HRR: autonomic control of circulation Flashcards
What are baroreceptors?
Mechanoreceptors that sense stretch and send signals to the brain
Where in the brain do baroreceptors send signals?
Medulla
Where are major places we find baroreceptors?
Aortic arch, carotid sinus
The carotid sinus sends its signals through the ___ nerve, while the aortic arch sends signals through the ___ nerve.
Glossopharyngeal (9); vagus (10)
Do carotid or aortic have a wider range for sensing pressure and elicit response?
Carotid
Describe the reflex loop for activating the PSNS.
- Carotid sinus baroreceptors send signals to the medulla via cranial nerve IX
- Signal synapses bilaterally at the solitary nuclei
- Solitary nucleus sends signals to dorsal nucleus of the vagus and the nucleus ambiguous
- The pre-ganglionic PSNS fibers run through the vagus nerve and to their effector where the post-sympathetic neuron will be (heart)
Describe the reflex loop for de-activating the SNS.
- Aortic arch baroreceptors send signals to the medulla via cranial nerve X
- Signal synapses bilaterally at the solitary nuclei
- Solitary nucleus sends signals to the vasomotor area in the medulla
- Neurons travel and synapse in the spinal cord between T1 and L2
- Pre-ganglionic SNS neurons are activated
- Pre-ganglionic SNS neurons travel to the sympathetic chain and synapse on post ganglionic neurons
- Post ganglionic neurons travel to effector tissue
Describe the orthostatic response.
- Venous pressure increases in lower extremities
- Blood volume shifts from center to periphery
- Central venous pressure and cardiac output decrease
- MAP decreases which lowers baroreceptors activation
- SNS goes up PSNS goes down
- HR and contractility increases, and vasoconstriction increases
What is the muscle pump effect?
Contraction of muscles is very effective at pushing blood upwards to prevent venous pooling
What is vasovagal syncope?
Emotional stress leads to massive PSNS stimulation
What is carotid sinus syncope?
Excessive activity of carotid sinus baroreceptors leads to large PSNS activation
What is micturition syncope?
A rapid release of urine from a distend bladder can cause a rapid reduction of MAP
What is orthostatic syncope?
Autonomic insufficiency from sitting to standing
Describe the autonomic response to circulatory shock.
- Reduced CO and MAP and/or cerebral ischemic response decrease the baroreceptors response
- SNS is ramped up and PSNS is inhibited
- HR and contractility increase, s does vasoconstriction
What is the valsalva maneuver?
A test for autonomic function; it measures arterial and esophageal pressure. You take a large inhale and hold your breath. This will cause a temporary increase in arterial pressure, but increased venous compression will lower venous return and then cause the atrial pressure to drop. This then leads to increased HR and vasoconstriction. When we exhale, this reverses.
