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Transcript
The Nervous System
Health Science 1
Ms. Marta Valdes, Instructor
Organs and Divisions
of the Nervous System
 Central nervous system (CNS)—
brain and spinal cord
 Peripheral nervous system
(PNS)—all nerves
Division Flowchart
Neuron
Neuron-basic cell of the nervous system consist of 3 main parts—
dendrites: conduct impulses to cell body of neuron
cell body & axon: conducts impulses away from cell body of neuron
3 main types of nerve cells
Sensory neuron
Interneuron
Motor neuron
Sensory neurons
Function—sensory: conduct impulses to the spinal cord and brain
Carries impulses from receptors e.g. pain receptors in
skin to the CNS( brain or spinal cord)
Interneuron
Interneuron: conduct impulses from sensory neurons to motor
neurons
Carries impulses from sensory nerves to
motor nerves.
Glia Cell
Glia (neuroglia) - Support cells, bringing the cells of nervous
tissue together structurally and functionally
Disorders of the Nervous System
 Disorders of nervous tissue
 Multiple sclerosis—characterized 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
Normal & Partially Destroyed
Myelin by Multiple Sclerosis
Nerves
 Nerve—bundle of peripheral axons
 White matter—brain or cord tissue
composed primarily of myelinated
axons (tracts)
 Gray matter—brain or cord tissue
composed primarily of cell bodies
and unmyelinated fibers
Nerves
 Nerve coverings—fibrous connective tissue
 Endoneurium—surrounds individual fibers within
a nerve
 Perineurium—surrounds a group (fascicle) of
nerve fibers
 Epineurium—surrounds the entire nerve
Nerve Impulses
 Definition—self-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
Impulse Pathway
The Synapse
 Definition—chemical compounds released
from axon terminals (of a presynaptic neuron)
into a synaptic cleft
 Neurotransmitters bind to specific receptor
molecules in the membrane of a postsynaptic
neuron, opening ion channels and thereby
stimulating impulse conduction by the
membrane
Transmission of Impulse (conduction)
Through the Synapse with Neurotransmitters
The Synapse
(Neurotransmitters)
 Names of neurotransmitters—
 Acetylcholine-1st neurotransmitter to be identified, lowers
heart rate
 Catecholamines - norepinephrine, dopamine, and serotonin
 Endorphins-"endorphin rush" refers to feelings of exhilaration
brought on by pain, danger, or other forms of stress
 Enkephalins- regulate "the neural processes of encoding and
processing noxious stimuli that have the potential to damage
tissue
 Nitric oxide (NO)-signaling molecule involved in many
physiological and pathological processes (nitroglycerine)
Example
 Parkinson’s disease—characterized by abnormally low levels of
dopamine in motor control areas of the brain; patients usually
exhibit involuntary trembling and muscle rigidity
 Depression - characterized by abnormally low levels of serotonin.
Signs of Parkinson’s Disease
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
 Function—gray 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
Divisions of the Brain
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.
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
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
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 cerebrum—mental processes of all
types, including sensations, consciousness, memory, and
voluntary control of movements
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”
 Cerebral palsy—condition 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
Central Nervous System
 Dementia—syndrome 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
Central Nervous System
 Seizure disorders
Definition
 Seizure—sudden burst of abnormal neuron
activity that results in temporary changes in
brain function
 Epilepsy—many forms, all characterized by
recurring seizures
 Petit mal
 Grand mal
Electroencephalogram (EEG)—graphic representation of
voltage changes in the brain used to evaluate brain activity

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
Central Nervous System
 Coverings and fluid spaces of the brain and
spinal cord
 Coverings
 Cranial bones and vertebrae
 Cerebral and spinal meninges—the dura mater,
arachnoid mater, and the pia mater
 Fluid spaces—subarachnoid spaces of
meninges, central canal inside cord, and
ventricles in brain
Peripheral Nervous System
 Cranial nerves
 Twelve pairs—attached to undersurface of the
brain
 Connect brain with the neck and structures in
the thorax and abdomen
 Spinal nerves
 Structure—contain dendrites of sensory
neurons and axons of motor neurons
 Function—conduct impulses necessary for
sensations and voluntary movements
Peripheral Nervous System
 Peripheral nerve disorders
 Neuritis—general term referring to nerve
inflammation
 Sciatica is inflammation of the sciatic nerve that
innervates the legs
 Neuralgia, or muscle pain, often accompanies neuritis
 Trigeminal neuralgia—recurring episodes of
stabbing pain along one or more branches of the
trigeminal (fifth cranial) nerve in the head
 Bell’s palsy—paralysis of facial features resulting
from damage to the facial (seventh cranial) nerve
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
Autonomic Nervous System
 Autonomic nervous system—motor neurons that
conduct impulses from the central nervous system to
cardiac muscle, smooth muscle, and glandular
epithelial tissue; regulates the body’s automatic or
involuntary functions
 Autonomic neurons—preganglionic autonomic
neurons conduct from spinal cord or brainstem to an
autonomic ganglion; postganglionic neurons conduct
from autonomic ganglia to cardiac muscle, smooth
muscle, and glandular epithelial tissue
Autonomic Nervous System
 Autonomic or visceral effectors—tissues
to which autonomic neurons conduct
impulses (i.e., cardiac and smooth
muscle and glandular epithelial tissue)
Autonomic Nervous System
 Composed of two divisions: the sympathetic
system and the parasympathetic system
 Autonomic conduction paths
 Consist of two-neuron relays (i.e., preganglionic
neurons from the central nervous system to
autonomic ganglia, synapses, postganglionic
neurons from ganglia to visceral effectors)
 In contrast, somatic motor neurons conduct all
the way from the CNS to somatic effectors with
no intervening synapses
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
Autonomic Nervous System
Parasympathetic nervous system
 Function
 Dominates control of many visceral
effectors under normal, everyday
conditions
Divisions of the ANS

Sympathetic - “fight or flight”
 Catabolic (expend energy)
 Mass activation prepares for
intense activity.
 Heart rate (HR) increases.
 Bronchioles dilate.
 Blood [glucose] increases.

Parasympathetic - “feed & breed”,
“rest & digest”
 Maintain homeostasis
 Normally not activated as a whole,
stimulation of separate
parasympathetic nerves.
 Relaxing effects:
 Decreases heart rate.
 Dilates visceral blood vessels.
 Increases digestive activity.

Dual innervations of many organs —
having a brake and an accelerator
provides more control
Activity: Paras. vs. Symp.
Autonomic Nervous System
 Autonomic neurotransmitters
 Cholinergic fibers—release acetylcholine
 Adrenergic fibers—release norepinephrine
(noradrenaline)
Autonomic Nervous System
 Autonomic nervous system as a whole
 Regulates the body’s automatic functions in
ways that maintain or quickly restore
homeostasis
 Many visceral effectors are doubly
innervated (that is, they receive fibers from
parasympathetic and sympathetic divisions
and are influenced in opposite ways by the
two divisions)
Autonomic Nervous System
 Disorders of the 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
 Neuroblastoma—highly malignant tumor of the
sympathetic nervous system, primarily
affecting young children
Neurological Conditions
Multiple sclerosis
CHOOSE A TOPIC FROM Cerebral Palsy
THE LIST OR ON YOUR Bell’s palsy
OWN
Migraine
 Research and write a 3 ADHD
Wernicke-Korsakoff Syndrome
page APA 6th edition
Alzheimer's Disease
research paper. I will
Encephalitis
explain the rules for
writing in APA. You can Epilepsy
find additional
Syncope
information and an
Febrile Seizures
example of the format in Parkinson’s Disease
the class website
Phineas Cage