Upload
others
View
5
Download
0
Embed Size (px)
Citation preview
1/18/2016
1
PNS continued
The Nervous System
Peripheral Nerve Regeneration
• Possible if cell body has not been damaged
• Axon underlying myelin sheath can regenerate
Figure 13.4 (1 of 4)
Endoneurium
Droplets
of myelin
Fragmented
axon
Schwann cells
Site of nerve damage
The axon
becomes
fragmented at
the injury site.
1
Figure 13.4 (2 of 4)
Schwann cell MacrophageMacrophages
clean out the
dead axon distal
to the injury.
2
Figure 13.4 (3 of 4)
Fine axon sprouts
or filaments
Aligning Schwann cells
form regeneration tube
3 Axon sprouts,
or filaments,
grow through a
regeneration tube
formed by
Schwann cells.
Figure 13.4 (4 of 4)
Schwann cell Site of new
myelin sheath
formation
4 The axon
regenerates and
a new myelin
sheath forms.
Single enlarging
axon filament
1/18/2016
2
Neuritis
• Inflammation of a nerve
– Sciatica
– Bell’s Palsy
Shingles
• Varicella Zoster virus
• Dorsal root ganglia
• Consistent with dermatome
• Vaccine
Multiple Sclerosis
• Loss of myelin in CNS � scleroses
– Visual disturbances
– Muscle weakness
• Autoimmune disorder
• Remissions
• Progressive
Central nervous system (CNS) Peripheral nervous system (PNS)
Motor (efferent) divisionSensory (afferent)division
Somatic nervoussystem
Autonomic nervoussystem (ANS)
Sympatheticdivision
Parasympatheticdivision
Figure 14.1
Autonomic Nervous System (ANS)
• Involuntary
• Sensory (afferent) pathways
• Motor (efferent) pathways
• Visceral reflex system
Structure of the ANS
�Sensory (afferent) pathway
� Visceral interoceptors (visceroceptors)
� Osmolarity
� Pressure
� Temperature
� Blood gases
� Chemical composition of plasma and body fluids
1/18/2016
3
Structure of the ANS
• Sensory (afferent) pathway
– Single sensory neuron from organ to CNS
• Cell body in dorsal root ganglion
• Synapse with association neurons in spinal cord
Figure 12.32
Somaticsensoryneuron
Dorsal root (sensory)
Dorsal root ganglion
Visceralsensory neuron
Somaticmotor neuron
Spinal nerve
Ventral root(motor)
Ventral horn(motor neurons)
Dorsal horn (interneurons)
Visceralmotorneuron
Interneurons receiving input from somatic sensory neurons
Interneurons receiving input from visceral sensory neurons
Visceral motor (autonomic) neurons
Somatic motor neurons
Autonomic Nervous System (ANS)
• ANS Motor (efferent) neurons
– Innervate smooth muscle, cardiac muscle and
glands
– Operate via subconscious control
• Efferent (motor) pathway
– Two motor neurons between CNS and effector
• Preganglionic neuron
– Cell body in CNS
• Postganglionic neuron
– Cell body in autonomic ganglion (outside CNS)
Autonomic Nervous System (ANS)
Skeletal muscle
Cell bodies in centralnervous system Peripheral nervous system Effect
+
+
Effectororgans
ACh
AChSmooth muscle
(e.g., in gut),
glands, cardiac
muscle
Ganglion
Adrenal medulla Blood vessel
ACh
ACh
ACh
NE
Epinephrine andnorepinephrine
Acetylcholine (ACh) Norepinephrine (NE)
Ganglion
Heavily myelinated axon
Lightly myelinated
preganglionic axon
Lightly myelinatedpreganglionic axons
Neuro-transmitterat effector
Unmyelinated
postganglionic
axon
Unmyelinated
postganglionic axon
Stimulatory
Stimulatory
or inhibitory,
depending
on neuro-
transmitter
and
receptors
on effector
organs
Single neuron from CNS to effector organs
Two-neuron chain from CNS to effector organs
SO
MA
TIC
NE
RV
OU
SS
YS
TE
M
AU
TO
NO
MIC
NE
RV
OU
S S
YS
TE
M
PA
RA
SY
MP
AT
HE
TIC
SY
MP
AT
HE
TIC
Figure 14.2
