Atrial Stretch Reflexes

In addition to the baroreceptor reflex, several other reflexes help to regulate blood pressure. The reflex control of ADH release by osmoreceptors in the hypothalamus and the control of an-giotensin II production and aldosterone secretion by the juxta-

glomerular apparatus of the kidneys have been previously discussed. Antidiuretic hormone and aldosterone increase blood pressure by increasing blood volume, and angiotensin II stimulates vasoconstriction to cause an increase in blood pressure.

Other reflexes important to blood pressure regulation are initiated by atrial stretch receptors located in the atria of the heart. These receptors are activated by increased venous return to the heart and, in response (1) stimulate reflex tachycardia, as a result of increased sympathetic nerve activity; (2) inhibit ADH release, resulting in the excretion of larger volumes of urine and a lowering of blood volume; and (3) promote increased secretion of atrial natriuretic peptide (ANP). The ANP, as previously discussed, lowers blood volume by increasing urinary salt and water excretion and by antagonizing the actions of angiotensin II.

Valsalva's maneuver is the term used to describe an expiratory effort against a closed glottis (which prevents the air from escaping—see chapter 16). This maneuver, commonly performed during forceful defecation or when lifting heavy weights, increases the intrathoracic pressure. Compression of the thoracic veins causes a fall in venous return and cardiac output, thus lowering arterial blood pressure. The lowering of arterial pressure then stimulates the baroreceptor reflex, resulting in tachycardia and increased total peripheral resistance. When the glottis is finally opened and the air is exhaled, the cardiac output returns to normal. The total peripheral resistance is still elevated, however, causing a rise in blood pressure. The blood pressure is then brought back to normal by the baroreceptor reflex, which causes a slowing of the heart rate. These fluctuations in cardiac output and blood pressure can be dangerous in people with cardiovascular disease. Even healthy people are advised to exhale normally when lifting weights.

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Responses

  • Deborah
    What is atrial stretch?
    8 years ago
  • Ferdinand
    Do atrial stretch reflexes slow the heart rate?
    8 years ago
  • luam
    What will happen to the atrial stretch receptors when the blood pressure increases?
    8 years ago
  • luciana
    When venous return is increased stretch receptors in the atria of the heart are activated?
    8 years ago
  • gimja
    When venous return is increased, stretch receptors in the atria are activated resulting in?
    6 years ago
  • CONRAD
    When venous return is increased, stretch receptors in the atria are activated. This results in?
    6 years ago
  • Miska
    What is atrial stretch reflex?
    4 years ago
  • segan
    How artrial stretch reflex regulate blood pressure?
    3 years ago
  • delfio
    What is atrial strech reflex?
    3 years ago
  • Heidi
    Why diuresis isn't stimulated during exercise although atrial stretch receptors are activated?
    2 years ago
  • stephanie
    What is the role of atria reflex in the regulation of atrial bllod pressure?
    1 year ago
  • Ruby Hill
    What are the atrial rteach receptors?
    11 months ago
  • teppo
    What do atrial stretch recptors do?
    10 months ago
  • Maria
    How stretching of atrium leads to tachycardia?
    9 months ago
  • SINIT
    Why do you increase anp in response to atrial stretch?
    4 months ago
  • ruby
    Where are atrial receptors located?
    2 months ago

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