Reflexes Flashcards
Stretch receptors in the right atrium are affected by
changes in CVP altering the distension of the atrium (preload)
Stretch receptors in the right atrium are attached to which afferent nerve
vagus
Stretch receptors in the right atrium signal to which areas in the brain
nucleus tractus solitarius (NTS) in the medulla
and paraventricular nucleus (PVN) in the hypothalamus
The effects stimulated by the volume receptor reflex when there is low blood volume
Increased SNS activity to kidney –> renal vasoconstriction –> less renal blood flow –> less filtration of plasma to kidney
Increased renin release –> more ATII –> Increased Na+ and water reabsorption
Increased ADH release from pituitary
So less urine, higher blood volume
The effects stimulated by the volume receptor reflex when there is high blood volume
Decreased SNS activity to kidney –> renal vasodilation –> more renal blood flow –> more filtration of plasma to kidney
Decreased renin release –> less ATII –> less Na+ and water reabsorption
Decreased ADH release from pituitary
Transient HR increase (Bainbridge reflex)
More urine, lower blood volume
The Bainbridge reflex aka the atrial reflex is
a transient increase in HR due to an increase in CVP/preload (blood volume) sensed by the low pressure baroreceptors
Baroreceptors are located
carotid sinus
aortic arch
Afferent nerve from carotid sinus baroreceptors
glossopharyngeal (IX)
Afferent nerve from aortic arch baroreceptors
vagus (X)
ABP =
TPR x CO
How baroreceptors alter SV (and so CO) via the CNS
veins constricting/dilating alters EDV
increased contractility lowers ESV
How baroreceptors alter TPR via the CNS
arteriolar constriction/dilation
Situations when the atria have more distention
lying down
large fluid intake by mouth
over-transfusion
Situations when the atria have less distention
standing (due to venous pooling)
haemorrhage
dehydration