Motor PathwaysAutonomic Nervous System (ANS)
• Visceral reflex system
– E.g., coughing, sneezing, swallowing, vomitting
1/18/2016
4
Figure 14.7
Spinal cord
Dorsal root ganglion
Autonomic ganglion
Stimulus
Response
Visceral sensory
neuron
Integration center� Spinal cord grey matter� Within gastrointestinal
tract wall
Sensory receptor
in viscera
2
3
1
5 Visceral effector
Efferent pathway(two-neuron chain)• Preganglionic neuron• Ganglionic neuron
4
A simple visceral reflex arc
Central nervous system (CNS) Peripheral nervous system (PNS)
Motor (efferent) divisionSensory (afferent)division
Somatic nervoussystem
Autonomic nervoussystem (ANS)
Sympatheticdivision
Parasympatheticdivision
Figure 14.1
Divisions at a Glance
• Sympathetic
– “Fight or Flight”
– NE and acetylcholine
– Thoracolumbar
• Parasympathetic
– “Rest and Digest”
– Acetylcholine
– Craniosacral
Dual Innervation
Salivaryglands
Eye
Skin*
Heart
Lungs
Liverand gall-bladder
Genitals
Pancreas
Eye
Lungs
Bladder
Liver andgall-bladder
Pancreas
Stomach
Cervical
Sympatheticganglia
Cranial
Lumbar
Thoracic
Genitals
Heart
Salivaryglands
Stomach
Bladder
Adrenalgland
Parasympathetic Sympathetic
Sacral
Brainstem
L1
T1
Figure 14.3
Dual Innervation
Cranial Outflow
Nerve Ganglia (Terminal Ganglia)
Effector Organ(s)
Oculomotor (III) Ciliary Eye
Facial (VII) Pterygopalatine Submandibular
Salivary, nasal, and lacrimal glands
Glossopharyngeal (IX)
Otic Parotid salivary glands
Vagus (X) Within the walls of target organs
Heart, lungs, and most visceral organs
Sacral
Outflow
S2-S4
Within the walls of target organs
Large intestine, urinary bladder, ureters, and reproductive organs
Parasympathetic Division Outflow
1/18/2016
5
Pterygopalatine
ganglion
Eye
Lacrimal
gland
Nasal
mucosa
Ciliary
ganglion
Pterygopalatine
ganglion
Submandibular
ganglion Submandibular
and sublingual
glands
CN III
CN VII
CN IXCN X
Otic ganglion
Parotid gland
Heart
Lung
Liver and
gallbladder
Stomach
Pancreas
Urinary
bladder
and ureters
Small
intestine
Large
intestine
S2
Pelvic
splanchnic
nerves
Genitalia
(penis,
clitoris, and vagina)
Rectum
Celiac
plexus
Inferior
hypogastric
plexus
Cardiac and
pulmonary
plexuses
S4
Preganglionic
Postganglionic
Cranial nerve
Figure 14.4
Parasympathetic
Division
= Craniosacral
Central nervous system (CNS) Peripheral nervous system (PNS)
Motor (efferent) divisionSensory (afferent)division
Somatic nervoussystem
Autonomic nervoussystem (ANS)
Sympatheticdivision
Parasympatheticdivision
Figure 14.1
Figure 14.6
Superior
cervical
ganglion
Middle
cervical
ganglion
Inferior
cervical
ganglion
Sympathetic trunk
(chain) ganglia
Pons
L2
T1
White rami
communicantes
Liver and
gallbladder
Stomach
Spleen
Kidney
Adrenal medulla
Small
intestine
Large
intestine
Genitalia (uterus, vagina, and
penis) and urinary bladder
Celiac ganglion
Inferior
mesenteric
ganglion
Lesser splanchnic nerve
Greater splanchnic nerve
Superior
mesenteric
ganglion
Lumbar
splanchnic
nerves
Eye
Lacrimal gland
Nasal mucosa
Blood vessels;
skin (arrector pili
muscles and
sweat glands)
Salivary glands
Heart
Lung
Rectum
Cardiac and
pulmonary
plexuses
Preganglionic
Postganglionic
Sacral
splanchnic
nerves
Sympathetic Division = Thoracolumbar
The Sympathetic Division
• Preganglionic neurons originate in the spinal
cord from T1 – L2
– Thoracolumbar division
• FYI: Lateral horns
Preganglionic
(Sympathetic)
Cell Bodies
The Sympathetic Division
1) Preganglionic fibers leave through ventral root of spinal cord
