ANS Flashcards
Function of ANS
-homeostasis and reproduction (HR, breathing)
-activity of internal organs (metabolism, digestion)
-activity of blood vessels
-Reflexes
Overview of ANS
-Mostly efferent axons not under conscious control of glands, muscles
-afferent carry info from organs to CNS
-controlled by hypothalamus
SNS: T1-L3
PNS: BS, S2-S4
ANS Flow of Info
Visceral/Vascular receptors < Limbic sys, hypothalamus, RF, SC < SNS, PNS, Hormones
ANS Receptors
Mechanoreceptors:
-BP in aorta, carotid sinus, lungs
-Stretch in veins, bladder, intestines
Chemoreceptors:
-02 in carotid and aortic bodies
-H/Co2 in medulla
-GLucose/electrolytes in hypthal
Nociceptors:
-damage to tissue walls and viscera
Thermoreceptors:
-changes in blood temp in hypthal
-external changes to skin
ANS Afferent Pathways
-enter through SC
Visceral Afferents: ascending neurons to BS, Hypthal, thalamus
-CN 7 & 9 Taste
-CN 9 & 10 Viscera: into solitary nucleus of medulla and pons
Visceral Nocicepive: nociceptive tracts relating to referred pain
-cause muscle guarding
BS control of ANS
Medulla: regulation through autonomic efferents in SC and vagus n
-HR, RR, vasoconstrictionn/dilation
Pons: respiration
Diencephalon and limbic role in ANS
-modulation of BS autonomic control
-hypothal
-most visceral input to thalamus is through limbic system
Divisions of ANS
Main:
-SNS: fight or flight
-PNS: rest and digest
Enteric NS: in gut for GI secretions and digestion
Cholinergergic Neurotransmitters
-acetylcholine
-all preganglionic neurons on ANS
-PNS post ganglionic neurons
Adrenergic Neurotransmitters
-Norepineophrine: most SNS postganglionic neurons
-Epinephrine: adrenal medulla
dopamine is precursor to norepinephrine and epinephrine
Preganlionic FIbers
-AB fibers
-neuron from CNS to ganglion
-acetylcholine
Postganglionic FIbers
-C fibers
-neuron from ganglion to effector organ
-acetylcholine (PNS) or norepinephrine (SNS)
Sympathetic NS (pre/post)
Preganglionic Neurons: cell bodies in lateral horn (T1-L3) exit through ventral root
-synapse w/ post neuron in communicating ramus (acetylcholine)
Postganglionic Neurons:
1. Cell bodies in sympathetic trunk to innervate smooth muscle and glands
2. Unpaired cells in ganglia < segmental spinal ganglia < abdominal and reproductive organs
- travel longer distances and closer to organs
Sympathetic NS Efferents
Efferents to Body:
-1 to adrenal medulla
- 2 tracts to periphery and viscera via paravertebral ganglion
- 2 tracts to abdominal and pelvic organs via paravertebral ganglion
T5-L2 pass through trunk w/o synapsing
Efferents to Head:
-originaes in hypothal and synapses in upper thoracic
-preganlionic fibers from upper throacic to cervical (stellate) ganglia via SNS trunk
SNS Function
-promote circulation to organs (increased SNS constricts, decreased dilates)
-fight or flight (dilation to muscles/lungs, contriction to gut, increase BP, BV, glucose)
-body temp regulation (sweating, goosebumps, dilation of skin BV)
Parasympathetic NS
-from BS to sacral cord lateral horns (S2-S4) < to end organs
-ganglia not interconnected like SNS
Preganlionic Neurons:
-BS Nuclei: CN 3 Edinger Westphal nuc, CN 7 superior salivatory nuc (lacrimal glands), CN 9/10 inferior salivatory nuc and nucleus ambiguus (salivary glands), CN 10 dorsal motor nucleus of vagus (heart, lungs, GI)
Lateral Horn S2-S4:
-pelvic nerves to B/B and external genitalia
PNS Function
-BS: rest and digest (constriction of pupils/lungs, decreased HR, digestion, glycogen synth)
-Sacral: regulates emtying of B/B and erection of penis and clitoris
SNS and PNS Synergy
-some actions are balanced by both systems
-some SNS activities controlling limbs and fac are not countered by PNS
-pupil contriction by PNS not countered by SNS
Breathing Rhythm Generator
-ant medulla blances arousal vs calm
-locus coeruleus responsible for arousal and alertness
-slow breathing inhibits locus c
Freeze, Fight, Flight
Freeze:
-co activation for SNS and PNS to prepare for action and optimize perception of threat
-amygdala recognizes threat < hypothal and ant medulla stimulate SNS < amygdala activates PNS for vagus to decrease HR and medulla to inhibit muscle contractions
Fight/Flight: PNS output decreases and SNS increases
Horner’s Syndrome
lesion of SNS preganglionic n to face ipsi, decreases adrenergic activation of nociceptors
-ptosis: droopy eyelid
-enopthalmos: sunken eye
-miosis: constricted pupil
-imaired sweating
-skin vasodilation (redness)
Peripheral Nerve Injuries
-SNS efferents affect circulation, breathing, sweating in area
SC Injuries
-depends on level and completeness
Complete in lumbar:
-B/B and sexual function
Complete injuries above T5
-homeostasis and temp, BP control
-Autonomic dysreflexia
Autonomic Dysreflexia
-irritantt below level of lesion causes ascending sympathetic unable to reach brain foor inhibition of BP
-contriction of BV and rapid BP increase
-skin below lesion is pale, above is red
-HR slows
-must induce orthostatic hypotension and check irriant
-cannot be stopped once it starts
Brainstem Injuries
-impaires efferent control of BP, HR, R
-dysfunction of CN nuclei
Cerebral injuries
-damage to nuclei in hypothal interferes with homeostasis
Orthostatic Hypotension
-decrease of 20 systolic and 10 diastolic, increased HR
-pooling of blood in limbs
-baroreceptor reflex to contric arteries
-fainting can be gravity reduced
Cause:
SCI, parkinson’s, neuropathy
Syncope
-fainting fom lack of blood flow to brain
Neural reflecive:
-emotional distress or pain or pressure on carotid sinus
-Vasovagal: medulla inhibits SNS and reduces HR
Orthostatic hypotension
Cardiac: arrhythmias or structure
