Nervous System Structure and Function Explained

Nervous System Information Processing

The nervous system receives, interprets, prepares a response, sends orders, and coordinates the functioning of the organs. It also performs mental and intellectual functions and is responsible for emotions and feelings.

Neurons and Synapses

Neurons are specialized cells throughout our bodies that have lost the ability to reproduce. The synapse generates and transmits impulses. When a neuron is stimulated, an electrical change occurs in the membrane, transmitting signals from the axon shaft to the dendrites.

Central Nervous System (CNS)

The CNS is composed of the brain (including the spinal bulb, brain stem, cerebrum, and cerebellum) and the spinal cord. It is protected by the meninges, cerebrospinal fluid, and the surrounding bone structure.

Components of the Brain (Encephalon)

• Spinal Bulb: An extension of the spinal cord that controls heartbeat, blood pressure, and respiration.
• Brain Stem (Tronco): Regulates and monitors the state of dreams and visual/auditory reflex actions; it has two hemispheres.
• Cerebrum: Responsible for instinctive and creative functions, imagination, and combination. The left hemisphere handles logical and analytical functions, computation, and reasoning.
• Cerebellum: Located on top, it regulates muscle movement and coordinates orders.

Spinal Cord

The spinal cord is a nerve cord running along the spine. The gray matter is shaped like a butterfly in the center, and the white matter is on the outside. The center contains a liquid called cerebrospinal fluid.

Peripheral Nervous System (PNS)

The PNS connects the nervous centers to receivers and consists of nerves:

Types of Nerves

• Sensory (Afferent): Transmits information from receptors toward the central nervous system (CNS).
• Motor (Efferent): Transmits information from the CNS toward the effector organs.
• Mixed: Contains both motor and sensory fibers.

Nerves by Location

• Cranial Nerves: 12 pairs originating from the skull (e.g., optical and auditory nerves).
• Spinal Nerves: 31 pairs originating from the vertebrae.

Autonomic Nervous System (ANS)

The ANS is responsible for regulating and coordinating all internal organs that do not depend on voluntary will. It has two types:

• Sympathetic: Activates body organs to intensify function.
• Parasympathetic: Causes relaxation of the organs, resulting in slower operation.

Nervous Acts

There are two types of nervous acts:

• Reflex Acts: Fast, automatic acts that do not involve the brain in their development.
• Voluntary Acts: Acts performed because we are prepared for them; these involve the brain.

Endocrine System

The Endocrine System consists of endocrine glands that produce hormones. Hormones are organic substances that travel through the blood until they reach specific cells (target cells or 'white' cells). The functions of this system are to coordinate and regulate body organs to ensure proper functioning.