Download Nervous system

Someday (maybe now), brain
research may show…
• Early warning of disease
• How to stop concussion injuries
(Toyota)
• Autism and Asperger’s Syndrome
• Sexual orientation
• Differences of the genders in addiction
• Treatment changes needed for
prescription drugs
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Divisions of the
Nervous System
• Central Nervous System (CNS)
• All nerves composing the:
•Brain
•Spinal cord
• Peripheral Nervous System
(PNS)
• Nerves outside the brain
and spinal cord, this
includes:
• Cranial nerves
• Spinal nerves
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Divisions of the
Nervous System
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Neuron Structure
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Meninges
• Membranes
surrounding CNS
• Protect CNS
• Three layers
• Dura mater – outer,
tough
• Arachnoid mater –
thin, web like
• Pia mater – inner,
very thin
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Meninges of the Spinal Cord
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Cerebrospinal Fluid
• Secreted by choroid
plexus
• Circulates in
ventricles, central canal
of spinal cord, and
subarachnoid space
• Completely surrounds
brain and spinal cord
• Clear liquid
• Nutritive and
protective
• Helps maintain stable
ion concentrations in
CNS
•**A spinal tap actually pulls this out for labs
and the body takes days to regenerate more.
Hence you get a “spinal headache” that lasts up
to 5 days.
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Ventricles
• Interconnected cavities
• Within cerebral
hemispheres and brain
stem
• Continuous with
central canal of spinal
cord
• Filled with
cerebrospinal fluid
(CSF)
• lateral ventricles
• third ventricle
• fourth ventricle
• cerebral aqueduct
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Brain:
Myelination of Axons
2 types of matter in the
brain:
White Matter
• Contains myelinated
axons, “nerve tracts”
Gray Matter
• contains
unmyelinated
structures
• cell bodies, dendrites
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Brain
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Brain
Major Parts
• Cerebrum
• two hemispheres
• Basal nuclei
• Diencephalon
• Brainstem
• Cerebellum
Functions:
• Interprets sensations
• Determines perception
• Stores memory
• Reasoning
• Makes decisions
• Coordinates muscular
movements
• Regulates visceral
activities
• Determines personality
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Hemispheres
• The left hemisphere is dominant in most individuals
• Dominant hemisphere (left)
controls:
• Speech
• Writing
• Reading
• Verbal skills
• Analytical skills
• Computational skills
• i.e. - Logical, linear,
right side of the body
• Non-dominant hemisphere
(right) controls:
• Nonverbal tasks
• Motor tasks
• Understanding and
interpreting musical and
visual patterns
• Provides emotional and
intuitive thought
processes
• i.e. – Emotional,
artistic, left side of the
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body
Lobes of Cerebral
Hemispheres
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Functions of the Cerebrum
• Frontal lobe – Motivation, impulsivity, short term
memory, “filtering” what is appropriate behavior,
aggression
• Parietal lobes – Integration of language, sound,
sensations, memory
• Temporal lobes – Hearing, language, long term
memory
• Occipital lobe – Reception of vison and interpretation
of visual information
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Functions of the Cerebral
Lobes
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Cerebellum
•Where:
• inferior to occipital lobes
• posterior to pons and medulla
oblongata
•What:
• two hemispheres
• vermis connects hemispheres
• cerebellar cortex – gray matter
• arbor vitae – white matter
• cerebellar peduncles – nerve
fiber tracts
• dentate nucleus – largest nucleus
in cerebellum
•Functions:
• Fine motor movements and
coordination, integration sensory
input and motor output, &
maintains posture
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Diencephalon
Thalamus
• Recognition of sensations (except smell)
• Pleasure, arousal, pain, alerting reflexes
• Gateway for sensory impulses heading to cerebral
cortex
• Channels impulses to appropriate part of cerebral
cortex for interpretation
Hypothalamus
• Autonomic center, temperature control, satiation cente
• Links nervous and endocrine systems
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Brain Stem
Combine to serve a major
reflex and relay center for
functions such as
breathing, heart rate,
vasomotor changes,
coughing, vomiting, and
blinking
Three Parts
1. Midbrain
2. Pons
3. Medulla Oblongata
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Midbrain
• Between diencephalon
and pons
• Contains bundles of
fibers that join lower parts
of brainstem and spinal
cord with higher part of
brain
• Cerebral aqueduct
• Cerebral peduncles –
bundles of nerve fibers
• Corpora quadrigemina –
centers for visual and
auditory reflexes
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Pons
• Rounded bulge on
underside of brainstem
• Between medulla
oblongata and midbrain
• Helps regulate rate and
depth of breathing
• Relays nerve impulses to
and from medulla oblongata
and cerebellum
