Peripheral
Nervous System
Four Basic Types of Tissues in
the Body
----------------------------------------------Epithelium (90% of tumors)
Muscular Tissue
Connective Tissue
Nervous Tissue
Objectives
Overview of the central and characteristics of the
peripheral nervous system
Characteristics of neurons and support cells
Organization of peripheral nerves
Nerve is
like
Epithelium
Origin of nerve is
ectoderm
like epidermis
(epithelium) of skin
Nervous Tissue
Functions: specialized for
the transmission, reception,
and integration of
electrical impulses
Distinguishing features:
Neurons – very large excitable cells with long
processes called axons and dendrites. The
axons make contact with other neurons or
muscle cells at a specialization called a
synapse where the impulses are either
electrically or chemically transmitted to
other neurons or various target cells (e.g.,
muscle). Others secrete hormones.
Nervous tissue
Glial cells – the supporting cells of nervous
tissue.
Nerves – collections of neuronal processes
bound together by connective tissue. Axons
may be coated by a myelin sheath
(“myelinated”) or simply protected by being
cradled in an indentation of a glial cell
(“unmyelinated”).
Nervous tissue
Distribution: comprise the
central nervous system.
Individual peripheral nerves
are found throughout the
body. Individual neurons
and clusters of neurons
(called ganglia) are found in
most organs.
Function of the Nervous System is
Communication
Dependent upon
special signaling
properties of neurons
Long processes of neurons
(e.g., 1 meter
motor neuraxon)
Function of the Nervous System is
Communication
Characteristics of neurons
Irritability - protoplasm capable to
react to various physical and
chemical agents
Conductivity - ability to transmit
the resulting excitation from
one locality to another
Types of Nerves
The Nervous System
Central nervous system (CNS)
– Brain and spinal cord
– Neurons and support neuroglia
The Nervous System
Peripheral nervous system (PNS)
All nervous tissue (neurons, support cells, and axons)
outside the brain and spinal cord
Activity of the Nervous System
Information
• Receive: receptors afferent pathway
• Process: CNS (centralization is
paramount)
• Transmit: efferent pathways  effect
Voluntary (conscious ) = somatic
Involuntary = autonomic
• Sympathetic - fight or flight
• Parasympathetic - vegetative
Cells and Functions of the
Nervous System
CNS
PNS
Function
astrocytes (BBB)
satellite cells
ion exchange
oligodendrocytes
Schwann cells
myelin
production
microglia
---
phagocytosis
Astrocytes
Microglia
Oligodendrocytes
Schwann cells - Myelin
Cells of the Nervous System
Neuronal Structure / Function
Structure
•
•
•
•
Perikaryon (soma, cell body)
Axon hillock - site of beginning of axon
Dendrites - reception
Axon (nerve) - transmission
Neuronal Structure / Function
Neuronal
Structure
/ Function
• http://www.youtube.com/watch?v=XgIaAs
_ONG4
Neuronal Structure / Function
NEURONAL STRUCTURE / FUNCTION
Axonal transport
Anterograde - toward terminal - kinesin
Retrograde - toward cell body - dynein
• Tetanus toxin
• Neurotropic viruses (herpes and rabies) use path to get to cell
body in CNS
Neuronal Structure / Function
Neuronal Structure/Function
Function of Myelin
Increase speed of condition
– 1 meter/sec TO 120 meters/sec
High-resistance low capacitance
– Insulator
Protection of axon
Possible nutritional role
Direct regenerating axons
Schwann Cell
Structure /
Function
Most peripheral nerves are
myelinated
1 Schwann cell/1 axon for
location
Formation of myelin sheath
• Nodes of Ranvier
• Schmidt-Lantermann clefts
• Neurokeratin network
Schwann Cell Structure / Function
Node of Ranvier
Node of Ranvier
Myelination and
Schwann Cells

http://www.youtube.com/watch?v=ifD1YG
07fB8&feature=related
Organization of Peripheral
Nerves
Ganglia - collections of nerve cell bodies
Smooth muscle
Smooth muscle
Remember Connective Tissue
Layers of Skeletal Muscle
Epimysium, Perimysium, and Endomysium
Organization of Peripheral Nerves
Nerve fibers - axons invested by connective tissue
Epineurum - surrounding entire nerve
Perineurum - surrounding fascicles –
constitutes the PNS blood barrier via tight
junctions between fibroblasts
Endoneurum - between individual nerve axons
Organization of Peripheral Nerves
PERINEURUM
Organization of Peripheral Nerves
PERINEURUM
Autonomic Nervous System
Sympathetic
- Fight or Flight
Parasympathetic
- Vegetative
Nerve Endings – Synapses
(Efferent Pathways)
Types
– Electrical: gap junctions, slow ion exchange
between cells, not common in mammals
– Chemical: rapid plus or negative response
Characteristics
– Synaptic vesicles (neurotransmitters)
– Synaptic cleft
Motor End Plate
Nerve Endings - Synapses
Motor
End Plate
Nerve Endings – Synapses
Pathways)
(Efferent
Nerve Endings –
Synapses
Nerve Endings - Synapses
Nerve Endings - Synapses
Nerve Endings - Synapses
Neuroactive Substance
Neurotransmitters - Acetylcholine
Neuromodulators - Receptor Coupled and
Second Messenger
Neurohormone - Serotonin, GABA slow
but widespread effect
Innervation of Muscle
Neurotransmitter Vesicles
Physiological Events at the
Synapse
Arrival of Action Potential
Opening of
Voltage-Gated ion
channels for Ca++ to
enter terminal
Influx of Ca++
Physiological Events at the
Synapse
Influx of Ca++ triggers
exocytosis of
neurotransmitters from
docked vesicles
Transmitter diffuses
across synaptic cleft
Physiological Events at the
Synapse
Transmitter binds to
receptors on postsynaptic membrane
Receptor binding causes
ion channels to open to
Na+ and causes
depolarization
Physiological Events at the
Synapse
Depolarization (equal Na+
inside and outside)
Depolarization –
Stimulation
Hyperpolarization –
Inhibition
Removal of transmitter
Summary of the Physiological Events at
the Synapse
• Arrival of action potential
at axon terminal
• Opening Ca++ channels
• Influx of Ca++ into axon
terminal
• Exocytosis of neurotransmitter
• Diffusion of neurotransmitter across synaptic cleft
• Binding of neurotransmitter to receptors on target cell
• Opening of Na+ channels causing depolarization of target
cell
• Removal of neurotransmitter
Vesicle Membrane is Recycled
Cycling of the Membrane
Cycling of the Membrane
Cycling of the Membrane
Nerve Endings - Synapses
Types of Synapses
Anodendritic Synapses

http://www.youtube.com/watch?v=70DyJ
wwFnkU&NR=1
Nerve Endings - Receptors
Receptors (Afferent Pathways)
• Neuromuscular Spindles
• Pacinian Corpuscles
• Meissner’s Corpuscles
Nerve Endings - Receptors
Receptors (Afferent Pathways)
Neuromuscular Spindles
Nerve Endings - Receptors
Pacinian Corpuscles
Nerve Endings - Receptors
Meissner’s Corpuscles
Nerve Endings - Receptors
Meissner’s Corpuscles
and other important corpuscles
Inner Ear
OLFACTORY
Summary
Nerve Endings - Receptors
Nerve Endings - Synapses
(Efferent Pathways) Summary
Regeneration of Axons