Autonomic NS and Visceral Reflexes Flashcards
General Actions of the Autonomic Nervous System
Involuntary control of glands, cardiac muscle, and smooth muscle
Responsible for visceral reflexes
What is another name for the
Autonomic Nervous System?
What does it contrast?
Visceral Motor System (unconscious control)
Contrasts the Somatic Nervous System (conscious control)
What are Visceral Reflexes?
Unconscious, automatic, sterotyped responses to stimulation of viscera effectors to stimuli
ex. A rise in blood pressure triggers a reflexive decrease in heart rate
What are the two sub-divisions of the Autonomic Nervous System?
Sympathetic Division: (Battle-mode)
Parasympathetic Division: (Rest and Digest mode)
What is the Sympathetic Division and what does it do?
- “fight or flight” responses for increased physical activity
- Increases heart rate and pumps more blood to skeletal muscles
- Reduces blood flow to skin and GI tract
Describe the Parasympathetic Division
- “Rest and Digest” responses with calming effect
- Decreases heart rate
- Simulates digestive and waste elimination
What is the Autonomic Tone?
Balanced activity of both sympathetic and parasympathetic division
(will shift according to body’s needs)
2 Neural Pathways of the Autonomic System
Preganglionic Fibers:
- Neurosoma in brainstem or spinalcord
- Axon terminates in ganglion
Postganglionic Fibers:
- Neurosoma in ganglion
- Axon extends to target area
Comparison of Somatic and Autonomic NS
Effectors
Somatic: Skeletal Muscle
Autonomic: Glands, smooth, and cardiac muscle
Comparison of Somatic and Autonomic NS
Type of Control
Somatic: voluntary
Autonomic: involuntary
Comparison of Somatic and Autonomic NS
Efferent Pathways
Somatic:
One nerve fiber from CNS to effector, no ganglia
Autonomic:
Two nerve fibers from CNS to effector, synapse at a ganglion
Comparison of Somatic and Autonomic NS
Distal Nerve Endings
Somatic: Neuromuscular junctions
Autonomic: Varicosities (enlarged veins)
Comparison of Somatic and Autonomic NS
Effect on target cells
Somatic: Always excitatory
Autonomic: Excitatory or Inhibitory
Comparison of Somatic and Autonomic NS
Effect on Denervation
Somatic: Flaccid Paralysis
Autonomic: Denervation Hypersensitivity
Describe the Sympathetic process in the Thoracolumbar Division
Arises from thoracic and lumbar regions
Preganglionic fibers exit out of spinal cord via spinal nerves (T1 to L2) and attach to Sympathetic Chain Ganglia
Post-ganglionic fibers branch exit of Sympathetic Chain Ganglia to Cervical and Coccygeal areas (above T1 and below L2)
Describe the Preganglionic and Postganglionic fibers in the Sympathetic Division
Preganglionic fibers:
Enter ganglia through white communicating rami
Postganglionic Fibers: Unmyelinated
Leave ganglia by various routs including gray communicating rami
Sympathetic Postganglionic Fibers Pathways
Spinal Nerve Route
Supports sweat glands, arrector muscles, and blood vessels of skin and skeletal muscles
Sympathetic Postganglionic Fibers Pathways
Sympathetic Nerve Route
Supports iris, salivary glands, lungs, heart, thoracic blood vessels, esophagus
(supports mainly thoracic organs and some cranial organs)
Sympathetic Postganglionic Fibers Pathways
Splanchic Nerve Route
Supports liver, spleen, adrenal glands, stomatch, intestines, kidenys, urinary bladder, reproductive organs
(Supports abdominal and pelvic organs)
Where are the Adrenal Glands?
Superior to each kidney (kidney hats)
Adrenal Cortex
- Outer layer of the Adrenal Glands
- Secretes steriod hormones
Adrenal Medulla
- Inner part of the Adrenal Glands
- Modified Sympathetic Ganglion
- Secretes epinephrine and norepinephrine
Describe the Parasympathetic Process in the Cranial Sacral Division
Arises from Cranial and Sacral Regions
Preganglionic Fibers exit out of pons, medulla oblongata, S2 to S4 of spinal cord and reach over to their target organs and 4 cranial ganglions
(Have long Preganglionic Fibers and short Postganglionic Fibers)
Name the 4 Cranial Nerves and their functions
Oculomotor Nerve (III): Controls lens and pupils
Facial Nerves (IV): Controls tear, salivary, and nasal glands
Glossopharyngeal Nerve (IX): Controls salivary glands
Vagus Nerve (X): provides branches for heart, lungs, esophagus, and other organs
(Vagus nerve contains 90% of parasympathetic preganglionic fibers)S
What are Splanchnic Nerves?
What do Pelvic Splanchnic Nerves carry?
Paired, autonomic nerves that carry both visceral Sympathetic and sensory fibers
Pelvic Splanchnic Nerves carry only Parasympathetic fibers
What is the Enteric Nervous System?
