Case 4 Flashcards by Rhian Jones

What G protein is linked to A2 receptors?

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What G protein is linked to B1 and B2 receptors?

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What G protein is linked to A1 receptors?

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What is the difference between Propanolol and Atenolol

Both beta blockers.

P is non selective (so not good for people with asthma) A is b1 selective.

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Name three Anticoagulants.

Warfarin

Heaprin

Ancrod

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Name two Thrombolytic agents. What do they do?

Tissue plasminogen activator

Streptokinase

Action: Hydrolyse clots.

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What is the action of warfarin?

Vitamin K antagonist.

Prevents synthesis of prothrombin and clotting factors.

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What is the action of heparin?

Accelerates the activity of antithrombin which inhibits the action of thrombin.

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What is the action of Ancrod?

It is a proteolytic enzyme.

It acts directly on fibrinogen to form an unstable form of fibrin which forms micro clots that are cleared from the blood by phagocytes.

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How does sheer stress protect from atherosclerosis?

Stimulates the production of NO

Inhibits LDL oxidation

Inhibits leukocyte adhesion

Inhibits smooth muscle proliferation

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Label the waves of this ECG trace (boxes in red)

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What is represented by box A?

PR segment

Conduction from AVN –> Bundle of His

*AVN conduction delay*

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What is represented by box B?

PR interval

Represents time from atrial depolarisation to ventricular depolarisation (0.12s - 0.20s)

*includes AVN conduction delay*

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What is represented by box C?

QRS complex

Ventricular depolarisation (<0.12s)

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What is represented by box D?

ST segement

All myocytes should now be depolarised (ST segment lies on the isoelectric line)

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What is represented by box E?

QT interval (0.34s-.43s)

Represents the ventricular action potential

Includes depolarisation and repolarisation of the ventricles.

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What makes up the 12 lead ECG?

1) UNIPOLAR leads –> 6 chest leads (V1-V6)
2) BIPOLAR leads –>

3 limb leads (I, II, III)

3 augmented leads (aVR, aVL, aVF)

10 ELECTRODES, 12 LEADS

An ECG shows deviating waves in leads II, III, avF. What part of the heart is most likely affected?

Inferior part.

II, III and aVF view the heart inferiorly.

How do you calculate heart rate from an ECG?

300 / number of big squares.

Use R R interval as reference for each square.

OR!

60 / (number of little squares x 0.04)

= 60 / (20 x 0.4) = 75bpm

Where are the baroreceptors found?

What nerves are linked to the baroreceptors?

Carotid SINUS (joins carotid sinus nerve - links to glossopharyngeal)

AORTIC ARCH (joins aortic nerve - links to vagus nerve)

Where are the chemoreceptors found?

Central - Brainstem, bathed in the CSF.

Peripheral - Carotid and Aortic BODIES

What condition does this ECG show?

1st degree heart block.

Prolonged PR interval - prolonged AVN delay.

What condition does this ECG show?

Second degree heart block.

Mobitz type 1.

PR interval gets progressively longer until an impulse fails to be conducted at all and the rhythm is reset.

What condition does this ECG show?

Second degree heart block.

Mobitz type 2.

PR interval is fixed.

Not every P wave is followed by a QRS complex.

Either 2:1 (2 P waves for every QRS) or

4:1 (4 P waves for every QRS)

What condition does this ECG show?

Third degree heart block. *_No conduction of impulses through the AVN._* Atrial and Ventricular depolarisation occur independent of one another.

What condition does this ECG show?

Atrial fibrillation. NO P waves! Disorganised, rapid, irregular contractions of the atria. Ventricular rhythm is irregular due to the twitches of impulses recieved by the AVN from the atria.

What condition do these ECGs show?

Atrial flutter. Top is 2:1 block. Bottom is 4:1 block. Appears "saw toothed". *_P waves are present._* Not as disorganised as atial fibrillation but contractions are rapid and abnormal.

What condition does this ECG show?

Ventricular tachycardia. Ventricles depolarise rapidly. It may be 'stable' (monomorphic) or 'unstable' (polymorphic)

What condition do these ECGs show?

Ventricular fibrillation (VF) NO QRS complexes. Very disorganised and uncoordinated. Depolarisation from multiple areas in the centricular myocardium.

How long is the cardiac cycle? (in seconds)

Total cycle = 0.8s

Name the three cell junctions that are present in the Intercalcated discs that join cardiac myocytes.

Desmosomes Adherens Gap

What are the BMI ranges for underweight? healthy? overweight? obese?

Underweight is under 18.5 Healthy is 18.5 to under 25 Overweight is 25 to 30 Obese is over 30 Morbidly obese is over 40.

How can you distinguish between STEMI and NSTEMI on an ECG?

***_NSTEMI_*** ST-depression, T-wave inversion. ***_STEMI_*** ST-elevation, T wave inversion _and_ pathological Q-waves Both have raised *_Troponin T and I_* as well as *_CK-MB and Myoglobin_* (less specific markers)

What are the four causes of systolic murmur?

aortic or pulmonary stenosis (narrowing) tricuspid/ mitral regurgitation (leaky valves)

What are the four causes of diastolic murmur?

aortic or pulmonary regurgitation mitral/ tricuspid stenosis

A peripheral artery is found to have 50% stenosis. Compared to a normal artery with no stenosis, by what factor has the flow of blood been decreased?

16 Flow = 1/r⁴. Therefore, flow (aka. resistance) in this artery would be decreased by a factor of 16.

What percentage of the coronary artery is filled with atherosclerotic plaque for it to be classed as a 'fixed' atherosclerotic plaque?

Fixed atherosclerotic plaques obstructing ***\>75%*** of the coronary artery are associated with stable angina.

Phases of SAN action potential?

3 phases NO resting potential Pre potential (Na+) - activated upon hyperpol Dep (Ca2+) Hyperpol (K+)

What is the action of ***Fibrates***?

Stimulate the activity of ***_LPL_*** so _cells take up more triglycerides_; by increasing HDL levels they promote the reverse cholesterol pathway which leads to more cholesterol being taken back to the liver for excretion in bile salts

What is the action of ***Bile Acid Sequestrants***?

Rarely used anymore but they work by ***binding to components of bile*** to ***prevent it from being reabsorbed*** from the gut. Less bile reabsorbed means less cholesterol reabsorbed

What happens to chylomicrons when they go through the blood stream? (hint: receptors --\> gaining and losing)

they gain ***apoC2*** and ***apoE*** from HDLs. \*ApoC2 = receptor for LPL\* in adipose, ***ApoC2*** binds to _Lipoprotein Lipase_ on endothelial cells. TAGs --\> fatty acids and glycerol. As chylomicron's triglyceride content reduces they ***lose apoC*** (donated back to HDL) so they only have _ApoE_ left meaning they are a _Chylomicron Remnant_. Chylomicron remnants (IDL) then travel to the liver where they bind with their ***apoE*** with the Chylomicron remnant receptor.

What makes up the ***_surface coat_*** and ***_core_*** of a lipoprotein?

surface coat = Unesterified cholesterol, phospholipids, apolipoproteins core = Triglycerides, cholesterol esters