Transcript PNS

Peripheral Nervous System
General Organization
Cranial Nerves
Spinal Nerves
Reflex Activity
Autonomic Nervous System
Somatic Sensory System
Exit
BASIM ZWAIN LECTURE NOTES
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General Organization
Background
Sensory
Nerves
Motor
endings
receptors
Nature
of stimulus detected
a. Mechanoreceptors
Generalized
sensory receptors
Types
i. Touch,based
vibration,
pressure,
stretch
Location
Classification
on nature
of information
1. b.
Function
a.
Neuromuscular
junction
Thermoreceptors
a.
Exteroceptors
a.b.Sensory
(afferent)
nerves
Complexity
Encapsulated
a.
Connect
brain
with
outside
world
Classification
based
on
site
ofand
origin
i.
Contact
between
motor
neuron
muscle
i.
Temperature
changes
i.
Surface
of
skin
i.i.a.
Sensory
information
from
periphery
to
CNS
Parallel
bundles
of
peripheral
axons
Simple
Meisner’s
corpuscles—low
frequency
vibration)
Function
i.a.
CNS
function
is
dependent
on
information
Free
dendritic
endings (unencapsulated)
a.
Cranial
nerves
ii.
Release
ACh
c.
Photoreceptors
Interoceptors
b.ii.Motor
(efferent)
nerves
a.
Enclosed
by
connective
tissue
corpuscles—high
frequency
2.Pacinian
Structural
components
i.b.
Most
sensory
receptors
(generalized)
a.
Activate
effectors
i.i.Free
Brain
origin
b.i.iii.
Varicosities
i.
Light
energy
i.
Visceroceptors
corpuscles—deep
pressure
a.Ruffini’s
Sensory
receptors
Motor
information
from
CNS
to periphery
b.
Some
may be
myelinated
b.
Complex
ii. Merkel
discs
i.
Release
of
neurotransmitter
b.
Spinal
nerves
i.
Contact
between
autonomic
motor
iv.
Muscle
spindles—muscle
stretch
ii.
Exclusively
in
the
retina
b.
Peripheral
nerves
and
ganglia
ii.
Visceral
organs
and
blood
vessels
iii.
Root
hair
plexus
c. Mixed
nerves
i. Special senses (vision, audition,
i.Proprioceptors
Arise
from
spinal
cord stretch
v.
Golgi
tendon
organs—tendon
Endings
and
visceral
effectors
and
organs,
c.
Efferent
motor
endings
d.
Chemoreceptors
c.
i. olfaction,
Include sensory
and
motor
gustation)
Smooth
and cardiac
muscle
Chemical
in solution
i.i. Musculoskeletal
organs
e. Nociceptors
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Exit i. Pain
BASIM ZWAIN LECTURE NOTES
Cranial Nerves
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
Cranial Nerve
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Sensory Function
YES—smell
YES—vision
NO
NO
YES—general sensation
NO
YES—taste
YES—audition; balance
YES—taste
YES—taste
NO
XII
Hypoglossal
NO
Exit
Motor Function
NO
NO
YES—eye muscles
YES—eye muscle
YES—chewing
YES—abducts eye
YES—facial expression
NO
YES—tongue and pharynx
YES—pharynx and larynx
YES—head and neck
movement
YES—tongue
BASIM ZWAIN LECTURE NOTES
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Spinal Nerves
Nomenclature
Structure
Nerves
Dermatomes
plexuses
1. Dorsal and ventral rootlets
3.Named
Fibers
of
different
rami
for
the
level
ofventral
theroot
vertebral
2. Dorsal
and
ventral
1.
Specific
to
ventral
rami
1.Area
ofare
skin
innervated
byexits
the
column
from
which
the nerves
cross
and
redistributed
3. Dorsal
root
ganglion
2.
Types
a.
31
spinal
nerves
cutaneous
branch
of
a
single
a.Branches
contain
fibers
originating
4. Spinal
nerve
a. Cervical
i.
8
cervical
(C1
– C8)nerves
spinal
nerve
from
different
spinal
5. Dorsal
ramus of spinal nerve
b.
Brachial
ii.All
12 Thoracic
(T1 – T8)
2.
spinal
nerves
(except
C1)
b.Innervation
arrives
via
multiple
6. 5Ventral
ramus
of spinal nerve
c.
Lumbar
iii.
Lumbar
(L1
–
L8)
Have
dermatomes
routes
7.
Rami
communicantes
iv. 5 d.
