Term
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Definition
glands
cardiac muscle
smooth muscle
regulates unconcious process that maintains homeostasis
– BP, body temperature, respiratory airflow
– Receptors detect internal stimuli -- stretch, etc |
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Term
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Definition
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Term
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Definition
Unconscious, automatic responses to stimulation of
glands, cardiac or smooth muscle |
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Term
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Definition
| detect internal stimuli -- stretch, blood chemicals, etc. |
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Term
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Definition
| transmit sensory signals to interneurons in the CNS |
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Term
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Definition
carry motor signals to effectors
– ANS is the efferent neurons of these reflex arcs |
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Term
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Definition
glands, smooth or cardiac muscle
– ANS modifies effector activity, rather than causing it |
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Term
ANS is made up of the efferent neurons of
reflex arcs |
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Definition
presynaptic neuron cell body located in CNS
– brain or spinal cord
• postsynaptic neuron cell body in peripheral ganglion |
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Term
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Definition
1. Sympathetic division (thorocolumbar division)
– “fight or flight”
– prepares body for physical activity
• increases heart rate, BP, airflow, blood glucose levels, etc
2. Parasympathetic division (craniosacral division)
– “rest & digest”
– calms many body functions and assists in bodily maintenance
– digestion and waste elimination
• Neither has universally excitatory or calming effects |
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Term
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Definition
• The normal rate of activity that represents the
balance of the two systems
• This balance shifts depending on the needs of
the body |
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Term
| Anatomy of Sympathetic NS |
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Definition
• Origin of presynaptic neurons
– lateral horns of gray matter of thoracic to lumbar cord
– fibers exit via spinal nerves T1-L2 leading to….
• Sympathetic chain ganglia (paravertebral
ganglia)
– On average 3 cervical, 11 thoracic, 4 lumbar, 4 sacral
and 1 coccygeal ganglia
– 2 branches called white and gray communicating
rami suspend ganglia from spinal nerve |
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Term
| Pathways of preganglionic fibers |
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Definition
Small myelinated preganglionic fibers travel
from the spinal nerve to the white
communicating ramus, then enter ganglia
– Some synapse immediately with a postganglionic fiber
– Some travel to higher or lower ganglia & synapse
– Some pass through chain without synapsing to reach
collateral ganglia via splanchnic nerves
• Unmyelinated postganglionic fibers leave
ganglia via gray communicating ramus |
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Term
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Definition
– each postganglionic cell may receive signals from
multiple preganglionic cells |
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Term
| Neuronal divergence predominates |
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Definition
each preganglionic cell branches and synapses on
multiple postganglionic cells
– There are ~ 17 postganglionic neurons for every
preganglionic neuron in the SNS
– produces widespread effects on multiple organs |
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Term
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Definition
Signals to effectors leave the sympathetic chain by 3 routes
- spinal nerve route
- sympathetic nerve route
splanchnic nerve route |
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Term
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Definition
– Effectors in body wall are innervated by sympathetic fibers that
travel through spinal nerves
– Sweat glands, piloerector muscles, blood vessels of skin & skeletal
muscles |
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Term
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Definition
Effectors in head and thoracic cavity are innervated by fibers in
specific sympathetic nerves
– Sweat, salivary, nasal glands; blood vessels, heart, iris |
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Term
| Splanchnic (visceral) nerve route |
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Definition
– Effectors in abdominal cavity are innervated by sympathetic fibers
in splanchnic nerves that lead to 3 major collateral ganglia
• celiac, superior and inferior mesenteric ganglion |
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Term
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Definition
Paired glands (1 left, 1 right)
• Sit on superior pole of each kidney
• Cortex (outer layer)
– secretes steroid hormones (androgens, cortisol, etc)
• Medulla
– modified sympathetic ganglion that secretes
neurotransmitters (in the form of hormones) into blood
rather than onto other neurons
• catecholamines - 85% epinephrine (aka adrenaline), 15%
norepinephrine
– complementary involvement in mass activation that
occurs during fight or flight reaction |
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Term
Paired glands (1 left, 1 right)
• Sit on superior pole of each kidney
• Cortex (outer layer)
– secretes steroid hormones (androgens, cortisol, etc)
• Medulla
– modified sympathetic ganglion that secretes
neurotransmitters (in the form of hormones) into blood
rather than onto other neurons
• catecholamines - 85% epinephrine (aka adrenaline), 15%
norepinephrine
– complementary involvement in mass activation that
occurs during fight or flight reaction |
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Definition
Origin of preganglionic fibers
– pons and medulla oblongata (cranial nerve nuclei)
– spinal cord segments S2-S4
• Pathways of preganglionic fibers
– cranial nerves III, VII, IX and X
• cardiac, pulmonary, esophageal, abdominal aortic plexus
– arising from sacral spinal cord
• pelvic splanchnic nerves & inferior hypogastric plexus
– enervate the pelvic and genital organs, regulating the emptying of the
urinary bladder and the rectum as well as sexual functions like
erection and orgasm
• Terminal ganglia in target organs due to normally
short postganglionic fibers |
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Term
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Definition
– narrows pupil
– focuses lens |
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Term
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Definition
– tear, nasal and salivary
glands |
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Definition
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Term
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Definition
– All major viscera as far as
proximal half of colon
– Cardiac, pulmonary, and
esophageal plexus |
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Term
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Definition
• Nervous system of the digestive system
• Composed of 100 million neurons found in the
walls of the digestive tract
– no components in CNS!
