Reflexes Flashcards
Bainbridge Reflex
Increase in HR following IVF bolus
induced by centralization of blood volume with VC or change in body position
Reflex also appears to mediate HR s assoc with respiratory sinus arrhythmia
Reverse Bainbridge Reflex
may cause bradycardia in face of hypotension during spinal, epidural anesthesia DT increase in venous capacitance, decreased CVP
Bainbridge Reflex: stimulus
distention of vena cavae/ RA DT increase in central blood volume.
Detected by atrial stretch receptors (mainly atrial B MR) at junction of vena cavae in RA, in pulmonary veins.
Bainbridge Reflex: Afferent Pathway
vagal afferents to medullary vagal nuclei; sensory nucleus of vagus: nucleus tractus solitaries.
Bainbridge Reflex: Efferent Pathway
inhibition of vagal PNS outflow to SA node (decrease in ADH release).
Nucleus ambiguous contains cell bodies for vagal motor neurons to cardiac ganglia
Benzold-Jarish Reflex
bradycardia, apnea, hypotension during severe hypovolemia when ventricle empty
AKA coronary chemo reflex
BJR: stimulus
Stimulation of ventricular chemoreceptors and mechanoreceptors
BJR: Afferent
Stimulation sent through C-fibers to the vagus nerve to the vasomotor portions of the brainstem (NTS)
BJR: Efferent
decreased sympathetic outflow (afferent fibers of BJR have a tonic inhibitory effector on vasomotor tone; stimulation leads to decreased vasomotor tone)
BRR
Increased BP, decreases HR
blood pressure sensed at carotid sinus, aortic sinus MR from distension
BRR: Afferent
Aortic sinus mechanoreceptors signal through Vagus nerve (CNX), carotid body sinus MR signal through glossopharyngeal nerve (CN IX) to nucleus of solitary tract (NTS) then to ventral medulla
BRR: Efferent
Medulla signals increases in PSNS activity (release more ACh), decreases SNS activity at SA node to increases HR
Opposite effect with hypotension/increased SNS tone to increase HR
Branham Reflex
Hypertension followed by decrease in HR
Compression or excision of an AV fistula (ex: PDA ligation) resulting in a transient hypertension –> decreased HR
Branham: Afferent
Vagus n. to NTS
OCR: afferent
short, long ciliary nerves merge with ophthalmic division of trigeminal nerve, ciliary ganglion –> Gassenan ganglion –> nucleus of trigeminal, vagus nerve
OCR: efferent
Vagal fibers increase tone to SA node
Dive Reflex
Apnea, decreased heart rate, severe vasoconstriction
Stimulated by submergence of snout of aquatic animal
Dive Reflex: Afferent
Fibers innervating paranasal areas (anterior nasal mucosa, innervated by infraorbital N, anterior ethmoidal nerve (AEN) from maxillary/ophthalmic divisions of trigeminal)
Send fibers to trigeminal sensory complex.
Projections sent to medullary dorsal horn (MDH) of spinal trigeminal nucleus relay autonomic pathways.
Dive Reflex: Efferent Pathway
Parasympathetic vagus nerve stimulated to SA node.
Neurons in rostral ventrolateral medulla (RVLM) increase sympathetic nerve discharge on peripheral vasculature.
Inhibition of respiration from somatostatin neurons in pre-botzinger complex, ventral respiratory column, retrotrapezoid nucleus silenced
Anrep Effect
Increase in aortic pressure = positive inotropic effect
Bayliss Effect
Stretch of vascular SmM –> muscle cox, increased resistance
Result: blood flow toward normal
Atrial Stretch R Reflex
Atrial distension = release of ANP
ANP = diuretic activity, VD, aldosterone secretion, endogenous antagonist of AGTII
+/- sinus tachycardia, SVT
Vasovagal reflex
decrease in venous return to heart - sinus bradycardia, hypotension
DT hypovolemia, orthostatic, compression of CdVC, regional ax
Craniocardiac Reflex
Stimulation of cranial nerves (I, II, V) = bradycardia, hypotension
