Autonomic nervous system
Causes of Autonomic dysreflexia
Bladder distension, UTI, Epididymitis, bowel impaction, gallstones, hemorrhoids, PUD, menstrual cramps, Pregnancy, intercourse, appedicitis, colitis, vaginitis, DVT, ingrown toenail, PE, sunburn, insect bite, pressure injuries, constrictive clothing trauma, medical procedures,
Overview of the ANS
Controls visceral functions, regulates homeostasis; concerned with BP, HR, RR, GI motility and secretions, body temp, metabolism, intracellular and extracellular fluid compositions, etc
GVE pathway
2 neurons; has a peripheral ganglion and these neurons are the ganglionic cells whose axons form the post ganglionic fibers
Sacral division of the parasympathetics
S2-S4; preganglionic fibers travel in the pelvic splanchnic nerves and synapse on postganglionic neurons in the walls of the organs they innervate; the postganglionic fibers innervate the lower colon, pelvic organs, and genitalia
1st direction the preganglionic sympathetic fiber could travel to
Synapse at that level in the ganglion of the paravertebral trunk with the neuron cell body of the post ganglionic fiber in the ganglion; the post ganglionic fiber would then return to the spinal nerve and travel to the periphery
Shivering thermogenesis
a 3rd factor that regulates body temp; controlled by the reticular system; shiver when cold to help warm up via the reticulospinal tract
Physiologic info
carried on nerves that convey parasympathetic info
Visceral afferents
carry information from the viscera to the CNS; they have receptors for nociceptive and physiological function; could be rapidly adapting (cough), slowly adapting (bladder fullness), some are specialized (chemical composition of blood); have slow conducting pathways; will enter the CNS through 2 routes: the spinal nerves or the cranial nerves
Lumbar splanchnic nerve
formed from L1-L2
Least splanchnic nerve
formed from T12
Great splanchnic nerve
formed from T5-T9
Lesser splanchnic nerve
formed from T9-T10 or T10-T11
Cranial nerve 3
the preganglionic fibers originate in the Edinger-Westphal nucleus in the midbrain; will synapse in the ciliary ganglion which is just behind the eye; the postganglionic peresympathetic fibers go to the eye and cause the pupil to constrict and accommodate the lens
Cranial nerve 9
the preganglionic fibers originate in the inferior salivatory nucleus of the medulla; they will synapse on the otic ganglion and the postganglionic fibers supply the parotid gland
Cranial nerve 7
the preganglionic fibers originate in the superior salivatory nucleus of the pons; some of the fibers will synapse in the pterygopalantine ganglion and the postganglionic fibers innervate the lacrimal and nasal glands; other preganglionic fibers synapse on the submandibular ganglion and innervate the salivary glands
Spinal cord and pelvic organs
the sacral spinal cord contains centers for urination, bowel function, and sexual function and the reflexive functions occur at the spinal cord level; voluntary control of these functions requires intact pathways between the organs and the cortex
Factors regulating body temp that sympathetic output controls
vasomotor tone (blood vessel diameter) and sudomotor tone (sweat glands)
If bladder is full and situation is appropriate
1) Frontal cortex will disinhibit the pons 2) Pons says go to the sacral spinal cord 3) Parasympathetics from the sacral spinal cord will initiate contraction of the bladder and relax the internal sphincter 4) Pons also sends signal to cord to excite inhibitory neurons to pelvic floor muscles so thet they relax 5) Micturition occurs
Pattern of paravertebral ganglia
3 cervical (superior, middle, and inferior, 10-11 thoracic ganglia, 3-5 lumbar ganglia, 3-5 sacral ganglia, and 1 coccygeal ganglion
General Somatic afferent fibers
GSA; sensory from skin and/or skeletal muscle
General Somatic efferent fibers
GSE; motor to muscles
General Visceral afferent fibers
GVA; sensory from the organ systems; some will parallel GVE fibers within the nerves and are involved with autonomic reflexes
General Visceral efferent fibers
GVE; motor to the organ systems; sympathetic and parasympathetic fibers
Visceral afferents carried on the cranial nerves
a major termination is the solitary nucleus (bull's eye) in the medulla along with the cranial nerve; most of the autonomic control will control at the brainstem level; some of the info will go into the insular cortex and postcentral gyrus; all the systems will communicate and act to influence the S, the PS, and the endocrine system
Vascular tone
a primarily sympathetic activity because they normally maintain some contraction of the vessel wall; an increase will lead to vasoconstriction and decrease will lead to vasodilation; Vasoconstriction=increased BP; vasodilation=decreased BP
