Week 8: Reflex control of circulation Flashcards
What results in the elimination of the sympathetic nerve activity?
drop in the mean aterial pressure
Sympathetic nerves innervate what elements of the cardiovascular system?
- blood vessels
- heart
Sympathetic nerves innervate which type of vessels?
- resistance vessels (arteries)
- capacitanec vessels (veins)
What innervation does the heart recieve?
- sympathetic (SA, AV node + cardiac muscle)
- parasympathetic ( only SA and AV nodes)
What is the pathway of the negative feedback regulation?
Setpoint → discriminator → forward signal → effector/s → regulated paramter → feedback signal
What are the three different types of receptors?
- high pressure receptors
- low pressure receptors
- chemoreceptors
What are the high pressure receptors and where are they located?
baroreceptors
located in the carotid sinus and in the aorta
Describe the baroreceptors in the carotid sinus
- predominantly elastic fibers (no collagen, no smooth muscle)
- sensitive to ↑ transmural pressure
- distention → stretch receptors
What is the graph displaying the relationship between arterial pressure and sinus nerve activity? What is significant?
The slope is largest at normal physiological range therefore the firing rate is very susceptible to change.
What is the major difference between the carotid baroreceptors and the aortic baroreceptors?
The dynamic range of the carotid baroreceptors is higher than the aoritc baroreceptors
Explain the graph displaying that the receptor potential ch changes in response to the elevation of arterial blood pressure
What are the receptor potential changes converted to?
action potential frequencies
Explain the graph
if the carotid is clamped the pressure in the carotid sinus is reduced due to the lack of blood flow
What is the graph representing the relationship between the isolated carotid sinus and systemic pressure?
Schematic scheme of the feed back regulation in response to ↑ mean arterial pressure
What is the response to sustained hyper tension in regards to the firing of the baroreceptors?
Where are the signals “passed to” when the receptors receive a high pressure signal?
aortic baroreceptors → vagus nerve
carotid sinus baroreceptors → herings nerve → glossopharingeal nerve
What makes up the cardioinhibitory area?
- dorsal motor nucleus of vagus (CN X)
- nucleus ambiguss (CN X and part of CN IX)
What is the pressure response in upright position?
correcting reflex activated within seconds
- venomotor activity (heterometric heart regulation)
- increased heart rate
- vasoconstriction
What is the pressure response when there is severe heamorhage?
- vasoconstriction
- splanchnic area
- kidney
What is the pressure response when there is heart stress?
skin vasodilation
What is the pressor response ?
the reduction of blood pressure in the high pressure system
Arterial blood pressure is normally kept in a relatively narrow range, what happens in the absence of high pressure baroreceptors?
large fluctuations
Where are baroreceptors in the low pressure system located? what do they do?
in the right atrium
sense primarily blood volume changes
What is the end result of intravenous infusion?
intravenous infusion
↓
increased right atrial pressure
↓
atrial receptors stimulated
↓
bainbrige reflex
↓
increased heart rate
End result: ↑ANP, ↓RAS
does NOT cause vasoconstriction
dilates renal arteries
prevents “stall blood” in veins
What happens in the situation of simultaneous pressure change in the arteries ?
vasoconstriction
What happens to low pressure receptors during volume depletion?
(fill gap with ↓ atrial receptor activity)
What happens during inspiration?
1. ↑ tension of the right atrium “bainbridge like effect”
- ↓ stroke volume
- respiratory center activity ↑
tension of lung mechanoreceptors ↑
3 composes the “crosstalk” (b/w respiratory and cardiac center)
What happens during sinus arrythmia?
What higher neural centers can modify medullary regulation?
motor cortex
cingulate
What role do chemoreceptors play?
dedicated to the regulation of the respiration
stimulate respiratory center
↑ ventillatory drive
Graph displaying the differencein sensitivities of chemoreceptors and baroreceptors
chemoreceptors operate only in times of emergency
What are the two classifications of chemoreceptors?
- central chemoreceptors (in medulla)
- peripheral chemoreceptors (aortic bodies, carotid bodies)
Draw the relation of intrinsic cardiovascular response to hypoxia, acidosis, and hypercapnia
Draw the cardiovascular/ respiratory response to hypoxia, acidosis, and hypercapnia
What is the cushings reflex?
↑ intracranial pressure
causes ischemic response of the central baroreceptor area
What does increaed intracranial pressure cause?
- strongly reduced blood flow in the medullary region
- activation of the vasomotor mechanism and cardioinhibitory area (vagus)
- bradycardia and very strong vasocontstriction “at any cost”
- kidneys could even ceise urine production due to how intense the vasoconstriction is
What happens in the Bezold-Jarish reflex?
the receptors in the left ventricular wall are effected (mechano and chemosensitive)
- bradycardia and hypotension (↑ parasymp and ↓ symp vasomotor activity)
- cardioprotective
can be activated e.g in myocardial ischemia/ infarction
What happens in moderate pain?
activation of vasomotor center
↑ heart rate and ↑ blood pressure
What happens in the occurence of strong pain and visceral pain?
parasympathetic activation
hypotension, bradycardia
