Cardiopulmonary Reflexes

CARDIOPULMONARY REFLEXES

Q. 1

True about volume receptors is all EXCEPT:

 A They are low pressure receptors
 B They provide afferents for thirst control
 C They are located in carotid sinus
 D

They mediate vasopressin release IA

Q. 1

True about volume receptors is all EXCEPT:

 A They are low pressure receptors
 B They provide afferents for thirst control
 C They are located in carotid sinus
 D

They mediate vasopressin release IA

Ans. C

Explanation:

They are located in carotid sinus REF: Ganong’s 22nd edition chapter-14, http://en.wikipedia.org/wiki/Low_pressure_receptor_ zones

Baroreceptors can be divided into two categories: high-pressure arterial baroreceptors and low-pressure baroreceptors (also known as cardiopulmonary or volume receptors)

BARORECEPTORS

 

High pressure baroreceptors

Low pressure baroreceptors

Synonym

Arterial baroreceptors

Cardiopulmonary baroreceptors, Volume

receptors

Location

Carotid sinus & Aortic arch

Great veins, right and left atria, and

pulmonary vessels

Pressure

sensitivity

> 60 mmHg blood pressure

< 60 mmHg blood pressure

Monitors/

Regulates

Systemic and cerebral blood

pressures

Regulation of blood volume (via

Vasopressin, renin and aldosterone)

Drinking is regulated by plasma osmolality and ECF volume in much the same fashion as vasopressin secretion. Water intake is increased by increased effective osmotic pressure of the plasma, by decreases in ECF volume

ECF volume also affects vasopressin secretion. Vasopressin secretion is increased when ECF volume is low and decreased when ECF volume is high. There is an inverse relationship between the rate of vasopressin secretion and the rate of discharge in afferents from stretch receptors in the low- and high-pressure portions of the vascular system.


Q. 2

Bain Bridge reflex causes:

 A

Increases Heart rate

 B

Decreases heart rate

 C

Decreases blood pressure

 D

Decreases distension of large somatic veins

Q. 2

Bain Bridge reflex causes:

 A

Increases Heart rate

 B

Decreases heart rate

 C

Decreases blood pressure

 D

Decreases distension of large somatic veins

Ans. A

Explanation:

A Bainbridge Reflex is a positive feedback mechanism in which there is a compensatory increase in heart rate, due to a rise in right atrial pressure. It is commonly referred to as an Atrial Reflex.

Bainbridge reflex, or atrial reflex: is an acceleration of the heart rate resulting from increased blood pressure in, or increased distension of, the large systemic veins and the right upper chamber of the heart.
  • Atrial stretch receptors are responsible for this.
  • Afferent signals: are carried through the vagus nerves to the medulla of the brain.
  • Efferent signals are transmitted back through vagal and sympathetic nerves to increase heart rate and strength of heart contraction.
Prevents damming of blood in the veins atria and pulmonary circulation. The reflex competes with the baroreceptor-mediated decrease in heart rate produced by volume expansion and is diminished or absent when the initial heart rate is high. Bain bridge Reflex can be eliminated by transection of the cardiac autonomic nerve supply and injection of atropine.
 
A “reverse” Bainbridge reflex has been proposed to explain the decreases in heart rate observed under conditions in which venous return is reduced, such as during spinal and epidural anesthesia, controlled hypotension, and severe hemorrhage. 
 
Ref: Complications in anesthesiology, edited by Emilio B. Lobato, M.D., Nikolaus Gravenstein, Robert R. Kirb,Page 300;  Essentials Of Medical Physiology, By Khurana,Page 198.

 


Q. 3

Bainbridge reflex in the heart is mediated by the following receptors:

 A

Atrial A and B receptors

 B

C fibers

 C

Atrial A receptors

 D

Atrial B receptors

Q. 3

Bainbridge reflex in the heart is mediated by the following receptors:

 A

Atrial A and B receptors

 B

C fibers

 C

Atrial A receptors

 D

Atrial B receptors

Ans. A

Explanation:

The A and B receptors are thought to mediate the increase in heart rate associated with atrial distension (such as can occur with intravenous infusions) known as the Bainbridge reflex.
 
Activation of atrial C fibers generally produces a vasodepressor effect (bradycardia and peripheral vasodilation).
 
Also know:
  • Type A receptors react primarily to heart rate but adapt to long-term changes in atrial volume. 
  • Type B receptors increase their discharge during atrial distension. 
  • C fibers arise from receptors scattered through the atria; these discharge with a low frequency and respond with increased discharge to increase in atrial pressure. 
Ref: Hoit B.D., Walsh R.A. (2011). Chapter 5. Normal Physiology of the Cardiovascular System. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst’s The Heart, 13e.

Q. 4

Depressor reflex, Bezold-Jarisch reflex, produced by the following stimulus:

 A

Atrial overload

 B

Myocardial infarction

 C

Ventricular distension

 D

Isotonic exercise

Q. 4

Depressor reflex, Bezold-Jarisch reflex, produced by the following stimulus:

 A

Atrial overload

 B

Myocardial infarction

 C

Ventricular distension

 D

Isotonic exercise

Ans. C

Explanation:

 
Ventricular distension can produce a powerful depressor reflex called the Bezold-Jarisch reflex; vagal afferents of this cardiopulmonary reflex are also activated by chemical stimulation (eg, prostanoids, cytokines, serotonin, and classically, Veratrum alkaloids). The central connections for this reflex are in the nucleus tractus solitarii, which has both sympathetic and parasympathetic synapses.
 
Ref: Hoit B.D., Walsh R.A. (2011). Chapter 5. Normal Physiology of the Cardiovascular System. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst’s The Heart, 13e.


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