Nervous System

Nervous System Overview

  • Nervous System Definition

    • A complex, highly organized system that coordinates all activities of the body.
    • Enables the body to respond and adapt to changes occurring both inside and outside the body.

  • Neuron

    • The basic structural unit of the nervous system.
    • Illustrated in Figure 7–31 (not provided in this transcript).

Types of Nerves

  • Nerves

    • Combinations of many nerve fibers located outside the brain and spinal cord.

  • Afferent (Sensory) Nerves

    • Carry messages from all parts of the body to the brain and spinal cord.

  • Efferent (Motor) Nerves

    • Carry messages from the brain and spinal cord to the muscles and glands.

Divisions of the Nervous System

  • Central Nervous System (CNS)

    • Comprises the brain and spinal cord.

  • Peripheral Nervous System (PNS)

    • Comprises the nerves that extend outside the brain and spinal cord.

Subdivisions of the Peripheral Nervous System

  • Somatic Nervous System

    • Carries messages between the CNS and the body.

  • Autonomic Nervous System

    • Contains the sympathetic and parasympathetic nervous systems.

Central Nervous System Detailed

  • Brain

    • A mass of nerve tissue well protected by membranes and the cranium (skull).

  • Main Sections of the Brain

    • Cerebrum

    • The largest and highest section of the brain.

    • Cerebellum

    • Located below the back of the cerebrum.

    • Diencephalon

    • Located between the cerebrum and midbrain.

    • Thalamus: Acts as a relay center, directing sensory impulses to the cerebrum.

    • Hypothalamus: Regulates and controls the autonomic nervous system.

    • Midbrain

    • Positioned below the cerebrum at the top of the brainstem.

    • Conducts impulses for eye and auditory reflexes.

    • Pons

    • Located below midbrain in the brainstem.

    • Responsible for conducting messages to other parts of the brain associated with chewing, tasting, and saliva production.

    • Medulla Oblongata

    • The lowest part of the brainstem.

    • Regulates heartbeat, respiration, swallowing, coughing, and blood pressure.

Spinal Cord and Protective Structures

  • Spinal Cord

    • Continues from the medulla oblongata and ends at the first or second lumbar vertebrae.

  • Meninges

    • Three membranes that cover and protect the brain and spinal cord.

  • Ventricles

    • Hollow spaces that connect with each other and with the space under the arachnoid membrane.

  • Cerebrospinal Fluid

    • Clear, colorless fluid that circulates continuously between the ventricles and through the subarachnoid space.

Peripheral Nervous System Details

  • Somatic Nervous System Details

    • Composed of 12 pairs of cranial nerves for special senses.
    • Composes 31 pairs of spinal nerves that carry messages to and from the spinal cord.

  • Autonomic Nervous System Functions

    • Helps maintain balance in the body’s involuntary functions.

Autonomic Nervous System Divisions

  • Sympathetic Nervous System

    • Division that allows the body to respond to emergencies and stress.

  • Parasympathetic Nervous System

    • Counteracts the actions of the sympathetic system after an emergency or stress.

Diseases and Abnormal Conditions

  • Amyotrophic Lateral Sclerosis (ALS)

    • Also known as Lou Gehrig’s disease.
    • Chronic, degenerative neuromuscular disease.

  • Carpal Tunnel Syndrome

    • Occurs when the median nerve and tendons passing through a canal or "tunnel" are pinched.

  • Cerebral Palsy

    • A nonprogressive, noncontagious disturbance in voluntary muscle action caused by brain damage.

  • Cerebrovascular Accident (CVA) or Stroke

    • Occurs when blood flow to the brain is impaired, leading to a lack of oxygen and destruction of brain tissue.

  • Concussion

    • A traumatic brain injury that affects brain function.

  • Encephalitis

    • Inflammation of the brain caused by a virus, bacterium, chemical agent, or as a complication of measles, chickenpox, or mumps.

  • Epilepsy

    • Also known as seizure syndrome; a brain disorder characterized by abnormal surges in electrical impulses in brain neurons.

  • Hydrocephalus

    • An excessive accumulation of cerebrospinal fluid (CSF) in the ventricles.

  • Meningitis

    • Inflammation of the meninges of the brain and/or spinal cord.

  • Multiple Sclerosis (MS)

    • A chronic, disabling condition resulting from degeneration of the myelin sheath in the CNS.

  • Neuralgia

    • Nerve pain experienced without stimulation of the nerve receptor.

  • Paralysis

    • Loss of voluntary muscle movement and coordination in specific body parts.

  • Parkinson’s Disease

    • A chronic, progressive condition involving degeneration of brain cells.

  • Shingles

    • Acute inflammation of nerve cells caused by the herpes virus.