5-ANS And Hypertension Flashcards
1
Q
Name the causes of secondary hypertension
A
- Reno-vascular
- Reno-parenchymal
- Adrenal causes
2
Q
Describe how Reno-vascular disease can lead to secondary hypertension
A
Renal artery stenosis Reduced perfusion pressure Increased renin production Activation of RAAS Vasoconstriction and increased Na absorption at other kidney
3
Q
Describe how renal-parenchymal disease can lead to secondary hypertension
A
Loss of local vasodilators Poor glomerular filtration Water and Na retention Increased plasma volume Kidney scars and shrinks
4
Q
Describe how adrenal causes can lead to secondary hypertension
A
-Conns syndrome: Aldosterone secreting tumour in adrenal gland, activating RAAS, causing hypokalemia
5
Q
What are the consequences of hypertension?
A
- Increased after load: LV hypertrophy-heart failure, increased o2 demand-myocardial ischaemia and MI
- Arterial damage - atherosclerosis: Stroke, renal failure, retinopathy and aneurysm
6
Q
What are the pharmacological ways to treat hypertension?
A
- Beta blockers to reduce sympathetic stimulation of renin release and vasoconstriction (but negative inotropy and chronotropy)
- Renin inhibitors prevent renin release from JGA
- ACE inhibitors prevent ANG 2 forming
- Aldosterone antagonist, prevents water and Na retention at kidneys
- Thiazide diuretics, inhibit Na/Cl co-transporter, reduces circulating volume
- Vasodilators: alpha 1 antagonists and l type calcium channel blockers, both relax vascular smooth muscle
7
Q
Name the 4 neurohumoral pathways that control long term blood pressure
A
- Renin-angiotensin-aldosterone-system (RAAS)
- Sympathetic nervous system
- Antidiuretic hormone (ADH)
- Atrial Natriuretic Peptide (ANP)
8
Q
Where is renin released from?
A
The granular cells of the juxtaglomerular apparatus in the afferent arteriole
9
Q
What factors (in the kidney) contribute to renin release?
A
- Macula densa detected lower NaCl concentration
- Juxtaglomerular apparatus detect sympathetic stimulation
- Baroreceptors detect lower renal perfusion pressure
10
Q
What effects does ANG II have on the body?
A
- Vasoconstriction
- Breaks down vasodilator bradykinin
- Stimulates adrenal gland to produce aldosterone
11
Q
What effects does aldosterone have on the kidneys?
A
- Increases water retention
- Increases Na absorption by activating apical Na and K channels
- Raises blood pressure
- Also increases basolateral Na extrusion
12
Q
What does the liver produce in RAAS?
A
The precursor angiotensinogen
13
Q
What is found in lungs for RAAS?
A
ACE - angiotensin converting enzyme
14
Q
How does the sympathetic nervous system reduce renal blood flow?
A
- Vasoconstriction of arterioles
- Decreased glomerular filtration rate therefore decreased Na excretion
15
Q
What effect does the sympathetic nervous system have on the proximal tubule?
A
- Activates apical Na/H exchanger in proximal tubule
- Activates basolateral Na/K/ATPase
16
Q
Which of the neurohumoral pathways stimulates renin release?
A
- Sympathetic nervous system
- RAAS
17
Q
What is the formula for mean arterial blood pressure?
A
Mean arterial blood pressure = CO X TPR
18
Q
What stimulates the release of ADH?
A
Increased plasma osmolarity Severe hypovolaemia (reduced blood volume)
19
Q
What are the effects of ADH?
A
- Increases water retention in distal nephron to form concentrated urine, controlling plasma osmolarity
- Vasoconstriction
- Stimulates apical Na/K/Cl co-transporter, increasing Na reabsorption
20
Q
What are the effects of ANP?
A
- Vasodilation of the afferent arteriole, which increases glomerular filtration rate
- Inhibition of Na reabsorption along nephron, causing natriuresis
21
Q
Where is ANP synthesised and stored?
A
Atrial myocytes
22
Q
How is ANP inhibited?
A
Reduced filling of heart
Less stretch
Less ANP released
23
Q
Define hypertension
A
A sustained increase in blood pressure
24
Q
What is the function of prostaglandins?
A
- Vasodilation to increase glomerular filtration rate
- Reduce Na reabsorption
- Buffer to excessive vasoconstriction by RAAS/SNS/high ANG II
25
What is the effect of dopamine on the kidneys?
- Vasodilation, increasing blood flow
| - Inhibits Na/H exchanger and Na/K/ATPase reducing reabsorption of NaCl
26
Where is dopamine formed and what is it formed from?