Adrenal medulla
acts as a peripheral sympathetic ganglia; preganglionic sympathetic fibers will travel through the splanchnic nerves to the adrenal gland and synapse; it secretes epinephrine (adrenaline) and norepinephrine directly into the blood stream; reinforces and prolongs the sympathetic effect
SC Lesions in the S2-S4 level
afferents or PS efferents will produce LMN signs; the reflex arc is lost; leaves a flaccid, paralyzed bladder; Problem: bladder will overfill, and urine will lea or dribble out when the bladder can no longer stretch; bowel and sexual functions will by similarly affected
Endocrine system
also regulates homeostasis and visceromotor functions; hormonal influence; develops slowly and has prolonged effects
Endocrine system and ANS
are both under the hypothalamic influence; both receive limbic and cortical inputs
Sympathetic preganglionic neurons
are divergent; they branch and synapse with many post ganglionic neurons (20+); diffuse response
ANS neurons
are either adrenergic or cholinergic and secrete neurotransmitters
Adrenergic receptors
are either alpha or beta; have subtypes and important pharmacologic applications
Cholinergic receptors
are either muscarinic or nicotinic; have subtypes and important pharmacologic applications
Peripheral ganglia of the sympathetics
are found primarily in the paravertebral ganglia and pre vertebral ganglia; some other scattered ones do exist; both locations are near the CNS
SC lesions above the sacral level
are solar to UMNL; have sacral level reflex arc but no descending influence; no voluntary control; will have a hypertonic, hyper reflexive bladder with decreased capacity; Problem 1) as the bladder stretches it will automatically empty; Problem 2) if the sphincter is hypertonic also, flow is obstructed and kidneys are damaged; bowel and sexual functions will by similarly affected; interfere with the transmission of sensory info from the pelvic organs to the brain and with descending control of the pelvic function
Response of the baroreceptor to the hypertensive crisis
attempts to shut down sympathetics by sending inhibitory signals but they are also block by the injured spinal cord; or attempts to decrease blood pressure by action of the parasympathetics (carried in the vagus nerve); these fibers will leave the brainstem and heart rate is slowed but it is inadequate to bring down the pressure
Difference between the autonomic and somatic nervous systems
autonomic functions are nonconscious; internal organs can often function independent of CNS input; the pathway involves 2 neurons as opposed to the 1 neuron pathway to skeletal muscle
Sympathetic pathways
axons of the preganglionic sympathetic neurons will leave the lateral horn of the spinal cord in the ventral horn of T1-L2 and travel to the sympathetic trunk
CNS
brain, brainstem, and spinal cord
SCI patients exposure to cold temps
can cause hypothermia because patient has lost the ability to shiver and vasocontrict; everything slows down
Sympathetics below the lesion
cause a pounding headache, visual changes, anxiety, pallor, piloerection
Lesion of spinal cord at higher levels
causes more serious problems because more segments of the cord lack descending sympathetic control
Effects of sympathetics on the eye
causes the eyes to dilate and the lids to elevate (wide-eyed)
Parasympathetic nervous system
cell bodies are found in the brainstem nuclei (nuclei of cranial nerves 3, 7, 9, 10) and sacral spinal cord (S2-S4/sacral visceromotor nucleus) between the dorsal and ventral horn; also known as the craniosacral division; have a long preganglionic fiber and short post-ganglionic fiber
Sympathetic nervous system
cell bodies of the preganglionic fibers originate in the spinal cord from T1-L2; found in the rexed lamina 7 in the intermerdiolateral cell column (lateral horn); the thoracolumbar division; have a short preganglionic fibers and long postganglionic fiber
Causalgia
complex regional pain syndrome, type 2; occurs with partial damage to the peripheral nerve, usually to an extremity; pain comes with stimuli that should not cause pain
CN 3, 7, 9, & 10
cranial nerves that carry parasympathetic fibers
Effects of parasympathetics on the lungs
decrease in bronchiole diameter and decrease in respiratory rate
Effects of parasympathetics on the heart
decrease in heart rate, decrease heart contractility, decrease blood pressure
Effects of parasympathetics on the head
decrease pupil size, cause accommodation (increase in curvature of the lens to see near) increase tear production
Anhidrosis
decreased or absent sweating
Sympathetics effect on GI and urinary systems
