1. Peripheral Nervous System

2. Place of the PNS in the structural organization of the nervous system
CNS
PNS
Sensory division
Motor division
Sympathetic
division
Autonomic
nervous
system
Somatic
nervous
system
Parasympathetic
division

3. Axon Blood vessels Perineurium Myelin sheath Endoneurium Perineurium
Structure of a nerve
Axon
Blood vessels
Perineurium
Myelin sheath
Endoneurium
Perineurium
Epineurium
Fascicle
Fascicle
Blood
vessels
Endoneurium
Nerve fibers
(a)
(b)

4. 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)

5. Distribution of spinal nerves
Cervical plexus
Cervical
nerves
C1– C8
Brachial plexus
Cervical
enlargement
Intercostal
Thoracic
nerves
T1– T12
nerves
Lumbar
enlargement
Lumbar plexus
Lumbar
nerves
L1– L5
Sacral plexus
Sacral
nerves
S1– S5
Cauda equina
Coccygeal
nerve C0

6. Formation of spinal nerves and rami distribution
Dorsal ramus
Ventral ramus
Spinal nerve
Intercostal nerve
Rami communicantes
Dorsal root ganglion
Ventral root
Sympathetic trunk
(chain) ganglion
Dorsal root
Thoracic cavity
Lateral cutaneous
Branches of
intercostal
nerve
Anterior cutaneous
Sternum
(b)

7. The cervical plexus Key: = Ventral rami Segmental branches Hypoglossal
nerve (XII)
Ventral
rami:
Lesser occipital
nerve C1
Greater auricular
nerve C2
Transverse cutaneous
nerve C3
Ansa cervicalis C4
Accessory nerve (XI) C5
Phrenic nerve
Supraclavicular
nerves

8. The brachial plexus Roots: Key: C4 Dorsal scapular = Roots C5 Nerve to
subclavius
= Trunks C6
Suprascapular
Upper
= Anterior
division
Posterior
divisions C7
Middle
Trunks
= Posterior
division C8
Lateral
Lower T1
Cords
Posterior
Long thoracic
Medial
Medial pectoral
Lateral pectoral
Axillary
Upper subscapular
Musculo-
cutaneous
Lower subscapular
Thoracodorsal
Radial
Medial cutaneous
nerves of the arm
and forearm
Median
(a)
Ulnar

9. Trunks Humerus Radial nerve Musculo- cutaneous nerve Ulna Radius
The brachial plexus
Trunks
Humerus
Radial
nerve
Musculo-
cutaneous
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
nerve
Digital
branch
(c)

10. Ventral rami: L1 Iliohypogastric Ilioinguinal L2 Iliohypogastric
The lumbar plexus
Ventral
rami: L1
Iliohypogastric
Ilioinguinal L2
Iliohypogastric
Femoral
Ilioinguinal
Lateral
femoral
cutaneous
Genitofemoral L3
Obturator
Lateral femoral
cutaneous
Anterior
femoral
cutaneous L4
Saphenous
Obturator L5
Femoral
Lumbosacral
trunk
(a)
Key:
= Ventral rami
(b)

11. Ventral rami: L4 Superior gluteal Superior gluteal L5 Inferior gluteal
The sacral plexus
Ventral
rami: L4
Superior
gluteal
Superior
gluteal L5
Inferior
gluteal
Lumbosacral
trunk
Pudendal S1
Inferior
gluteal
Sciatic
Posterior
femoral
cutaneous
Common
fibular S2
Tibial
Common
fibular S3
Posterior
femoral
cutaneous
Tibial S4
Sural
Pudendal
Deep
fibular S5
Sciatic C0
Superficial
fibular
(a)
Key:
Plantar
branches
= Ventral rami
(b)

12. Activity 2 Activity 3 Identify spinal chord tracts
Identify Major nerve plexuses and Peripheral nerves

13. The Autonomic Nervous System (ANS)

14. Place of the ANS in the structural organization of the nervous system
CNS
PNS
Sensory division
Motor division
Sympathetic
division
Autonomic
nervous
system
Somatic
nervous
system
Parasympathetic
division

15. 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.

