Cardiac Physiology Flashcards
all tissues only _____ away from?
a few cell diameters away from a thin walled capillary that carry nutrients/O2 and take away waste/CO2
for efficient pumping, we need ____-___ _____?
one way valves –> prevent backflow
which valves are where in the heart
tricuspid: b/w right atrium and ventricle. mitral left. aortic valve and pulmonary valves.
systolic pressure sequence: when ventricle contracts what happens to pressures and valves
ventricular pressure higher than atrial so AV valve shuts –> ventricular pressure rises, no flow = isovolumic contraction –> until it rises above arterial level then the forward valve opens and pressure drives the flow forward
diastolic pressure sequence: when ventricle relaxes what happens to pressures and valves
ventricular pressure < arterial so forward valve shuts; ventricular pressure falls but no flow = iso volumic relaxation, until it falls below atrial level then the back valve (AV valve) opens and pressure form atria fills the ventricle
what makes heart sounds
when a valve shuts
what parts of steth to listen to what
larger diaphragm for high frequency sounds, pressed firmly against skin. smaller bell for low freq, pressed lightly to skin
S1 and S2: what causes these sounds
S1 = closing of AV (tricuspid and mitral) valves = when ventricular systole begins. S2 = closing of ventricular-arterial (pulmonic, aortic) valves = beginning of diastole
S2 splitting: what is the order?
A2 then P2 –> P slightly later because delay of diastolic back pressure of pulmonary arteries when breathing in (negative intrathoracic pressure)
when is systole/diastole in relation to heart sounds
systole between S1 to S2. diastole from S2 to next S1
heart muscle unit of structure is? composed of?
sarcomere: thick myosin filaments and thin actin filaments
how is actin/moysin arranged? how are sarcomeres arranged? what other structures are there?
arranged hexagonally so each thick surrounded by 6 thin filaments. individual sarcomeres connect to each other = myofibrils. mitochondria, SR, T-tubule branches, at least one nucleus = muscle cell
intercalated diskc
specialized region of membrane in cardiac muscle: gap junction at interface of cardiac fibres = structural and electrical continuity between cells
each actin molecule has ____ site? actin molecules joined how? connected by? resting conditions?
myosin binding site. joined end to end to form a beads on a string structure –> connected by longitudinal tropomyosin molecule –> under resting conditions tropomyosin blocks myosin binding site of actin molecule
tropomyosin molecules has a ____ complex? which is composed of? which bind?
toponin complex: composed of troponins I (actin), T (tropomyosin) and C (calcium when avail)
titin: structure? purpose?
large, long –> partially coiled structure that acts like a spring = stretching of sarcomere will stretch titin = adds elastic recoil to muscle fiber
plasma membrane called? invaginations?
sarcolemma: invaginate into myocardial cell at 90 degrees = T-tubules; continuous with extracellular space
sarcoplasmic reticulum where? forms what?
runs longitudinally in a myocardial cell, parallel to myofilaments –> forms terminal cisternae when it contacts T tubule system
actin and myosin filaments overlap: what causes contraction? what happens when depolarized?
interaction of myosin heads with actin molecules. depol = Ca channels open along SR and t tubules, go into cardiac cell –> Ca induced Ca release from SR
power stroke: what happens when calcium exits SR
Ca binds troponin C = conformational shift that exposes myosin binding sites on actin –> cross bridge formation, bending of myosin head, pulling actin along myosin
what two things are critical for muscle contraction
calcium, ATP
things that can affect binding of Ca to troponin C
more Ca released from SR = better binding. degree of stretch of sarcomere. interaction w/ myosin light chains. cellular milieu: pH, redox state, ion conc, etc.
