ANS Flashcards
Target Organs Innervated by ANS
Cardiac muscle
Smooth muscle
glands
Structural motif
2 neuron relay: one is the preganglionic neuron in the CNS. Then there is a ganglion that exists outside the CNS where the presynapses with a posganglionic neuron.
ACH
Used in poth pre to post neurons. ACH is used at teh PNS site of action.
NE
NE used at the site of action for SNS except for sweat glands and some vasodilatory fibers that ALSO use ACH.
Divergence
The SNS will have axons from one preganglionic cell synapse on numerous ganglia and therefore synapse with many post ganglionic cells, on average 1: 10. The PNS 1:3
SNS spinal level
SNS is thoracolumbar so T1 to L2. The neurons live in the lateral horn as the IML cell column. Their axons then access the peripheral ganglia and commonly the ones that make up the sympathetic trunk of the body , which are at ALL LEVELS of the sp cd and the target tissue is VERY broad.
PNS
craniosacral outflow. It only goes to a few different organs really.
How does the SNS get to the head
Through the vascular system. The superior cervical ganglion at the top of the IML will send out SNS postganglionic fibers to the glands of the face and such to shut down crying and salivation through constricting down the blood supply to these areas. So not stopping function, but cut off energy.
Prevertebral ganglia
The:
Celiac
Superior mesenteric
Inferior mesenteric
SNS to adrenal medulla
Pass through paravertebral ganglion en route to adrenal medualla. EPI released to act systemically in the body. This will mainly be fear response . So AMYGDALA to stria terminalis to hypothalamus paraventricular nuclei to parvocellular cells. CRH released. Cortisol stimulated. Also other paraventricular outflow that will cause SNS activity in the body to increase mainly in the adrenal MEDULLA to cause systemic release of EPI and the wide SNS effects through the body.
Gray rami
Preganglionic axons have many options and these are going through the gray rami. ALL spinal nerves contain gray rami.
White rami
Take preganglionic SNS fiberts to the sympathetic trunk. So the WHITE RAMI are from the paraventricular trunk to the sp cd. They are white because they are MYELINATED . These white ramin only exist from T1 to L2.
T1 to L2
ONLY T1 to L2 contain the WHITE rami that reflex back to the spinal nerve from IML column.
What do the gray rami do
Take the postsynaptic sympathetic fibers back to the spinal nerves and to the output organs and this is why they exist at every level.
4 CN that comprise of the PNS
CN III, VII, IX, X
Edinger-Westphal nucleus
CNIII: PNS axons that runs from the Brainstem Nucleus the Edinger-Westpal nucleus to the peripheral ganglion, the ciliary ganglion and gets to the sphincter pupillae m and cause the pupillary light reflex so constrict the eye
Superior Salivatory
CNVII: PNS axons that run from the Brainstem nucleus, the Superior Salivatory nucleus, to the peripheral ganglion the Pterygopalatine ganglion. From the Pterygopalatine ganglion they will travel to the lacrimal gland and the sublingual and the submandibular glands.
Inferior Salivatory
CN IX: PNS axons that run from the Brainstem nucleus the Inferior Salivatory nucleus to the Peripheral nucleus, the Otic ganglion. It runs to the parotid gland for more salivation.
Dorsal Motor Nucleus
CNX: PNS axons that run from the Brainstem nucleus, the Dorsal Motor Nucleus, to the Peripheral ganglion, the Myenteric and Submucosal (terminal) and end in smooth muscle; and glands of the GI tract.
S2-S4
Level of the spine that send out PNS fibers called PELVIC SPLANCHNIC nerves that go the pelvic splanchnic ganglia in the structures that are below the inferior mesenteric ganglion, so the ureter, the bladder, the genitals, and the uterus, and a little part of the bowel. This is good for urination.
Vasovagal syncope symptoms
muscle weakness
warn sensation
nausea
sweating
Idiology of vasovagal syncope
Not fully understood.
CN10 activation.
