Hypertension ( complications, physiology and pathophysilogy )
Complications:
1- eye: retinopathy
2- cardiac: left ventricular hyperatrophy
, coronary artery disease ( angina of infarction )
and myocardial fibrosis .
3- vascular: arteriosclerosis
4- brain: encephalopathy , cerebral thrombosis and intracranial haemorrhage.
5- renal: bengin or malignant nephrosclerosis.
Physiology ( blood pressure control ):
1- sympathetic nervous system: When a drop in blood pressure occurs, pressure sensitive neurons (baroreceptors in the heart, vena cava and aortic arch) cause signals to be sent to the cardiovascular centers in the brain. After the impulses are sent to the brain, a response occurs through which the sympathetic system increases, which in turn increases output of the heart and blood vessels and reduce the parasympathetic system.
2- renin angiotensin aldosterone system: when blood pressure drops, the angiotensinogen is secreted from the liver, and then comes the renin (secreted from the cells near the glomeruli in the kidneys) and converts the angiotensinogen into angiotensin I and then comes the angiotensin convert enzyme (ACE) secreted from the lung and converts the angiotensin I into angiotensin II and thus these processes lead to an increase in water and salt retention in the kidneys, and to an increase in the anti-diuretic hormone, which results in an increase in blood pressure.
In the sympathetic nervous system, stimulation of:
1- beta 1 adrenoceptors on the heart : increase cardiac output
2- beta 1 adrenoceptors on kidney: increase renin
3- alpha 1 adrenoceptors on smooth muscle: increase peripheral resistance