• Has its own reflex arcs
• Regulates motility and secretion of digestive
enzymes and acid in concert with the ANS |
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Term
| Neurotransmitters & Receptors |
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Definition
cholinergic fibers secrete ACh while adrenergic fibers
secrete NE (nor-epinephrine)
– only postganglionic sympathetic fibers are adrenergic |
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Term
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Definition
Acetylcholine binds to 2 classes of receptors
Nicotonic receptors
muscarnic receptors |
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Term
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Definition
• occur on all ANS postganglionic neurons, adrenal
medulla, on skeletal muscle
• excitatory when ACh binding occurs |
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Term
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Definition
• occur on all glands, smooth muscle & cardiac
muscle that receives cholinergic innervation
• either excitatory or inhibitory when ACh binding
occurs |
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Term
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Definition
2 categories of NE receptors
– alpha adrenergic receptors
• NE binding is excitatory
– beta adrenergic receptors
• NE binding is inhibitory
• Exceptions to normal results (EPSP or IPSP)
– existence of subclasses of each receptor type
• alpha 1 and 2; beta 1 and 2
• Function by means of 2nd messengers
– beta receptors activate cyclic AMP
– Alphas2 receptors suppress it
– Alpha1 receptors use calcium |
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Term
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Definition
– antagonistic effects oppose each other
• exerted through dual innervation of same effector cells
– heart slowed down or speeded up
• exerted because each division innervates different cells
– pupillary dilator muscle & constrictor pupillae change pupil size
– Cooperative effects seen when 2 divisions act on
different effectors to produce a unified effect (salivation)
• parasympathetic NS increases salivary serous cell secretion
• sympathetic NS increases salivary mucous cell secretion
• Both divisions do not innervate an organ equally |
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Term
| Control Without Dual Innervation |
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Definition
Adrenal medulla, arrector pili muscles, sweat
glands & many blood vessels receive only
sympathetic fibers
• Sympathetic tone is a baseline firing frequency
• provides partial constriction called vasomotor tone
– increase in firing frequency = vasoconstriction
decrease in firing frequency = vasodilation
• Vasomotor tone can shift blood flow from one
organ to another according to changing needs
– sympathetic stimulation increases blood to skeletal &
cardiac muscles -- reduced blood to skin |
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Term
| Sympathetic and Vasomotor Tone |
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Definition
Sympathetic division
prioritizes blood vessels
to skeletal muscles and
heart in times of
emergency, stress, or
exercise
Blood vessels to skin
vasoconstrict to
minimize bleeding if
injury occurs during
stress or exercise |
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Term
Central Control of Autonomic
Function |
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Definition
ANS is regulated by several levels of the CNS
– Cerebral cortex
• influenced by our emotions
– Hypothalamus
• fight or flight responses originate here
– Reticular formation
• can respond directly to sensory input from cardiac,
vasomotor, & GI tract
– Spinal cord
• defecation & micturition reflexes are integrated in the
spinal cord |
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Term
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Definition
enhance sympathetic activity
– stimulate receptors or norepinephrine release |
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Term
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Definition
suppress sympathetic activity
– inhibit norepinephrine release or block receptors |
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Term
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Definition
enhance activity while
Parasympatholytics suppress activity |
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Term
| Management of clinical depression |
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Definition
Prozac blocks reuptake of serotonin to prolong its moodelevating
effect
– MAO inhibitors interfere with breakdown of monoamine
neurotransmitters
• Caffeine competes with adenosine (inhibitory causing
sleepiness) by binding to its receptors |
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Term
A fractured spine, and subsequent severing of the spinal cord at C2 results in duadriplegia.
How is it that the patient's vital organs continue to function? |
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Definition
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Term
Ephedrine and pseudoephedrine are the main ingredients in some very popular cold
remedies. Ephedrine and pseudoephedrine act to: |
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Definition
| mimic the sympathetic division |
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