The Nervous System is very important to the management of our lives. It regulates all basic life by working alongside all the other systems to ensure that homeostasis is being maintained. As a whole it acts as the control center or the boss of our body and essentially tells everything else in our body what to do.

What is the Nervous System?

The Nervous System: An Overview

The Central Nervous System

The Central Nervous System (CNS) is composed of the Brain and the Spinal Cord.

The Brain is a very complex organ within the body. This is the master control center of the whole Neurvous System. It is housed in and protected by the skull.

The Spinal Cord is composed of nervous tissue that is protected by bones of the vertebral column. It carries signals between the brain and the peripheral nervous system.

The Spinal Cord

THE SPINAL CORD

This structure is separated into 5 sections.

There are 8 pairs of Cervical Nerves. This section runs from the brain to the base of the neck.

There are 12 pairs of Thoracic Nerves. This section runs from the base of the neck to the middle of the back.

There are 5 pairs of Lumbar Nerves. This section runs along the back where the abdominal portion of the body is located.

There are 5 pairs of Sacral Nerves. This section is part of the sacrum.

There is 1 pair of Coccygeal Nerves. This section is related to the tail bone.

The Spinal Cord

The Spinal Cord Contains:

GRAY MATTER: Is located on the inside of the cord and resembles a butterfly in shape. It is composed of neuron cell bodies and dendrites, interneurons and glial which appears gray.

WHITE MATTER: Is located surrounding the gray matter. It is composed of myelinated axons of neurons which appear white.

The Brain

In an adult the brain weighs about 3lbs.

It is the central control center for not only the nervous system but for the whole body.

It is a very complex organ composed of many different parts.

Brain's Forms

of Protection

THE CRANIUM/SKULL: This is the hard bone surrounding the brain. Inside the cranial cavity the brain is housed. It floats around in fluid called cerebral spinal fluid (CSF).

THE MINIGES: This is a set of there membranes that cover and protect the brain.

The Dura Matter: The outer most layer. This layer doubles around the brain. It attaches to the skull and separates the two hemispheres of the brain. This is the thickest layer that provides the most protection.

The Arachnoid Matter: This is the middle layer. It looks cilliated and acts similar to a web.

The Pia Matter: This is the innermost layer that lays tight against the brain and spinal cord. This is a very thin layer.

Cerebrospinal Fluid (CSF): This is a fluid located between the arachnoid and pia matter. This acts as an extra protection layer.

The Brain's Main Functional Areas

THE HINDBRAIN: Sits directly atop the spinal cord and includes:

The Medulla Oblongata: Governs the rhythm of breathing and strength of the heart beat. Controls reflexes such as swallowing, sneezing and vomiting.

The Pons: The center that helps to regulate breathing.

The Cerebellum: The largest region of the hindbrain. It is found at the back of the brain and coordinates voluntary movements.

THE MIDBRAIN: This is the smallest of the 3 brain regions. It primarily relays information from the sensory organs to the forebrain.

THE BRAIN STEM: Composed of the pons, medulla oblongata and the midbrain.

The Brain's Main Functional Areas

THE FOREBRAIN: The most highly developed of the 3 brain regions and includes:

The Cerebrum: Information is processed and sensory input and motor responses are integrated. This is divided into 2 hemispheres and 4 lobes.

The Cerebral Hemispheres: The 2 halves of the brain (the left side and the right side).

The Thalamus: Responsible for relaying incoming sensory signals.

The Hypothalamus: Located below the thalamus. Controls the homeostatic adjustments in the function of internal organs.

THE DIENCEPHALON: A part of the brain that contains the thalamus, hypothalamus (controls the endocrine system) and the pineal gland (produces certain hormones).

A CLOSER LOOK AT THE CEREBRUM

Each cerebral hemisphere has deeply folded outer layer of gray matter called the cerebral cortex. Each hemisphere receives signals primarily from the opposite side of the body. The left side deals mainly with speech, analytical skills and math. Where the right deals mainly with visual-spatial relationships, music and creative activities. It is divided into the parietal, frontal, temporal and occipital lobes. This area contains motor areas, sensory areas and association areas located in the different lobes.

The Cerebrum and the Limbic System

THE LIMBIC SYSTEM

This system circles around upper brain stem. It includes thalamus, amygdala, hypothalamus and hippocampus. This system influences the basic body functions regulated by the hypothalamus and controls our emotions such as anger, pleasure, satisfaction, fear and sexual arousal. It interacts closely with the prefrontal cortex and connects with other brain regions.

The Four Lobes of the Brain

THE FRONTAL LOBE: Associated with speech, problem solving and behavioral control. This is also where the primary motor cortex is located (controls coordinated movements of the skeletal system).

THE PARIETAL LOBE: Associated with speech, pain/ touch receptors, spacial orientation and sensations from internal organs.

THE TEMPORAL LOBE: Associated with smell, hearing, memory and emotion.

THE OCCIPITAL LOBE: Associated with vision.

The Perepheral Nervous System

Consists of nerves and other nervous system structures outside of the Central Nervous System that branch off of the spinal cord. There are 31 pairs of spinal nerves and 12 pairs of cranial nerves that carry signals to (via afferent neurons) and from (via efferent neurons) the CNS.

This system is divided into the Somatic and Autonomic Nervous Systems. The Autonomic System is then divided into the Sympathetic and Parasympathetic Nervous Systems.

Somatic vs. Autonomic Nervous Systems

SOMATIC NERVOUS SYSTEM

The Somatic Nervous System is composed of somatic nerves. These nerves carry signals that are related to movements of the head, trunk and limbs.

Sensory axons carry information from receptors in the skin, skeletal muscles and tendons to the CNS. The motor axons deliver commands from the brain and spinal cord to skeletal muscles.

AUTONOMIC NERVOUS SYSTEM

The Autonomic Neveous System is composed of autonomic nerves. These nerves carry signals between internal organs and other structures. This system insures that all of the involuntary movements and functions occur properly.

This system is then divided into the sympathetic and the parasympathetic nervous systems.

Sympathetic vs. Parasympathetic Nervous Systems

SYMPATHETIC NERVOUS SYSTEM

The sympathetic Nervous System is prominent in times of danger, stress, excitement and hard physical activity.

Sympathetic Nerves produce the fight-or-flight response.

PARASYMPATHETIC NERVOUS SYSTEM

The Parasympathetic Nervous System is prominent during low-stress, deescalating and quiet situations. Autonomic Nerves tend to slow down the body.