Cardiac Physiology

Question 1

all tissues only _____ away from?

Answer 1

a few cell diameters away from a thin walled capillary that carry nutrients/O2 and take away waste/CO2

Question 2

for efficient pumping, we need ____-___ _____?

Answer 2

one way valves –> prevent backflow

Question 3

which valves are where in the heart

Answer 3

tricuspid: b/w right atrium and ventricle. mitral left. aortic valve and pulmonary valves.

Question 4

systolic pressure sequence: when ventricle contracts what happens to pressures and valves

Answer 4

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

Question 5

diastolic pressure sequence: when ventricle relaxes what happens to pressures and valves

Answer 5

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

Question 6

what makes heart sounds

Answer 6

when a valve shuts

Question 7

what parts of steth to listen to what

Answer 7

larger diaphragm for high frequency sounds, pressed firmly against skin. smaller bell for low freq, pressed lightly to skin

Question 8

S1 and S2: what causes these sounds

Answer 8

S1 = closing of AV (tricuspid and mitral) valves = when ventricular systole begins. S2 = closing of ventricular-arterial (pulmonic, aortic) valves = beginning of diastole

Question 9

S2 splitting: what is the order?

Answer 9

A2 then P2 –> P slightly later because delay of diastolic back pressure of pulmonary arteries when breathing in (negative intrathoracic pressure)

Question 10

when is systole/diastole in relation to heart sounds

Answer 10

systole between S1 to S2. diastole from S2 to next S1

Question 11

heart muscle unit of structure is? composed of?

Answer 11

sarcomere: thick myosin filaments and thin actin filaments

Question 12

how is actin/moysin arranged? how are sarcomeres arranged? what other structures are there?

Answer 12

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

Question 13

intercalated diskc

Answer 13

specialized region of membrane in cardiac muscle: gap junction at interface of cardiac fibres = structural and electrical continuity between cells

Question 14

each actin molecule has ____ site? actin molecules joined how? connected by? resting conditions?

Answer 14

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

Question 15

tropomyosin molecules has a ____ complex? which is composed of? which bind?

Answer 15

toponin complex: composed of troponins I (actin), T (tropomyosin) and C (calcium when avail)

Question 16

titin: structure? purpose?

Answer 16

large, long –> partially coiled structure that acts like a spring = stretching of sarcomere will stretch titin = adds elastic recoil to muscle fiber

Question 17

plasma membrane called? invaginations?

Answer 17

sarcolemma: invaginate into myocardial cell at 90 degrees = T-tubules; continuous with extracellular space

Question 18

sarcoplasmic reticulum where? forms what?

Answer 18

runs longitudinally in a myocardial cell, parallel to myofilaments –> forms terminal cisternae when it contacts T tubule system

Question 19

actin and myosin filaments overlap: what causes contraction? what happens when depolarized?

Answer 19

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

Question 20

power stroke: what happens when calcium exits SR

Answer 20

Ca binds troponin C = conformational shift that exposes myosin binding sites on actin –> cross bridge formation, bending of myosin head, pulling actin along myosin

Question 21

what two things are critical for muscle contraction

Answer 21

calcium, ATP

Question 22

things that can affect binding of Ca to troponin C

Answer 22

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.