Heart histology

Question 1

where is smooth muscle found

Answer 1

in walls of hollow contracting organs
blood vessels
urinary bladder
respiratory tract
digestive tract
reproductive tract

Question 2

where is cardiac muscle found

Answer 2

heart

Question 3

where is skeletal muscle found

Answer 3

large body muscles responsible for movement

Question 4

structure of smooth muscle tissue

Answer 4

cells are short, spindle shaped and non striated
single central nucleus

Question 5

function of smooth muscle

Answer 5

moves flood, urine and controls diameter of respiratory and blood vessels

Question 6

structure of cardiac muscle

Answer 6

cells = short, branched, striated
single nucleus, cells are interconnected by intercalated discs
cardiac myocytes = branches

Question 7

function of cardiac muscle

Answer 7

circulates blood
maintains BP

Question 8

structure of skeletal muscle

Answer 8

cells = long, cylindrical , striated, multinucleate

Question 9

functions of skeletal muscle

Answer 9

moves and stabilises the position of the skeleton, guards entrance and exits to digestive, respiratory and urinary tracts, generates heat, protects organs

physical association between T tubule and SR = excitation wave directly couple with SR where an excitation wave directly couple with the SR

Question 10

PACE

Answer 10

preload
afterload
contractility
hEart rate

Question 11

preload

Answer 11

volume of blood in heart prior to contraction

Question 12

afterload

Answer 12

load against which the heart has to contract to eject the blood

Question 13

contractility

Answer 13

the relative ability of the heart to eject a stroke volume (SV) at a given prevailing afterload (arterial pressure) and preload (end-diastolic volume; EDV).

Question 14

Pressure - volume relationship of the left ventricle

Answer 14

1. isovolumetric contraction
2. LV ejection
3. isovolumetric relaxation
4. LV filing

Question 15

stroke volume equation

Answer 15

volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction.

SV= EDV-ESV

end diastolic volume - end systolic volume

Question 16

Increase end diastolic volume

Answer 16

increase stroke volume
increase contractility
more blood per contraction

Question 17

myocardial infarction severity and contractility

Answer 17

Artherscelerotic plaque = lack of oxygen - scarring tissue after MI = hypertrophy - fibrosis
Severity and contractility link

increased severity = decreased ventricular contractility and compliance = risk of Heart failure

Question 18

what are systolic contraction and diastole compliance determined by

Answer 18

determined by the structural properties of the cardiac muscle (e.g., muscle fibers and their orientation, and connective tissue) as well as by the state of ventricular contraction and relaxation.

Question 19

flabby weak ventricle effect on systolic contraction, diastolic compliance and stroke volume

Answer 19

fall in contractility
systolic contraction decreases
therefore store volume falls

Question 20

stiff fibrotic ventricle effect on systolic contraction, diastolic compliance and stroke volume

Answer 20

fal in compliance
diastolic compliance decreases
stoken volume falls

Question 21

what is used to quantify contractility

Answer 21

ejection fraction

Question 22

ejection fraction equation

Answer 22

EF = SV/EDV
stroke volume / end diastolic volume

Question 23

normal EF

Answer 23

normally between 55-75% under resting conditions

Question 24

EF of >75%

Answer 24

hypertrophic cardiomyopathy

Question 25

EF of <40%

Answer 25

muscle is weakened and you may have heart failure.

Question 26

how are experimental models used

Answer 26

measure contractility to understand myocyte damage/death and research for new therapies mimic in vivi cardiomyocytes contraction

Question 27

how are muscle fibres orientated and why

Answer 27

Multidirectional orientation Different deep vs middle vs superficial Different regions of heart = different strain patterns = take average = mimic within model complex to ensure efficient and directional movement of blood

Question 28

strain

Answer 28

amount muscle is stretched important to muscle function

Question 29

how can we map myocardial strain patterns

Answer 29

map through computer analysis orientation of muscle fibres multidirectional orientation

Question 30

sinusoidal wave pattern

Answer 30

equal on both sides muscle length over time wave pattern stretch proportional both sides generates force = destretch systolic and diastole force

Question 31

net power

Answer 31

net power is area between on graph = developed force (systole) (energy generated) passive force (diastole) (energy lost) change strain pattern = change net power of muscle

Question 32

optimal strain pattern

Answer 32

12%

Question 33

if strain amplitude is beyond 12% (+/-6)

Answer 33

power output reduces passive force increases = structural proteins resist overstretching of myofibrils

Question 34

length force relationship

Answer 34

increased starting muscle length = increases net power until optimum = after that power decreases change muscle length until optimum level = starts to decrease again more calcium = more contractility

Question 35

resting HR in man

Answer 35

70-90 bpm (1.2-1.5Hz) at rest

Question 36

max HR man

Answer 36

220 bpm - age (+/-) 10 bpm (3.7Hz)

Question 37

max Power output and factors that alter power output

Answer 37

3,5Hz muscle length, cycle frequency, strain amplitude

Question 38

aged heart

Answer 38

age associated disease - ischemic heart disease left ventricle thickening increase cardiomyocyte size loss of cardiomyocytes increase extracellular matrix decrease oxygen consumption decreased max HR reduce cardiac function decrease EF decrease responsiveness to adrenergic stimulation

Question 39

why use certain models

Answer 39

In two different models by using ages vs normal = don’t get the same results = so important to select the right model - need to look at many aspects to see whether you are mimicking it as closley as possible