Overview The Nervous System

The nervous system of the human is the most highly organized system of the body. The overall function of the nervous system is control and coordination of the human body.

 It consists of the brain, the spinal cord and the nerves.

 The functional, structural unit of the nervous system is the nerve cell called the neuron.

 The neuron has extensions of various lengths from its cell body called dentrites and axons.  Each cell many have many dendrites but only one axon.

 The dendrite receives an impulse and passes it to the cell body, then to the axon where it is passed on to muscle, glands, or another neuron.

 There are three types of neurons: sensory, motor, and connecting or associative neurons.

 Neurons do not connect with each other but send impulses over spaces called synapses.

Central Nervous System  Includes the brain and spinal cord. The nerves of the brain and spinal cord do not have the special coating called neurilemma, which allows nerve cells to repair.

Peripheral Nervous System  Composed of all the nerves extending from the brain (cranial nerves) and the spinal cord (spinal nerves).  The peripheral nervous system connects the central nervous system to various body structures.

Peripheral Nervous System  Cranial nerves carry impulses to and from the brain, and spinal nerves carry impulses to and from the spinal cord.

Autonomic Nervous System  The autonomic nervous system controls the involuntary or automatic activities of vital internal organs such as the heart, blood vessels and organs of digestion.

The Brain  The brain is a complex mass of tissue protected by the bony structure of the cranium.  The brain is further protected by membrane coverings called the meninges and cerebrospinal fluid.

The Brain  There are three major parts to the brain: The cerebrum The cerebrum Cerebellum Cerebellum Brain stem Brain stem

The Brain  The cerebrum, the largest part of the brain, is divided into two hemispheres.  Each hemisphere is further divided into four lobes. Each lobe of the cerebral hemispheres controls specific functions.  They are identified as the frontal, parietal, occipital, and temporal lobes.

The Lobes of the Brain  Frontal Lobe The cells in the right side control the voluntary motor movements of the left side of the body. The cells in the right side control the voluntary motor movements of the left side of the body. The left side controls the right side. The left side controls the right side. The frontal lobe also controls speech. The frontal lobe also controls speech.

The Lobes of the Brain  Parietal Lobe This area receives and interprets nerve impulses from the sensory receptors for pain, touch, heat and cold. The parietal lobe also helps determine distance, size, and shape. This area receives and interprets nerve impulses from the sensory receptors for pain, touch, heat and cold. The parietal lobe also helps determine distance, size, and shape.

The Lobes of the Brain  Occipital Lobe Located at the back of the brain over the cerebellum, this lobe contains the visual area controlling eyesight. Located at the back of the brain over the cerebellum, this lobe contains the visual area controlling eyesight.

The Lobes of the Brain  Temporal Lobe This lobe is located on the sides of the brain. This lobe is located on the sides of the brain. It contains areas which control auditory hearing and olfactory smell. It contains areas which control auditory hearing and olfactory smell.

The Brain  The outer layer of the cerebrum is gray nerve tissue called the cerebral cortex.  It is formed with deep folds causing elevated portions called convolutions and furrows or grooves called fissures.  These folds increase the surface area of the cerebral cortex.

The Brain  The cerebral cortex controls conscious thought, judgment, memory, reasoning, and willpower.

The Brain  Beneath the gray matter of the cerebral cortex lay the thalamus and hypothalamus.  The thalamus acts as a relay center for sensory impulses to the cerebral cortex.  The hypothalamus controls temperature, sleep, water balance, and chemical activities.

The Cerebellum  Located at the back and lower part of the brain, the cerebellum coordinates the muscular movements of the body, such as balance in walking and sitting.

The Brainstem  Made up of three parts; midbrain, pons and medulla.  This part of the brain controls and regulates respiration and the heart and blood vessels.

The Spinal Cord  The spinal cord is made up of nerve fibers protected by the bony structure of the vertebra and the spinal fluid.  The function of the spinal cord is to serve as a pathway to and from the brain.

Diseases Affecting the Nervous System  Nerve cells often do not repair themselves so damage can cause permanent loss of function.  Damage to the brain and spinal cord by force or injury may result in death or paralysis.

Diseases Affecting the Nervous System  Other diseases affecting the nervous system are Parkinsons, seizures, multiple sclerosis, meningitis, and Cerebral vascular accident commonly called a stroke, (which also affects the circulatory system).  Infections and tumors may also occur causing illness affecting the nervous system.