FACTOID # 15: A mere 0.8% of West Virginians were born in a foreign country.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
RELATED ARTICLES
People who viewed "Baroreceptor" also viewed:
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Baroreceptor


Baroreceptors (or baroceptors) in the human body detect the pressure of blood flowing though them, and can send messages to the central nervous system to increase or decrease total peripheral resistance and cardiac output.


Baroreceptors can be divided into two categories, high pressure arterial baroreceptors and low pressure baroreceptors (also known as cardiopulmonary receptors).


Arterial Baroreceptors

There are baroreceptors present in the arch of the aorta, and the carotid sinuses of the left and right internal carotid arteries.


Baroreceptors act to maintain mean arterial blood pressure to allow tissues to receive the right amount of blood.


If blood pressure falls, such as in shock, baroreceptor firing rate decreases. Signals from the carotid baroreceptors are sent via the glossopharyngeal nerve (cranial nerve IX). Signals from the aortic baroreceptors travel through the vagus nerve (cranial nerve X). This information is integrated in the medulla oblongata which sends messages to the heart muscle, the cardiac pacemaker and the arterioles and veins of the body.


The heart will begin to beat faster, and contract more forcefully. This increases cardiac output. The arterioles and veins contract (vasoconstriction and venoconstriction), this increases total peripheral resistance. Both these things serve to bring mean arterial blood pressure back to normal.


Baroreceptors work by detecting the amount of stretch. The more the baroreceptor walls are stretched, the more frequently they generate action potentials. The arterial baroreceptors have a lower threshold of around 70 mmHg (typical arterial blood pressure is around 80_90 mmHg). Below this the receptors stop firing signals completely, any further decrease in pressure will cause no additional effect. At this low pressure however the response of chemoreceptors becomes more vigorous, especially below 60 mmHg.


Baroreceptors respond very quickly to maintain a stable blood pressure, but they only respond to short term changes. Over a period of days or weeks they will reset to a new value. Thus, in people with essential hypertension the baroreceptors behave as if the elevated blood pressure is normal and aim to maintain this high blood pressure.


Low pressure Baroreceptors

These are found in the large veins and in the walls of the atria of the heart. The low pressure baroreceptors are involved with the regulation of blood volume. The blood volume determines the mean pressure throughout the system, in particular in the venous side where most of the blood is held.


The low pressure baroreceptors have both circulatory and renal effects, they produce changes in hormone secretion which have profound effects on the retention of salt and water and also influence intake of salt and water. The renal effects allow the receptors to change the mean pressure in the system in the long term.


Denervating these receptors fools the body into thinking that we have too low blood volume and initiates mechanisms which retain fluid and so push up the blood pressure to a higher level than we would otherwise have.


  Results from FactBites:
 
vasodilators (1440 words)
This causes the cardiac function curve to shift up and to the left (not shown in figure).
Adding to this afterload effect is the influence of enhanced sympathetic stimulation due to a baroreceptor reflex in response to the fall in arterial pressure, which increases heart rate and inotropy.
Although not shown in this figure, reduced cardiac output causes a fall in arterial pressure, which reduces afterload on the left ventricle and leads to baroreceptor reflex responses, both of which can shift the cardiac function curve up and to the left.
baroreceptor - definition of baroreceptor in Encyclopedia (498 words)
Baroreceptors (or baroceptors) in the human body detect the pressure of blood flowing though them, and can send messages to the central nervous system to increase or decrease total peripheral resistance and cardiac output.
There are baroreceptors present in the arch of the aorta, and the carotid sinuses of the left and right internal carotid arteries.
Baroreceptors act to maintain mean arterial blood pressure to allow tissues to receive the right amount of blood.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m