Download Outline 11

Outline 11
The Autonomic Nervous System
General Properties of the Autonomic Nervous System
 General Actions
o Autonomic means “____________-governed” – the ANS usually controls
actions without our conscious intent or awareness
o The ANS can be defined as a motor nervous system that controls glands,
cardiac muscle, and _________________ muscle
o It can be called the visceral motor system for more direct comparisons to
the somatic nervous system, which controls ____________________
muscles
o Visceral effectors do not depend on the ANS to ____________________,
but the ANS adjusts their activity to the body’s changing needs (by
speeding them up or slowing them down, for example)
 Visceral Reflexes
o The ANS is responsible for unconscious, automatic, stereotyped responses
to stimulation that involve ____________________ receptors and
effectors
o Autonomic activity involves a reflex arc that includes receptors, afferent
neurons leading to the CNS, interneurons in the CNS, efferent neurons
carrying motor signals away from the CNS, and effectors
 Example:
 high blood pressure activates baroreceptors in the
________________________ and aortic arteries
 They transmit signals via the glossopharyngeal nerves to
the medulla oblongata
 The medulla integrates this information and sends
_________________________ signals back to the heart via
the vagus nerve
 The vagus nerves slow down the heart and
_____________________ blood pressure
 Divisions of the Autonomic Nervous System
o The sympathetic division adapts the body for physical
_________________ (the fight or flight response)
 Increases alertness, heart rate, blood pressure, pulmonary airflow,
blood glucose, blood flow to cardiac and skeletal muscle
 Decreases blood flow to the skin and ______________________
tract
o The parasympathetic division has a calming effect on the body (the resting
and digesting state)
o The two operate simultaneously to produce a background rate of activity,
and the balance between sympathetic and parasympathetic activity is
shifted, depending on the ___________________ of the body

Neural Pathways
o The ANS has components of both the central and peripheral nervous
system
o In autonomic pathways, the signal must travel across ____________
neurons to get to the target organ
 The signal must cross a synapse where the two neurons meet in an
autonomic ganglion
 The first neuron, called the ________________________ neuron,
has a soma in the brainstem or spinal cord and an axon that
terminates in a ganglion
 The second neuron, called the postganglionic neuron, extends from
the _____________________ to the target cells.
Anatomy of the Autonomic Nervous System
 The Sympathetic Division
o Called the thoracolumbar division because it arises from the thoracic and
____________________ regions of the spinal cord
o The preganglionic neurons lead to the sympathetic chain of ganglia along
each side of the vertebral column
 Preganglionic neurons are myelinated
 The sympathetic chains extend above and below the thoracic and
lumbar regions
o After entering the sympathetic chain, preganglionic fibers may follow any
of three courses:
 They may ___________ in the ganglion and synapse immediately
with a postganglionic neuron
 They may travel up or down the chain and synapse in ganglia at
other levels
 They may pass through the chain without synapsing and continue
as splanchnic __________________
o Nerve fibers leave the paravertebral ganglia by three routes
 Some exit by way of the gray ramus, return to the spinal nerve, and
travel the rest of the way to the target organ
 Some leave the chain by way of sympathetic nerves that extend to
the ____________, lungs, esophagus, and thoracic blood vessels
 Some (preganglionic) neurons pass through the ganglia without
synapsing.
 Beyond the ganglia, they form the greater, lesser, and least
splanchnic nerves.
 These splanchnic nerves lead to the ___________________
ganglia where they synapse with postganglionic neurons
 The Adrenal Glands
o The adrenal glands rest above the ______________________
o Each adrenal gland is actually two glands with different functions
 The adrenal cortex (outer gland) secretes steroid hormones
 The adrenal medulla (inner gland) is a modified sympathetic
ganglion





