Human Phys 5.3 Flashcards
What are chemoreceptors sensitive to?
Oxygen lack
CO2 excess
H+ ion excess
Where are peripheral chemoreceptors located?
In carotid bodies near the carotid bifurcation and on the arch of the aorta
What does activation of chemosensitive receptors result in?
Excitation of the vasomotor center
When are chemoreceptors stimulated?
When partial oxygen falls below 60 mmHg
What is the CNS ischemic response activated in response to?
Cerebral ischemia
What does reduced cerebral blood flow cause?
CO2 build up which stimulates vasomotor center and increases arterial pressure
What is one of the most powerful activators of the sympathetic vasoconstrictor system?
CNS ischemic response
What does a prolonged CNS ischemia have?
A depressant effect on the vasomotor center
Cushing reaction steps
Increased cerebrospinal fluid pressure
Compression of cerebral arteries
Decreased blood flow
Cushing reaction leads to increased BP
Blood flow is restored
What do low pressure baroreceptors in atria and pulmonary arteries do?
Minimize arterial pressure changes in response to changes in blood volume
What does increase in blood volume activate?
Low pressure baroreceptors which in turn lower arterial pressure
How does activation of low pressure baroreceptors enhance Na+ and water excretion?
Decreasing rate of antidiuretic hormone
Increasing glomerular filtration rate
Decreasing Na+ reabsorption
Increase in blood volume causes what?
Increase in atrial stretch
Increased natriuretic peptide and decreased renal sympathetic activity
Increased sodium and water excretion
Bainbridge reflex
Increase in atrial pressure causes increase in HR by 75% which increases CO to push out more blood and lower pressure (15% due to mechanical stretch on sinus node)
What does the bainbridge reflex help prevent?
Damming of blood in veins, atrial, and pulmonary circulation
What is the bainbridge reflex response to high pressure receptors?
Decreased HR
What is the bainbridge reflex response to low pressure receptors?
Increase HR
Increase CO
Increase renal perfusion
Increased Na+ and water excretion
What do stretch receptors in the atria transmit signals to in the bainbridge reflex?
Medulla via vagal afferents and sympathetic efferents signals are transmitted back to increase HR and contractility
How do intravenous infusions increase HR?
Through bainbridge reflex
How does the intravenous infusions decrease HR?
Baroreceptors
What do baroreceptors and chemoreceptors also stimulate?
Abdominal muscles
What does abdominal muscles contracting help increase?
Venous return and CO
What does inspiration lead to?
HR acceleration
What does expiration lead to?
HR deceleration (due to activity of vagal fibers increasing)
What does spillover from inspiratory centers stimulate?
Vasomotor center
What does decreased intrathoracic pressure lead to?
Increased venous return
What does relieving stretch on high pressure arterial receptors cause in the baroreceptor reflex?
Tachycardia
What does stretching low pressure atrial receptors cause in the bainbridge reflex?
Tachycardia