decreases their processes because there is no time for this in a crisis; decreases peristalsis, decreases secretions, and decreases blood flow to kidneys and gut
Ptosis
drooping of the upper eyelid
Poor thermoregulation
due to a SCI, there is an interruption of the descending sympathetic input preventing thermoregulatory sweating below the level of the lesion in response to ambient temp; to compensate there may be excessive sweating above the level of the lesion; SCI patients should avoid temp extremes
Limbic system
emotions, mood, motivation; produces autonomic responses like blush of embarrassment, tears of joy, tachycardia or anxiety; modulates autonomic activity
Functions of the Parasympathetics
energy conservation/rest and digest, stores energy-forms glycogen and stores fats; remember sludd and 3 decreases: salivation, lacrimation, urination, digestion and defecation, and decrease in HR, airway diameter, and pupil diameter; increase GI and GU functions-peristalsis secretion of digestive juices, increase pancreatic secretions, and causes defecation and urination; causes and erection; affects the head, heart, lungs as well
Viceral afferents carried on the spinal nerves
enter the spinal cord via the dorsal root (cell bodies in the DRG) and may synapse with the visceral efferents producing and autonomic reflex or ascend to the brainstem and above producing a supra spinal reflex (ascending in the spinoreticular tract and ALS
Overall result autonomic dysreflexia process
excessive sympathetic outflow below the lesion and excessive parasympathetic outflow above the lesion; the PS and S systems function independent of one another; there is no feedback loop because it is interrupted by the spinal cord lesion (info will not reach the hypothalamus or brainstem); may lead to MI, CVA, arrhythmia (life threatening); will occur when patient is recovering from spinal shock; hypertensive reflex will normally resolve after stimulus is removes
Preganglionic neuron
extends from the CNS to the ganglion (myelinated)
Postganglionic fibers
extends from the peripheral ganglion to the effector organ (non-myelinated)
Paravertebral ganglia
found in the paravertebral trunk (sympathetic trunk); groups of the postganglionic cell bodies; are located on either side of the vertebral column; are interconnected via the nerve fibers that are forming the trunks, which extend the length of the vertebral column; the number of ganglia are similar but do not exactly match the number of the spinal nerves;
Pre-vertebral ganglia
found near branches of major arteries off of the abdominal aorta
Stellate ganglion
fusion of the inferior cervical ganglion and the 1st cervical ganglion; looks like a star
Ganglion
group of nervous cell bodies outside the CNS
Afferent fibers
info to the CNS
Medulla
has a cardiovascular system
Autonomic nervous system
has immediate response with short term effect; can increase HR to 2x the normal in 3-5 seconds, can double arterial pressure in 10-15 seconds; acts rapidly and with intensity
Hypothalamus for body temp
has intrinsic receptors that respond to the temp of the blood that passes through it; is the generator of the thermal set point and thermoregulatory response; efferents project from here to the thoracolumbar spinal cord to influence the sympathetics
SCI patients exposure to high temps
have a great risk of heat strokes; key symptom is dry flushed skin
Pons and medulla
have centers for respiration
Spinal nerves
have four functional components that are general; carries GSA, GSE, GVA, and GVE fibers
Autonomic clinical coorelations
horner's syndrome which will have symptoms of mitosis, ptosis, flushing, and anhidrosis, peripheral nerve damage, causalgia, spinal cord lesions
Normal conditions with blood pressure
if BP drops too low, CN 9 and 10 will detect it b/c they carry sensory info from the carotid sinus and pressure receptors in the aortic arch; that info is conveyed to the brainstem (solitary nucleus) and it activates a vasopressor center which tells sympathetics to increase HR and increase vasoconstriction to bring pressure up
Effects of sympathetics on the heart
increase HR, BP, contractility, blood flow to the heart and dilate coronaries (everything to increase cardiac output
Effects of sympathetics on the lungs
increase in dilation of bronchioles, increase RR because need to move air in and out of the lungs and meet increased demand for oxygen
Efferent fibers
info away from the CNS
How Autonomic dysreflexia occurs
