Nervous System 2b
Chapter 11
Autonomic Nervous System
• A division of the peripheral nervous
system
• Remember: the sympathetic nervous
system is associated with the “bear”
• The parasympathetic nervous system is
associated with the “book”
Sympathetic NS
Parasympathetic NS
Originates in the
Originates in the cranial
thoracolumbar egments
nerves and sacral
of the spinal cord
segments of the cord
(Thoracolumbar system)
(craniosacral system)
Synapses in ganglia near
the spinal cord
Synapses in ganglia near
the visceral effector
Synapses with neurons to
several organs
Synapses with neurons to
a single organ
Effect is widespread
Effect is local
Sympathetic NS
Fight or flight
Preganglionic fibers
release ACh
(cholinergic)
Postganglionic fibers
release norepinephrine
(adrenergic)
Receptors are 1,2,
β1, β2
Parasympathetic NS
Maintenance functions:
feed and breed
Preganglionic fibers
release ACh
Postganglionic fibers
release Acetylcholine
Receptors are nicotinic
and muscarinic
• Notice: even though it is small in the
previous slide – the adrenal gland is
innervated by the sympathetic nervous
system. When the sympathetic nervous
system is activated, it causes
norepinephrine and epinephrine to be
released from the adrenal medulla into the
blood stream. It takes about 20 minutes for
these hormones, which mimic the effects
of the sympathetic nervous system, to be
inactivated.
Cranial Nerves
• Part of the peripheral N.S.
• Twelve pairs
• Designated by Roman Numerals
I – Olfactory – sensory nerve that functions in
the sense of smell
II – Optic nerve – arises from the retina of the
eye and functions in vision
III – Oculomotor – mostly motor function –
most of the muscles of the eye, eyelid, and
pupillary constriction
• IV – Trochlear – moves the superior oblique
muscle of the eye that passes through a ring
of tissue called the trochlea
• V – Trigeminal – three branches – motorchewing; sensory – skin of the face
• VI – Abducens – lateral rectus eye muscle –
abducts the eye
• VII – Facial nerve – motor to muscles of
facial expression and secretion of saliva and
tears; sensory – taste and proprioception
• VIII –vestibulococholear – sensory –hearing
and equilibrium (balance)
• IX – Glossopharyngeal – motor- secretion of
saliva; sensory – taste, regulation of blood
pressure, and proprioception of muscles
involved in swallowing
• X – Vagus – “the wanderer” - motor- smooth
muscle contraction and relaxation, secretion of
digestive fluids; heart, lungs – parasympathetic
innervation; sensory from visceral organs it
supplies and proprioception.
• XI – Accessory nerve – motor: swallowing
and movements of the head
Sensory - proprioception
• XII – Hypoglossal – motor- movement of
tongue during speech and swallowing
sensory- proprioception
One more thing…..
• The blood supply to the brain has many
alternate pathways, or anastomoses. The
blood vessels that supply the brain, the
vertebral arteries and the internal carotid
arteries, form branches and link at the base of
the brain in a structure called the Circle of
Willis. This means that if a blood clot blocks
the flow of blood through one pathway, that
area of the brain can still be supplied through
an alternate vessel.