Heart histology Flashcards

1
Q

where is smooth muscle found

A

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

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2
Q

where is cardiac muscle found

A

heart

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3
Q

where is skeletal muscle found

A

large body muscles responsible for movement

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4
Q

structure of smooth muscle tissue

A

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

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5
Q

function of smooth muscle

A

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

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6
Q

structure of cardiac muscle

A

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

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7
Q

function of cardiac muscle

A

circulates blood
maintains BP

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8
Q

structure of skeletal muscle

A

cells = long, cylindrical , striated, multinucleate

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9
Q

functions of skeletal muscle

A

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

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10
Q

PACE

A

preload
afterload
contractility
hEart rate

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11
Q

preload

A

volume of blood in heart prior to contraction

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12
Q

afterload

A

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

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13
Q

contractility

A

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).

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14
Q

Pressure - volume relationship of the left ventricle

A
  1. isovolumetric contraction
  2. LV ejection
  3. isovolumetric relaxation
  4. LV filing
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15
Q

stroke volume equation

A

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

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16
Q

Increase end diastolic volume

A

increase stroke volume
increase contractility
more blood per contraction

17
Q

myocardial infarction severity and contractility

A

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

18
Q

what are systolic contraction and diastole compliance determined by

A

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.

19
Q

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

A

fall in contractility
systolic contraction decreases
therefore store volume falls

20
Q

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

A

fal in compliance
diastolic compliance decreases
stoken volume falls

21
Q

what is used to quantify contractility

A

ejection fraction

22
Q

ejection fraction equation

A

EF = SV/EDV
stroke volume / end diastolic volume

23
Q

normal EF

A

normally between 55-75% under resting conditions

24
Q

EF of >75%

A

hypertrophic cardiomyopathy

25
Q

EF of <40%

A

muscle is weakened and you may have heart failure.

26
Q

how are experimental models used

A

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

27
Q

how are muscle fibres orientated and why

A

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

28
Q

strain

A

amount muscle is stretched
important to muscle function

29
Q

how can we map myocardial strain patterns

A

map
through computer analysis
orientation of muscle fibres
multidirectional orientation

30
Q

sinusoidal wave pattern

A

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

31
Q

net power

A

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

32
Q

optimal strain pattern

A

12%

33
Q

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

A

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

34
Q

length force relationship

A

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

35
Q

resting HR in man

A

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

36
Q

max HR man

A

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

37
Q

max Power output and factors that alter power output

A

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

38
Q

aged heart

A

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

39
Q

why use certain models

A

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