It consists of _________________ postganglionic neurons
It is innervated by preganglionic neurons
When stimulated, the adrenal medulla secretes epinephrine
and norepinephrine into the bloodstream
The Parasympathetic Division
o Called the craniosacral division because it arises from the brain and sacral
regions of the spinal cord
o The preganglionic neurons end in terminal ganglia in or near the target
organ
o Parasympathetic fibers leave the brainstem by way of four
_____________ nerves
 Oculomotor nerve – postganglionic fibers run to the papillary
constrictor muscles of the eye
 _________________ nerve – postganglionic fibers run to the
salivary glands in the floor of the mouth
 Glossopharyngeal nerve – postganglionic fibers run to the parotid
salivary glands below and anterior to the ears
 Vagus nerve – postganglionic fibers run to the heart, the lungs, the
esophagus, the stomach, liver, and proximal half of the colon
o Additional parasympathetic fibers arise from levels S2 to S4 of the spinal
cord
 Postganglionic nerve fibers run to the distal half of the large
intestine, the rectum, urinary bladder, and reproductive organs
The _________________ Nervous System
o The digestive tract has a nervous system of its own
o The enteric nervous system regulates the motility of the esophagus,
stomach, and intestines and the secretion of digestive enzymes and acid
Autonomic Effects
 Neurotransmitters and Receptors
o Some nerve fibers of the ANS are ______________________
 They secrete acetylcholine (Ach)
 Examples:
 Preganglionic fibers of both divisions
 Postganglionic fibers of the parasympathetic division
 A few sympathetic postganglionic fibers (those of some
sweat glands and blood vessels)
o Some nerve fibers of the ANS are ______________________
 They secrete norepinephrine (NE)
 Examples:
 Most sympathetic postganlionic fibers
 Dual Innervation
o Most of the viscera receive nerve fibers from both the sympathetic and
parasysmpathetic division
 Example: the sympathetic division dilates the ______________,
and the parasympathetic division constricts the pupil

o Dual innervation is not always necessary – some have sympathetic
stimulation only
 Sympathetic fibers to a blood vessel have a baseline sympathetic
tone that keeps the vessel in a state of partial constriction
 An increase in stimulation causes vasoconstriction
 A drop in stimulation causes vasodilation
Central Control of Autonomic Function
o The midbrain, pons, and medulla oblongata house the nuclei of cranial
nerves that mediate several autonomic responses
 Pupillary constriction
 Lacrimal and _____________________ gland secretion
 Blood pressure regulation
 Control of thoracic and abdominal viscera
o These regions of the brain are influenced by the hypothalamus
 The hypothalamus is influenced by the cerebral cortex and limbic
system
 Side Note: What is the Limbic System?
 Ring (limbus) of structures on the medial side of the
cerebral hemisphere incirclilng the corpus callosum and the
thalamus
 Experiments have shown that it hase significant roles in
emotion and memory
 Plays roles in feelings of anger, fear, hunger, pleasure – so
an emotion like fear can have an effect on the body by
indirectly affecting the autonomic nervous system
o The spinal cord contains nuclei of autonomic control
 Defecation and micturition are reflexes if the brain is unable to
consciously inhibit them
Effects of the Sympathetic and Parasympathetic Nervous Systems
Target
Eye



Dilator of Pupil
Constrictor of Pupil
Ciliary Muscle and Lens
 _____________ Gland
Integumentary System
 Sweat Glands
 Piloerector Muscles
Adrenal Medulla
Circulatory System
 _________ Rate and Force
 Deep Coronary Arteries
 Blood Vessels of Viscera
 Blood Vessels of Skeletal Muscle
 Blood vessels of skin
Respiratory System
 Bronchi and Bronchioles
Urinary System
 Kidneys
 Bladder Wall
 Internal Urinary Sphincter
Digestive System
 Salivary Glands
 Gastrointestinal Motility
 Gastrointestinal Secretion
 ______________
 Pancreatic Enzyme Secretion
Reproductive System
 ___________ or Clitoral Erection
 Glandular Secretion
 Orgasms, Smooth Muscle Roles
 Uterus
Sympathetic
Effect
Parasympathetic
Effect
Pupillary dilation
No effect
Relaxation for
far vision
none
No effect
Pupillary constriction
Contraction for
near vision
Secretion
Secretion
Hair erection
Hormone secretion
No effect
No effect
No effect
Increased
Vasodilation
Vasoconstriction
Vasodilation
Vasoconstriction
Decreased
Vasoconstriction
Vasodilation
No effect
Vasodilation
Bronchodilation
Bronchoconstriction
Reduced urine output No effect
No effect
Contraction
Contraction
Relaxation
mucus secretions
Decreased
Decreased
Glycogen breakdown
Decreased
saliva secretions
Increased
Increased
Glycogen synthesis
Increased
No effect
No effect
Stimulation
Relaxation
Labor Contractions
Stimulation
Stimulation
No effect
No effect