Control Of Blood Pressure Flashcards
Define Hypertension and state the normal BP range
Sustained increase in BP
Normal BP: 90/60 to 120/80
What range is Stage 1 Hypertension;
When Measured In clinic
When measured at home or in ambulance (HBPM/ ABPM)
Clinic: >/= 140/90
HBPM/ ABPM: >/= 135/85
What range is Stage 2 Hypertension;
When Measured In clinic
When measured at home or in ambulance (HBPM/ ABPM)
Clinic: >/= 160/100
HBPM/ ABPM: >/= 150/95
What range is Severe Hypertension when measured In clinic
Clinic: >/= 180 systolic or 110 diastolic
Differentiate between the 2 types of hypertension
Which of the 2 is more common, what percentage of al hypertension cases?
Primary: Unknown cause, 95% of all cases
Secondary: When cause can be defined
Name 5 target organs targeted by hypertension
Brain Heart Arteries Eyes Kidneys
What are 2 ways of regulating BP
Short term (Baroreceptor reflex) Long term (Controls the balance of Na and thus ECF)
How does Baroreceptor affect TPR and CO to regulate BP
Adjust Sympathetic and Parasympathetic input to heart to alter CO
Adjust Sympathetic input to Peripheral Resistance Vessels to alter TPR
What are the 4 pathways that control BP in the long-term
- RAAS (Renin-Angiotension-Aldoesterone System)
- Sympathetic Nervous System
- Antidiuretic hormone (ADH)
- Atrial Nattiuretic Peptide (ANP)
In the RAAS, where is Renin released from
What 3 factors stimulate its release
- from the Granular cells of the Juxtaglomerular apparatus (JGA)
- Reduced NaCl delivery to distal tubule
- Reduced perfusion pressure in kidney
- Sympathetic stimulation to JGA
Describe the Pathway of substance conversions and the enzymes required
What are 3 functions of the final substance in the pathway
- Angiotensinogen-> Angiotensin I by Renin
- Angiotensin I-> Angiotensin II by ACE (Angiotensin Converting Enzyme)
Angiotensin II;
- Causes vasoconstriction
- Stimulates Na+ reabsorption at kidney
- Stimulates aldosterone (released from adrenal cortex)
What are the 2 types of Angiotensin II receptors are there?
Which receptor are the main actions via?
What are the actions of Angiotensin II at the following 5 sites;
- Arterioles
- Kidney
- SNS (Sympathetic)
- Adrenal cortex
- Hypothalamus
AT1 and AT2, Main actions via AT1
- Vasoconstriction
- Stimulates Na+ reabsorption
- Increased NA release
- Stimulates Aldosterone release
- Stimulates ADH release
Describe the action of aldosterone on the kidney in 4 steps
- Acts on cells of collecting duct
- Stimulates Na+ (and thus H2O reabsorption)
- Activates apical Na channel (ENaC) and apical K channels
- Increases Na extrusion via Na-K Pump
Explain the relationship between ACE and Bradykinin
How does Bradykinin affect vasculature? What does ACE therefore further cause vasoconstriction
As well as converting Angiotensin I-> II, ACE breaks down Bradykinin to Peptide Fragments.
Bradykinin is a vasodilator, so because of ACE, less vasodilation takes place
What 2 effects do ACE inhibitors have
What builds up and how can this present
- Prevent Angiotensin I—> II
- Prevent Bradykinin-> Peptide Fragments
Bradykinin buildup-> Dry cough (Vasodilation in lung)
What are 3 effects of the SNS Pathway in Long-term BP Regulation
- Reduce renal blood flow
- Stimulate Na reabsorption in PCT
- Stimulate renin release
What is the main role of ADH, how does it affect water reabsorption
What 2 things stimulates ADH release
Formation of concentrated urine by retaining water.
Increased water absorption in distal nephron
- Increased plasma osmolarity
- Severe hypovolaemia
Name 2 non-main functions of ADH (Arginine Vasopressin)
Stimulates Na reabsorption in thick ascending limb
Vasoconstriction
What do natriuretic peptides promote
Where are they synthesised and stored
When are they released
Na excretion
In atrial Myocytes, released in response to stretch
What does ANP cause, how does this affect Glomerular Filtration rate
what does it inhibit
Vasodilation, Increased GFR
Inhibits Na reabsorption
What do Prostaglandins act as? name 2 effects
What do they buffer against
When are they important
Vasodilator, Enhanced GFR, reduced Na reabsorption
Buffer to excessive vasoconstriction
When AGII levels are high
Where is dopamine formed
Where are their receptors present
What are 2 functions of Dopamine
Formed In kidney
Present on renal blood vessels and cells of PCT and Thick Ascending Limb
- Vasodilation
- Reduced Na reabsorption
How does Renovascular disease cause (Secondary) hypertension in 4 steps
- Renal Artery Stenosis-> Reduced perfusion to that kidney
- Increased renin production (due to perfusion)
- Activation of RAAS
- Vasoconstriction and Na retention at OTHER kidney
How does Renal parenchymal disease cause (Secondary) hypertension in 2 stages
- Earlier stage may be Loss of vasodilator substances
2. In later stage, Na and H2O retention due to inadequate glomerular filtration
Name 3 adrenal diseases that cause hypertension and explain how
Conn’s Syndrome: Aldosterone secreted-> Hypertension and Hypokalemia
Cushing’s Syndrome: Excess cortisol acts on Aldosterone receptors-> Na and H2O retention
Tumour of adrenal medulla: Phaemochromocytoma secreted Adrenaline and NA
What is the effect of an Angiotensin II receptor antagonist
Blocked action of Angiotensin II—> Diuretic and vasodilator effects
What are 2 types of vasodilators that can be used to treat hypertension
What are 2 types of diuretics that can be used to treat hypertension
L-type Ca channels blockers
A1 receptor blockers
Thiazides diuretics (Reduce circulating volume) Aldosterone antagonists
Why are Beta Blockers less commonly used to treat hypertension
Blocked B1 receptors in heart-> Reduced heart rate and contraction force
