Physiology Flashcards
How is the heart muscle supplied with blood?
Coronary arteries
What is stroke volume?
The volume of blood ejected by each ventricle per heartbeat
What does cardiac muscle need to contract?
Extracellular calcium ions
What does the plateau phase in ventricular muscle action potential?
Calcium ion influx through voltage-gated calcium channels
What does a long refractory period in cardiac muscle prevent?
Generation of tetanic contraction (continuous contraction) - protects heart
What happens to the sodium channels in the plateau phase?
They are in the depolarised closed state
SV = ?
End Diastolic Vol (EDV) - End Systolic Vol (ESV)
How is stroke volume regulated?
Intrinsic (within the heart itself) and extrinsic (nervous and hormonal control)
What is cardiac preload?
Initial stretching of the cardiac myocytes prior to contraction - indicated by EDV
What is the EDV determined by?
Venous return to the heart
What is Starling’s law of the heart?
The greater the EDV, the greater the SV
How does stretch affect troponin?
Increases it’s affinity for calcium ions
If venous return increases, what happens to EDV and SV?
They also increase
What is afterload?
Resistance into which the heart is pumping
If there is continuously increased afterload (e.g. untreated hypertension), what happens?
Ventricular muscle mass increases (ventricular hypertrophy) to overcome the resistance
Ventricular muscle is supplied by which type of nerve fibres?
Sympathetic
What is the neurotransmitter for the sympathetic nerve fibres supplying the ventricle?
Noradrenaline
What effect does sympathetic stimulation have on the force of contraction?
Increases it
What effect does sympathetic stimulation have on the heart rate?
It increase it
What does Inotropic refer to?
Force of contraction
What does chronotropic refer to?
Heart rate
What does vagal stimulation have a major influence on?
Heart rate
Why does vagal stimulation have so little effect on force of contraction?
There is very little parasympathetic innervation (if any) of the ventricles
Where are adrenaline and noradrenaline released from?
Adrenal medulla
What chronotropic and inotropic effects do noradrenaline and adrenaline have?
Minor effects compared with effects of noradrenaline from sympathetic nerves
What is cardiac output?
The volume of blood pumped by each ventricle per minute
CO = ?
SV x HR
Describe blood flow across the heart, starting with the right atrium
Right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary veins -> left atrium -> left ventricle -> aorta -> body tissues -> SVC -> right atrium
What is the structure of a lipoprotein?
What are the five classifications of lipoproteins?
Chylomicrons, Very low-density lipoproteins (VLDL), Intermediate-density lipoproteins (IDL), Low-density lipoproteins (LDL) and High density lipoproteins (HDL)
What effect does HDL have on CHD and atherosclerosis?
Has a protective effect - the lower the amount of HDL, the higher the risk of CHD
What are the normal triglyceride levels?
2.3mmol/L
What do statins do and how?
Statins reduce amount of cholesterol in body. Act as HMG CoA reductase inhibitors and block the cholesterol synthesis pathway -> acetyl CoA isn’t then made into cholesterol
What actions do statins have that aren’t on lipids?
Improvement of endothelial dysfunction, increased nitric oxide bioavailability, antioxidant properties, inhibition of inflamm responses, stabilisation of atherosclerotic plaques
What are some of the clinical markers of dyslipidaemia?
xanthelasms (xanthomas of the eyelids), tendon xanthomas, tuberous xanthomas, eruptive xanthomas, striate palmar xanthomas
What effects does hypertension have on the arteries?
Can cause widening of the arteries - puts strain on the lining, can cause the artery muscle to thicken - restricts blood flow
What are the two types of hypertension?
Essential hypertension (no underlying cause) and secondary hypertension (underlying cause)
What are the lifestyle modifications to reduce hypertension?
Lose weight, limit alcohol intake, increase physical activity, reduce salt intake, stop smoking, limit intake of foods rich in fat and cholesterol
What is the system of treatment for a recently diagnosed hypertensive treatment who is 55 years or older or black?
STEP 1: calcium-channel blocker or thiazide-type diuretic
STEP 2: Add an ACE inhibitor to initial treatment
STEP 3: All three drugs from above
STEP 4: Add further diuretic therapy or and alpha/beta blocker, consider referral
What is the sytem of treatment for a newly diagnosed hypertensive patient who is younger than 55 years old?
STEP 1: ACE inhibitor
STEP 2: Add either a calcium-channel blocker or a thiazide-type diuretic
STEP 3: All of the above
STEP 4: Add further diuretic therapy or an alpha/beta blocker
What effects does smoking have in relation to cardiovascular disease?
Increase blood pressure, decreases HDL, damages arteris and blood cells, increases risk of MI
What is the metabolic syndrome?
Constellation of major risk factors, life-habit risk factors and emerging risk factors
CLUE: distinctive body type with increased abdominal circumference
What risk scoring do we use?
The Assign score (assign-score.com)
Main therapeutics for tackling ischaemia?
Antianginal medications (calcium blockers, nitrates, beta blockers), revascularisation (angioplasty, CABG) and risk factor modification
Main therapeutics for tackling atherothrombosis?
Aspirin, Statins, beta blocker, ACE inhibitor, exercise, smoking cessation, symptom control (antianginal medications and possibly revascularisation)