Sacral
(S1 regions
– S8)
Sacral
Dermatomes
overlap
i.3.
More
than
a
single
spinal nerve
a.
Autonomic
fibers
v. 1 Coccygeal (C0)
serves
each limb muscle
8. Sympathetic
chain ganglion
Exit
BASIM ZWAIN LECTURE NOTES
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Reflex Activity
Background
Components
Stretch
and deep
of a tendon
reflex arc
reflexes
Muscle spindles
1. Receptor (site of stimulus action)
Sequence of events
2. 1.
Sensory
neuron (transmits
the afferent
Stimulus-response
sequence
a. Stretching muscle activates muscle spindle
a. Consist
of CNS)
intrafusal fibers
impulse
to
the
a.
Unlearned
Extrafusal
muscle
fiberssensory fiber to
b. Impulse
carried
by
primary
b. Wrapped center
by afferent sensory endings
3. Integration
b.i.cord
Unpremeditated
a.
Skeletal
muscle
spinal
Type
Ia
fibers
a. Monosynaptic
reflex
(single
synapse)
Innervated
by alpha
(a) motor
c.ii.b.
Involuntary
c. Activates
alpha
motor
neuron
Type
II fibers
b. Polysynaptic
(multiple synapses with
neurons
c.Mediated
Gamma
(g) by
efferent
fibers
i. Sends
efferent
signal
to muscle
(effect)
2.
spinal
cord
circuits
chains
of interneurons)
i.
Innervate
contractile
region
of spindle
d. Stretched
muscle
contracts
a.
Information
may
ultimately
4. Motor
neuron
(conducts
efferent impulse
ii.
Maintain
spindle
sensitivity
e. Antagonist
muscle
is reciprocally inhibited
relayed
to
the
brain
from integration center to effector
5. Effector (muscle fiber or gland)
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BASIM ZWAIN LECTURE NOTES
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Autonomic Nervous System
5. Neurotransmitter
9.
10.
Sympathetic
Parasympathetic
response
response
Division
Preganglionic Postganglionic
a. ACh
acts
locally
8.6.Function
2.Cell
bodies
of alllength
lower autonomic motor
Fiber
Somatic
Nervous
System
i. ACh a.
always
has
a stimulatory
effect
a.
Pupil
dilated
Divisions
work
in
concert
a.
Pupils
constrict
neurons
lie
outside
the
CNS
a.
Parasympathetic
4.
Divisions
differ
based
on:
1.
Voluntary
i.b.Increase
e.
Increased
metabolic
blood
rate
pressure
NE
has
spreads
far
and
can dision
exert
its effects
3.
Divisions
d.
Constricts
bronchioles
b.
Secretory
responses
inhibited
b.
Parasympathetic
b. Stimulates
secretory
activity
Sympathetic
ACh
NE
a.
Autonomic
ganglia
i.
Long
preganglionic
1.Autonomic
Nervous
System
is
involuntary
a.
Neurotransmitter
type
Voluntary
muscle
movement
i.a.Glucose
i.Increases
Constricts
is
released
most
into
vessels
blood
over
distances
when
circulated
in the blood
e.long
activity
of
digestive
system
a.
Sympathetic
c.
Stimulates
sweating
i. b.
Salivation
i.
Maintenance
of
function
b.
Neurons
are
postganglionic
ii.
Short
postganglionic
(autonomic
functions
are
carried
out
Fiber
length
ii.
Lipolysis
f.
Bronchioles
dilate
Adrenergic
receptors
2.c.Sensory
information
to
the
CNS
f. Causes
erection
(penis
and
clitoris)
d.Heart
Heart
function
b.
Parasympathetic
c.
function
ii.by
Energy
conservation
c.
Driven
preganglionic
neurons
whose
b.
Sympathetic
without
conscious,
voluntary
control)
j.
Increased
g.
Decreased
alertness
activity
ofganglia
digestive
system
c.
Location
of
i.
Alpha—stimulatory
i.
Vasodilation
3.
Organization
of
cell
bodies
i.
Increases
rate
i.Sympathetic
Decreases ACh
ratedivision
Parasympathetic
ACh
c.
h.a.
Causes
h.
Piloerection
ejaculation
(vaginal
reverse
peristalsis)
ii.
Beta—inhibitory
(except
in
the
heart
when
cell
bodies
are
in
the
spinal
cord
or
brainstem
i.
Short
preganglionic
Function
ii.d.