16. Comparison of somatic and autonomic nervous systems
Central
nervous system
Peripheral nervous system
Effector organs
Acetylcholine
Somatic nervous system
Skeletal muscle
Acetylcholine
Norepinephrine
Smooth
muscle
(e.g., in
gut)
Ganglion
Sympathetic
division
Acetylcholine
Epinephrine and
norepinephrine
Autonomic
nervous
system
Blood
vessel
Glands
Adrenal medulla
Acetylcholine
Cardiac
muscle
Para-
sympathetic
division
Ganglion
Key:
= Preganglionic axons
(sympathetic)
= Postganglionic axons
(sympathetic)
= Myelination
= Preganglionic axons
(parasympathetic)
= Postganglionic axons
(parasympathetic)

17. Overview of the subdivisions of the ANS
Parasympathetic
Sympathetic
Eye
Eye
Brain stem
Salivary
glands
Skin*
Cranial
Salivary
glands
Sympathetic
ganglia
Heart
Cervical
Lungs
Lungs T1
Heart
Stomach
Thoracic
Stomach
Pancreas
Liver
and gall-
bladder
Pancreas L1
Liver and
gall-
bladder
Adrenal
gland
Lumbar
Bladder
Bladder
Genitals
Genitals
Sacral

18. Parasympathetic (craniosacral) division of the ANS
Eye
CN III
Lacrimal
gland
CN VII
CN IX
Nasal
mucosa
CN X
III: Oculomotor
VII: Facial
IX: Glossopharyngeal
X: Vagus
Ciliary ganglion
Submandibular
and sublingual
glands
Pterygopalatine
ganglion
Parotid gland
Submandibular
ganglion
Heart
Cardiac and
pulmonary
plexuses
Otic ganglion
Lung
Liver and
gallbladder
Celiac
plexus
Stomach S2
Pancreas S4
Large
intestine
Pelvic
splanchnic
nerves
Small
intestine
Inferior
hypogastric
plexus
Rectum
Urinary bladder
and ureters
Genitalia (penis, clitoris, and vagina)

19. 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.

20. Sympathetic (thoracolumbar) division of the ANS
Eye
Lacrimal
gland
Nasal
mucosa
Sympathetic trunk
(chain) ganglia
Midbrain
Superior
cervical
ganglion
Pons
Blood vessels; skin (arrector pili
muscles and sweat glands)
Medulla
Middle
cervical
ganglion
Salivary glands
Heart
Inferior
cervical
ganglion
Cardiac and pulmonary
plexuses
Lung T1
Greater splanchnic nerve
Lesser splanchnic nerve
Liver
and gall-
bladder
Celiac ganglion
Stomach L2
Superior
mesenteric
ganglion
White rami
communicantes
Spleen
Adrenal gland
Aortic
plexus
on aorta
Kidney
Lumbar
splanchnic nerves
Small
intestine
Inferior
mesenteric
ganglion
Large
intestine
Rectum
Sympathetic
division
(thoracolumbar)
Inferior
hypogastric
plexus
Genitalia (uterus, vagina, and
penis) and urinary bladder

21. 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.

22. Sympathetic trunks and pathways
Spinal cord
Dorsal root
Ventral root
Dorsal white
column
Sympathetic
trunk ganglion
Sympathetic trunk
(chain) ganglion
Body of a
vertebra
Lateral horn
(visceral motor zone)
Dorsal root ganglion
Sympathetic trunk
Thoracic
splanchnic
nerves
Ventral ramus
of spinal nerve
Gray ramus
communicans
Intercostal nerve 2
Intercostal muscle
of thorax
White ramus
communicans
Rib
(a)
Ventral root
Dorsal ramus
of spinal nerve 3 2 1 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
Splanchnic
nerve
Blood vessels
Collateral
(prevertebral) ganglion
such as the celiac 3
To effector
Skin (arrector
pili muscles
and sweat
glands)
Target organ
(in abdomen)
(b)

23. Activity 4
Locate the ANS chains in the models.

25. 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.

