Transcript General Anatomy of the Autonomic Nervous System

General Anatomy of the
Autonomic Nervous System
Human Anatomy 5th ed. 2005
Benjamin Cummings
Introduction to ANS
• Regulates activity of smooth muscle,
cardiac muscle and glands
• Operates without conscious control
• Named autonomic because was thought to
be AUTONOMUS (working without CNS)
Human Anatomy 5th ed. 2005
Benjamin Cummings
Autonomic Nervous System
• But to operate it depends on continuous
flow of sensory input from:
– Visceral organs and
– Blood vessels(not consciously perceived) into
– INTEGRATING CENTERS IN THE CNS.
Human Anatomy 5th ed. 2005
Benjamin Cummings
Autonomic Nervous System
• Structurally then ANS includes:
– Autonomic sensory neurons
– Integrating centers in the CNS
– Autonomic motor neurons to smooth
muscle, cardiac muscle and glands
Where in the CNS? Hypothalamus and brain
stem
Human Anatomy 5th ed. 2005
Benjamin Cummings
Comparing the ANS and Somatic NS
• Structurally then SNS includes:
– Somatic sensory neurons
– Integrating centers in the CNS (Cortex)
– Somatic motor neuron to skeletal muscles
only
Human Anatomy 5th ed. 2005
Benjamin Cummings
Comparing the ANS and Somatic NS
• Somatic- the effect of a motor neuron is
always excitation
• Autonomic- the effect of a motor neuron is
either excitatory or inhibitory
Human Anatomy 5th ed. 2005
Benjamin Cummings
Autonomic Nervous System
• Makes all routine adjustments in
physiological systems.
• The ANS pathway from the CNS to the
effector always involves 2 neurons
synapsing in an autonomic ganglion
Human Anatomy 5th ed. 2005
Benjamin Cummings
ANS
– Preganglionic (neuron #1) – cell body is
in the CNS, axon extends to the ganglion
outside the CNS
– Postganglionic (neuron #2) – cell body is
in the ganglion, axon extends to the
visceral effector
Human Anatomy 5th ed. 2005
Benjamin Cummings
Nerve Fibers of the ANS
• Preganglionic (neuron #1)
– Always myelinated
– Neurotransmitter is always ACh
• Postganglionic (neuron #2)
– Always nonmyelinated
– Neurotransmitter is Ach or
norepinephrine
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
Subdivisions of the ANS
• Sympathetic Division
– Fight-or-flight
• Parasympathetic Division
– Rest-and-digest
• These divisions are anatomically distinct
Human Anatomy 5th ed. 2005
Benjamin Cummings
Sympathetic
• Sympathetic division (thoracolumbar)
– Cell bodies for all the neurons #1 reside
in the thoracic and lumbar portions of the
spinal cord.
• T1 – L2
Human Anatomy 5th ed. 2005
Benjamin Cummings
Sympathetic
– Stimulates
• heart beat
• tissue metabolism,
• increases alertness,
• prepares the body to deal with
emergencies
• (“fight or flight” division)
Human Anatomy 5th ed. 2005
Benjamin Cummings
T1-L2
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic
•Parasympathetic division (craniosacral)
–Cell bodies reside in the brain stem (cranial
nerves) or in the sacral portion of the spinal
cord.
Human Anatomy 5th ed. 2005
Benjamin Cummings
Cranial & Sacral
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic
– Slows the heart rate,
– inhibits senses,
– prepares the body for rest and relaxation;
(“rest and digest” division).
Human Anatomy 5th ed. 2005
Benjamin Cummings
The Sympathetic Division
Human Anatomy 5th ed. 2005
Benjamin Cummings
Sympathetic Chain Ganglia
– Synapses of neurons #1 and #2 are in a
chain of ganglia that run alongside the
spinal cord
– Extends on both sides of the vertebral
column
– Carries preganglionic fibers and cell
bodies of postganglionic neurons
Human Anatomy 5th ed. 2005
Benjamin Cummings
Ganglia
Human Anatomy 5th ed. 2005
Benjamin Cummings
Anatomy of the chain
• Rami communicantes from the spinal
nerves connect to the chain
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
A closer look at spinal nerves
Human Anatomy 5th ed. 2005
Benjamin Cummings
Routes of Preganglionic Axons
• Cell bodies of neurons #1 lie in the lateral
gray horns of the spinal cord
• The axons of neurons #1 leave the spinal
cord via the ventral root
• These axons pass to the spinal nerve
• Axons leave the spinal nerve via the white
branches (rami communicantes)
• Connect with the sympathetic chain ganglia
Human Anatomy 5th ed. 2005
Benjamin Cummings
Routes of Preganglionic Axons
• There are 3 possible routes that sympathetic
neurons may follow
• Possibility #1: synapses within the
ganglion at that level and
– Second neuron leaves at that level via the
gray ramus communicans, exits to the
visceral effector
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
Routes of Preganglionic Axons
• Possibility #2: neuron #1 goes up or down
the chain and synapses at some other level.
– Second neuron: leaves at that other level
via the gray ramus communicantes, and
exits to the visceral effector.
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
Routes of Preganglionic Axons
• Possibility #3: neuron #1 does not synapse
in the chain (exception!!) but exits and
synapses in a collateral ganglion near a
major blood vessel.