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Medulla Oblongata
• Enlarged continuation of
spinal cord
• Conducts ascending and
descending impulses
between brain and spinal
cord
• Contains cardiac,
vasomotor, and respiratory
control centers
• Contains various nonvital reflex control centers
(coughing, sneezing,
swallowing, vomiting)
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Spinal Cord
• Serves as a super highway for
connecting the PNS to the CNS
• A slender column of nervous
tissue continuous with brain
• Extends downward through
vertebral canal
• Begins at level of foramen
magnum and terminates near
first and second lumbar
• Contains gray matter and white
matter
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Cross Section of Spinal
Cord
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Tracts of the Spinal Cord
• Ascending tracts conduct sensory impulses to the
brain
• Descending tracts conduct motor impulses from the
brain to motor neurons reaching muscles and glands
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Nervous System
Cell Types of Neural Tissue
• neurons
• neuroglial cells
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Classification of Neurons –
Structural Differences
Bipolar
• two processes
• eyes, ears, nose
Unipolar
• one process
• ganglia
Multipolar
• many processes
• most neurons of
CNS
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Classification of Neurons –
Functional Differences
Sensory Neurons
• afferent
• carry impulse to CNS
• most are unipolar
• some are bipolar
Interneurons
• link neurons
• multipolar
• in CNS
Motor Neurons
• multipolar
• carry impulses
away from CNS
• carry impulses to
effectors
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Types of Neuroglial Cells
in the CNS
Astrocytes
• CNS
• scar tissue
• mop up excess
ions
• induce synapse
formation
• connect neurons to
blood vessels
Oligodendrocytes*
• CNS
• myelinating cell
Microglia
• CNS
• phagocytic cell
Ependyma
• CNS
• ciliated
• line central canal of
spinal cord
• line ventricles of brain
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* Problem with these in MS
Types of Neuroglial Cells
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Regeneration of a Nerve
Axon
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The Synapse
Nerve impulses
pass from neuron
to neuron at
synapses
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Synaptic Transmission
Neurotransmitters are
released when
impulse reaches
synaptic knob
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Resting Membrane Potential
• inside is negative
relative to the
outside
• polarized
membrane
• due to distribution
of ions
• Na+/K+ pump
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Local Potential Changes
• caused by various stimuli
• temperature changes
• light
• pressure
• environmental changes affect
the membrane potential by
opening a gated ion channel
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Local Potential Changes
35
Impulse Conduction
36
Nervous System
Subdivisions
37
Neurotransmitters
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CNS Clinical Application
Cerebral Injuries and Abnormalities
Cerebrovascular Accident (CVA)
• “Stroke”
• Loss of blood supply to a region of the brain resulting in
damage to the brain and resulting loss of function.
• If only temporary this is called a TIA or Transient Ischemic
Attack.
• Brain tissues die
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CNS Clinical Application
Cerebral Injuries and Abnormalities
Cerebral Palsy
• Damage to the motor areas of the brain before or during birth
resulting in a variety of motor dysfunctions.
• Caused by blocked cerebral blood vessels during
development
• Seizures
• Learning disabilities
Seizure
• Uncoordinated firing of neurons resulting in altered states of
consciousness
• Grand Mal – loss of consciousness and violent muscle
contractions
• Petit Mal – sudden lapse of conscious activity (seem to stare
into space)
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CNS Clinical Application
Concussion
• brain jarred against
cranium
• loss of consciousness
• temporary loss of memory
(depending upon level of
injury)
• mental cloudiness
• headache
• recovery research has
changed
• could lead to
depression or
aggressive behaviors
• NFL vs. Scientific
Research
Head Injury
• Permanent damage
to the brain as a
result of direct
trauma
Normal brain
NFL player
Alzheimer brain
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CNS Clinical Application
Cerebral Injuries and Abnormalities
Parkinson’s Disease
• A progressive brain degeneration associated
with a decrease in Dopamine.
• Symptoms initially include resting tremors,
rigidity, shuffling gait, and blank expressions.
• (Michael J. Fox was diagnosed at a young age)
Alzheimer’s Disease
• A progressive brain degeneration associated with a decrease
in acetylcholine.
• Symptoms include memory loss, confusion, and
disorientation.
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CNS Clinical Application
Cerebral Injuries and Abnormalities
Migraine Headaches
• Severe head pain often times accompanied by nausea and
vomiting, light and sound sensitivity.
• Usually preceded by visual disturbances or “auras”.
