Term
| What is the difference between the autonomic system and the somatic system? |
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Definition
ANS
Involuntary branch of PNS, ie automated
Controls activity of cardiac and smooth muscle, and glands
Maintains homeostasis
Somatic
Voluntary muscle control |
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Term
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Definition
Parasympathetic and sympathetic divisions
Enteric system |
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Term
| ANS is considered primarily an afferent or an efferent system? |
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Definition
| An efferent system (motor) |
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Term
| Both parasympathetic and sympathetic pathways consist of ____________ that exit the CNS and innervate an organ |
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Definition
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Term
| Sympathetic and Parasympathetic have pre-ganglia located where? |
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Definition
Sympathetic: lateral horn
Parasympathetic: brainstem nuclei and sacral |
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Term
| What receptors that stimulate the ANS? |
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Definition
Mechanoreceptors
-Aortic baroreceptors, carotid sinuses, lungs
Chemoreceptors
-Carotid and aortic bodies, medulla, hypothalamus
Nociceptors
-Viscera, arterial walls
Thermoreceptors
-Hypothalamus, skin |
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Term
| Afferent Pathways from visceral receptors via: |
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Definition
Cranial nerves
Facial (VII)
Glossopharyngeal (IX)
vagus (X)
And Dorsal roots |
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Term
| Pre-ganglionic neurons are what type of motor neurons? |
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Definition
-type B motor neurons
-Cell bodies in the lateral horn of T-L spinal cord
-Myelinated axons
-Short neurons that synapse onto post-ganglionic neurons in the sympathetic ganglia
-Although, some pre-ganglionic neurons synapse directly with cells in the adrenal medulla |
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Term
| Post-ganglionic neurons are what type of motor neurons? |
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Definition
-type C motor neurons
-Terminate on effector organs
-Unmyelinated |
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Term
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Definition
| single preganglionic neuron synapses with many postganglionic neurons |
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Term
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Definition
| One postganglionic neuron receives input from several preganglionic neurons |
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Term
| Cranial parasympathetic pre-ganglionic neurons travel in: |
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Definition
CN III, VII, IX, X
75% of all parasympathetic outflow is from the Vagus nerve, CN X!!! |
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Term
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Definition
cell bodies within brainstem nuclei and sacral spinal cord
Myelinated
Fibers are long |
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Term
| Peripheral Ganglia (postganglionic neurons)on or near effector organ |
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Definition
Postganglionic axons are short
Specificity of parasympathetic action
Lack of preganglionic divergence |
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Term
| Are all preganglionic neurons are cholinergic? |
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Definition
All preganglionic neurons are cholinergic
-Release acetylcholine
E-ffect (excitation or inhibition) depends on receptor that acetylcholine binds with…
-Cholinergic receptors can be nicotinic or muscarinic |
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Term
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Definition
Parasympathetic postganglionic neurons are cholinergic
Release acetylcholine onto cholinergic receptors on the effector organ
Sympathetic postganglionic neurons are adrenergic
Release norepinephrine onto adrenergic receptors on the effector organ |
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Term
| Parasympathetic Postganglionic effector organ receptors |
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Definition
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Term
| Sympathetic Postganglionic effector organ receptors |
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Definition
muscarinic or adrenergic
Muscarinic receptors bind Ach
Adrenergic receptors bind epi- and norepi- |
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Term
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Definition
Mimic the SNS
Promote actions of NE or Inhibit muscarinic actions of Ach |
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Term
| Parasympathomimetic Drugs |
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Definition
Mimic the PSNS
Promote the muscarinic actions of Ach, or Inhibits actions of NE |
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Term
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Definition
Sympathomimetic
A muscarinic receptor antagonist
Blocks parasympathetic action
Allows dominance of sympathetic action
Dilates pupils |
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Term
Parasympathomimetic Drugs
Beta blockers and Alpha blockers |
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Definition
Beta blockers
-Reduce HR
-Prevent arrhythmias
Alpha blockers
-Treat high BP (block alpha-1 receptors on vascular smooth muscle) |
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Term
| Autonomic Reflexes control what reflexes? |
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Definition
Baroreceptor Reflex
Micturition Reflex
Erection Reflex |
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Term
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Definition
Controls short-term changes in blood pressure
Sensors in the carotid sinus and aortic arch are stretched in response to increased arterial BP or relaxed in response to decreased arterial BP
This signals the brainstem that BP is elevated or decreased
If BP is elevated, excitatory drive to sympathetic preganglionic neurons is reduced and excitatory drive to parasympathetic preganglionic neurons is increased
Arterial dilation decreases BP
If BP is decreased excitatory drive to sympathetic preganglionic neurons is increased, and excitatory drive to parasympathetic preganglionic neurons is decreased |
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Term
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Definition
Controls filling and emptying of the bladder
Distension of the bladder activates stretch receptors, triggering a reflex that is relayed through the pons
Afferent transmission to the sacral SC and pons
Efferent impulses return to bladder via parasympathetic pelvic splanchnic nerves
Contraction of detrusor muscle of bladder, and
Relaxation of the internal sphincter |
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Term
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Definition
A potentially life-threatening disorder that typically occurs in individuals with SCI above T6 level
Caused by an inability to control sympathetic responses for temperature regulation and circulatory control
Sensory stimuli from smooth muscle with post-ganglionic sympathetic innervation below the lesion level send impulses via visceral afferents to the spinal cord and up the lateral spinothalamic tract and dorsal column pathway (fasciculus gracilis).
