Lecture 4: Mechanism of Hypertension - pathophysiology Flashcards
What are the values for prehypertension?
120 - 139 / 80 - 89
What are the values for Stage I ?
140 - 159 / 90 - 99
What are the values for stage II?
160 - 179 / 100 - 109
What are the values for stage III?
> 180 / > 110
What are the determinants of blood pressure?
Mean systemic arterial pressure - which is the product of cardiac output and total peripheral resistance
What percentage of hypertension cases are primary?
90 - 95%
What percentage of hypertension cases are secondary?
5%
What can cause secondary hypertension?
- Renal or renovascular disease
- Endocrine disease
- Contraction of the aorta
- Latrogenic: hormonal/ oral contraceptive, NSAIDs
What endocrine diseases can cause secondary hypertension? (4)
- Phaechomocytoma
- Cushings syndrome
- Crohns Syndrome
- Acromegaly and hypothyroidism
What are the common causes of secondary hypertension?
- Intrinsic renal disease
- Renovascular disease
- Mineralocortacoid excess
- Sleep breathing disorder
What are the uncommon causes of secondary hypertension? (4)
- Phaechomocytoma
- Glucocoticoid excess
- Coarction of Aorta
- Hyper/ Hypothyroidism
What causes renovascular hypertension?
- Atherosclerosis 75-90%
- Fibromascular dysplasia 10-25% (more common in young patients, espescially females)
What are the risk factors for hypertension? (12)
- Family history
- Smoking
- Diabetes
- Obesity
- Hypercholestolaemia
- Physical inactivity
- Stress
- Infection
- Hypertension
- Microalbuminia or estimated GFR < 60mL/min
- Age ( >55 men, 65 woman)
- Lifestyle
What are the target organs for hypertension?
- CVS (heart and blood vessels)
- The kidneys
- Nervous system
- Eyes
What are the effects on the CVS of hypertension?
- Ventricular hypertrophy, dysfunction and failure
- Arrhythmias
- Coronary heart disease, acute MI
- Arterial aneurysm, dissection and rupture
What are consequences of hypertension on the heart?
LV hypertrophy
- Increased workload of LV
- Increased afterload
- LV tries to compensate for increased workload
What is LV hypertrophy a major risk factor for?
- Ischemic heart failure
- Arrhythmias
- Heart failure
- Sudden death
What are the effects of hypertension on the kidneys?
- Glomerular sclerosis leading to impaired kidney function and finally end stage kidney disease
- Reduction in GFR
- Ischemic kidney disease especially when renal artery stenosis is the cause of hypertension (secondary)
What are the effects of hypertension on the nervous system?
- Stroke, intracerebral and subaranchnoid hemorrhage
- Cerebral atrophy and dementia
What are the effects of hypertension on the eyes?
- Retinotherapy, retinal hemorrhages and impaired vision
- Vitreals hemorrhage, retinal detatchment
- Neuropathy of the nerves, leading to extraocular muscle paralysis & dysfunction
Where do nerve impulses that monitor joint movements come from?
Proprioreceptors
Where do nerve impulses that monitor blood pressure come from?
Baroreceptors
Where do nerve impulses that monitor blood acidity come from?
Chemoreceptors
What nerves cause a decrease in heart rate?
Vagus nerves - parasympathetic
What nerves cause an increase in heart rate?
Cardiac accelerator nerves - sympathetic
What nerves cause vasoconstriction of blood vessels?
Vasomotor nerves - sympathetic
What are the determinants of blood pressure?
- Blood volume
- Overall compliance
- Cardiac output
- Vascular resistance
What is blood volume?
The volume of blood available in the system
What is overall complance?
The elastic characteristics of the vessels contribute to the overall pressure
What is cardiac output?
Related to two other factors - heart rate and stroke volume
What are the sympathetic fibres of the heart?
Noradrenaline - B1 receptors
What do the sympathetic fibres of the heart do?
Increase the permeability of the nodal cell plasma membrane to Na and Ca
What are the parasympathetic nerves of the heart?
Acytylecholine M2 receptors
How do you regulate arterial blood pressure?
- Baroreceptol reflex
- Chemoreceptor reflex
What controls long term blood pressure?
The kidneys
What does a reduction in renal pressure result in?
Intrarenal redistribution of pressure and increased absorption of salt and water
What does a decrease in pressure in renal arterioles and sympathetic activity result in?
Renin production - angiotensin II production
What does angiotensin II do?
- Causes direct constriction of renal arterioles
- Stimulation of aldosterone synthesis - sodium absorption and increase in intravascular blood volume
How is RAAS activated?
In response to reduced blood flow.