Dilates
coronary
vessels
Lie within
spinal
cord
or
brainstem
ii.
Constricts
coronary
vessels
i. Emergence
it is excitatory)
ii. Long
postganglionic
b. Targets are
controlled
monosynaptically
ii. Intense muscular activity
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BASIM ZWAIN LECTURE NOTES
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Somatic Sensory System
Background
Mechanical
Organization
Somatic
Somatosensory
Pain
andSensory
Its Senses
Control
of Somatic
Cortex
Pathways
Sensory Information
Types
Types of
of receptors
somatic sensation receptors
DCML
Pathway
Spinal
segments
c.
Two
different
mechanosensitive
1.
Experiment--three
Mechanoreceptors--sensitive
beakers of water: one
to
physical
cold, one
Somatotopy
4.
Proprioceptors
1.
Mechanoreceptors
2.
Nociceptors
Characteristics
1.
In
the
DCML
pathway
information
ascends
3.
Thermoreceptors
Information
carried
in
each
pathway
remains
1.
30
spinal
segments
consisting
of
paired
proprioceptors:
Mechanism
of
function
3.
hot,
Brain
one
lukewarm.
chemicals
One
finger
from
one
hand
into
Classification
Pathways
1.
Mapping
of
the
body's
surface
sensations
onto
a
distortion
Posterior
parietal
lobe
2.
Several
ST
Pathway
brain
regions
can
suppress
pain
a.
Body
position
Responds
to
many
kinds
of
stimuli
Differences
between
somatic
senses
and
a.Pacinian
(sensitive
to
vibration
(250-350
Hz),
Free,and
unmyelinated
nerve
endings
3.
Regulation
Characteristics
of
pain
Mechanical
energy
1.
Pain
is
influenced
cognitively
through
the
dorsal
column
on
the
ipsilateral
Dermatomes
separate
a.
Brain
temperature
is
tightly
regulated
dorsal
ventral
roots
hot;
one
finger
from
the
other
hand
into
cold.
After
i.
Muscle
spindles-consist
of
specialized
brain
structure
1.
Stimuli
applied
to
skin
deform
or
change
a.
Endorphins
1.
1.
Free
Dorsal
nerve
column-medial
endings
c.
Ruffini's
ending-not
well
understood
2.
Nociceptors--respond
to
damaging
stimuli
Primary
somatosensory
cortex
receives
Anatomy
PAG
1.
Information
(periacqueductal
crosses
gray
to
the
matter)
contralateral
project
i.
Where
the
body
is
Note:
Like
other
sensory
receptors,
(usually
mechanical)
other
senses
involved
in
fine
discrimination
ofcortex
texture
orinto
b.
Signal
that
body
tissue
is
being
damaged
a.
1.
Overlap
Pain
can
between
be
modified
the
dermatomes
by
non-painful
1.
Easily
differentiated
2.
Hyperalgesia
side
of
the
spinal
cord
Two
basic
systems
Segmental
organization
of
spinal
nerves
&
Nociception
1.
Segregated
all
the
way
to
the
(close
to
37C,
brain
function
changes
above
some
time
period,
immerse
both
simultaneously
2.
Features
of
the
map:
a.
Not
continuous,
b.
Not
2.
Spinal
segments
are
divided
into
4
groups:
intrafusal
muscle
fibers
distributed
among
receptor
i.
Share
many
opioid
properties
and
bind
to
a.
lemniscal
Nociceptors
pathway
DCML
d.
Mercel's
disks
(light
pressure
and
3.
Thermoreceptors--sensitive
to
changes
in
simple
segregated
streams
of
sensory
1.
Parietal
lobe
side
in
the
spinal
cord
to
the
raphe
(serotonin)
that
sends
axons
to
ii.
Direction
of
movement
temperature
receptors
adapt.
They
respond
to
3.
At
least
four
senses
(temperature,
body
Receptors
are
distributed
throughout
other
moving
stimuli
that
cause
vibrations
c.
In
most
tissues,
not
brain
b.
sensory
Cervical
input
dermatomes:
(i.e.,
rub
the
above
skin
the
around
sternum
a
a.Stimulus
frequency
a.
Tissue
already
damaged
is
much
more
2.
Synapses
in
the
medulla
1.
Pain
and
temperature
the
lukewarm.
Thetemperature)
finger
from
the
hot
senses
the
innervation
of
skin
are
related
1.
