Lecture Outline
Adapted from Martini Human Anatomy 7th ed. / Session:
Section:
Days / Time: Instructor: / FALL
52999
MW 5:00 PM – 9:20 PM
RIDDELL
Chapter 17
The Nervous System
Authonomic Nervous System
Introduction
The autonomic nervous system functions outside of our conscious awareness
The autonomic nervous system makes routine adjustments in our body’s systems
The autonomic nervous system:
Regulates body temperature
Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions
A Comparison of the Somatic and Autonomic Nervous Systems
Autonomic nervous system
Axons innervate the visceral organs
Has afferent and efferent neurons
Afferent pathways originate in the visceral receptors
Somatic nervous system
Axons innervate the skeletal muscles
Has afferent and efferent neurons
Afferent pathways originate in the skeletal muscles
Subdivisions of the ANS
The autonomic nervous system consists of two major subdivisions
Sympathetic division
Also called the thoracolumbar division
Known as the “fight or flight” system
Parasympathetic division
Also called the craniosacral division
Known as the “rest and repose” system
Subdivisions of the ANS
Sympathetic division
Thoracic and upper lumbar nerves synapse in ganglia near the spinal cord
Sympathetic activation results in:
Increased metabolism and alertness
Parasympathetic division
Synapses are located near the target organ
Parasympathetic activation results in:
Energy conservation
Subdivisions of the ANS
Sympathetic division
All preganglionic fibers release acetylcholine. The effects are stimulatory.
Most postganglionic fibers release norepinephrine.The effects are stimulatory.
Parasympathetic division
All preganglionic fibers release acetylcholine. The effects are stimulatory.
Postganglionic fibers release acetylcholine but the effects can be inhibitory.
The Sympathetic Division
Sympathetic division consists of:
Preganglionic neurons between T1 and L2
Two types of ganglionic neurons near the vertebral columns: sympathetic chain ganglia (lateral to the vertebral column) and collateral ganglia (anterior to the vertebral column)
Specialized neurons in the interior of the suprarenal gland
The Sympathetic Division
Sympathetic division
Preganglionic neurons
Cell bodies are in the lateral gray horns
Axons enter the ventral roots
Sympathetic chain ganglia (paravertebral ganglia)
Control effectors in the body wall, head, neck, limbs, and thoracic cavity
The Sympathetic Division
Sympathetic division
Collateral ganglia (prevertebral ganglia)
Neurons innervate effectors in the abdominopelvic cavity
Specialized neurons
Modified sympathetic ganglion in the suprarenal gland
Neurons release neurotransmitters that act like hormones
The Sympathetic Division
Sympathetic Chain Ganglia
The ventral root joins a dorsal root
Forms a spinal nerve
Passes through an intervertebral foramen
White ramus branches off the spinal nerve
Goes to a nearby sympathetic chain ganglion
The Sympathetic Division
Functions of Sympathetic Chain Ganglia
Reduction of circulation to the skin
More circulation to skeletal muscles
Stimulates more energy production by skeletal muscles
Releases stored adipose
Stimulation of arrector pili muscles
Dilation of pupils
Increased heart rate
Dilation of respiratory tubes
The Sympathetic Division
Anatomy of the Sympathetic Chain Ganglia
Each spinal nerve consists of:
Preganglionic and postganglionic fibers
There are:
cervical sympathetic chain ganglia
thoracic sympathetic chain ganglia
lumbar sympathetic chain ganglia
sacral sympathetic chain ganglia
coccygeal sympathetic chain ganglia
The Sympathetic Division
Collateral Ganglia
Preganglionic neurons originate in the inferior thoracic and superior lumbar areas of the spinal cord
Fibers pass through the sympathetic chain ganglia without synapsing
Converge to form the greater, lesser, and lumbar splanchnic nerves
Splanchnic nerves converge on the collateral ganglia
The Sympathetic Division
Functions of the Collateral Ganglia
Reduction of flow of blood to the visceral organs
Decrease in activity of the digestive organs
Stimulation of the release of glucose from glycogen in the liver
Stimulates adipose cells to release energy reserves
Relaxation of smooth muscles in the urinary bladder
Cause ejaculation in males
The Sympathetic Division
Anatomy of the Collateral Ganglia
Splanchnic nerves innervate:
Celiac ganglion: fibers innervate the stomach, duodenum, liver, gallbladder, pancreas, spleen, and kidney
Superior mesenteric ganglion: fibers innervate the small intestine and the first parts of the large intestine
Inferior mesenteric ganglion: fibers innervate the kidney, urinary bladder, sex organs, and terminal ends of the large intestine
The Sympathetic Division
Suprarenal Medullae
Fibers pass through sympathetic chain and the celiac ganglion without synapsing
Proceed to the suprarenal medulla
Fibers then synapse on modified neurons that when stimulated will release neurotransmitters that act as hormones:
