PNS (Exam 2) Flashcards
T/F
Most drugs either have a direct effect on the central nervous system or a side effect on the system.
False
peripheral
T/F
Any PNS alteration in normal function could be life-threatening to the individual.
True
PNS broken down into two major components
Somatic (skeletal muscle)
Autonomic (SNS and PNS)
Somatic nervous system controls..
skeletal muscles
Somatic Skeletal
Autonomic nervous system
controls other bodily functions required for life
subdivided into:
Sympathetic nervous system
Parasympathetic nervous system
T/F
the peripheral nervous system is a subdivision of the autonomic system.
False
Peripheral NS:
Autonomic (sympathetic & parasymp)
Somatic
Somatic Nervous System
Provides CNS and reflexive control of skeletal muscles.
Gap junctions
Na ions flow between fibers here to allow stimulation
contraction of all linked fibers (motor unit)
T/F
There is a nerve for every muscle fiber.
False
That is too much work
body clumps fibers together as motor unit
one nerve innervates the unit
T/F
large muscle groups (glutes, biceps, triceps, calves) have less fibers per motor unit.
False
small muscles (fingers) = fewer muscle fibers per unit (finer control)
Nerve fibers leave spinal cord from ___.
all levels
Motor nerves synapse at ….
only at their final destination (the muscle)
the motor end plate
T/F
There are no motor unit synapses in the SC.
True
T/F
The Autonomic NS provides reflexive control of skeletal muscles
False
Somatic NS
NMB affect which part of the nervous system?
Somatic
Suxx Somatic
motor units
groups of muscle fibers
innervated by a single nerve fiber with axonal branches going to individual muscle fibers
T/F
All motor nerves are myelinated
True
Somatic NS
NT at motor end plate
receptor type
acetylcholine
nicotinic (N1 type [old term], neuromuscular nAChR)
Transmission down motor axonal link occurs how quickly
~1/10 of a second
<2/10 sec
⭐️
NACHr (nicotinic) receptor
nicotonic = ionophore
pentameric
2 Ach bind to open
Na+ influx
raises internal voltage
depolarization
Autonomic Nervous System
controls…
body homeostasis
BP, RR, Temp
internal/smooth muscles (not skeletal)
Regulates hormonal secretions
tone & motility of smooth muscles
Most tissues (except _____) are innervated by at least one branch of the ___.
skeletal muscles
Autonomic NS
serves as a positive and negative control system
Many tissues innervated (or serviced) by both branches (sympathetic and parasympathetic)
T/F
Most tissues are innervated by only one branch of the autonomic NS.
False
most are innervated by both branches of the ANS (parasymp & symp)
“override”
Blocking one system (parasymp or symp) allows other to take over
Predominant control system of the heart
Parasympathetic
Ganglion
collection of nerves that synapse
signals travel towards destination tissue
ganglia location
sympath vs parasymp
sympathetic: close to SC (paravertebral chain)
parsymp: closer to innervated tissue
some exceptions exist
sometimes ganglia can be used by both symp & parasymp
ganglionic receptors of symp & and parasymp are
nicotinic
“ganglionic nicotinic”
“nAChR”
“neuronal”
neuronal refers to
ganglionic nicotinic receptors
the preganglionic neurons of both symp & parasymp use which NT?
ACh
both cholinergic
T/F
the N2 receptor is the only receptor that can control Autonomic output and transmission to post-ganglionic fibers.
False
they are the single most important but not the only one
post-ganglionic fibers
exit ganglion and travel to tissue they innervate
Sympathetic
Post Ganglionic/end organ tissue receptor
adrenergic
(norepi)
Sympathetic
Post Ganglionic/end organ tissue NT
Norepi
Parasymp
Postganglionic fiber/end organ
cholinergic
muscarinic (primarily G-protein)
T/F
Post-ganglionic receptors of the parasympathetic nervous system are ionophores.
False
muscarinic (G-protein)
Mainly controls sedentary functions.
Parasympathetic Nervous System
Parasympathetic Nervous System
actions
Stimulates:
Digestion
peristalsis
HCL acid production
salivation
lacrimation
Miosis (smaller pupils)
T/F
Controlling the lens allows us to alter pupil diameter.
False
Use iris to control pupil diameter
mydriasis vs miosis
mydriasis: dilation
miosis: constriction
myDriasis = Dilate
ciliary muscle
controls lens; focusing
Parasympathetic control shifts the eye’s focus ____
closer
accomodation
focusing in on shorter distance
Ie: reading
Parasympathetic Nervous System
Exits spinal column from ….
cranio-sacral regions (upper and lower regions).
Synapses at ganglia close to innervated tissue.
Parasympathetic
Parasympathetic
ratio of incoming to outgoing fibers
1:1
provides fine control
Parasympathetic
NT @ pre-ganglionic (N2, neuronal nAChR) & post-ganglionic (muscarinic)
ACh
N2 receptor
Preganglionic receptor
nicotinic
“nAChR”
“neuronal”
Sympathetic
Exits spinal column from…
thoraco-lumbar regions
Synapses at ganglia (paravertebral chain) that lies close spinal cord
Sympathetic
Sympathetic NS
ratio of incoming to outgoing fibers
1:10 to 1:100
wider control
1 pre-gang fiber exits spinal column → 100 fibers exiting ganglia
(vs Parasympathetic 1:1 ratio; finer control)
Sympathetic
NT @ pre & post-ganglionic synapse
pre-ganglionic: ACh
post-ganglionic: Norepi (mostly)
T/F
Norepi is the sole post-ganglionic NT in Sympathetic nervous system.
False
Dopamine and epi are also present (catecholamines)
paravertebral chain
series of ganglia that lies close to spinal column
normal ganglia of sympathetic NS
they synapse here
Which has more precise control?
Sympathetic
Parasympathetic
Parasympathetic (1:1 ratio incoming:outgoing fibers)
(Sympathetic = 1:10 to 1:100)
“Parasym = Precise”
Adrenal Medulla
acts as a giant ganglion
pre-gang fibers can go straight here instead of paraverteb. chain
mechanism for affecting wide-ranging tissues
Adrenal Medulla vs normal ganglion
Adrenal Medulla:
NTs in cell body & its cells release NTs directly into bloodstream
-no axon stimulation
-does not use synapse
-secretes epinephrine : norepinephrine in an 80:20 ratio
(vs post-gang receptor that secretes mostly norepi)
The adrenal medulla is stimulated by…
preganglionic Ach release from Sympathetic system
Adrenal Medulla
secretion
epi : norepi
80:20 ratio
directly into bloodstream
Epi vs Norepi
Epi:
more constriction of BV
lasts longer in bloodstream
both are quickly metabolized in blood
Anticholinergics override which system?
Parasympathetic
sympathetic will take over
Primary tone of GI tract
what would an anticholinergic do?
parasympathetic
decreases GI output