In the kidneys, formed from circulating L-Dopa
27
What does the ANS control in the CVS?
- Heart rate
- Force of contraction
- Peripheral resistance of blood vessels
- Amount of vasoconstriction
28
What is the electrical activity of the heart controlled by?
The vagus nerve
29
What is the preganglionic input to the heart?
Vagus nerve
30
What do the postganglionic fibres of the parasympathetic system release?
Acetyl choline
31
What receptors does acetyl choline bind to and what effect does this have on the heart?
Ach binds to M2 receptors
Negative chronotropic effect
Reduces AVN conduction velocity
32
What do the postganglionic fibres of the sympathetic system release?
Noradrenaline
33
What does noradrenaline bind to and what effect does this have on the heart?
Act on b1 adrenoreceptors
Positive chronotropic effect
Positive inotropic effect
34
How does noradrenaline increase the force of contraction?
- Act on b1 adrenoreceptors in myocardium to increase cAMP
- Activates PKA
- Phosphorylation of calcium channels increases influx during action potential plateau
- increased calcium uptake in the sER
- increased sensitivity of contractile machinery to calcium therefore increased force of contraction
35
Describe the stages of an action potential in the SAN
1) opening of fast L type calcium channel (upwards stroke)
2) closing of calcium channels and opening of potassium channels (downwards stroke)
3) Slow depolarisation of pacemaker potential (aka funny current) (slow increase)
36
What effect does sympathetic input have on pacemaker potential?
Speeds up pacemaker potential - increases heart rate
37
What effect does parasympathetic input have on pacemaker potential?
Slowed down pacemaker potential, decreased heart rate
38
What does increased sympathetic output do to vascular smooth muscle?
Binds to a1 receptors, causing vasoconstriction
39
What does decreased sympathetic input do to vascular smooth muscle?
Binds to a1 receptors, causing vasodilation
40
What does circulating adrenaline bind to preferentially and at high concentrations?
Preferentially binds to B2 receptors
| At high concentrations will bind to a1 receptors
41
Describe how activating B2 receptors leads to vasodilation of vascular smooth muscle
```
Increased cAMP
Activation of PKA
Opening of potassium channels and inhibition of MLCK
No actin cross bridges form
Vasodilation
```
42
Describe how activation of a1 receptors leads to vasoconstriction of vascular smooth muscle
Increased IP3 production
Extracellular calcium influx, intracellular calcium released from stores
Causing contraction of muscle
43
What effect does increased metabolite concentration have on vascular smooth muscle
Strong vasodilator effect
44
What are the three classes of drug that act on the ANS?
Sympathomimetics
Adrenoreceptor antagonists
Cholinergics
45
What triggers the baroreceptor reflex?
Increased arterial pressure causing stretching
46
What response does the baroreceptor reflex promote?
Bradycardia
| Vasodilation
47
Why isn't the baroreceptor reflex triggered in hypertension?
Persistent increases in blood pressure reset the baroreceptor reflex to a higher threshold
48
What kind of drug is salbutamol and what does it treat?
Sympathomimetic, B2 agonist
| Treats asthma as it relaxes airway
49
What kind of drug is dobutamine and what does it treat?
Sympathomimetic, B1 agonist
| Treats caridogenic shock (pump failure), as it has a positive chronotropic effect and increases cardiac output
50
What kind of drug is adrenaline and what does it treat?
Sympathomimetic, non selective agonist
| Treats cardiac arrest and anaphylactic shock
51
What kind of drug is miodrine and what does it treat?
Sympathomimetic, a1 agonist
| Treats postural hypotension
52
What kind of drug is prazosin and what does it treat?
Adrenoreceptor antagonist, a1 antagonist
| Treats hypertension as it inhibits noradrenaline on smooth muscle, preventing vasoconstriction
53
What kind of drug is propanolol and what does it do?
Adrenoreceptor antagonist, B antagonist
Negative inotropy and chronotropy (B1)
BUT
Bronchoconstriction (B2)
54
Why is atenolol used preferentially to propanolol?
Atenolol is selective B1 antagonist so less risk of bronchoconstriction
55
What kind of drug is pilocarpine and what does it treat?
Cholinergic, muscarinic agonist
| Treats glaucoma as it activates constrictor pupillae muscle
56
What kind of drug is atropine and what does it do?
Cholinergic, muscurinic antagonist
Positive chronotropic effect
Bronchial dilation
Pupil dilation- used in eye exams
57
Which afferent nerve receptors detect high pressure changes and which low pressure changes?
Baroreceptors detect high pressure changes
| Atrial receptors detect low pressure changes
