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Transcript
Peripheral Nervous System
Place of the PNS in the structural organization of the nervous system
CNS
PNS
Sensory division
Sympathetic
division
Parasympathetic
division
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Motor division
Autonomic
nervous
system
Somatic
nervous
system
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Structure of a nerve
Axon
Blood vessels
Perineurium
Myelin sheath
Endoneurium
Perineurium
Epineurium
Fascicle
Fascicle
Blood
vessels
(a)
Endoneurium
Nerve fibers
(b)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Spinal Nerves and Nerve Plexuses
• Characteristics:
– Somatic sensation (conscious) and somatic motor control (voluntary
control) of skeletal muscles.
– Includes cranial nerves: I, II, IV-VI, VIII, XI and XII.
– Spinal nerves: 31
•
•
•
•
•
Cervical: 8 (above C1, and below C1-C7)
Thoracic: 12 (below T1-T12)
Lumbar: 5 (below T1-T5)
Sacral: 5 ( below S1-S5)
Coccygeal: 1 exit coccyx
– Mixed nerves
• Sensory
• Motor
– Dorsal and ventral rami (nerve branches)  plexuses (network of nerves)
Distribution of spinal nerves
Cervical plexus
Brachial plexus
Cervical
nerves
C1– C8
Cervical
enlargement
Intercostal
nerves
Thoracic
nerves
T1– T12
Lumbar
enlargement
Lumbar plexus
Sacral plexus
Cauda equina
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Lumbar
nerves
L1– L5
Sacral
nerves
S1– S5
Coccygeal
nerve
C0
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Formation of spinal nerves and rami distribution
Dorsal ramus
Ventral ramus
Spinal nerve
Rami communicantes
Intercostal nerve
Dorsal root ganglion
Ventral root
Sympathetic trunk
(chain) ganglion
Dorsal root
Thoracic cavity
Lateral cutaneous
Anterior cutaneous
Sternum
(b)
Branches of
intercostal
nerve
The cervical plexus
Key:
= Ventral
rami
Segmental
branches
Hypoglossal
nerve (XII)
Lesser occipital
nerve
Ventral
rami:
C1
Greater auricular
nerve
C2
Transverse cutaneous
nerve
C3
Ansa cervicalis
C4
Accessory nerve (XI)
Phrenic nerve
Supraclavicular
nerves
C5
The brachial plexus
Roots:
Key:
Dorsal scapular
= Roots
Nerve to
subclavius
Suprascapular
= Trunks
= Anterior
division
= Posterior
division
Cords
C4
C5
C6
Upper
Posterior
divisions
C7
Lateral
C8
Posterior
T1
Middle
Trunks
Lower
Long thoracic
Medial
Medial pectoral
Lateral pectoral
Axillary
Musculocutaneous
Radial
Median
(a)
Ulnar
Upper subscapular
Lower subscapular
Thoracodorsal
Medial cutaneous
nerves of the arm
and forearm
The brachial plexus
Trunks
Humerus
Radial
nerve
Musculocutaneous
nerve
Ulna
Radius
Ulnar nerve
Median
nerve
Radial nerve
(superficial
branch)
Dorsal branch
of ulnar nerve
Superficial branch
of ulnar nerve
Digital branch
of ulnar nerve
Muscular
branch
Median
Digital
nerve
branch
(c)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
The lumbar plexus
Ventral
rami:
L1
Iliohypogastric
Ilioinguinal
Iliohypogastric
Ilioinguinal
Genitofemoral
L2
Femoral
Lateral
femoral
L3 cutaneous
Obturator
Lateral femoral
cutaneous
Anterior
L4 femoral
cutaneous
Saphenous
Obturator
Femoral
L5
Lumbosacral
trunk
(a)
Key:
= Ventral rami
(b)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
The sacral plexus
Ventral
rami:
L4
Superior
gluteal
L5
Lumbosacral
trunk
Inferior
gluteal
Common
fibular
Tibial
Posterior
femoral
cutaneous
Pudendal
Sciatic
(a)
Key:
= Ventral rami
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
S1
S2
S3
S4
S5
C0
Superior
gluteal
Inferior
gluteal
Pudendal
Sciatic
Posterior
femoral
cutaneous
Common
fibular
Tibial
Sural
Deep
fibular
Superficial
fibular
Plantar
branches
(b)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
• Activity 2
– Identify spinal chord tracts
• Activity 3
– Identify Major nerve plexuses and Peripheral
nerves
The Autonomic Nervous System
(ANS)
Place of the ANS in the structural organization of the nervous system
CNS
PNS
Sensory division
Sympathetic
division
Parasympathetic
division
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Motor division
Autonomic
nervous
system
Somatic
nervous
system
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Characteristics of the ANS
• Regulates body function unconsciously.
