Physio Ch. 14, Cardiovascular

hrdcorhrvivor's version from 2017-04-18 03:58


Question Answer
cardiac muscle tissue differs from skeletal muscle in 3 wayssmaller, branch and contain intercalated discs (gap junctions allow ions to move rapidly between cells), depends on extracellular calcium for contraction
cardiac myofiberscontractile: 99% of cardiac myocytes, do the pumping, dont initiate their own APs. conductive: do not contract, conduct their own APs
excitation contraction coupling in cardiac muscle1. AP opens L type voltage gated channels 2. calcium enters cells, leads to opening of RyR channels via CICR 3. increase in calcium leads to calcium sparks that create signal 4. contraction
relaxationsimilar to skeletal, but calcium is both stored in SR and removed from cell via Na+/Ca2+ exchanger
myocardial APssimilar to skeletal, rapid depol due to Na+ influx, steep repol due to K+ efflux. requires calcium, RMP is -90mV
AP 4 steps1. resting potential na+ channels open 2. depol: na+ channels close 3. plateau: ca2+ channels open, fast K+ channels close 4. repol: ca2+ channels close, slow K+ channels open 4. resting potential
autorhythmic APsunstable membrane potentials called pacemaker potentials, start at -60mV and drift upward, caused by I-f channels
nervous control of contractilitycatecholamines and digitalis have positive inotropic effect. cate: increase calcium available, digit: decrease removal of calcium from cytosol
HR and PSNSincrease K+ efflux, decrease calcium, hyperpolarizes cell, negative chronotropic effect, decrease HR
HR and SNSincreases Na+ and calcium influx, increases depol, positive chronotropic effect, increase HR
cardiac conduction systemSA node, internodal tracts and bachmann's bundle, AV node, AV bundle, right and left bundle branches, purkinje fibers
ECGsum of mult APs in many cardiac myofibers, 3 bipolar electrodes, waves of depol deflect recording up/down depending on placement of electrode
p waveatrial depol
QRS complexventricular depol
t waveventricular repol
P-R intervalatrial depol and systole as well as onset of vent depol
S-T segmentrepresents period when ventricles are depol and systole occurs
Q-T intervalvent depol and repol
premature ventricular contract PVCventricles contract first before atria
torsade de pointespolymorphic ventricular tachycardia
hypocalcemiacan lead to decrease HR and BP, as heart fails it will cause vent tachycardia
S1heard at end of QRS complex as pressure rises in vent
S2heard toward end of T wave as repol of vent completes and pressure falls
wiggers diagramshows relationship between cardiac cycle, ECG, heart sounds and pressures in left vent and aorta
preloaddegree of stretch prior to contraction
contractilityintrinsic ability of cardiac muscle cells to contract at any given fiber length
afterloadcombination of end diastolic volume and arterial resistance, force used to overcome resistance in bv
cardiac outputvolume of blood pumped by one vent in a given period of time CO= HR x Stroke Volume
stoke volumeamount of blood pumped out during one vent contraction SV= EDV-ESV
frank starling lawstroke volume proportional to EDV, heart pumps all blood returned to it: increase in venous return, increased preload, increased EDV, increased SV