The Nervous System Health Science 1

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The Nervous SystemHealth Science 1
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Organs and Divisions of the Nervous System

• Central nervous system (CNS)brain and spinal
  cord
• Peripheral nervous system (PNS)all the nerves
  12 pairs of cranial nerves extending from the
  brain and 31 pairs of spinal nerves extending
  out from spinal cord, divides into
• Somatic - carries messages between CNS and body
• Autonomic- contains sympathetic and
  parasympathetic which work together to control
  involuntary body function

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Division Flowchart
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Nervous System Function (CNS)

• It is the communication and coordination system
  in the body
• It receives messages from stimuli all over the
  body
• The brain interprets the message
• The brain responds to the message and carries out
  an activity
• The brain is also the seat of intellect and
  reasoning

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Nervous System Function (PNS)

• To control the autonomic or involuntary
  activities of the body
• To act as the reflex center of the body

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Cells of the Nervous System

• Neurons (Nerve cell) The basic structural unit
  of the nervous system. It transmits messages from
  one cell to the next
• Dendrites conduct impulses toward cell body of
  neuron, there are several dendrites
• Cell body - The largest part, contain the
  nucleus and much of the cytoplasm, most the
  metabolic activity of the cell, including the
  generation of ATP (Adenine Triphosphate Compound
  that store energy and synthesis of Proteins).
• Axon conducts impulses away from cell body of
  neuron, only one axon
• Axons have a lipid (fat) covering called Myelin
  Sheath which increases impulse transmission and
  insulates axon

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Cells Cont.

• Synapse spaces between axon of one cell and
  dendrite of another cell where messages are
  transmitted. They never touch
• Neurotransmitters Special chemicals located at
  the end of each axon that allow the nerve
  impulses to pass from one neuron to another.

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The Synapse (Neurotransmitters)

• Names of neurotransmitters
• Acetylcholine
• catecholamines (norepinephrine, dopamine, and
  serotonin)
• endorphins
• enkephalins
• nitric oxide (NO), and other compounds

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Transmission of Impulse (conduction)
Through the Synapse with Neurotransmitters
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Neurons classified according to function

• Sensory (Afferent) carry messages (conduct
  impulses) from all body parts to the spinal cord
  and brain
• Motor (Efferent) Carry messages (conduct
  impulses) from brain and spinal cord to muscles
  and glands
• Interneurons (Associative) conduct impulses from
  sensory neurons to motor neurons

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Cells of the Nervous System

• Glia (neuroglia) Insulate, support, and protect
  the neurons
• All neurons possess the characteristics of being
  able to react when stimulated (irritability) and
  pass impulse to other neurons (conductivity)

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Disorders of the Nervous System

• Disorders of nervous tissue
• Multiple sclerosischaracterized by myelin loss
  in central nerve fibers and resulting conduction
  impairments
• Tumors
• General name for nervous system tumors is neuroma
• Most neuromas are gliomas, glial tumors
• Multiple neurofibromatosischaracterized by
  numerous benign tumors

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Disorders of the Nervous System Cont.

• Tumors
• General name for nervous system tumors is neuroma
• Most neuromas are gliomas, glial tumors
• Multiple neurofibromatosischaracterized by
  numerous benign tumors

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Reflex Arcs

• Nerve impulses are conducted from receptors to
  effectors over neuron pathways or reflex arcs
  conduction by a reflex arc results in a reflex
  (that is, contraction by a muscle or secretion by
  a gland)

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Nerve Impulses

• Definitionself-propagating wave of electrical
  disturbance that travels along the surface of a
  neuron membrane
• Mechanism
• A stimulus triggers the opening of Na channels
  in the plasma membrane of the neuron
• Inward movement of positive sodium ions leaves a
  slight excess of negative ions outside at a
  stimulated point marks the beginning of a nerve
  impulse

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Impulse Pathway
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Signs of Parkinsons Disease

• Parkinson diseasecharacterized by abnormally low
  levels of dopamine in motor control areas of the
  brain

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Central Nervous System

• Divisions of the brain
• Brainstem
• Consists of three parts of brain named in
  ascending order, they are the medulla oblongata,
  pons, and midbrain
• Functiongray matter in the brainstem functions
  as reflex centers (for example, for heartbeat,
  respirations, and blood vessel diameter) sensory
  tracts in the brainstem conduct impulses to the
  higher parts of the brain motor tracts conduct
  from the higher parts of the brain to the spinal
  cord

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Central Nervous System

• Diencephalon
• Structure and function of the hypothalamus
• Consists mainly of the posterior pituitary gland,
  pituitary stalk, and gray matter
• Acts as the major center for controlling the ANS
  therefore, helps control the functioning of most
  internal organs
• Controls hormone secretion by anterior and
  posterior pituitary glands therefore it
  indirectly helps control hormone secretion by
  most other endocrine glands
• Contains centers for controlling appetite,
  wakefulness, pleasure, etc.

