Pns 7-

1. 1084SMS
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DrMohanadRAlwan

2. Now that we’ve looked at
spinal and cranial nerves, we
can examine the divisions of
the PNS.
The PNS is broken down into
a sensory and a motor
division.
We’ll concentrate on the
motor division which contains
the somatic nervous system
and the autonomic nervous
system.

3. Peripheral Nervous SystemPeripheral Nervous System
·Nerves and ganglia outside the central
nervous system
·Nerve = bundle of neuron fibers
·Neuron fibers are bundled by connective
tissue

4. Structure of a NerveStructure of a Nerve
·Endoneurium
surrounds each fiber
·Groups of fibers are
bound into fascicles
by perineurium
·Fascicles are bound
together by
epineurium

7. Parasympathetic ganglion

8. Classification of NervesClassification of Nerves
·Mixed nerves – both sensory and motor
fibers
·Afferent (sensory) nerves – carry impulses
toward the CNS
·Efferent (motor) nerves – carry impulses
away from the CNS

9. Spinal NervesSpinal Nerves
·There is a pair of spinal
nerves at the level of
each vertebrae.
Dorsal root ganglion – cell bodies of
sensory neurons
Dorsal root – axons of sensory neurons
Ventral root – axons of motor neurons
31 pairs of spinal nerves

10. Spinal NervesSpinal Nerves

11. 3 kinds of neurons connect CNS
to the body
◦Sensory
◦Motor
◦Interneurons
Motor - CNS to muscles and
organs
Sensory - sensory receptors to
CNS
Interneurons: Connections
Within CNS
Spinal
Cord
Brain
Nerves

12. 12

13. 13
Nervous System
Central Nervous System
(CNS)
Peripheral Nervous
System (PNS)
Autonomic Nervous System
(ANS)(involuntary)
Somatic nervous
System (voluntary)
Sympathetic Nervous
System
Parasympathetic
Nervous System

14. Copyright © 2005 Pearson
Education, Inc., publishing as
Benjamin Cummings

15. 15
Stimulus
Sensory System
CNS
MotorSystem (neurone)
Somatic system
(voluntary)
Autonomic system
(involuntary)
Striated muscle Smooth muscle & glands
Effector
Response
(Brain / spinal cord)
(neurone)

16. Nerves to/from spinal cord
◦Control muscle
movements
◦Somatosensory inputs
Both Voluntary and reflex
movements
Skeletal Reflexes
◦simplest is spinal reflex
arch
Muscle
Motor
Neuron
Interneuron
Skin receptors
Sensory
Neuron
Brain

17. ◦Cell bodies of motor neurons reside in CNS (brain or
spinal cord)
◦Their axons (sheathed in spinal nerves) extend all the
way to their skeletal muscles

18. Structure of spinal nerves: Somatic pathwaysStructure of spinal nerves: Somatic pathways
dorsal root
dorsal root
ganglion
ventral root
spinal
nerve
dorsal
ramus
ventral
ramus
dorsal
horn
ventral
horn
somaticsomatic
sensorysensory
nervenerve
(GSA)(GSA)
somaticsomatic
motormotor
nervenerve
(GSE)(GSE)
CNS
inter-
neuron
Mixed SpinalMixed Spinal
NerveNerve
gray ramus
communicans
white ramus
communicans
sympathetic
ganglion

20. Autonomic Nervous SystemAutonomic Nervous System
·The involuntary branch of the nervous
system
·Consists of only motor nerves
·Divided into two divisions
·Sympathetic division
·Parasympathetic division

21. Two divisions:
◦Sympathetic
◦Parasympatheitic
Control involuntary functions:
◦Heartbeat
◦Blood pressure
◦Respiration
◦Perspiration
◦Digestion
Can be influenced by thought and emotion

22. 2 divisions:
◦Sympathetic
“Fight or flight”
“E” division
Exercise, excitement,
emergency, and
embarrassment
◦Parasympathetic
“Rest and digest”
“D” division
Digestion and diuresis

23. “ Fight or flight” response
Release adrenaline and
noradrenaline
Increases heart rate and
blood pressure
Increases blood flow to
skeletal muscles
Inhibits digestive functions
CENTRAL NERVOUS SYSTEM
Brain
Spinal
cord
SYMPATHETIC
Dilates pupil
Stimulates salivation
Relaxes bronchi
Accelerates heartbeat
Inhibits activity
Stimulates glucose
Secretion of adrenaline,
nonadrenaline
Relaxes bladder
Stimulates ejaculation
in male
Sympathetic
ganglia
Salivary
glands
Lungs
Heart
Stomach
Pancreas
Liver
Adrenal
gland
Kidney

