autonomic nervous system

ANS regulates

circulation, respiration, digestion, metabolism, secretions, body temp, reproduction

ANS sensory receptors

mechanoreceptors, chemoreceptors, nociceptors, thermoreceptors
same ones exist in somatic system
bring info back to CNS, can also impact function of somatic muscle

referred pain

collateral branch of autonomic afferent to 2nd order ALS neuron so brain interprets visceral pain as somatic, poor localization

sympathetic function

fight or flight, mobilize body energy, maintain optimal blood supply in organs

parasympathetic function

rest and digest, conserve energy

SNS/PSNS effect eye

pupil diameter: SNS dilates, PSNS constricts
lens curvature: PSNS increases

SNS/PSNS effect heart

contraction rate: SNS increase, PSNS decrease
contraction force: SNS increases

SNS/PSNS effect lungs

bronchi diameter: SNS widens, PSNS narrows
blood vessel diameter: SNS vasodilates
secretions: PSNS increases

SNS/PSNS effect sweat glands

SNS increase sweat production

SNS/PSNS effect salivary glands

SNS increase thick secretion, PSNS increase thin profuse secretion

SNS/PSNS effect lacrimal glands

PSNS increase tear production, SNS increase vasomotor to blood vessels of lacrimal gland

SNS/PSNS effect adrenal medulla

SNS increase secretion epi/norepi

SNS/PSNS effect GI tract

peristalsis: SNS decrease, PSNS increase
secretions: SNS decrease, PSNS increase

SNS/PSNS effect liver

SNS increase glucose release, PSNS increase glycogen synthesis

SNS/PSNS effect pancreas

secretions: SNS decrease, PSNS increase

SNS/PSNS effect bowel and bladder

emptying: SNS decrease, PSNS increase

SNS/PSNS effect external genitalia

PSNS increase erection

SNS effect on blood vessels

all from epi/norepi
skin: alpha receptor, vasoconstriction of arterioles to decrease radiation of heat from skin
skeletal muscle: alpha receptor, vasoconstriction of venules and veins to increase TPR and BP
heart: beta receptor, dilation for more blood available to heart

ANS distribution

PSNS in cranial nerves and sacral cord
SNS T1-L2 preganglionic cell bodies in lateral horn
SNS more diffuse impact, PSNS more local/targeted

sympathetic system

preganglionic in lateral horn T1-L2, leaves via ventral horn and synapses in sympathetic chain ganglion with postganglionic which is unmyelinated
short then long
exception: preganglionic to adrenal gland that acts as 2nd neuron and releases epi/norepi into bloodstream for more systemic effects

parasympathetic system

CN nucleus or intermediate sacral cord gray matter, vagus is primary nerve
preganglionic travels most of way to organ before synapsing with postganglionic neuron
long then short

neurotransmitters of ANS

preganglionic all use Ach which goes to nicotinic receptors
SNS: epi/norepi mainly to adrenergic receptors, some use Ach to muscarinic receptors
PSNS: Ach to muscarinic receptors

SNS distribution

chain ganglia extend above/below thoracic, allows SNS input to ext higher/lower
cervical: stellate ganglion, middle and sup cervical ganglion - lower lesion will cause SNS loss above
some outlying ganglia

sympathetic efferent paths

nucleus in lateral horn → preganglionic → white ramus → sympathetic chain ganglion → gray ramus → postganglionic → effector

parasympathetic efferent paths

parasympathetic nuclei in CN or sacral cord → preganglionic → close to effector organ → postganglionic → effector

enteric nervous system

large number nerve cells in myenteric and submucosal plexuses, largely self-sufficient but receives SNS and PSNS input
peristalsis: coordinated waves of smooth muscle contraction

central autonomic network

areas that project to preganglionic cells of SNS and PSNS, regulation from above to activate
solitary nucleus, hypothalamus, reticular formation - ventrolat medulla is vasopressor center (stimulation increases peripheral vascular resistance and CO)

horner’s syndrome

stellate ganglion lesion, some CNS lesions
ipsi face impairments: ptosis, pupillary constriction, vasodilation, loss of sweating

syncope

brief fainting due to inadequate blood supply to head
neural reflexive: cardiogenic (stress), situational, hypersensitive carotid sinus syndrome (dysregulates BP)
cardiac arrhythmias, orthostatic from autonomic failure

baroreceptor reflex

baroreceptors detect change in BP
baroreceptors go to solitary nucleus which receives body organ info (CN IX and X afferents), SNS or PSNS activate to normalize BP

baroreceptor SNS part

baroreceptors less active → less excitation solitary nucleus → less inhibition vasopressor medullary center → excites sympathetic preganglions → increase vessel tone (vasoconstriction) and increase HR and contractility to increase BP

baroreceptor PSNS part

baroreceptors more active → excite solitary nucleus → excite vagal motor center → inhibition to decrease HR and contractility to decrease BP