initial afferents in the PNS transmit info up the spinal cord through the spinothalamic tract and dorsal columns and collateral branches from tracts carrying noxious info facilitate sympathetic neurons in the cord; this info will be blocked at the level of the lesion; a widespread sympathetic surge from the cells in the intermediolateral gray (lateral horn) of the thoracolumbar spinal cord and the surge will travel through the splanchnic nerves; results in widespread casoconstriction and peripheral artery hypertension; the baroreceptors in the neck (carotid sinus and aortic arch) will detect the hypertensive crisis and take info to the brain (CN 9 & 10/to the solitary nucleus)
Splanchnic nerves
innervates the organs in the abdominal and pelvic cavities; are preganglionic fibers; formed from T5 and below; greater, lesser, least, lumbar and sacral (pelvic are parasympathetic); are preganglionic sympathetics that synapse on the pre vertebral ganglia
Sacral SC, PS, or afferent neuron lesions
interfere with reflexive control of the pelvic organs
Spinal cord lesions
interrupt ascending and descending ANS signals; cord at level and below the lesion are cut off from brain input; level of injury will determine deficits
Normal body temp
is achieved by descending sympathetic innervation from the hypothalamus
Micturition reflex
is an autonomic reflex, but can be inhibited or facilitates by centers in the cortex and brainstem (pons); if it is inappropriate to urinate the cortex will inhibit the reflex and send a message to skeletal muscle in the floor of the pelvis (levator ani) to contract via the corticospinal tract (acts as an external sphincter and reinforces the internal sphincter)
Nociceptive info
is carried on nerves that convey sympathetic efferents
Solitary nucleus
is the main sensory nucleus of the brainstem and relays info to the other nuclei in the medulla, pons, hypothalamus, thalamus, and limbic system
Hypothalamus
is the master controller of homeostasis; modulates HR, RR, water absorption, metabolism, temperature, pituitary functions, etc
Cranial nerve 10
is the vagus nerve; carries 75% of the parasympathetic innervation for the body; the preganglionic fibers originate in the dorsal motor nucleus of vagus and synapse on postganglionic neurons located in the walls of the viscera; they innervate the thoracic and abdominal organs (heart, organs, GI system, etc)
Bladder control
it is an organ composed of smooth muscle (detrusor muscle) with an internal splinter (smooth muscle) and external sphincter (skeletal muscle) which are located in the urethra; as it fills, sympathetics inhibit contraction of the bladder wall and contract the internal sphincter (an involuntary process); proprioceptors are sensitive to stretch in the bladder wall and when they feel a certain amount of tension, they will send info to the reflex center in the sacral spinal cord; the reflex center will send parasympathetic efferents to initiate voiding and cause the detrusor muscle contraction and relaxation of the internal sphincter
Sympathetics
large distribution: visceral organs of the thorax, abdomen, pelvis, and head and blood vessels; includes the limbs and body wall (periphery) and skin (sweat glands, blood vessels, arrestor pili of hair follicles
Parasympathetics
limited distribution: viscera of thorax, abdomen, pelvis, head, and a few blood vessels; not a significant distribution to the periphery
Spinal lesions in regard to ANS
loss of descending hypothalamospinal and reticulospinal tracts will cause an overall reduction in sympathetic activity; means a decrease in blood pressure (loss of vascular tone=vasodilation), slow heart rate (bradycardia), orthostatic hypotension
Peripheral nerve damage
loss of sympathetic efferents to an extremity that case loss of vascular tone, loss of sweating, and loss of temp control in affected nerve distribution
Functions of the sympathetics
maintain optimal blood supply to the organs that are in demand of it, prepares for vigorous exercise, fight or flight role, emotions will excite it, associated with E situations (exercise, excitement, emergency, embarrassment); adrenal medulla releases adrenaline (E); non essential activists will slow down; need to increase energy sources so increase blood glucose, break down glycogen and fats, and increase blood flow to liver, increases sweating and vascular tone (shunt blood to areas that need it and divert it from ones that don't; affects the heart, lungs, eye, GI and urinary system as well
Homeostasis
maintenance of an optimal internal environment regardless of influences
3rd direction the preganglionic sympathetic fiber could travel to
may ascend or descend to synapse on the postganglionic neurons that project to targets in the head or chest (forming cardiac nerves and thoracic nerves
2nd direction the preganglionic sympathetic fiber could travel to
may enter the paravertebral trunk and ascend or descend to synapse on a ganglion at another level; the postganglionic fibers may then join the spinal nerve at the new level and travel to the periphery
