Download AUTONOMIC NERVOUS SYSTEM

AUTONOMIC
NERVOUS
SYSTEM
• Parasympathetic Nervous System
• Sympathetic Nervous system
• Enteric Nervous System
DEFINITIONS
• Somatic nervous system= CNS and
PNS neurons involved in sensory info
and voluntary actions, innervate skin
and muscles
• Visceral NS = Neurons in CNS and PNS
that control of glands and muscles in
the autonomic nervous system such as
smooth muscle around blood vessels.
• Proceeds without conscious intention
but can be influenced by volition.
DEFINITIONS
• Autonomic Nervous System=
autonomic nerves and ganglia in the
PNS that control internal organs such
as heart, kidney (viscera)
• These organs also regulated by the
neuroendocrine system located in the
brain
FUNCTION OF ANS
• Organs are innervated by both
sympathetic and parasympathetic
fibers
• generally antagonize each other
to maintain homeostasis and
respond to sensory and emotional
information
FUNCTION
SYMPATHETIC NS
innervate all organs, skin and arteries
always active, under influence of
hypothalamus to maintain homeostasis
readies body for action. increases heart
rate blood pressure, blood to muscles
away from viscera.
FUNCTION
PARASYMPATHETIC NS
• innervate all organs except liver, skin
and arteries
• always active to maintain homeostasis
• causes relaxation and inhibits activity
of innervated end organ
• Except increases digestion and few
other activities
• blood pressure & heart rate decreases,
blood flow directed from muscle to
viscera
DEFINITIONS
• Preganglionic neurons and fibers
synapse on postganglionic autonomic
neurons
• Postganglionic neurons and fibers
synapse on end organ, gland, smooth
muscle
• Sensory neurons ends in a specialized
receptor or naked ending located in
target
• Motor neurons synapse directly on
muscle or glands
Autonomic NS Terms
• autonomic neurons are
preganglionic neuron with
preganglionic axons that synapse
on autonomic postganglionic
neurons and then the
postganglionic axon synapses on
organ, gland, smooth muscle,
cardiac muscle cell.
SYMPATHETIC NS
• Fear: neurons in hypothalamus
and brain stem activate adrenal
glands that secrete adrenalin aka
epinephrine
• postganglionic fibers use
norepinephrine as
neurotransmitter
ANATOMY Of
SYMPATHETIC NS::
• short preganglionic fibers and long
postganglionic fibers
• ganglia lie close to spinal cord in the
paravertebral chain aka sympathetic
chain
• some ganglia lie in body cavity such as
superior cervical, celiac and
mesenteric
SYMPATHETIC NS
• preganglionic neurons are found in
lateral horns of thoracic and lumbar
spinal cord levels only
• fibers always leave the spinal cord
through the
white communicating
ramus
• Fibers have 3 different directions to
travel
FUNCTION
PARASYMPATHETIC NS
• innervate all organs except liver, skin
and arteries
• always active to maintain homeostasis
• causes relaxation and inhibits activity
of innervated end organ
• Except increases digestion and few
other activities
• blood pressure & heart rate decreases,
blood flow directed from muscle to
viscera
ANATOMY
• preganglionic fibers arise from
brain stem and travel in cranial
nerves 3 oculomotor, 7 facial, 9
glossopharyngeal, 10 vagus
• Also arise from sacral spinal cord
and travel in spinal nerves S2-S4
PARASYMPATHETIC
ANATOMY
• preganglionic fibers synapse in
ganglia close to or in the
innervated organ
• Possess a long preganglionic
fiber
and
a
short
postganglionic fiber
PARASYMPATHETIC
ANATOMY
• preganglionic fiber travels in spinal nerve
• Do not connect with paraverterbral ganglion
chain so do not travel in white or grey
communicating rami
• terminate in parasympathetic
located close to target organ
ganglion
• postganglionic fibers use acetylcholine as
neurotransmitter
AUTONOMIC BRAIN
• Hypothathalums
(homeostatic
regulatory center) regulates brain
stem (pons, medulla) that influence
autonomic nervous system
• Hypothalamus connected to the limbic
center so emotions influence hypo to
influences autonomic NS
Enteric NS FUNCTION::
•
•
•
•
controls digestion and elimination
regulates intestinal peristalsis
regulates blood flow through gut
regulates secretions from intestinal
glands
• functions autonomously using sensory
information in a closed loop and is
modulated by para and symp input
Enteric NS ANATOMY
• 100 million neurons as many as the
spinal cord (50 billion in brain)
• Network of two sets of ganglia and
nerves in the gut.
– Myenteric plexus with ganglia and nerves
lying in between longitudinal and circular
muscle layers
– Submucosal plexus with ganglia and
nerves in the submucosa
• Receive input from para, sym and
sensory neurons