Nervous system of the digestive tract that doesn’t come from the CNS
Innervates smooth muscle and glands
Enteric Nervous System functions
Regulates:
- Motility of the Esophagus, stomach and intestines
- Secretion of DIgestive Enzymes and Acids
Comparison of Sympathetic and Parasympathetic Divisions
Origin of the CNS
Sympathetic: Thoracolumbar
Parasympathetic: Craniosacral
Comparison of Sympathetic and Parasympathetic Divisions
Location of ganglia
Sympathetic:
Sympathetic chain ganglia located ventral and lateral to the spinal cord
Parasympathetic:
Terminal ganglia near or within target organs
Comparison of Sympathetic and Parasympathetic Divisions
Fiber lengths
Sympathetic:
Long Preganglionic Fibers
Short Postganglionic Fibers
Parasympathetic:
Short Preganglionic Fibers
Long Postganglionic Fibers
Comparison of Sympathetic and Parasympathetic Divisions
Neuronal Divergence
Sympathetic:
Extensive
Parasympathetic:
Minimal
Comparison of Sympathetic and Parasympathetic Divisions
Area of Effect on Body System
Sympathetic:
Often widespread and general
Parasympathetic:
More local and specific
Comparison of Sympathetic and Parasympathetic Divisions
Effects on Pupil
Sympathetic:
Dilation (Grows larger)
Parasympathetic:
Constriction (Grows smaller)
Comparison of Sympathetic and Parasympathetic Divisions
Effects on Lens of Eye
Sympathetic:
Thinning for far vision
Parasympathetic:
Thickening for near vision
Comparison of Sympathetic and Parasympathetic Divisions
Lacrimal (tear) glands
Sympathetic: None
Parasympathetic: Secretion
Comparison of Sympathetic and Parasympathetic Divisions
Sweat Glands
Sympathetic:
Secretion
Parasympathetic:
Usually no effect but produces palmar sweating
Comparison of Sympathetic and Parasympathetic Divisions
Arrector Muscles
Sympathetic: Hair erection
Parasympathetic: No effect
Comparison of Sympathetic and Parasympathetic Divisions
Heart Rate
Sympathetic: Increased
Parasympathetic: Decreased
Comparison of Sympathetic and Parasympathetic Divisions
Blood vessels of most viscera
Sympathetic: Vasoconstriction
Parasympathetic: No Effect but dilates GI blood vessels
Comparison of Sympathetic and Parasympathetic Divisions
Blood Vessels of Skeletal Muscles
Sympathetic: Vasodilation
Parasympathetic: No effect
Comparison of Sympathetic and Parasympathetic Divisions
Blood vessels of Skin
Sympathetic: Vasoconstriction
Parasympathetic: Usually no effect, dilates some facial blood vessels causing blushing
Comparison of Sympathetic and Parasympathetic Divisions
Bronchioles
Sympathetic:
Bronchodilation (Increased air to lungs)
Parasympathetic:
Bronchoconstriction (Decreased air to lungs)
Comparison of Sympathetic and Parasympathetic Divisions
Kidneys
Sympathetic: Reduced urine output
Parasympathetic: No effect
Comparison of Sympathetic and Parasympathetic Divisions
Muscle of bladder wall
Sympathetic: No effect
Parasympathetic: Constriction, emptying bladder
Comparison of Sympathetic and Parasympathetic Divisions
Types of Secretion from Salivary Glands
Sympathetic: Thick mucous secretion
Parasympathetic: Thin serous secretion
Comparison of Sympathetic and Parasympathetic Divisions
Gastrointenstinal Motility
Sympathetic: Decreased
Parasympathetic: Increased
Comparison of Sympathetic and Parasympathetic Divisions
Gastrointestinal Secretion
Sympathetic: Decreased
Parasympathetic: Increased
Comparison of Sympathetic and Parasympathetic Divisions
Liver
Sympathetic: Glycogen breakdown
Parasympathetic: Glycogen Synthesis
Comparison of Sympathetic and Parasympathetic Divisions
Pancreatic Enzyme Secretion
Sympathetic: Decreased
Parasympathetic: Increased
Comparison of Sympathetic and Parasympathetic Divisions
Penis and Clitoris
Sympathetic:
Loss of erection
Parasympathetic:
Erection
Comparison of Sympathetic and Parasympathetic Divisions
Ejactulation
Sympathetic: Stimulation
Parasympathetic: No effect
What do Cholinergic Fibers do?
Secrete ACh
Which neurons secrete ACh?
- Preganglionic nerouns of both divisions
- Postganglionic neurons of Parasympathetic Division
- Few postganglionic neurons of the Sympathetic Division
What are Muscarinic Receptors?
ACh receptors found on involuntary effectors (smooth and cardiac) in the parasympathetic nervous system and in sympathetic cholinergic fibers
What are Nicotinic receptors?
ACh receptors found on postganglionic neurons of both autonomic systems
What do Adrenergic Fibers do?
They are cells that secrete Norepinephrine (NE)
Secreted by sympathetic postganglionic adrenergic fibers
What are Alpha and Beta Adrenergic receptors?
What do they do?
Both Alpha and Beta adrenergic receptors are found on some effector target cells found on Sympathetic Adrenergic fibers
Alpha-Adrenergic receptors: will excite
Beta-Adrenergic Receptors: will inhibit
What are two types of Sympathetic fibers?
Sympathetic Cholinergic Fibers: secrete ACh, they have Muscarinic receptors
Sympathetic Adrenergic Fibers:
secrete NE, they have Alpha and Beta Adrenergic Receptors
