AUTONOMIC NERVOUS SYSTEM. DR. MUNISHA AGARWAL DR. SAURABH TANEJA. www.anaesthesia.co.in firstname.lastname@example.org. PARASYMPATHETIC Long preganglionic fibers Short postganglionic fibers Function : Conserves energy 1 preganglionic synapses with 1 postganglionic fibre . SYMPATHETIC
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DR. MUNISHA AGARWAL
DR. SAURABH TANEJA
Long preganglionic fibers
Short postganglionic fibers
Function : Conserves energy
1 preganglionic synapses with 1 postganglionic fibre
short preganglionic fibers
long post ganglionic fibers
Function : fight/ flight response
one preganglionic synapses with many postganglionic fibresSYMP. & PARASYMP. NS.
Cranial nerves III, VII, IX, X, bulbar portion of XI , S2,3,4 (craniosacral)
CN III to eye,
CN VII to lacrimal, nasal and submaxillary glands.,
CN IX to parotid glands;
vagus to heart, lungs, oesophagus, stomach, small intestine, liver, gall bladder pancreas & upper part of the uterus
the sacral part innervates distal colon, rectum, bladder, lower portions of uterus & external genitalia
T1 – L2 (thoracolumbar)
22-24 ganglia on each side
thoracic (10-12), lumbar (4),
T1 to head,
T2 to neck & heart,
T3- T6 to chest,
T7-T11 to abdomen, T12-L2 to legs
Tests involving changes in the heart rate measure injury to parasympathetic system
After changes in HR, changes occur in the measures of Blood pressure that reflect sympathetic injury.
impaired venous return,
causing decreased stroke volume & decreased BP that reaches a plateau because of peripheral vasoconstriction i.e. increased systemic vascular resistance, with a compensatory tachycardia
After 15-20 sec. there is a rebound overshoot of BP to above baseline
(due to persistent peripheral arteriolar vasoconstriction and increased cardiac adrenergic tone),
accompanied by reflex bradycardia, with heart rate below baseline for about 1 min.
this rebound overshoot in phase IV, however, can be detected by inflating a cuff to just at SBP and then having the patient valsalva.
Without changing the cuff pressure, the sounds will disappear during breath holding , and on release the sounds will reappear and can be followed up to detect the rebound overshoot in BP.
an important clue to a neurogenic cause is aggravation or precipitation of symptoms by autonomic stressors (meal, hot bath, exercise, alcohol consumption).
intact autonomic nervous system
control of external sphincter
CEREBRAL CORTEX :
Smoothly : dry (sympathectomised)
Irregularly/ unevenly : moist, perspiring skin
placing a strip of sterile filter paper in the lower conjunctival sac and measuring the degree of wetting over 5 minutes.
supine values are decreased in postganglionic disorders (autonomic neuropathy or pure autonomic failure) and may fail to increase in preganglionic or postganglionic disorders (e.g. multiple system atrophy).
tyramine (releases NE from postganglionic terminals) and phenylephrine (denervation supersensitivity- directly acting α1 agonist) used.
In a postganlionic lesion, the response to tyramine is reduced & there is excessive response to subthreshold doses of phenylephrine.
↓ BP @ induction ↑ need for vasopressors
(parasympathetic dysfn RSI required)
hesitancy, decreased voidingfrequency, incontinence & UTI);
(increases with age and duration of disease);
in diabetic foot; pain & temp senses are lost before loss of touch & vibration senses.
↑ BP, ↓ flow to periphery, flushing & sweating above
the lesion & ↓ HR
hyperthermia due to loss of normal sweating response, may occur