4th direction the preganglionic sympathetic fiber could travel to
may pass through the sympathetic chain without synapsing and form one of the splanchnic nerves; will eventually synapse on the pre vertebral ganglia; the postganglionic fiber will travel to the organ that they innervate
If temp is too low
need heat conservation; hypothalamus directs cutaneous vasoconstriction via the sympathetics and shivering via the reticulospinal tracts; sympathetics will increase metabolism by causing adrenal medulla to secrete E and in turn heat production increases
Orthostatic hypotension
occurs because of loss of baroreceptor reflex; the descending command is blocked with a spinal cord lesion, pressure will remain low, and there will be a lack of blood flow to the brain; syncope occurs (fainting); once patient is horizontal, gravity aids blood flow to brain and recovery occurs; strong emotions can elicit a similar response b/c emotions cause vasodilation of the arterioles within muscles which will lead to <BP and fainting
Spinal shock
occurs immediately after traumatic SCI, functions below the level of the lesion are lost including the somatic and autonomic reflexes (BP, sweating, bowel and bladder emptying); after several week most will see return of some cord function and some reflex below the lesion returns; neurons involved may become excessively excitable (hyperactive)
Horner's syndrome
occurs with interruption to the sympathetic pathway to the head; causes mitosis, ptosis, flushing and anhidrosis; symptoms will be ipsilateral
Special functional components
only exist in cranial nerves
Preganglionic parasympathetic neurons
only synapse with 4 or 5 post ganglionic neurons; usually all in the same effector organ; localized response
What we can do for patient with AD
patient may not be aware of cause as the inciting event doesn't reach the conscious level; look for and remove stimuli if possible: bladder overfilling, blocked catheter, impacted bowel, excessive muscle stretch; monitor BP, attempt to sit patient up (orthostatic position)
Thalamus
projects to the limbic system; modulates autonomic activity
Mitosis
pupil constriction
Flushing
red face; loss of vascular tone
Reflexive functions of the bladder, bowel, and male sexual organs
require intact afferent, lumbar, and sacral spinal cord segments, and somatic and autonomic efferents
Voluntary functions of the bladder, bowel, and male sexual organs
require intact neural pathways between the organ and the cerebral cortex
Cholinergic neurons
secrete acetylcholine (Ach); most of the parasympathetic postganglionic neurons and some of the sympathetic postganglionic neurons
Adrenergic neurons
secrete epinephrine (E) and norepinephrine (NE); most of the sympathetic postganglionic neurons
Reticular system
sets the ARAS (ascending reticular activating system) in motion; causes alertness, can't sleep with pain, and/or full bladder awakens you
PNS
spinal nerves (31 pairs) and cranial nerves 3-12
Visceral
supplies smooth muscle, cardiac muscle, and glandular secretory cells
Somatic
supplies the sin and skeletal muscle
Subdivisions of the ANS in the PNS
sympathetic and parasympathetic; some also consider the enteric nervous system (intrinsic nervous system of GI tract) to be a 3rd
Autonomic dysreflexia
sympathetic hyperreflexia; caused by excessive action of the sympathetic nervous system and occurs with spinal cord lesions above T5/T6; initiated by noxious or painful stimuli below the lesion (overstretched bladder/rectum); is a medical emergency and if you cannot find problem and resolve it then the patient needs to be referred to the ER
Autonomic tone
the balance between inputs from both the sympathetic and parasympathetic innervation into an organ; is regulated by the hypothalamus (if it increases sympathetic action it will decrease parasympathetic activity); however there can be time where the action of S and PS is unopposed (change in the curvature of the lens is a PS function)
Ganglion impar
the coccygeal sympathetic paravertebral ganglion; where the two sympathetic trunks join
If temp is too high
the hypothalamus tells the ANS that heat dissipation is needed and sympathetic cause cutaneous vasodilation and sweating
Peripheral ganglia of the parasympathetics
typically found near or within the wall of the visceral effectors and are called terminal ganglia; discrete ganglia have specific names in the cranial region
Antagonist functions with synergist effects
when the S and PS offer opposing actions that provide optimal organ function
Parasympathetics above the lesion
will cause bradycardia, vasodilation with flushing, nasal congestion, sweating
Lesion above T5/T6
will have 3 dysfunctions: autonomic dysreflexia, poor thermoregulation, orthostatic hypotension