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