Blood pressure regulation by baroreceptors
Reports or information related to blood pressure variations in the arterial system (the level, volume and chemical composition of the blood) can be sensed and gathered through specific receptors. There are the following receptors: baroreceptors, chemoreceptors and receptors from heart atrium chambers and chambers (A, B and C type, natriuretic peptide).
Picture 1. Anatomic picture of aortal /carotid nerves.
Main nerves connecting the area of the baroreceptors with the hypothalamus
through spinal chord with Nervus Glossopharygeus (IX nerve) and Nervus Vagus (X)
There are two types of baroreceptors shown in the Picture. One type is found in
the carotidal sinus at the point of forking of the carotidal artery, and the
other type is in the aortal wall. There are also receptors scattered between
these "main" receptors. Baroreceptors are terminal part of nerve fibrils, which
forks in adventitia and meiya of the carotidal sinus and the above mentioned
part of the aorta.
In which way does the increased blood pressure stimulate baroreceptors?
Increased blood pressure in the arterial system causes the stretching of the
blood vessel wall, and even of the receptor itself. It means that the increased
blood pressure causes the stretching of elastic blood vessel. When stretched,
the receptor reacts and has effects on the newly generated situation. The
activity of baroreceptors is continuous, or we could better say they are always
"awake" and continuously responding to blood pressure variations. Received
stimuli due to blood pressure variation, its increase or drop, are sent to
corresponding brain centres. These "centres" are also continuously active,
sending the received "information" toward parasympaticus or sympaticus. If the
influence of sympaticus is decreased, the heart rhythm slows down and the
diameter of blood vessels increases, resulting in the drop in blood pressure in
the arterial system.
When the blood pressure reaches 220 mmHg, the frequency of impulses from
corresponding nerve is close to the maximum response. Normal heart (provided
that also CNS is balanced) imposes to the receptors alternately the systolic and
diastolic pressure. During variation of the blood pressure, when it is in the
phase of dropping, the receptors stop their activity, even when the pressure is
above the threshold when their intervention normally begins. It means that the
receptors are sensitive not only to medium arterial pressure, but also to the
speed of arterial pressure variations
The hypothalamus, as the emotion centre, may cause the increase in the blood
pressure, by sending gathered information (impulses) through the sympaticus in
case of: anger, fear or uneasiness (feelings that the modern man goes to bed and
wakes up with). Over a certain period of time a chronic hypertension will
appear. This is, to some extent, an explanation of the mass occurrence of
hypertension in our region.
When will we write the diagnosis: dg hypertensia
arterialis?
|
Systolic pressure |
Diastolic pressure |
|
Normal - increased- 130 - 139 mmHg |
Increased- 9o mmHg and more |
|
Normal - increased- 130 - 139 mmHg |
Normal - increased - 85 – 89 mmHg |
|
Ideal 129 or lower |
Ideal 84 or lower |
A physician will write the diagnosis hypertensia arterialis if the blood pressure measurements made during more than two visits to the physician, show the values exceeding the ideal pressure values.
|
PHISIOLOGIC STATUS |
PATOLOGIC STATUS |
HABITS, LIFESTYLE |
|
- Age |
- Hypertension |
- Smoking |
Risk factors for cardiovascular diseases (RFCD) can be
divided into three categories: physiologic, pathologic and those depending on
lifestyle and habits.
Some states of pain, or suffering, which may be increased by worry, or strong
desire which cannot be realized (in case of poverty, struggle for survival,
unfair competition, constant psychic tension), cause the increased secretion of
cateholamines. Cateholamines have effects on the pancreas (on beta cells), which
causes the decreased secretion of insulin. Insulin suppression increases the
activity of the cyclic AMP, which increases FFA (free fatty acids) in the
plasma. They cause damage to the metabolism of myocardium.
Cateholamines produce bad effects also to the liver. They
cause in the liver the glycogenolisis increasing in this way the content of
glucose in the blood. It also causes disorders of the metabolism of myocardium
(the heart muscle). Decreased quantity of insulin causes additional metabolic
disorders. The increased blood pressure and obesity occurs with most of these
patients. This is still the realistic picture of our everyday survival and the
cause of the occurrence of the hypertension disease.
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