What is hypertension ?

• Sustain elevation of systemic arterial pressure 
• Systolic pressure over 140 / 90 mmHg in adult at least 3 consecutive visits to the doctor 

Types of hypertension

1. Primary / essential hypertension – cause is unknown . Seen in 92 % of the population 
2. The secondary hypertension – cause is known seen in 7 5 of the population 

• Renal cause – 

• Renal artery stenosis

• Glomerular nephritis 

• Chronic renal failure 

• Polycystic kidney disease 

• Endocirine causes 

• Conn’s disase 

• Adrenal hyperplasia 

• Pheocromocytoma 

• Cushing’s syndrome 

• Acromegaly 

• Corctation of aorta 

Physiological basis of hypertension due to renal cause 

Renal artery stenosis

• Renal artery stenosis 
• Reduce renal arteriolr pressure 
• Activate rennin/ angiotensin/ aldestorone mechanisms 
• Excess salt and water retention 
• Increase total blood volume 
• Increases venous return 
• Increase EDV/ stroke volume 
• Increase cardiac output 
• Increase Blood pressure 

Glomerular nephrits

• In glomerular neohritis glomerulus loss it ability to excrete salt and water 
• Therefore salt and water retain in the body and increase total blood volume 
• Due to increase total blood volume blood pressure as previously explains 
• In chronic kidney disease also salt and water retention occur therefore blood pressure increase 

Physiological basis of hypertension endocrine cause 

Conn’s disease

• Minaralocorticoid excess 
• Excess salt and water retention 

Cushing’s disease

• Glucocorticoid excess 
• Minerelocorticoid like action of glucocorticoids
• Enhance the action of catecholamine on vasoconstriction 
• Increase total peripheral resistance 

Congenital adrenal hperplasia 

• Increase secretion of ACTH 
• Increase secretion of aldesterone 
• Excess salt and water retention 

Pheocromocytoma ( adrenal medullary tumor)

• Increase release of chatacholamines 
• Increase chonotrophic and inotrophic effect on heart and blood vessels 
• Increase cardiac output and total peripheral resistance 
• Blood pressure increases 

Baroreceptor mechanism in hypertension

• Hypertension stimulates baroreceptors in carotid arch and carotid sinuses 
• The impulse travels via IX and X cranial nerve 
• Stimulate nucleus of tractus solitaries 
• Increase inhibition of vasomotor area 
• Inhibit sympathetic discharge 
• Impulse stimulates dorsal motor nucles of vagus 
• Stimulate parasympathetic discharge 
• Due to increase parasympatheric discharge and reduce sympathetic discharge 
• Heart rate reduces 
• Contractility of myocardium reduce( SV reduce ) 
• Therefore the cardiac output reduce 

• Venodilatation 
• Increase venous pooling 
• Reduced venous return 
• Then reduce cardiac output 

• Arteriolar dilation 
• Reduces total peripheral resistance 

• Eventually all mechanisms act to reduce  Blood pressure

This Page

has moved to a new address:

https://www.physiologyexam.com

Sorry for the inconvenience…

Redirection provided by Blogger to WordPress Migration Service