Basics Exam 2 -Diana

Question 1

Normal Supine position

Answer 1

1. Venous return to heart increases
   Pooled blood from lower extremities towards the heart
   Increased preload, stroke volume, CO
2. Increase BP activates afferent baroreceptors
   Aorta (via vagus) and walls of carotid sinuses (via glossopharyngeal)
   Decreased sympathetic outflow
   Increased parasympathetic impulses to SA node and myocardium
   Results in compensatory decreased HR, stroke volume, and CO
3. Mechanoreceptors activated (Atria and ventricle)
   a)Decrease sympathetic outflow muscle and splanchnic vascular beds
   b)Atrial reflexes activated
   Regulate renal sympathetic nerve activity, plasma renin, atrial natriuretic peptide, arginine vasopressin

Question 2

Supine under anesthesia

Answer 2

1. General anesthesia, muscle relaxants, positive pressure ventilation, neuraxial blockade:
   a)Interfere with venous return, arterial tone, and autoregulation mechanisms
   b)Vulnerable to uncompensated circulatory changes in position
2. Sympathectomy
   reduces preload and blunts cardiac responses (So essentially taking your body’s normal responses away)

Question 3

Spontaneous ventilation-Pulmonary

Answer 3

1. Small change in negative intrathoracic pressure
   a) Due to diaphragmatic displacement and chest wall expansion
   Pb) romotes venous return due to reduced pressure in great veins and right atrium

Question 4

Supine position anesthesia

Answer 4

Supine position
FRC decreased  cephalad displacement of diaphragm
Contribution to ventilation of the chest wall compared with the diaphragm decreases from 30% to 10%
The preferential perfusion of the dependent portion of lung is dominated by gravity