– Neuron #2 travels from that ganglion to
the visceral effector.
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
Where are the Collateral Ganglia ?
• Location –Near a major blood vessel
– Celiac ganglion
• Innervates upper abdominal viscera
– Superior mesenteric
• Innervates middle abdominal viscera
– Inferior mesenteric
• Innervates lower abdominal & pelvic organs
Human Anatomy 5th ed. 2005
Benjamin Cummings
The Adrenal Medulla
• Yet another type of innervation:
– Going to the adrenal medulla
– No synapse in ganglia
– No synapse in collateral ganglia
– YES synapse in the adrenal medulla
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
Adrenal Medulla
• Only preganglionic neurons are in this
pathway
• Neuron #1 stimulates the medulla,
• The medulla releases norepinephrine and
epinephrine (adrenaline) to blood
Human Anatomy 5th ed. 2005
Benjamin Cummings
Adrenal Medulla
Figure 17-06
Human Anatomy 5th ed. 2005
Benjamin Cummings
Effects of Sympathetic Stimulation
• Widespread
– The sympathetic chain allows one
preganglionic fiber to synapse with many
postganglionic neurons
• Enhanced & prolonged by the adrenal
medulla
Human Anatomy 5th ed. 2005
Benjamin Cummings
Convergence
• See heart
Human Anatomy 5th ed. 2005
Benjamin Cummings
Neurotransmitters of Sympathetic
Division
• Preganglionic fibers release acetylcholine
(Ach) Therefore they are called:
– Cholinergic
• Postganglionic fibers (most) release
norepinephrine (NE) (=noradrenaline)
– Adrenergic
• Adrenal medulla releases norepinephrine
and epinephrine (adrenalin)
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
Functions of the
Sympathetic Division
•
•
•
•
•
•
Heart: increases rate
Lung bronchioles: dilates bronchioles
Salivary glands: produce viscous fluid
Stomach: decreases motility
Pupil: dilates
Sweat glands: produce secretions
Human Anatomy 5th ed. 2005
Benjamin Cummings
Summary of Sympathetic Division
• Cell bodies are found in the thoracic and
lumbar portions of the spinal cord
• Preganglionic fibers are short, connect to
the sympathetic chain, and synapse with
long postganglionic fibers
• Preganglionic fibers produce ACh,
postganglionic fibers produce NE or Ach
• “Fight or flight” division
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
The Parasympathetic Division
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic division
• Cell bodies are in the brain or in the gray
matter of the spinal cord (sacral region)
• Neurons #1 exit the cranial region through
cranial nerves 3, 7, 9, & 10 or
• Neurons #1 exit the spinal cord through the
sacral spinal nerves
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic
Figure 17-02b
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic
• Neurons #1 are long and synapse with
neurons #2 (short) in ganglia
• Ganglia are found on, or
– near the visceral effector
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic ganglia
Figure 17-09
Human Anatomy 5th ed. 2005
Benjamin Cummings
Neurotransmitter of Parasympathetic
Division
• Preganglionic fibers: Acetylcholine
• Postganglionic fibers: Acetylcholine
Human Anatomy 5th ed. 2005
Benjamin Cummings
Human Anatomy 5th ed. 2005
Benjamin Cummings
General Functions of the
Parasympathetic
• Prepares the individual for rest and repose
• “Rest & digest” division
Human Anatomy 5th ed. 2005
Benjamin Cummings
Effects on various organs:
•
•
•
•
•
Heart: decreases rate
Lung bronchioles: constricts
bronchioles
Salivary glands: produces watery fluid
fluid
Stomach: increases motility
Pupil: constricts
Sweat glands: reduces secretions
Human Anatomy 5th ed. 2005
Benjamin Cummings
Summary of the Parasympathetic
Division
• Cell bodies are found in the brain and in the
sacral region of the spinal cord
• Preganglionic fibers are long and synapse
with short postganglionic fibers on or near
the target viscera
• Both preganglionic and postganglionic
fibers produce Ach
• “Rest & digest” division
Human Anatomy 5th ed. 2005
Benjamin Cummings
Relationship Between the Sympathetic and
Parasympathetic Divisions
• Most organs receive dual innervation
• It is a tug of war between the two
Human Anatomy 5th ed. 2005
Benjamin Cummings
ANS either increases excitation or
inhibits the activity
– Ex. Sympathetic fibers increase heart
rate, parasympathetic fibers decrease
heart rate.
– Homeostasis comes from the balance of
the two.
Human Anatomy 5th ed. 2005
Benjamin Cummings
ANS either increases excitation or
inhibits the activity
Ex.#2 Sympathetic fibers decreases stomach
motility.
Parasympathetic fibers increase stomach
motitlity
Human Anatomy 5th ed. 2005
Benjamin Cummings
Parasympathetic innervation
• The cranial nerve fibers involved are motor control smooth muscle & glands in the upper body
– Cranial nerve #3 – lens & pupil
– Cranial nerve #7 – lacrimal glands,
submandibular & submaxillary glands
(salivary)
– Cranial nerve #9 – parotid gland (salivary)
– Cranial nerve #10 - viscera of thorax &
abdomen
• Sacral nerves innervate the kidneys, colon, & sex
Human Anatomy 5th ed. 2005
organs
Benjamin Cummings