Epinephrine and norepinephrine
The Sympathetic Division
Functions of the suprarenal medullae
Increase alertness by activating the reticular activating system
Increase cardiovascular and respiratory activity
Increase muscle tone
Increase the mobilization of energy reserves
Increased release of lipids from adipose cells
Increased breakdown of glycogen in liver cells
The Sympathetic Division
Sympathetic activation and neurotransmitter release
Sympathetic ganglion fibers release acetylcholine at the synapse with ganglionic neurons
These are cholinergic synapses
The stimulation of ganglionic neurons causes the release of norepinephrine at the neuroeffector junction
These terminals are adrenergic
Some ganglionic neurons also release acetylcholine
Especially at the neuroeffector junctions of skeletal muscles
The Sympathetic Division
Summary of the Sympathetic Division
Consists of parallel chains on either side of the spinal
cord
Preganglionic fibers are short and extend from the
spinal cord to the sympathetic chain
Postganglionic fibers are long and extend from the spinal cord to the body organs
The sympathetic division shows considerable divergence
All preganglionic neurons release ACh / most postganglionic neurons release norepinephrine
The Parasympathetic Division
Parasympathetic Division
Preganglionic neurons are in the brain stem and sacral segments
Preganglionic neurons do not diverge as much as the sympathetic division
Therefore, the parasympathetic division is more localized and specific as compared to the sympathetic division
Postganglionic neurons are near (terminal) the target organ or within (intramural) the target organ
The Parasympathetic Division
Organization and Anatomy of the Parasympathetic Division
Preganglionic fibers leave the brain via:
CN III (to the intrinsic eye muscles, pupil, and lens)
CN VII (to the tear glands and salivary glands)
CN IX (to the parotid salivary glands)
CN X (to the visceral organs of the thoracic cavity and abdominal cavity)
Preganglionic fibers leave the sacral region via:
Pelvic nerves (to the visceral organs in the inferior portion of the abdominopelvic cavity
The Parasympathetic Division
Functions of the Parasympathetic Division
Pupil constriction
Secretion of digestive enzymes from digestive glands
Increased smooth muscle activity of the digestive system
Stimulation and coordination of defecation
Contraction of the urinary bladder
Constriction of respiratory passages
Reduced heart rate
Sexual arousal
The Parasympathetic Division
Parasympathetic Activation and Neurotransmitter Release
All preganglionic and postganglionic fibers release ACh at their synapses and neuroeffector junctions
Most stimulations are short lived due to the immediate breakdown of ACh by acetylcholinesterase
The Parasympathetic Division
Plasmalemma Receptors and Responses
Two types of ACh receptors are found on the postsynaptic plasmalemmae:
Nicotinic receptors: respond to nicotine
Found on surfaces of parasympathetic and sympathetic ganglionic neurons
Muscarinic receptors: respond to muscarine
Found on surfaces of parasympathetic cholinergic neuroeffector junctions
The Parasympathetic Division
Summary of the Parasympathetic Division
Involves CN III, CN VII, CN IX, and CN X
Involves sacral segments S2 to S4
All parasympathetic neurons are cholinergic
Release of ACh stimulates nicotinic receptors on ganglionic neurons
Release of ACh on neuroeffector junctions stimulates muscarinic receptors
Relationships between the Sympathetic and Parasympathetic Divisions
Sympathetic
Widespread effect on visceral organs
Parasympathetic
Modifies the activity of structures innervated by specific cranial nerves and pelvic nerves
Most vital organs are innervated by both the sympathetic and parasympathetic nerves
The two often oppose (antagonistic) each other
Relationships between the Sympathetic and Parasympathetic Divisions
Anatomy of Dual Innervation
Head region
The parasympathetic fibers accompany the sympathetic fibers to the target organ
Thoracic and abdominopelvic regions
The parasympathetic and sympathetic fibers mingle together forming plexuses
Cardiac plexus
Pulmonary plexus
Esophageal plexus
Celiac plexus
Inferior mesenteric plexus
Hypogastric plexus
Visceral Reflexes
Provide autonomic motor responses to:
Modify or facilitate higher centers
All are polysynaptic
Reflexes can be:
Long reflexes
Short reflexes
Visceral Reflexes
Long Reflexes
Visceral sensory neurons go to the CNS via the dorsal roots
There are interneurons within the CNS
Information is “interpreted” in the spinal cord or brain
ANS sends motor commands to the visceral organs
Visceral Reflexes
Short Reflexes
Sensory nerve impulses go to the ganglionic neurons
Motor commands are distributed by the postganglionic fibers
Impulses bypass the CNS
© 2012 Pearson Education, Inc. Page 1 of 6 BIO 218 F 2012 CH 17 Martini Lecture Outline