Peripheral Nervous System,
Types of PNS,
Spinal nerves,
Types of neuron (3 basic types),
Plexus,
Cranial nerves,
Autonomic nervous system,
Structure of Neuron,
Human Anatomy and Physiology-I,
Syllabus As per PCI,
B. Pharm-I
3. Introduction:
• The peripheralnervoussystem(PNS) is one of the
two main parts of the nervous system, the other
part is the central nervous system (CNS).The
PNS consists of the nerves and ganglia outside of
thebrain and spinal cord. Themain function of
the PNS is to connect the CNSto the limbs and
organs, essentially serving asarelay between the
brain and spinal cord and the rest of the body.
• The central nervous system interprets
information, and the peripheral nervous
system gathers and transmits information.
4. Cont…
• Thesenerves extend from the central
nervous system to the outermost areas of
the body.
• The nervous system is divided into the
o Peripheral nervous system (PNS)
o Central nervous system (CNS)
5. which consistsof
that makeup
which is dividedinto
TheNervous
System
is dividedinto
SensorynervesMotor nerves
Autonomicnervous
system
Somaticnervous
system
Centralnervous
system
Peripheralnervous
system
Sympathetic
nervoussystem
Parasympathetic
nervous system
6. Typeof PNS
• Theperipheral nervous systemisdividedinto
the somaticnervoussystemandthe autonomicnervous
system.In the somatic nervous system, the cranial nervesare
part of thePNS.
1. Motor Division –impulses from CNSto musclesor
glands
• TwoParts:
– SomaticNervousSystem
– Autonomic NervousSystem
2. SensoryDivision –transmits impulses fromsense
organsto CNS
7. The somatic nervous
system regulates
voluntary movements
Ex: Walking
– sympathetic nervous system:
action and stress (Fight or
Flight)
– parasympathetic
nervous system: calms
the body, conserves
energy
The autonomic nervous system
controls involuntary functions
Ex: Digestion
The Peripheral Nervous System: Collection of nerves that
links the CNS to muscles and other organs (Sensory
neurons/motor neurons)
Maintain homeostasis
8. Cont…
• The peripheral nervous system is divided into
the somatic nervous system, and the autonomic
nervous system. The somatic nervous system is
under voluntary control, and transmits signals
from the brain to end organs such as muscles.
The sensory nervous system is part of the
somatic nervous system and transmits signals
from senses such as taste and touch to the
spinal cord and brain. The autonomic
nervous system is a 'self-regulating' system
which influences the function of organs
outside of voluntary control, such as the heart
rate, or the functions of the digestive system.
9. Spinalnerves
• Peripheral NervousSystemconsists of:
• i) 31pairs of SpinalNerves
• ii) There are 31pairs of spinal nerves that leavesthevertebral
canal (formed by 33vertebrae) by passingthrough the
intervertebral foramina. Theyare named and grouped according
to the vertebrae withwhich they are associated:
• pairs of CranialNerves.
8cervical
12thoracic
5lumbar
5sacral
1coccygeal
10. Neuron
• Neuronsaremade up of the followingparts:
– Thenucleus(which contains the geneticorganelles)
– Thesoma (or cellbody)
– Dendrites (branch-like structures which receive
information from other neurons)
– Axons (long tubular pathways which send information to
other parts of thebrain)
– An (axonal) presynaptic terminal. The presynaptic terminal
connects to other neurons via synapses. Many axons are
surrounded by myelin, which help axons quickly send signals
over longdistances.
12. Coveringof neuron:
Each nerve consists of bundles of nerve fibers each
of which is covered with fine connective tissues,
which is;
1. Endo neurium: is a layer of delicate connective
tissue around the myelin sheath (i.e. protective
covering) of eachmyelinated nerve fiber.
2. Peri neurium: Nerve fibers are bundled
together into groups known as fascicles, each
surrounded by a protective sheath known as the
perineurium.
3. Epi neurium: is the outermost layer of dense
irregular connective tissue surrounding a
peripheralnerve.
13.
14. Basic types of neurons
Neuronsare divided on the basisofstructures and
size.
Thereare 3different types ofneurons:
Multipolar neurons: one axon,many
dendrites
Bipolar neurons: one axon,onedendrite
Pseudo unipolar neurons: Oneprocessthat
branches in two.
15.
16. 1.MULTIPOLAR NEURONS.
• Theseneurons contain anumber of dendrites and
one axon.They are the most common type
of neurons and they canbe found more orless
anywhere in the nervoussystem.