– Cardiac muscle, smooth muscle, glands.
• Consists of chains of 2 motor neurons.
– Preganglion neuron: located in the CNS.
– Ganglion neuron: synapses with pregalnglion, outside
the CNS and its axon synapses with the effector
organ.
• Sympathetic (fight or flight) functions are
antagonistic to the Parasympathetic (resting and
digesting) functions.
Comparison of somatic and autonomic nervous systems
Central
nervous system
Peripheral nervous system
Effector organs
Acetylcholine
Somatic nervous system
Skeletal muscle
Acetylcholine
Sympathetic
division
Norepinephrine
Smooth
muscle
(e.g., in
gut)
Ganglion
Acetylcholine
Autonomic
nervous
system
Epinephrine and
norepinephrine
Blood
vessel
Glands
Adrenal medulla
Acetylcholine
Parasympathetic
division
Cardiac
muscle
Ganglion
Key:
= Preganglionic axons
(sympathetic)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
= Postganglionic axons
(sympathetic)
= Myelination
= Preganglionic axons
(parasympathetic)
= Postganglionic axons
(parasympathetic)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Overview of the subdivisions of the ANS
Parasympathetic
Sympathetic
Eye
Brain stem
Salivary
glands
Heart
Eye
Skin*
Cranial
Cervical
Sympathetic
ganglia
Salivary
glands
Lungs
Lungs
T1
Heart
Stomach
Stomach
Thoracic
Pancreas
Liver
and gallbladder
Pancreas
L1
Liver and
gallbladder
Adrenal
gland
Lumbar
Bladder
Bladder
Genitals
Genitals
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Sacral
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Parasympathetic (craniosacral) division of the ANS
Eye
Lacrimal
gland
Nasal
mucosa
Submandibular
and sublingual
glands
CN III
CN VII
CN IX
CN X
III: Oculomotor
Ciliary ganglion
VII: Facial
Pterygopalatine
ganglion
IX: Glossopharyngeal
X: Vagus
Parotid gland
Submandibular
ganglion
Cardiac and
pulmonary
plexuses
Otic ganglion
Celiac
plexus
S2
Heart
Lung
Liver and
gallbladder
Stomach
Pancreas
S4
Pelvic
splanchnic
nerves
Inferior
hypogastric
plexus
Large
intestine
Small
intestine
Rectum
Urinary bladder
and ureters
Genitalia (penis, clitoris, and vagina)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Characteristics of the
Parasympathetic Division
• Preganglion axons are located in the cranial
nerves in the immediate area to be stimulated.
• Terminal or intramural ganglion, which emits a
short axon to the organ, synapse with the
preganglion ganglion.
• Sacral region ganglions synapse to pelvic
splanchnic nerves that travel to the pelvic cavity.
