Blood Pressure

There are a number of factors that must be taken into account in order to attain homeostasis through regulating blood pressure, controlled by the hypothalamus. They are heart rate, blood-vessel dilation, water balance, ambient temperature, metabolic rate, respiratory rate (breathing), detoxification, hormones, blood sugar level, and disease.

If one of those is out of balance the blood pressure goes up and stays up until the imbalance is corrected, if it can be corrected.

Homeostasis is the ability of the body to maintain an internal environment that is constant, regardless of outside influences. The body controls blood pressure, temperature, respiration and even blood glucose levels by using several internal mechanisms to keep things constant. Blood pressure remains within normal limits through the utilization of both RAPID AND SLOW mechanisms. Working together, the mechanisms strive to maintain an approximate blood pressure of 120/80 mm Hg.

The baroreceptor reflex is one of the most important fast acting homeostatic mechanisms involved in regulating blood pressure. This consists of receptors, sensory nerves, the medulla oblongata and motor nerves, all working together. Another rapid acting mechanism in the regulation of blood pressure is the secretion of epinephrine and norepinephrine by the adrenal gland.

There are several mechanisms that deal with the long-term control of blood pressure. The renin-angiotensin-aldosterone mechanism is the most important. The kidneys secrete renin into the bloodstream, where it interacts with angiotensin. Angiotensin causes blood vessels to constrict and also causes the secretion of aldosterone. Aldosterone increases the amount of water and sodium absorbed by the kidneys, which leads to an increased amount of salt and water in the bloodstream. This combination of activities causes blood pressure to rise.

When an individual is diagnosed with high blood pressure, it is often complicated to pinpoint the exact cause of the condition. However, there are a number of contributing factors that can result in this particular condition.

1) One of the first factors that can play a large role in the development of high blood pressure is being overweight. It is essential that an individual maintains a weight level that is appropriate to their body mass index, or BMI, as this is a great prevention measure for this complication.

2) The second factor that may play a role in the development of high blood pressure is inactivity. Individuals who fail to participate in at least three to four hours of physical exercise on a weekly basis are likely to have higher blood pressure numbers then the people who do exercise regularly.

3) High blood pressure may be experienced if an individual consumes a high level of alcohol on a regular basis, or they smoke. Both of these lifestyle choices can be extremely detrimental to an individuals health levels.

4) Individuals who consume a high amount of salt on a regular basis have been found to experience high blood pressure. It is important to have a small intake of salt for basic body function, however, if too much salt is consumed, it can prove to be devastating to the health of an individual.

5) Genetics plays a large role when it comes to blood pressure health. Those that come from a family that has a history of blood pressure problems are likely to experience these same types of issues. This is often referred to as "genetic predisposition".

6) Those that do not consume foods that are high in calcium may experience high blood pressure. It is also essential to eat foods that contain high potassium levels. A decrease in either two of these ingredients can drastically increase blood pressure numbers.

Firstly, just to clarify, hypovolemic shock results from a large-scale loss of blood, and may be characterized by an elevated heart rate and intense vasoconstriction.

Blood pressure is controlled by nervous, renal, and hormonal mechanisms. All of these control systems are highly integrated. I don't know if the user above mentioned this, but antidiuretic hormone and aldosterone function in blood pressure control. The neural controls responsible for controlling blood pressure operate via reflex arcs chiefly involving the following components: baroreceptors and the associated afferent fibers, the vasomotor center of the medulla, vasomotor (efferent) fibers, and vascular smooth muscle. The neural controls are directed primarily at maintaining adequate systemic blood pressure and altering blood distribution to achieve specific functions.

I am officially confused.  Is the B/P of 60/40 not indicative of low blood pressure?  Sp, if this is the case, how does high B/P play a role in this question.
Please help.

Thanks to all

Yes, yes, it is.

So, in the case of the patient mentioned above, which would be the 5 parameters that control b/p homeostasis?
Thanks

Here's my take...

The blood pressure is determined by the rate of blood flow produced by the heart (cardiac output), and the resistance of the blood vessels to blood flow. This resistance is produced mainly in the arterioles and is known as the systemic vascular resistance (SVR) or the peripheral vascular resistance (PVR).

Pretty much: Blood pressure = cardiac output x SVR

Physiological mechanisms to maintain normal blood pressure are listed below:

1. Autonomic nervous system responses
2. Capillary shift mechanism
3. Hormonal responses
4. Kidney and fluid balance mechanisms

The autonomic nervous system is the most rapidly responding regulator of blood pressure and receives continuous information from the baroreceptors (pressure sensitive nerve endings) situated in the carotid sinus and the aortic arch. This information is relayed to the brainstem to the vasomotor centre (VMC). A decrease in blood pressure causes activation of the sympathetic nervous system resulting in increased contractility of the heart (beta receptors) and vasoconstriction of both the arterial and venous side of the circulation (alpha receptors).   
 
The Capillary fluid shift mechanism refers to the exchange of fluid that occurs across the capillary membrane between the blood and the interstitial fluid. This fluid movement is controlled by the capillary blood pressure, the interstitial fluid pressure and the colloid osmotic pressure of the plasma. Low blood pressure results in fluid moving from the interstitial space into the circulation helping to restore blood volume and blood pressure. 
 
Hormonal mechanisms exist both for lowering and raising blood pressure. They act in various ways including vasoconstriction, vasodilation and alteration of blood volume. The principal hormones raising blood pressure are:

(a) Adrenaline and noradrenaline secreted from the adrenal medulla in response to sympathetic nervous system stimulation. They increase cardiac output and cause vasoconstriction and act very rapidly.

(b) Renin and angiotensin production is increased in the kidney when stimulated by hypotension. Angiotensin is converted in the lung to Angiotensin II, which is a potent vasoconstrictor. In addition these hormones stimulate the production of aldosterone from the adrenal cortex which decreases urinary fluid and electrolyte loss from the body.       



This system is responsible for the long term maintenance of blood pressure but is also activated very rapidly in the presence of hypotension. 
 
The kidneys help to regulate the blood pressure by increasing or decreasing the blood volume and also by the renin-angiotensin system described above. They are the most important organs for the longterm control of blood pressure.

Therefore, blood pressure is controlled by several physiological mechanisms acting in combination. They ensure that the pressure is maintained within normal limits by adapting their responses both in the short and long term to provide an adequate perfusion to the body tissues.

Thanks a lot.  This is makes more sense.