Stimulus often from bladder and/or bowel
Stimulus can only travel rostrally as far as the lesion level in the spinal cord
A massive and unchecked sympathetic response (reflex) occurs below the lesion level due to release of norepinephrine at adrenergic postganglionic terminals |
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Term
| Paroxysmal Sympathetic Hyperactivity |
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Definition
Predominantly observed after severe traumatic brain injury
Hypoxia is a significant factor
Previously identified as “dysautonomia”, the term “paroxysmal sympathetic hyperactivity”, or PSH, is now promoted for common nomenclature
Trauma induces a marked sympathetic response:
Increased HR
Increased RR
Increased BP
Redistribution of blood to skeletal muscle and CNS
Diaphoresis
Hyperthermia
This is a normal response to TBI, but the problem with PSH is that it is excessive and unchecked
Loss of homeostasis
Destructive rather than protective |
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Term
| What is the Culprit in PSH? |
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Definition
Increased sympathetic activation,
or
Increased parasympathetic activation AND increased sympathetic activation?
Related to TBI, the predominant clinical evidence is for increased sympathetic activation alone.
Hence the term: paroxysmal sympathetic hyperactivity
Has very bad outcomes. |
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Term
| Management of PSH with drugs... |
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Definition
Opiods
Used in general anesthesia; Inhibit synaptic transmission in pain pathways of brain and spinal cord
Gabapentin
Often used in spasticity management, it causes inhibition in the spinal cord, with decresed excitation of alpha motor neurons
Benzodiazepines
For example, valium; a general anesthetic
Centrally-acting alpha agonists and beta antagonists
Alpha-2 agonists stimulate alpha-2 receptors in the brain and brainstem, causing inhibition of sympathetic discharge from the vasomotor center in the brainstem |
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Term
| Complex Regional Pain Syndrome |
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Definition
Efferent fibers of the SNS trigger sensations of intense burning pain
Possibly by direct activation of nociceptive afferents
Possibly by non-synaptic electrical cross-talk, called ephaptic transmission
May occur after peripheral nerve injury or after viral infection, or after local trauma
Symptoms unrelated to severity of initial trauma
May not be confined to a single peripheral n distribution
Tx: includes PT, mobilization, antidepressants |
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Term
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Definition
A disorder of the peripheral vascular innervation
Symptoms include:
Vasoconstriction of toes, fingers, edges of ears and tip of nose
Paleness, coldness of affected body parts |
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Term
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Definition
A fall in BP with upright posture
Sustained drop in systolic BP (≥20 mmHg) or diastolic (≥ 10 mmHg) BP within 3 minutes of standing up
May be related to impaired arterial baroreceptor reflex
Symptoms:
Dizziness
Weakness/fatigue
Blurred vision
Mental status changes
Shakiness
Vertigo
Anxiety/pallor
Heart palpitations
Clammy feeling
nausea |
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Term
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Definition
Damage to the superior cervical ganglia or preganglionic cell bodies
Loss of sympathetic innervation to the head
Effects:
Small pupillary diameter (loss of innervation of dilator muscle of iris; parasympathetic fibers innervating circular muscle of the iris act unopposed)
Drooping eyelid (lack of sympathetic innervation to Muller’s muscle)
Anhidrosis, or loss of sweating to the head
Vasodilation of the skin and face
May be unilateral or bilateral |
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Term
| Diabetic autonomic neuropathy |
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Definition
Common in long-standing type 1 and 2 diabetes mellitus
Impaired sympathetic and parasympathetic post-ganglionic fibers
Impotence, bladder dysfunction, nocturnal diarrhea, GI dysfunction, orthostatic hypotension |
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Term
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Definition
Demyelination of ANS fibers leads to impaired cardiac baroreflex
Hyper- or hypotension may result
Cardiac arrhythmias occur |
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Term
| Parkinson’s Disease and Autonomic Dysfunction |
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Definition
Pre-motor symptoms of PD
May precede the onset of disease by years
Include autonomic dysfunction and impaired olfaction
Autonomic symptoms include:
Orthostatic hypotension (systolic drop of > 20 mmHg, diastolic of > 10 mmHg within 2-3 min of position change)
Poor GI motility (most commonly, constipation)
Thermal dysregulation (sweating; intolerance to heat or cold)
Urinary frequency, urgency, and incontinence
Reduced sexual drive and sexual dysfunction
Sialorrhea – excessive saliva in the mouth |
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