Sympathetic (thoracolumbar) division of the ANS
Midbrain Superior
cervical
Pons ganglion
Eye Lacrimal
gland
Nasal
mucosa
Sympathetic trunk
(chain) ganglia
Blood vessels; skin (arrector pili
muscles and sweat glands)
Medulla Middle
cervical
ganglion
Inferior
cervical
ganglion
T1
Salivary glands
Heart
Cardiac and pulmonary
plexuses
Lung
Greater splanchnic nerve
Lesser splanchnic nerve
Liver
and gallbladder
Celiac ganglion
L2
Stomach
Superior
mesenteric
White rami
communicantes ganglion
Spleen
Aortic
plexus
on aorta
Lumbar
splanchnic nerves
Inferior
mesenteric
ganglion
Adrenal gland
Kidney
Small
intestine
Large
intestine
Rectum
Sympathetic
division
(thoracolumbar)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Inferior
hypogastric
plexus
Genitalia (uterus, vagina, and
penis) and urinary bladder
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Characteristics of the Sympathetic
Division
• Preganglion are located in the lateral ramus of the spinal chord
T1 – L2. Axon leaves the chord via ventral root  the spinal nerve
 the ventral ramus white ramus communicans 
paravertrebral ganglion in the sympathetic chain.
• Preganglion axon may:
– Synapse with a same level sympathetic ganglion chain neuron.
– Travel up or downward through the sympathetic chain in the paravertebral
region to another ganglion.
• (Postganglionic reenter spinal nerve through gray ramus communicans to
travel in dorsal or ventral ramus to innervate organs).
– Skip the ganglion and form part of the splanchnic nerves, which travele to
the organ to synapse with prevertebral or collateral ganglion.
• Celiac, superior mesenteric, inferior mesenteric, hypogastric ganglia.
Sympathetic trunks and pathways
Dorsal root
Ventral root
Sympathetic trunk
(chain) ganglion
Lateral horn
(visceral motor zone)
Spinal cord
Sympathetic
trunk ganglion
Body of a
vertebra
Dorsal white
column
Dorsal root ganglion
Sympathetic trunk
Ventral ramus
of spinal nerve
Gray ramus
communicans
Thoracic
splanchnic
nerves
Intercostal nerve
Intercostal muscle
of thorax
Rib
(a)
2
White ramus
communicans
Ventral root
Dorsal ramus
of spinal nerve
3
1
1.Synapse in
paravertebal region at
the same level
2. Synapse in chain
ganglion at different
level
3. Synapse in
prevertebral region
anterior to vertebral
column
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
2
1
Splanchnic
nerve
Blood vessels
Skin (arrector
pili muscles
and sweat
glands)
To effector
Collateral
(prevertebral) ganglion
such as the celiac
3
Target organ
(in abdomen)
(b)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
• Activity 4
– Locate the ANS chains in the models.
Human Reflex Physiology
• Definition:
– Rapid, predictable and involuntary motor
response to stimuli through pathways called
reflex arcs.
• Two systems
– Autonomic reflexes (unconscious): digestion,
sweating etc.
– Somatic reflexes: activate skeletal muscles.
Hierarchy of motor control
Interactions
Control level
Programs and instructions
(modified by feedback)
Structures involved
Highest (precommand)
Cerebellum and basal nuclei
Internal
feedback
Feedback
Middle
Projection areas
Motor cortex (pyramidal system)
and brain stem nuclei (vestibular,
red, reticular formation, etc.)
Segmental motor
controls (CPG)
Lowest
Spinal cord
Sensory
input
Reflex activity
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Motor
output
CNG: central pattern
generator
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
The basic components of all human reflex arcs
Spinal cord (in cross section)
Stimulus
2 Sensory neuron
1 Receptor
4 Motor neuron
Skin
3 Integration center
Interneuron
5 Effector
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
The reflex arc
• Characteristics: Structurally (number of neurons
involved)
– Monosynaptic arc: one synapse
– Polysynaptic arc: one or more association neurons.
• Somatic Reflexes (skeletal muscle effectors)
– Stretch reflexes: Postural and locomotion reflexes.
• Muscle spindle stimuli/Golgi organ in tendons
(stretching) initiates reflex.
– Reciprocal inhibition: antagonistic efferent
muscles are relaxed (damped).
– Patellar reflex (activity 1).
