Physiology 3120 Lecture Notes - Lecture 5: Stroke Volume, Vagus Nerve, Cardiac Muscle
12 Jan 2017
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Cardiac output = heart rate x stroke volume. Sv: the amount of blood ejected by the ventricle on each contraction. The major factors which control stroke volume: Left vagus nerve innervates left ventricle: closes some l-type ca2+ channels, decreased contractility of heart (decreased ca2+ entry , decreased sv decreased co (ii) stroke volume and preload (and edv) contraction. Preload: extent of filling of the heart before: (cid:498)load(cid:499) on the heart (muscle) just before it, load: amount of blood in the heart contracts. It is directly related to edv: increased edv = increased preload (stretching ventricular muscle, increased force of contraction of the ventricle, increased in sv. ** also stretching increases troponin"s affinity for (cid:498)the greater the heart is filled during diastole, the during systole(cid:499) Known as the frank-starling law of the heart. This shows the heart can adapt to changing loads greater will be the quantity of blood pumped. Skeletal muscle: greater overlap more crossbridges more forceful contraction.