2) Fibers join spinal nerve
3) Spinal nerve divides at ventral rami
4) Rami branch immediately into white rami communicans
5) Join sympathetic (paravertebral) ganglia
Figure 14.5a
Spinal cord
Dorsal root
1) Ventral root
5) Sympathetic trunk ganglion
Sympathetic
trunk
Rib
3) Ventral ramus
Gray ramus
communicans
4) White ramus communicans
Thoracicsplanchnic nerves
(a) Location of the sympathetic trunk
2) Spinal nerve
1/18/2016
6
Sympathetic Trunk Ganglia
• Form longitudinal pathways adjacent to vertebral column
• Each spinal nerve has an associated ganglion (except in cervical
region, where several ganglia fuse)
Figure 14.6
Superior
cervical
ganglion
Middle
cervical
ganglion
Inferior
cervical
ganglion
Sympathetic trunk
(chain) ganglia
Pons
L2
T1
White rami
communicantes
Liver and
gallbladder
Stomach
Spleen
Kidney
Adrenal medulla
Small
intestine
Large
intestine
Genitalia (uterus, vagina, and
penis) and urinary bladder
Celiac ganglion
Inferior
mesenteric
ganglion
Lesser splanchnic nerve
Greater splanchnic nerve
Superior
mesenteric
ganglion
Lumbar
splanchnic
nerves
Eye
Lacrimal gland
Nasal mucosa
Blood vessels;
skin (arrector pili
muscles and
sweat glands)
Salivary glands
Heart
Lung
Rectum
Cardiac and
pulmonary
plexuses
Preganglionic
Postganglionic
Sacral
splanchnic
nerves
Sympathetic Division = Thoracolumbar
The Sympathetic Division
• Sympathetic trunks and pathways
–Upon entering a sympathetic trunk ganglion a
preganglionic fiber may do one of the following:
1. Synapse with a ganglionic neuron within the same ganglion
Figure 14.5b (1 of 3)
To effector
Blood vessels
Skin (arrector
pili muscles
and sweat
glands)
Dorsal root ganglionDorsal ramus of
spinal nerve
Dorsal root
Sympathetic
trunk ganglion
Lateral horn (visceral
motor zone)
Ventral root
Sympathetic trunk
Gray ramus
communicansWhite ramus
communicans
Ventral ramus of
spinal nerve
Synapse at the same level
(b) Three pathways of sympathetic innervation
1
Sympathetic Trunks and Pathways
• Sympathetic trunks and pathways
–Upon entering a sympathetic trunk ganglion a
preganglionic fiber may do one of the following:
2. Ascend or descend the sympathetic trunk to
synapse in another trunk ganglion
Figure 14.5b (2 of 3)
To effector
Blood vessels
Skin (arrector
pili muscles
and sweat
glands)
Synapse at a higher or lower level
(b) Three pathways of sympathetic innervation
2
1/18/2016
7
Sympathetic Trunks and Pathways
• Sympathetic trunks and pathways
–Upon entering a sympathetic trunk ganglion a
preganglionic fiber may do one of the following:
3. Pass through the trunk ganglion and emerge
without synapsing
Figure 14.5b (3 of 3)
Splanchnic nerve
Collateral ganglion
(such as the celiac)
Target organ
in abdomen
(e.g., intestine)
Synapse in a distant collateral ganglion
anterior to the vertebral column
(b) Three pathways of sympathetic innervation
3
Sympathetic Trunks and Pathways
• Sympathetic trunks and pathways
–Upon entering a sympathetic trunk ganglion a
preganglionic fiber may do one of the following:
3. Pass through the trunk ganglion and emerge
without synapsing» Eventually synapse with post-ganglionic neurons in collateral
ganglia, enter an autonomic plexus, and innervate abdominal
viscera
» Form splanchnic nerves
Figure 14.5a
Spinal cord
Dorsal root
Ventral root
Sympathetic
trunk ganglion
Sympathetic
trunk
Rib
Ventral ramus
of spinal nerve
Gray ramus
communicans
White ramus
communicans
Thoracicsplanchnic nerves
(a) Location of the sympathetic trunk