The stretch reflex
Interneuron
1 Afferent impulses
from stretch
receptor to
spinal cord
Initial
stimulus:
muscle
stretch
Cell body of
sensory neuron
Motor neuron
serving quadriceps
2 Efferent
impulses to
alpha (a) motor
neurons cause
contraction
of the stretched
muscle that
resists/reverses
the stretch
Motor neuron
serving antagonist
muscle group
(hamstrings)
–
Spinal cord
(L2–L4)
Patella
Muscle
spindle
Quadriceps
(extensors)
Muscle
spindle
Patellar
ligament
3 Efferent impulses
to antagonist
muscles are
damped
(reciprocal
inhibition)
Hamstrings
(flexors)
Key:
+ Excitatory synapse
– Inhibitory synapse
(a)
(b)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
The Golgi tendon reflex
Quadriceps
(extensor)
Golgi
tendon
organ
Hamstrings
(flexor)
Spinal cord
Interneurons
+
+
+
–
Key:
+ Excitatory synapse
– Inhibitory synapse
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Afferent fiber
from Golgi
tendon organ
Efferent fiber
to muscle
associated
with stretched
tendon
Efferent fiber
to antagonistic
muscle
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Operation of the muscle spindle
Muscle
spindle
Intrafusal
muscle fiber
Primary
sensory (la)
nerve fiber
Extrafusal
muscle fiber
Time
Time
Time
Time
(a) Unstretched
muscle;
AP frequency
constant
(b) Stretched muscle;
AP frequency
increased
(c) a Motor neuron
stimulation only; no
APs, unable to signal
length changes
(d) a - g Neuron
coactivation;
AP frequency
constant
AP: Action Potential
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Anatomy of the muscle spindle and Golgi tendon organ
g Efferent motor fiber to spindle
Secondary
sensory
endings
(type II fiber)
Primary
sensory
endings
(type Ia fiber)
Muscle spindle
Connective
tissue capsule
Capsule
a Efferent
motor fiber
to extrafusal
muscle
fibers
Extrafusal
muscle
fiber
Intrafusal
muscle
fibers
Sensory
fiber
Tendon
Golgi tendon
organ
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Somatic Reflexes
• Crossed extensor reflex: Withdrawal reflex,
followed by extension of the opposite limb.
• Activity 2?
The crossed-extensor reflex
Interneurons
+
+
–
Afferent
fiber
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
–
+
Efferent
fibers
Efferent
fibers
Extensor
inhibited
Flexor
stimulated
Key:
+ Excitatory synapse
– Inhibitory synapse
+
Flexor
inhibited
Extensor
stimulated
Arm movements
Right arm
(site of stimulus)
Left arm (site of
reciprocal activation)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Somatic Reflexes
• Autonomic Reflexes
– Pupillary reflexes
– Salivary reflex
• Reaction time of a reflex
– Relative to the myelination of an axon andits
length relative to the interneuron or association
center.
– Visual stimulus 150-300 ms.
Somatic Reflexes
• Superficial cord reflex: Abdominal,
cremaster and plantar reflexes.
• Plantar reflex. Normal pyramidal activity, toes
flex and move close together. Activity 3.
– Cranial nerve reflex: optical (motor) nerves.
• Corneal reflex (V). Activity 4
Autonomic reflexes
• Pupillary reflexes.
– Cranial nerve II, III.
• Actvity 6: Contralateral response, ipsilateral
response.
– Ciliospinal reflex. Pupilary.
– Salivary reflex. Smooth/skeletal muscles.
Visceral reflexes
Sensory
receptor in
viscera
Dorsal
root
ganglion
Stimulus
Central
nervous
system
Visceral
Visceral reflex arc
(sensory)
(Autonomic reflex)
fiber
Postganglionic
axon
Response
Visceral
effector
Ganglionic
neuron
Autonomic
ganglion
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Integration center
(may be preganglionic
neuron)
Preganglionic axon
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Referred pain
Heart
Lungs and
diaphragm
Liver
Gallbladder
Gallbladder
Heart
Appendix
Liver
Stomach
Pancreas
Small
intestine
Ovaries
Colon
Kidneys
Urinary
bladder
Ureters
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.