26. Hierarchy of motor control
Interactions
Control level
Structures involved
Programs and instructions
(modified by feedback)
Highest (precommand)
Cerebellum and basal nuclei
Internal
feedback
Feedback
Projection areas
Middle
Motor cortex (pyramidal system)
and brain stem nuclei (vestibular,
red, reticular formation, etc.)
Segmental motor
controls (CPG)
Lowest
Spinal cord
Sensory
input
Reflex activity
Motor
output
CNG: central pattern generator

27. The basic components of all human reflex arcs
Spinal cord (in cross section)
Stimulus 2
Sensory neuron 3
Integration center 1
Receptor
Motor neuron
Interneuron
Skin 4 5
Effector

28. 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).

29. Interneuron Cell body of sensory neuron 1 Afferent impulses
The stretch reflex
Interneuron
Cell body of
sensory neuron 1
Afferent impulses
from stretch
receptor to
spinal cord
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) –
Initial
stimulus:
muscle
stretch
Spinal cord
(L2–L4)
Muscle
spindle
Patella
Quadriceps
(extensors)
Muscle
spindle
Patellar
ligament
Hamstrings
(flexors) 3
Efferent impulses
to antagonist
muscles are
damped
(reciprocal
inhibition)
Key:
+ Excitatory synapse
– Inhibitory synapse
(a)
(b)

30. The Golgi tendon reflex
organ
Quadriceps
(extensor)
Hamstrings
(flexor)
Spinal cord
Interneurons + +
Afferent fiber
from Golgi
tendon organ – +
Efferent fiber
to muscle
associated
with stretched
tendon
Key:
+ Excitatory synapse
– Inhibitory synapse
Efferent fiber
to antagonistic
muscle

31. Operation of the 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

32. Anatomy of the muscle spindle and Golgi tendon organ
 Efferent motor fiber to spindle
Secondary
sensory
endings
(type II fiber)
a Efferent
motor fiber
to extrafusal
muscle
fibers
Primary
sensory
endings
(type Ia fiber)
Extrafusal
muscle
fiber
Muscle spindle
Intrafusal
muscle
fibers
Connective
tissue capsule
Sensory
fiber
Capsule
Tendon
Golgi tendon
organ

33. Somatic Reflexes
Crossed extensor reflex: Withdrawal reflex, followed by extension of the opposite limb.
Activity 2?

34. The crossed-extensor reflex
Interneurons + + – + + –
Efferent
fibers
Afferent
fiber
Efferent
fibers
Extensor
inhibited
Flexor
inhibited
Flexor
stimulated
Flexes
Arm movements
Extensor
stimulated
Extends
Key:
+ Excitatory synapse
– Inhibitory synapse
Right arm
(site of stimulus)
Left arm (site of
reciprocal activation)

35. Somatic Reflexes Autonomic Reflexes Reaction time of a reflex
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 ms.

36. 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

37. Autonomic reflexes Pupillary reflexes. Cranial nerve II, III.
Actvity 6: Contralateral response, ipsilateral response.
Ciliospinal reflex. Pupilary.
Salivary reflex. Smooth/skeletal muscles.

38. Dorsal root ganglion Sensory receptor in viscera Central nervous
Visceral reflexes
Dorsal
root
ganglion
Sensory
receptor in
viscera
Central
nervous
system
Stimulus
Visceral
(sensory)
fiber
Visceral reflex arc
(Autonomic reflex)
Postganglionic
axon
Visceral
effector
Response
Integration center
(may be preganglionic
neuron)
Ganglionic
neuron
Autonomic
ganglion
Preganglionic axon

39. Heart Lungs and diaphragm Liver Gallbladder Gallbladder Heart Liver
Referred pain
Heart
Lungs and
diaphragm
Liver
Gallbladder
Gallbladder
Heart
Appendix
Liver
Stomach
Pancreas
Small
intestine
Ovaries
Colon
Kidneys
Urinary
bladder
Ureters