Spinal Cord Injury
• Damage to the spinal cord resulting in loss of function
corresponding to the level of injury
• Paralysis
• Paraplegia
• Quadriplegia
Meningitis
• Inflammation or infection of the meninges can be viral or
bacterial.
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CNS Clinical Application
Multiple Sclerosis
• The immune system, T-cells, attack a component of myelin in the central
nervous system by crossing the blood-brain barrier into the CNS.
•These T-cells not only injure myelin, but secrete chemicals that damage
axons and recruit more damaging immune cells to the site of inflammation.
• Lesions are caused in the brain or spinal cord, noted by MRI’s.
• Common symptoms: fatigue, numbness, gait, balance or coordination
problems, bladder or bowel dysfunction, vision problems, vertigo or
dizziness, pain, cognitive function, emotional changes, depression, muscle
spasticity, and more
Many people in the world suffer from MS.
Terri Garr (Actress-Young Frankenstein) & Montel Williams (Talk Show Host)
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Clinical Application
Drug Addiction
• occurs because of the complex interaction of
neurons, drugs, and individual behaviors
• understanding how neurotransmitters fit
receptors can help explain the actions of
certain drugs
• drugs have different mechanisms of action
• several questions remain about the biological
effects of addiction, such as why some
individuals become addicted and others do not
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Life-Span Changes
• Brain cells begin to die before birth
• Over average lifetime, brain shrinks 10%
• Most cell death occurs in temporal lobes
• By age 90, frontal cortex has lost half its neurons
• Number of dendrite branches decreases
• Decreased levels of neurotransmitters
• Fading memory
• Slowed responses and reflexes
• Increased risk of falling
• Changes in sleep patterns that result in fewer sleeping hours
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Divisions of the
Nervous System (again)
• Central Nervous System (CNS)
• All nerves composing the:
•Brain
•Spinal cord
• Peripheral Nervous System
(PNS)
• Nerves outside the brain
and spinal cord, this
includes:
• Cranial nerves
• Spinal nerves
48
Divisions of the
Nervous System
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Peripheral Nervous System
• Cranial nerves arising from the brain
• Somatic fibers connecting to the skin and skeletal muscles
• Autonomic fibers connecting to viscera
• Spinal nerves arising from the spinal cord
• Somatic fibers connecting to the skin and skeletal muscles
• Autonomic fibers connecting to viscera
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Structure of a Peripheral
Nerve
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Types of Neuroglial Cells
in the PNS
Schwann Cells
• produce myelin found on peripheral
myelinated neurons
• speed neurotransmission
Satellite Cells
• support clusters of neuron cell bodies (ganglia)
52
Function of Peripheral
Nervous System (PNS)
Carry information between the body and the CNS.
Afferent (Sensory) Nerves
• Picks up sensory information and delivers it to the CNS
Efferent (Motor) Nerves
• Carry motor information to muscles (skeletal, smooth,
or cardiac) and glands
Divisions of the Motor Division
• Somatic – carries information to skeletal muscle
• Autonomic – carries information to smooth muscle,
cardiac muscle, and glands
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Autonomic Nervous System
• Functions without conscious effort
• Controls visceral activities
• Regulates smooth muscle, cardiac muscle, and glands
• Efferent fibers typically lead to ganglia outside CNS
Two Divisions
1. Sympathetic – prepares body for fight or
flight situations
2. Parasympathetic – prepares body for
resting and digesting activities
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Sympathetic Division
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Parasympathetic Division
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Cranial Nerves
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Cranial Nerves I and II
Olfactory (I)
• Sense of smell
• Fibers transmit
impulses
associated with
smell
Optic (II)
• Sense of sight
• Fibers transmit
impulses
associated with
vision
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Cranial Nerves III and IV
Oculomotor (III)
• some sensory
• Proprioreceptors
• Primarily motor
• Motor impulses to
muscles that move
eyeball
• raise eyelids
• move the eyes
• focus lens
•adjust light entering
eye
Trochlear (IV)
• Some sensory
•
Proprioreceptors
• Primarily motor
• Hearing
• Motor impulses to
muscles that move
the eyes
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Cranial Nerve V
Trigeminal (V)
• mixed
• Ophthalmic division
• Sense of touch
• Sensory from surface of
eyes, tear glands, scalp,
forehead, and upper eyelids
• Maxillary division
• sensory from upper teeth,
upper gum, upper lip, palate,
and skin of face
• Mandibular division
• Sensory from scalp, skin of
jaw, lower teeth, lower gum,
and lower lip
• Motor to muscles of
mastication and muscles in
