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Peripheral Nervous System - Coggle Diagram
Peripheral Nervous System
How it is structured:
Nerves + ganglia outside of the brain and spinal cord
connecting the CNS to limbs and organs
Not protected by the bone of the spine, skull or BBB, leaving it exposed to
toxins
or
mechanical injuries
Divided into:
Somatic
Autonomic
SoNS
Functions
Responsible for
voluntary movements
controlled by
skeletal muscles
Responsible for
reflexes
through the
reflex arc
Neural pathway controlling an
immediate response to a particular stimulus
(
reflex
). It connects two fibers, one sensory, and one motor,
without the involvement of the CNS
. Since the CNS is not involved, the response can be
much quicker
Pain perception
Involves unmyelinated C fibers
and thinly myelinated Aδ fibers, which differ in terms of strength and speed of signal transmission
Can be influenced by
Genetic alterations
Alcohol abuse
Pain can be controlled through
Anesthesia
Epidural anesthesia
Involve
cocaine analogs
which have a
high affinity for Na+ channels
and block them, therefore
preventing depolarization by blocking Na+ influx
Targets pain fibers located in the outer layers of spinal cord, in the epidural space
Adverse effects
CNS
: depression of activity
CVS
: contractile force decreases, hypotension, risk of cardiovascular collapse
To limit the side effects on the CVS that could derive from injecting anesthetic agents in the BV rather than the epidural space, adrenergic agents (
epinephrine
) are injected beforehand: if tachycardia is observed, it means that molecules are being injected in the BV
Allergic reactions
to the administered compounds
Systemic toxicity
: vomiting, hyperventilation, fainting
Administered
locally
to avoid adverse effects
Opioids
Disadvantages:
addiction potential
+
inhibition of IS
Recently, a non-opioid treatment for moderate to severe pain was approved (SUZ)
How it works
Composed of
afferent
(
sensory
) and
efferent
(
motor
) nerves
A stimulus is perceived through
sensory receptors
Sensory fibers
transmit information via
dorsal root ganglia
toward the
spinal cord
Through the spinal cord, the signal reaches the
CNS
, where it is integrated and processed
Motor signals exit via
ventral roots
of spinal cord
Signal transmission to the
effector muscles
via motor fibers
ANS
Autonomic
/
visceral
/
involuntary
Functions
Controls body functions below the level of consciousness (hearth rate, digestion, respiration...)
Controls all the innervated structures, with the exception of skeletal muscles
(controlled by SNS)
Can work together with the SoNS (ex. breathing)
Divided into:
SNS
Functions
Controls the "
fight or flight
" response
Innervate
sweat glands
,
pilomotor muscle
,
BV
,
visceral organs
Nt
post-ganglionic:
norepinephrine
post-ganglionic in the
adrenal medulla
:
epinephrine
+
norepinephrine
pre-ganglionic:
Ach
It includes the
adrenal medulla
, considered a modified ganglion of the SNS
Releases
epinephrine
+
norepinephrine
directly into the
bloodstream
It directly connects the SNS with the
systemic circulation
Adrenergic receptors of the SNS
ENS
Functions
Control of
peristalsis
(motor neurons)
Perception of
mechanical and chemical conditions
in the
GI tract
(sensory neurons)
Secretion of
digestive enzymes
Can also operate
independently
from the CNS
Nt
5-HT
+
DA
The functions of the CNS and gut are strongly interconnected via the
gut-brain axis
. The
gut microbiota
plays a role in modulating the functions and health of both organs
NDD
inflammation
and
dysbiosis
as the
initial step
of a process leading to
PD
PSNS