Sensory
process
that
signals
that
Thalamus
and
below
that
scaled
to
the
human
body,
c.provides
Relative
size
of
the
cervical,
thoracic,
lumbar,
sacral
ordinary
(extrafusal)
muscle
fibers;
detect
a.
Alters
the
ionic
permeability
of
the
receptor
opioid
receptors
in
the
brain
b.
a.
Thermoreceptors
Touch
and
proprioception
Tactile
discrimination
temperature
information
Post-central
gyrus
the
2.
spinal
Ascends
cord
via
(5-HT
the
spinothalamic
is
inhibitory,
block
tract
iii.
Speed
of
movement
sudden
changes
in
temperature.
position,
touch
&
pain)
body
as
opposed
to
being
concentrated
b.
Meissner's
corpuscle
(most
common
d.
Types
of
damage
detected
c.Thoracic
bruise)
dermatomes:
top
of
sternum
tosenses
waist
b.
Stimulus
pressure
water
to
be
cold
and
the
finger
from
the
cold
sensitive
to
pain
cortex
devoted
to
each
body
part
is
correlated
with
3.
Crosses
over
and
ascends
via
the
medial
2.
Touch
and
Proprioception
2.
Area
of
skin
innervated
by
the
dorsal
roots
trigger
pain
a.
Ventral
posterior
(VP)
nucleus
receives
the
b.
Specialized
receptors
that
can
perceive
3.
Each
segment
is
named
after
vertebra
from
changes
in
muscle
length
creating
generator
potentials
ii.
Opioid
receptors
are
throughout
body,
but
2.
2.
Encapsulated
Spinothalamic
pathway
ST
e.
Hair
follicle
receptor
4.
Proprioceptors--monitor
body
position
2.
Integration
takes
place
in
the
posterior
i.
Most
complex
processing
occurs
in
cortex
synaptic
3.
Synapses
activity)
in
the
thalamus
(VP)
b.
Receptors
in
the
skeletal
muscles
(more
in
4.
Place,
pressure,
sharpness,
texture,
and
at
small,
specialized
locations
receptor
in
glabrous
skin
(smooth,
hairless),
same
water
to
be
hot.
Why?
Adaptation--the
hot
i.
Mechanical-strong
pressure
(sharp
objects)
the
density
of
sensory
input
(i.e.,
lips
versus
the
d.Lumbar
a.
Gate
Theory
dermatomes:
of
Pain-circuit
front
of
in
legs
spinal
&stomach
cord
c.
Receptive
field
Nociceptors
are
sensitized
by
various
lemniscus
to
the
thalamus
(VP)
of
a
single
spinal
segment
is
a
dermatome
information
and
projects
to
the
changes
in
temperature
as
small
as
0.01C.
which
nerves
emerge
(cervical:
C1
C8,
ii.
Golgi
tendon
organs-distributed
among
i.
Trigger
action
potentials
especially
in
brain
and
particularly
in
brain
a.
a.
Most
Pain
and
cutaneous
temperature
receptors
5.
Chemoreceptors--respond
to
certain
parietal
cortex
4.
Projects
to
the
cortex.
movement
lecture)
and
cold
receptors
adapted
(stopped
firing).
When
skin
on
your
calf)
&
d.
Size
is
related
to
importance
duration
can
be
accurately
gauges
sensitive
to
vibration
(
low
frequency
,
30-50
Hz)
ii.
Thermal
(different
from
temperature)-e.Sacral
dorsal
root
dermatomes
(back
of
legs
&
genitals)
substances
released
by
damaged
tissue
4.
Synapses
in
VP
thalamus
somatosensory
cortex
c.
Two
types
(warm--begin
firing
at
30C-45C
thoracic:
T1
T12,
lumbar:
L1
L5
&
sacral:
S1
collagen
fibers
in
tendons
and
detects
areas
that
process
and
modulate
nociceptive
chemicals
immersed
in
lukewarm,
only
the
unadapted
of
the sensory
input
(i.e.,
fingerto
tipbe
versus
elbow)
Active
when
tissues
begin
destroyed
(protaglandins,
histamines,
etc.)
5.
Projects
to
the
cortex
(above
causes
damage
and
pain)
&cord)
cold--changes
S5)
in
muscle
tension
information
receptors
were
(PA,
available.
raphe,
You
and
need
spinal
both
to
sense
iii. Chemical--environmental
agents or those
below
35C
to
10C)
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lukewarm,
etc.
Exit
BASIM
ZWAIN LECTURE
NOTES
from tissues
itself--pH,
histamine,
etc.