Division Origin of
Fibers Length of
Fibers Location
of Ganglia
Sympathetic Thoracolumbar region of the spinal cord
Short preganglionic and long postganglionic
Close to spinal cord
Parasympathetic Brain and sacral spinal cord (craniosacral)
Long preganglionic and short postganglionic
In visceral effector organs
Differences Between the Divisions Neurotransmitters in the ANS
• Cholinergic fibers release the neurotransmitter ACh
– All ANS preganglionic axons
– All parasympathetic postganglionic axons
• Adrenergic fibers release the neurotransmitter NE
– Most sympathetic postganglionic axons
– Exceptions: sympathetic postganglionic fibers
secrete ACh at sweat glands and some blood vessels
in skeletal muscles
1/18/2016
8
Figure 14.2
+
AChSmooth muscle
(e.g., in gut),
glands, cardiac
muscle
Ganglion
Adrenal medulla Blood vessel
ACh
ACh
ACh
NE
Epinephrine andnorepinephrine
Acetylcholine (ACh) Norepinephrine (NE)
Ganglion
Lightly myelinated
preganglionic axon
Lightly myelinated
preganglionic axons
Unmyelinated
postganglionic
axon
Unmyelinatedpostganglionic axon
Stimulatory
or inhibitory,
depending
on neuro-
transmitter
and
receptors
on effector
organs
Two-neuron chain from CNS to effector organs
AU
TO
NO
MIC
NE
RV
OU
S S
YS
TE
M
PA
RA
SY
MP
AT
HE
TIC
SY
MP
AT
HE
TIC
Adrenal Medulla
“Sympathomimetic”
Receptors for Neurotransmitters
• Cholinergic receptors for ACh
• Adrenergic receptors for NE
Cholinergic Receptors
• Two types of receptors bind ACh
1. Nicotinic
2. Muscarinic
• Named after drugs that bind to them and mimic
ACh effects
Cholinergic Receptors
• Nicotinic receptors– Blocked with curare
• Poison arrows and blow darts
• Used as a muscle relaxant for surgery (safer alternatives now available)
– Effect of ACh at nicotinic receptors
• Always stimulatory
Cholinergic Receptors
�Muscarinic
�Blocked by atropine
�Effect of ACh at muscarinic receptors
�Can be either inhibitory or excitatory
�Depends on the receptor type of the target organ
Clarification, PNS 8: 2d.
acetylcholine is not always stimulatory. It IS always stimulatory at nicotinic and somatic receptors. It may be
inhibitory or excitatory at muscarinic receptors.
1/18/2016
9
Adrenergic Receptors
• Two types
– Alpha (α) (subtypes α1, α2)
– Beta (β) (subtypes β1, β2, β3)
• Effects of NE depend on which subclass of
receptor predominates on the target organ
Table 14.2
Ignore
Ignore
Cardiovascular Pharmacology
• Heart
– β1 - Excitatory in heart
• increases heart rate, conduction velocity, and contraction
strength
• Major blood vessels
– β2 – Inhibitory
• Vasodilation
– α1 – Excitatory
• Vasoconstriction
Cardiovascular Pharmacology
• Adrenergic blockers
– Used to treat hypertensive disease
– α1 blockers - produce vasodilation
– β1 blockers - decrease heart rate and blood
pressure
Interactions of the Autonomic
Divisions
• Most visceral organs have dual innervation
• Dynamic and precise control of visceral activity
– Sympathetic division increases heart and respiratory
rates, and inhibits digestion and elimination
– Parasympathetic division decreases heart and
respiratory rates, and allows for digestion and the
discarding of wastes
Salivaryglands
Eye
Skin*
Heart
Lungs
Liverand gall-bladder
Genitals
Pancreas
Eye
Lungs
Bladder
Liver andgall-bladder
Pancreas
Stomach
Cervical
Sympatheticganglia
Cranial
Lumbar
Thoracic
Genitals
Heart
Salivaryglands
Stomach
Bladder
Adrenalgland
Parasympathetic Sympathetic
Sacral
Brainstem
L1
T1
Figure 14.3