Peripheral venous pooling >
Splanchnic pooling activates low-pressure mechanoreceptors (interpreted by brain as increased venous pressure) >
Withdrawal of sympathetic activity and increas in vagal activity
Inappropriate periperal vasodlation and bradycardia> hypotension and syncope
ANS component of baroreceptor reflex: receptors ?
stretch receptors in the carotid sinus (IX) , and
stretch receptors in the aortic arch (X)
ANS component of baroreceptor reflex: afferent limb
glossopharnygeal n. (IX) and vagus n. (X)
ANS component of baroreceptor reflex: CNS Processing
nucleus solitarius
ANS component of baroreceptor reflex: Efferent Limb
a) Parasympathetic: axons of vagus nerve (X) from neurons in dorsal motor nucleus (cardioinhibitory response)
b) SNS: intermediolateral cell column of spinal cord; cardiostimulatory and pressor response)
Characteristics of Horner’s syndrome
Ptosis Miosis Anhidrosis Enophthalmos (apparent) -Loss of sympathetic innervation (dilator pupillae m. and superior tarsal m. ( of Mueller) , facial sweat glands
Causes of Horner’s
Damage to the superior cervical ganglion. Also if the hypothalamus tract called the hypothalamospinal tract is damaged because this is the one that carries the input to the SNS in the first place.
Hypothatlamospinal tract
Fibers whose cell bodies are in the paraventricular nucleus of the hypothalamus will send their axons down the lateral brainstem and spinal cord (next to the spinothalamic tract) and then synapse in the IML column of the spine, first level. The cell bodies here send their preganglionic SNS axons to the SCG, and the SCG sends its postganglionic fibers to the eye by virtue of having them climb the ICA.
Wallenberg Syndrome (lateral medullary syndrome)
The descending hypothalamospinal tract descends laterally in the brainstem and the medulla specifically. So lateral medullary syndrome will cause SNS damage as well.
Wallenberg Syndrome (lateral medullary syndrome) sypmptoms
Dysarthria Dysphagia Contralateral loss of pain and temperature Ipsilateral loss of facial sensation Horner's syndrome
Wallenberg Syndrome (lateral medullary syndrome) causes
PICA damage that creates a wedge lesion that compromises the nucleus solitarious to give you dysarthria, dysphagia and also damage to the trigeminal tracts for sensation to the ipsilateral face and spinothalamic tract to the contralateral body. Because the hypothalamospinal tract also descends in the lateral brainstem, this stroke will cause Horner’s as well.
The dyarthria and dysphagia are due to KO of Vagus
Checkerboard
Brainstem stroke is going to have checkerboard damage in the body.
Medial medullary syndrome
KO of the hypoglossal LMN. Thus the tongue will lick the side of the lesion. There will be contralteral deficit in both the touch and pain pwy of the body since they have crossed below this site.
Autonomic dysreflexia
Spike in BP that the PNS cannot contain. The HR decreases as a response to this (PNS compensation)
Characteristics of autonomic dysreflexia
PAROXYSMAL HTN with sweating, flushing, slow HR (
Common cause of autonomic dysreflexia
spinal cord injury
Micturition
S2-S4> pelvic splanchnic nerves > inferior hypogastric plexus > postganglionic fibers > detrussor m. > contraction (micturation)
Urinary storage:
Intermediolateral cell column T11-L2> lumbar splanchnic nerves> internal urethral sphincter> contraction> storage
-Somatic motor innervation (S2-S4/ pudendal n. ) > external urethral sphincter > contraction > storage.
Males reproductive fnx
Sexual stimulation> Erection (purely vascular and is controlled by PNS division)
Ejaculation consists of 2 processess: emission & ejaculation. These processes are under SNS and somatic control.
Female reproductive fnx
Ilioinguinal and perineal (somatic) nerves supply external genitalia. Internal reproductive structures receive not only autonomic innervation, but also regulated by hormones
Hirshprung’s dz
Congenital absence of myenteric (Auerbach's) plexus; failure to ganglion cells located between layers of muscularis externa. No peristalsis in denervated colon (which appears small) compared to proximal part of colon which becomes distended Surgical correction (reversible colonoscopy initially, followed by surgical reanastomosis to rectum/anus) .
