect the CNS with the limbs, senses, and organs. It has two parts:

• Somatic Nervous System: Controls voluntary movements and receives external stimuli.
• Autonomic Nervous System: Controls visceral functions and acts below the level of consciousness.
  • Sympathetic Nervous System: Its general actions prepare and mobilize the body's resources under stress.
  • Parasympathetic Nervous System: Responsible for stimulating activities that occur when the body is at rest.

Detecting the Environment

Human beings have mechanisms to perceive changes to interact with the internal or external environment:

1. Stimulus: Detectable changes in the external or internal environment, such as temperature, light, or glucose levels.
2. Receptors: Cells sensitive to certain types of stimuli.
3. Information Processing: Systems to carry out a coordinated response, either quick or slow.
4. Response: Carried out by effectors.

Sense Organs

Smell (Olfaction)

Located in the nose, the olfactory system detects chemical substances dissolved in the air. Inside the nose, in the upper part, the olfactory receptors trap molecules dissolved in the air. A signal is sent to the olfactory bulb and continues to the brain, where it is interpreted.

Touch

Touch is a perception resulting from the activity of neural receptors, generally located in the skin but also in the tongue, throat, mucosa, and organs.

Taste

The gustatory system allows humans to distinguish between safe and harmful food. The five specific tastes received by gustatory receptors are salty, sweet, bitter, sour, and umami (which means "delicious" in Japanese).