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Central Nervous System

• Structure and function of the Thalamus
• Dumbbell-shaped mass of gray matter in each
  cerebral hemisphere
• Relays sensory impulses to cerebral cortex
  sensory areas
• In some way produces the emotions of pleasantness
  or unpleasantness associated with sensations

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Central Nervous System

• Cerebellum
• Second largest part of the human brain
• Helps control muscle contractions to produce
  coordinated movements so that we can maintain
  balance, move smoothly, and sustain normal
  postures
• Recent evidence shows the cerebellum may also
  have wider coordinating effects, assisting the
  cerebrum and other regions of the brain

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Central Nervous System

• Cerebrum
• Largest part of the human brain
• Outer layer of gray matter is the cerebral
  cortex made up of lobes composed mainly of
  dendrites and cell bodies of neurons
• Interior of the cerebrum composed mainly of white
  matter (that is nerve fibers arranged in bundles
  called tracts)
• Functions of the cerebrummental processes of all
  types, including sensations, consciousness,
  memory, and voluntary control of movements

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Central Nervous System

• BRAIN DISORDERS
• Destruction of brain tissue
• Cerebrovascular accident (CVA)hemorrhage from or
  cessation of blood flow through cerebral blood
  vessels a stroke. Opposite side is usually
  affected. Thrombolytic must be given quickly to
  avoid further damage
• Cerebral palsycondition in which damage to motor
  control areas of the brain before, during, or
  shortly after birth causes paralysis (usually
  spastic) of one or more limbs

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Central Nervous System Disorders

• Dementiasyndrome that includes progressive loss
  of memory, shortened attention span, personality
  changes, reduced intellectual capacity, and motor
  control deficit
• Alzheimer disease (AD)brain disorder of the
  middle and late adult years characterized by
  dementia
• Huntington disease (HD)inherited disorder
  characterized by chorea (purposeless movement)
  progressing to severe dementia
• HIV (also causes AIDS) can infect neurons and
  thus cause dementia

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Central Nervous System

• Seizure disorders
• Definition
• Seizuresudden burst of abnormal neuron activity
  that results in temporary changes in brain
  function
• Epilepsymany forms, all characterized by
  recurring seizures

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Central Nervous System

• Spinal cord
• Outer part is composed of white matter made up of
  many bundles of axons called tracts interior
  composed of gray matter made up mainly of neuron
  dendrites and cell bodies
• Functions as the center for all spinal cord
  reflexes sensory tracts conduct impulses to the
  brain, and motor tracts conduct impulses from the
  brain

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Central Nervous System

• Coverings and fluid spaces of the brain and
  spinal cord
• Coverings
• Cranial bones and vertebrae
• Cerebral and spinal meningesthe dura mater,
  arachnoid mater, and the pia mater
• Fluid spacessubarachnoid spaces of meninges,
  central canal inside cord, and ventricles in
  brain

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Peripheral Nervous System

• Cranial nerves (12)
• attached to undersurface of the brain
• Connect brain with the neck and structures in the
  thorax and abdomen
• Spinal nerves (31)
• Structurecontain dendrites of sensory neurons
  and axons of motor neurons
• Functionconduct impulses necessary for
  sensations and voluntary movements

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Peripheral Nervous System

• Peripheral nerve disorders
• Neuritisgeneral term referring to nerve
  inflammation
• Sciatica is inflammation of the sciatic nerve
  that innervates the legs
• Neuralgia, or muscle pain, often accompanies
  neuritis
• Trigeminal neuralgiarecurring episodes of
  stabbing pain along one or more branches of the
  trigeminal (fifth cranial) nerve in the head
• Bells palsyparalysis of facial features
  resulting from damage to the facial (seventh
  cranial) nerve

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Peripheral Nervous System

• HERPES ZOSTER OR SHINGLES
• Viral infection caused by chickenpox virus that
  has invaded the dorsal root ganglion and remained
  dormant until an episode of shingles
• Usually affects a single dermatome, producing
  characteristic painful plaques or vesicles

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Autonomic Nervous System

• Autonomic nervous systemmotor neurons that
  conduct impulses from the central nervous system
  to cardiac muscle, smooth muscle, and glandular
  epithelial tissue regulates the bodys automatic
  or involuntary functions

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Autonomic Nervous System

• Composed of two divisions the sympathetic system
  and the parasympathetic system

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Autonomic Nervous System

• Sympathetic nervous system
• Function
• Serves as the emergency or stress system,
  controlling visceral effectors during strenuous
  exercise and strong emotions (anger, fear, hate,
  or anxiety)
• Group of changes induced by sympathetic control
  is called the fight-or-flight response

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Autonomic Nervous System

• Autonomic nervous system as a whole
• Regulates the bodys automatic functions in ways
  that maintain or quickly restore homeostasis
• They receive fibers from parasympathetic and
  sympathetic divisions and are influenced in
  opposite ways by the two divisions

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Autonomic Nervous System

• Parasympathetic nervous system
• Function
• Dominates control of many visceral effectors
  under normal, everyday conditions

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Autonomic Nervous System

• Autonomic nervous system as a whole
• Regulates the bodys automatic functions in ways
  that maintain or quickly restore homeostasis
• They receive fibers from parasympathetic and
  sympathetic divisions and are influenced in
  opposite ways by the two divisions

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Disorders of Autonomic Nervous System

• Stress-induced disease
• Prolonged or excessive response to stress can
  disrupt normal functioning throughout the body
• Examples of stress-induced conditions
• Heart disease
• Digestive problems
• Reduced resistance to disease
• Tumors
• Neuroblastomahighly malignant tumor of the
  sympathetic nervous system, primarily affecting
  young children