floor of mouth
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Cranial Nerves VI and VII
Abducens (VI)
• Primarily motor
• Motor impulses
to muscles that
move the eyes
• Some sensory
with
proprioreceptors
Facial (VII)
• Mixed
• Sensory from
taste receptors
• Motor to muscles
of facial
expression, tear
glands, and
salivary glands
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Cranial Nerves VIII and IX
Vestibulocochlear (VIII)
• Sensory
• Vestibular branch
• Sensory from
equilibrium receptors
of ear (balance)
• Cochlear branch
• Sensory from
hearing receptors
Glossopharyngeal (IX)
• Mixed
• Sensory from pharynx,
tonsils, tongue, and
carotid arteries
• Motor to salivary
glands and muscles of
pharynx
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Cranial Nerve X
Vagus (X)
• Mixed, widespread
• Somatic motor to
muscles of speech and
swallowing
• Autonomic motor to
viscera of thorax and
abdomen
• Sensory from pharynx,
larynx, esophagus, and
viscera of thorax and
abdomen
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Cranial Nerves XI and XII
Accessory (XI)
Hypoglossal (XII)
• Primarily motor
• Primarily motor
• Cranial branch
• Motor to muscles of
• motor to muscles of soft
the tongue
palate, pharynx, and
• Some
larynx
proprioreceptors
• Spinal branch
• Motor to trapezius and
sternocleidomastoid;
some proprioreceptors
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Review: Functions of
Cranial Nerves
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Spinal Nerves PNS
• 31 paired nerves that exit through
the intervertebral, sacral and
coccygeal foramina
• 31 pairs
• 8 cervical
•(C1 to C8)
• 12 thoracic
•(T1 to T12)
• 5 lumbar
•(L1 to L5)
• 5 sacral
•(S1 to S5)
• 1 coccygeal
•(Co)
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Nerve Roots
Ventral root (anterior or
motor root)
• Axons of motor
neurons whose cell
bodies are in spinal
cord
Dorsal root
(posterior or sensory
root)
• Axons of
sensory neurons
in the dorsal root
ganglion
Spinal nerve
• Union of ventral
root and dorsal root
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Nerve Plexuses
Nerve plexus – complex
networks formed by
anterior branches of spinal
nerves; fibers of various
spinal nerves are sorted
and recombined
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Cervical Plexuses
Cervical Plexus
• Formed by
anterior branches
of C1-C4
• Lies deep in the
neck
• Supply muscles
and skin of the
neck
• C3 – C5
contribute to
phrenic nerves
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Brachial Plexuses
• C5-T1
• Lies deep within shoulders
• Musculocutaneous nerves
• supply muscles of anterior
arms and skin of forearms
• Ulnar and median nerves
• supply muscles of forearms
and hands
• supply skin of hands
• Radial nerves
• supply posterior muscles of
arms and skin of forearms
and hands
• Axillary nerves
• supply muscles and skin of
anterior, lateral, and posterior
arms
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Lumbosacral Plexuses
• T12 – S5
• Extend from lumbar
region into pelvic cavity
• Obturator nerves
• supply motor
impulses to adductors
of thighs
• Femoral nerves
• supply motor
impulses to muscles of
anterior thigh and
sensory impulses from
skin of thighs and legs
• Sciatic nerves
• supply muscles and
skin of thighs, legs,
and feet
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Dermatome
• An area of skin that the sensory nerve fibers of a
particular spinal nerve innervate
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Myotome
• A muscle group innervated by a certain spinal segment
Reflex Arcs
Reflexes – Automatic responses to specific stimuli
Reflex arc – short pathway reflexive information follows
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General Components of a
Spinal Reflex
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Reflex Behavior
• Patellar tendon
• Example is the knee-jerk reflex
• Simple monosynaptic reflex
• Helps maintain an upright posture
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Reflex Behavior
• Achilles tendon
• Example is the ankle jerk
• Simple monosynaptic reflex
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Reflex Behavior
• Blink reflex
• Crainial nerves: afferent (CN V) and
efferent (CN VII)
• Lightly touch the cornea with a pulled
portion of a q-tip to look for a blink
response
Reflex Behavior
• Example is a withdrawal reflex
• Prevents or limits tissue damage
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Reflex Arc
• Example crossed extensor reflex
• Crossing of sensory impulses within the reflex center
to produce an opposite effect
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Reflex Arc
• Example Babinski reflex
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PNS Clinical Application
Bell’s Palsy
• Inflammation of the facial nerve resulting in paralysis of one
side of the face.
Trigeminal Neuralgia
• Inflammation of the trigeminal nerve resulting in severe pain
in the face and twitching of the muscles of mastication
Nerve Entrapment
• Compression of a nerve by soft tissue.
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