For example:
• Pyramidal neurons in the cerebralcortex
• Purkinjeneurons in the cerebellum
• Motor neurons in the anterior horn of the spinal
cord
17. 2.BIPOLAR NEURONS
• Bipolar neurons have only two process that connect
to the cell body: one dendrite and one axon. (This is
easy to remember as, generally speaking, the prefix
“bi” refers tothe number two)
• Bipolar neurons are only found in specific areasof
the nervoussystem:
• In the retina
• In the nose (receptors of the olfactoryepithelium)
18. 3.PSEUDO UNIPOLAR NEURONS
• There is only one process (this gives usthe “unipolar
part”) that branches into two (which is why we add
“pseudo” at the beginning… It doesn’t look
unipolar). Thisprocess is structurally similar to that
of an axon, but it can receive informationaswell.
• Pseudounipolar neurons canbe found in the
spinal ganglions.
19. MINIMUM POINTSTOREMEMBER:
• Neuronsare the typeof cells. Theyare made
of:
• Acell body-called the soma
• Dendrites that receiveinformation
• Anaxonthat transmits informationto
another cell.
• Neuronsare polarized in that theinformation can
only travel in one direction: dendrite to axon.
20. Synapsis:
There are 3 types of
synaptic connections
between 2neurons:
a) Axodendritic
b) Axosomatic
c) Axoaxonic
21. Function:
• The primary role of nerve is to transmit information
from the anterior horn cells (i.e. one type of nerve cell)
to muscles for motor system (Efferent Pathway) &
from the sensory receptors to the spinal cord or CNS
for the sensorysystem(AfferentPathway)
• Although functionally nerves may seem similar to
electrical wires, there are vast differences between
them.
• At the molecular level, a complex set of chemical and
electrical events allows nerve to propagate an
electrical signal.
22. Branches:
• Immediately after emerging from the
intervertebral foramina spinal nerves divide into
branches:posterior ramus and anteriorramus.
• Posterior ramus supply skin and muscles of back
and anterior ramus (branch of a bone, in
particular those of the jawbone) forms the
plexus.
• There are five large plexusesof mixed nerves formed on
eachsideof the vertebralcolumn:
1. Cervical
2. Brachial
3. Lumbar
4. Sacral
5. Coccygeal
23.
24.
25.
26.
27.
28. Cranialnerves:
• Cranialnervesare the nervesthat emergedirectly from
the brain (including the brainstem), incontrast to spinal
nerves(which emergefrom segmentsof the spinal cord).
10of 12of the cranial nerves originate in the brainstem.
Cranialnervesrelay information between the brain and
parts of thebody, primarily to and from regionsofthe
headand neck.
• Theterminal nerves,olfactory nerves(I) and optic
nerves(II) emergefrom the cerebrum orforebrain, and
the remaining ten pairs arise from the brainstem,
which isthe lower part of the brain.
32. Autonomic Nervoussystem:
• The autonomic or involuntary part of the nervous
system controls the autonomic function of the
body. i.e. initiated below the level of the
cerebrum. The effect of autonomic activity are
rapid and the effectors organsare:
• Smooth muscles ( change in airway or blood
vesseldiameter)
• cardiacmuscle(changesin heartrate)
• Glands(increaseor decreasesecretion)
33. TheAutonomic NervousSystem:
• Regulateactivity of smooth muscle,cardiac
muscle& certainglands
• Structures involved
1. general visceralafferentneurons
2. general visceralefferent neurons
3. integration center within thebrain
• Receivesinput from limbic systemandother
regions of thecerebrum.
34. Autonomic versusSomaticNS
• Somatic nervoussystem
– consciously perceived sensations
– excitation of skeletalmuscle
– one neuron connects CNSto organ
• Autonomic nervoussystem
– unconsciouslyperceived visceral sensations
– involuntary inhibition or excitation of smooth
muscle, cardiacmuscle or glandularsecretion
– two neurons needed to connect CNStoorgan
• preganglionicand postganglionicneurons
36. 44
BasicAnatomy of ANS
• Preganglionicneuron
– cell body in brain or spinalcord
– axonismyelinated type Bfiber that extendsto autonomicganglion
• Postganglionicneuron
– cell body lies outside the CNSin an autonomic
ganglion
– axon is unmyelinated type Cfiber that terminates
inavisceral effector
37. Sympathetic NervousSystem:
• Thesympathetic nervous system
originates in the spinal cord and itsmain
function is to activate the physiological
changesthat occur during the fight or
flight response.
• This component of the autonomic nervous
system utilizes and activates the release of
norepinephrinein thereaction.
38. Parasympathetic NervousSystem:
• The parasympathetic nervous system
originates in the spinal cord and medullaand
works with the sympathetic nervoussystem.
• Its main function is to activate the "rest and
digest" responseand return thebody
to homeostasis after the fight or flight
response.
• Thissystemutilizes and activates the releaseof
the neurotransmitteracetylcholine.