24. Basic organization
◦Issues from T
1-L
2
◦Preganglionic fibers form the lateral gray horn
◦Supplies visceral organs and structures of superficial
body regions
◦Contains more ganglia than the parasympathetic division

25. “ Rest and digest ”
system
Calms body to conserve
and maintain energy
Lowers heartbeat,
breathing rate, blood
pressure
CENTRAL NERVOUS SYSTEM
Brain
PARASYMPATHETIC
Spinal
cord
Stimulates salivation
Constricts bronchi
Slows heartbeat
Stimulates activity
Contracts bladder
Stimulates erection
of sex organs
Stimulates gallbladder
Gallbladder
Contracts pupil

27. Summary of autonomic differences
Autonomic nervous system controls physiological arousal
Sympathetic
division (arousing)
Parasympathetic
division (calming)
Pupils dilate EYES Pupils contract
Decreases SALVATION Increases
Perspires SKIN Dries
Increases RESPERATION Decreases
Accelerates HEART Slows
Inhibits DIGESTION Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones

28. Voluntary
Skeletal muscle
Single efferent neuron
Axon terminals release
acetylcholine
Always excitatory
Controlled by the cerebrum
Involuntary
Smooth, cardiac muscle;
glands
Multiple efferent neurons
Axon terminals release
acetylcholine or
norepinephrine
Can be excitatory or
inhibitory
Controlled by the
homeostatic centers in the
brain – pons,
hypothalamus, medulla
oblongata

30. Most internal organs are
innervated by both branches
of the ANS which exhibit
antagonistic control
A great example is heart rate.
An increase in sympathetic
stimulation causes HR to
increase whereas an increase in
parasympathetic stimulation
causes HR to decrease

31. Exception to the dual innervation rule:
Sweat glands and blood vessel smooth muscle are only
innervated by symp and rely strictly on up-down control.
Exception to the antagonism rule:
Symp and parasymp work cooperatively to achieve male
sexual function. Parasymp is responsible for erection while
symp is responsible to ejaculation. There’s similar ANS
cooperation in the female sexual response.

32. Both ANS divisions share the same
general structure.
◦Autonomic pathways always
consist of 2 neurons in series.
◦They synapse in an autonomic
ganglion – would this be outside
the CNS
◦The 1
st
neuron in the autonomic
pathway is the preganglionic
neuron,
Cell body in CNS, myelinated, and
projects to the autonomic
ganglion.
◦While the 2
nd
neuron is the
postganglionic neuron.
Cell body in autonomic ganglion,
unmyelinated, and projects to the
effector or organ.

33. Sympathetic
CNS
ganglion
short preganglionic
neuron
long postganglionic
neuron
target
Parasympathetic
CNS
ganglion
long preganglionic
neuron
target
short postganglionic
neuron
Overview of the Autonomic Nervous SystemOverview of the Autonomic Nervous System
Differences between Sympathetic & ParasympatheticDifferences between Sympathetic & Parasympathetic
Relative Lengths of Neurons

34. Parasympathetic
Overview of the Autonomic Nervous SystemOverview of the Autonomic Nervous System
Differences between Sympathetic & ParasympatheticDifferences between Sympathetic & Parasympathetic
Neurotransmitters
ACh, +
NE (ACh at sweat glands),
+ / -, α & ß receptors
ACh, + / -
muscarinic receptors
• All preganglionics release acetylcholine (ACh) & are excitatory (+)
• Symp. postgangl. — norepinephrine (NE) & are excitatory (+) or inhibitory (-)
• Parasymp. postgangl. — ACh & are excitatory (+) or inhibitory (-)
Sympathetic
• Excitation or inhibition is a receptor-dependent & receptor-mediated response
Potential for pharmacologic
modulation of autonomic responses
ACh, +

35. Point of CNS OriginPoint of CNS OriginT1  L2
(thoracolumbar)
Brainstem,
S2  S4
(craniosacral)
Site of Peripheral Site of Peripheral
GangliaGanglia
Paravertebral – in
sympathetic chain
On or near target
tissue
Length of Length of
preganglionic fiberpreganglionic fiber
Short Long
Length of Length of
postganglionic fiberpostganglionic fiber
Long Short

36. NT at Target NT at Target
SynapseSynapse
Norepinephrine
(adrenergic
neurons)
Acetylcholine
(cholinergic
neurons)
Type of NT Type of NT
Receptors at Receptors at
Target SynapseTarget Synapse
Alpha and Beta
(a and b)
Muscarinic
NT at GanglionNT at Ganglion Acetylcholine Acetylcholine
Receptor at Receptor at
GanglionGanglion
Nicotinic Nicotinic

39. In the following tables, note the effects of the
sympathetic and parasympathetic nervous
systems on various body organs.

