Human Nervous System: Brain Structure and Functions

Anatomy and Functions of the Human Brain

The brain is the largest organ of the Central Nervous System (CNS) and is divided into several parts, each with specific functions. Its structure is organized into lobes:

• Frontal Lobe: Located at the front of the brain, it is responsible for functions such as thinking.
• Parietal Lobe: Positioned behind the frontal lobe, it is responsible for processing sensory information related to touch, temperature, and pain.
• Temporal Lobe: On the sides of the brain, it is essential for sound processing.
• Occipital Lobe: At the back of the brain, it specializes in visual processing.

Key Brain Structures

• Cerebellum: Located at the lower back of the brain, its main function is to coordinate muscle movements.
• Medulla Oblongata: This part of the brainstem connects the brain to the spinal cord. It is crucial for regulating involuntary functions.
• Thalamus: Situated in the center of the brain, it acts as a kind of "relay station" for sensory information coming to the brain.
• Hypothalamus: Found below the thalamus, it is a key structure in regulating vital functions and producing hormones.
• Neurohypophysis: It is responsible for storing and releasing hormones produced by the hypothalamus.
• Adenohypophysis: It produces and releases several hormones that regulate various functions in the body.

The Meninges: Protective Membranes

The meninges are membranes that wrap around and protect the CNS. They consist of three layers:

• Dura Mater:
  • Location: Outermost layer and is closest to the bone of the skull and the spinal column.
  • Function: It provides robust protection and acts as a barrier against infections.
  • Type of Tissue: It is primarily composed of dense connective tissue.
• Arachnoid:
  • Location: Middle layer, between the dura mater and the pia mater.
  • Function: It allows for the circulation of cerebrospinal fluid, which protects and nourishes the CNS.
  • Type of Tissue: Loose connective tissue and has a web-like appearance.
• Pia Mater:
  • Location: Innermost layer and is in direct contact with the surface of the brain and spinal cord.
  • Function: It provides structural support and protection to the neurons.
  • Type of Tissue: Made up of loose connective tissue.

The Peripheral Nervous System (PNS)

The peripheral nervous system (3,4) acts as a connection for all the body stimuli and moves them to the CNS. It is composed of neurons and neuronal processes found outside the CNS. The main role of the peripheral nervous system is to convey the input information, or stimuli, that the body is able to sense to the CNS, and to carry the commands from the CNS to the different organs and parts. It can be divided into an afferent sensory component and an efferent somatic component.

Motor and Autonomic Subdivisions

The motor component is subdivided into a somatic part and an autonomic part. The somatic part is related to the control of voluntary movements of skeletal striated muscles, while the autonomic part is related to the involuntary movement of internal organs and viscera.

The Parasympathetic System

The parasympathetic system (5) is related to energy saving. Parasympathetic fibers release acetylcholine. There are organs where a competition between the sympathetic and parasympathetic systems occurs, such as the heartbeat or eye pupil dilation.