Transcript Autonomic nervous system

The State Medical and Pharmaceutical University “Nicolae Testemitanu”
Republic of Moldova
Department of
Human
Anatomy
The Anatomy of the
Autonomic Nervous
System
Lecturer Globa Lilian
Divisions of the NS
• CNS Central Nervous
System
–Brain & spinal cord
Divisions of the NS
• PNS Peripheral Nervous
System
–Cranial nerves 12 pairs
–Spinal nerves 31 pairs
–Ganglia (sensitive and
autonomic)
–Nervous plexus
Cranial and Spinal Nerves
Somatic System
• Somatic system includes nerves that
take sensory information from
external sensory receptors to the
CNS and motor commands away
from the CNS to the skeletal
muscles.
– Primarily voluntary
– Reflexes are automatic, involuntary
responses to a stimulus.
Autonomic System
• Autonomic system regulates the
activity of cardiac and smooth
muscles and glands.
• Is involuntary
• 2 component parts:
– Sympathetic division brings about “fight
or flight” responses. (norepinephrine)
– Parasympathetic division brings about
relaxed responses or “housekeeper
system” (acetycholine)
The autonomic divisions
• Parasympathetic
• Sympathetic
• slow down the body
activity when the body
is not under stress
• increase overall body
activity during times of
stress, excitement or
danger
• fight or flight response
• Rest and digest
• hormone epinephrine
Sympathetic and
Parasympathetic
• Are Antagonistic
• Work towards the automatic,
subconscious maintenance of
homeostasis.
• The Peripheral Nervous System
– The autonomic nervous system
– Somatic nervous system
• The part of the peripheral nervous system
that controls the movement of skeletal muscles
or transmits somatosensory information to the
central nervous system.
– Autonomic nervous system
• The portion of the peripheral nervous system
that controls the body’s vegetative functions.
• The Peripheral Nervous System
– The autonomic nervous system-sympathetic
division
– Sympathetic division
• The portion of the autonomic nervous system that
controls functions that accompany arousal and
expenditure of energy.
– Sympathetic ganglia
• Nodules that contain synapses between
preganglionic and postganglionic neurons of the
sympathetic nervous system.
• The Peripheral Nervous System
– The autonomic nervous system-sympathetic
division
– Preganglionic neuron
• The efferent neuron of the autonomic nervous
system whose cell body is located in a cranial
nerve nucleus
or in the intermediate horn of the spinal gray
matter
and whose terminal buttons synapse upon
postganglionic neurons in the autonomic nervous
system.
Postganglionic neuron
• Neurons of the autonomic nervous system that
form synapses directly with their target organ.
• The Peripheral Nervous System
– The autonomic nervous system-sympathetic
division
– Adrenal medulla
• The inner portion of the adrenal gland, located
atop the kidney, controlled by sympathetic nerve
fibers; secretes epinephrine and norepinephrine.
• The Peripheral Nervous System
– The autonomic nervous systemparasympathetic division
– Parasympathetic division
• The portion of the autonomic nervous system that
controls functions that occur during a relaxed
state.
• Supports activities involved with increases in the
body’s supply of stored energy including
salivation, gastric and intestinal motility, secretion
of digestive juices, and increased blood flow to the
gastrointestinal system.
Autonomic nerve fibers
• Motor pathways of somatic nervous
system – SINGLE NEURON links CNS
+ skeletal muscle
• Autonomic nervous system – motor
pathway needs TWO NEURONS
– PREGANGLIONIC FIBER – has
cell body in CNS , axon synapses in
autonomic ganglion; second neuron
– POSTGANGLIONIC FIBER extends to visceral effector
Efferent fibers of ANS
• 1. Preganglionic fibers
• 2. Postganglionic fibers
1
2
Simple Nerve Path
Reflex Arc
Sympathetic division
• Thoracolumbar division C8-L2
• Preganglionic fibers in thorax &
lumbar regions; leave spinal nerves
thru white rami & enter
sympathetic ganglia
• Paravertebral ganglia – occur as
chains along sides of vertebral
column
• Ganglia + fibers that connect them =
sympathetic trunks
• Collateral ganglia - within
abdomen near large blood vessels
• Preganglionic fibers that enter
paravertebral ganglia can synapse
within ganglia , can move up or
down synaptic trunk & synapse; or
may pass thru paravertebral ganglia
& synapse in collateral ganglia
• Axons of second neuron ( postganglionic fiber) leave paravertebral
ganglia via gray rami & return to
spinal nerve before going to effector
• White rami – myelinated; gray ramiunmyelinated
• Exception –
• Preganglionic fibers pass thru
sympathetic ganglia and extend to
medulla of adrenal glands
• Stimulation causes release of
norepinephrine & epinephrine
Parasympathetic division
• Cranio-sacral division
• Neurons of brainstem & sacral region
• Preganglionic fibers – long, go to
ganglion near or within various
organs; myelin
• Postganglionic fibers – short;
unmyelinated
• Cranial region – CN III, VII, IX, X
• Sacral region – motor to viscera of
pelvic cavity s2-s4
Divisions of the ganglia
• Sympathetic Nervous System
1. Paravertebral ganglia
2. Prevertebral ganglia
• Parasympathetic Nervous System
3. Paraorganic ganglia
4. Intraorganic ganglia
Fight or Flight:
parasympathetic
and sympathetic
are the 2 divisions of
the Autonomic
nervous system;
which functions
without conscious
effort controls
visceral activities
regulates smooth
muscle, cardiac
muscle, and glands
Autonomic neurotransmitters
• Preganglionic fibers – S & P –
acetylcholine – cholinergic fibers
• Postganglionic fibers – P =
acetylcholine
• Postganglionic fibers – S –
norepinephrine = adrenergic fibers
• Exceptions post g fibers that
stimulate sweat glands &
vasodilation = ACh
Actions of autonomic
neurotransmitters
• Ach - muscarine receptors &
nicotinic receptors
• Muscarine receptors – all
postganglionic parasym. fibers &
sympathetic cholinergic fibers –
response excitatory & slow
• Nicotinic receptors – pre & post
ganglionic fibers of para & sym response rapid, excitatory
• Adrenal gland releases epi & norepi
as hormones but only norepi can be
used as neurotransmitter by SNS
• Adrenergic receptors – alpha & beta
• Alpha – causes vasoconstriction
• Beta – causes bronchiodilation
• Acetylcholinesterase – decomposes
Ach
• Norepi removed by active transport
back into nerve endings
Referred pain