40. Target OrganTarget Organ Parasympathetic Parasympathetic
EffectsEffects
Sympathetic Sympathetic
EffectsEffects
Eye (Iris)Eye (Iris)
Stimulates constrictor
muscles. Pupil
constriction.
Stimulates dilator
muscles. Pupil dilates.
Eye (Ciliary Eye (Ciliary
muscle)muscle)
Stimulates. Lens
accommodates – allows
for close vision.
No innervation.
Salivary GlandsSalivary Glands
Watery secretion. Mucous secretion.
Sweat GlandsSweat Glands
No innervation. Stimulates sweating in
large amounts.
(Cholinergic)
GallbladderGallbladder
Stimulates smooth muscle
to contract and expel bile.
Inhibits gallbladder
smooth muscle.
Arrector PiliArrector Pili
No innervation Stimulates contraction.
Piloerection
(Goosebumps)

41. Target OrganTarget Organ Parasympathetic Parasympathetic
EffectsEffects
Sympathetic Sympathetic
EffectsEffects
Cardiac MuscleCardiac Muscle
Decreases HR. Increases HR and force of
contraction.
Coronary Blood Coronary Blood
VesselsVessels
Constricts. Dilates
Urinary Bladder; Urinary Bladder;
UrethraUrethra
Contracts bladder smooth
muscle; relaxes urethral
sphincter.
Relaxes bladder smooth
muscle; contracts urethral
sphincter.
LungsLungs
Contracts bronchiole
(small air passage)
smooth muscle.
Dilates bronchioles.
Digestive OrgansDigestive Organs
Increases peristalsis and
enzyme/mucus secretion.
Decreases glandular and
muscular activity.
Liver Liver
No innervations No innervation (indirect
effect).

42. Target OrganTarget Organ Parasympathetic Parasympathetic
EffectsEffects
Sympathetic Sympathetic
EffectsEffects
KidneyKidney
No innervation. Releases the enzyme
renin which acts to
increase BP.
PenisPenis
Vasodilates penile
arteries. Erection.
Smooth muscle
contraction. Ejaculation.
Vagina; ClitorisVagina; Clitoris
Vasodilation. Erection.Vaginal reverse
peristalsis.
Blood CoagulationBlood Coagulation
No effect. Increases coagulation
rate.
Cellular Cellular
MetabolismMetabolism
No effect. Increases metabolic rate.
Adipose TissueAdipose Tissue
No effect. Stimulates fat breakdown.

43. Target OrganTarget Organ Parasympathetic Parasympathetic
EffectsEffects
Sympathetic Sympathetic
EffectsEffects
Mental ActivityMental Activity
No innervation. Increases alertness.
Blood VesselsBlood Vessels
Little effect. Constricts most blood
vessels and increases
BP. Exception – dilates
blood vessels serving
skeletal muscle fibers
(cholinergic).
UterusUterus
Depends on stage of the
cycle.
Depends on stage of the
cycle.
Endocrine Endocrine
PancreasPancreas
Stimulates insulin
secretion.
Inhibits insulin secretion.

44. Preganglionic fibers have their somat in the lateral
horns of the thoracic and lumbar spinal cord.
Preganglionic fibers leave the cord via the ventral
root and enter a white ramus communicans to
enter a chain ganglion – which is part of the
sympathetic trunk.
Let’s look at a picture!

47. Certain splanchnic nerves synapse on hormone-producing cells of the adrenal
medulla – the interior of the adrenal glands which sit upon the kidneys.
How does this
contribute to the
“diffuseness” of
sympathetic activity?

48. The Hypothalamus is the Boss:
◦Its anterior and medial regions direct parasympathetic
function while its posterior and lateral regions direct
sympathetic function
◦These centers exert control directly and via nuclei in
the reticular formation (e.g., the cardiovascular centers
in the MO, respiratory centers in MO and pons, etc.)
◦The connection of the limbic system to the
hypothalamus mediates our “flight or flight” response
to emotional situations.

51. I will open ur
mouth like my
toy