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cardiology and respiratory > cardiac cycle and control > Flashcards

cardiac cycle and control Flashcards

1
Q

what do gap junctions allow for

A

cell to cell conduction and propagation of an action potential through the whole myocardium

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2
Q

process of excitation contraction coupling

A

1- calcium ion moves into cardio myocytes via t tubules and binds to troponin
2- causing conformational change in tertiary structure of troponin and exposes actin binding site
3- ca binds to Ryanodine receptor to release more ca from SR.
4- actin myosin cross bridges formed using atp , part of the power stroke , pulls actin and myosin together

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3
Q

how is the actin myosin bridge formed

A

calcium binds to troponin
conformational change in the tertiary structure and exposes binding site of myosin
myosin heads link with actin through action of atpase
myosin head pivots causing muscle contraction

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4
Q

why does cardiac muscle contraction last longer than skeletal

A

due to faster calcium channels

increased permeability to membrane for k after action potential

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5
Q

symapthetic stimulation of the heart

A

incease HR
increase force of contraction
increase CO

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6
Q

Physiological parasympathetic stimulation of the heart

A

decrease HR
decreases force of contraction
increases cardiac output

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7
Q

what is sympathetic stimulation of the heart caused by

A

adrenaline and noradrenaline

by increasing adenlyl cyclase

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8
Q

what is absolute refractory period

A

period where the cell is completely unexcitable

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9
Q

What is the electrode for ecg

A

what you place on the body to pick up signals

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10
Q

what is a lead for ecg

A

a plane in which you are looking in the heart

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11
Q

p wave?

A

atrial depolarisation

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12
Q

qrs complex?

A

ventricular depolarisation

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13
Q

t wave

A

ventricular repolarisation

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14
Q

where do leads 1-6 go

A

on the chest

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15
Q

how many leads on the right chest

A

2

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16
Q

how many leads on the left chest

A

4

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17
Q

stroke volume DEFINE AND EQUATION

A

amount of blood ejected in one heartbeat

end diastolic - end systolic

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18
Q

what happens during isovolumetric contraction

A

ventricular contraction, increases ventricular pressure, , AV valves close

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19
Q

factors affecting stroke volume

A

preload, afterload, contractility

PAC

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20
Q

what is cardiac preload

A

Initial stretching of cardiac myocytes prior to contraction

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21
Q

factors that affect preload

A

atrial contractility, heart rate, valvular resistance , ventricular compliance

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22
Q

Function of avn

A

Delays impulse and allows atria to empty into ventricle

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23
Q

Purpose of refractory period

A

Prevents excessive contraction

Allows time for the heart to fill

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24
Q

What is long QT syndrome

A

Abnormality of k channels
Slower k release delays depolarisation
Delayed depolarisation increases risk of early afterdepolarisations

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25
Q

Where is the san located

A

Near the opening of svc on the superior lateral wall of RA

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26
Q

What is ohms law

A

Voltage = current x resistance

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27
Q

Normal timing for p wave

A

80-100ms

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28
Q

Normal timing of QT interval

A

Men 350-440

Women 350-460

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29
Q

How many bipolar , unipolar chest and limb leads

A

Three bipolar

Three unipolar limb six unipolar chest leads

30
Q

Where do all the six chest electrodes go

A

V1- 4th intercostal space at right sternal angle
V2- 4th intercostal space at the left sternal angle
V3- midway between v2+v4
V4- 5th intercostal space in midclavicular line
V5- left anterior auxiliary at same level as v4
V6- left mid auxiliary lane at the same horizontal level as 4+5

31
Q

Names of the 4 steps of cardiac cycle

A

Diastole
Isovolumetric contraction
Systole
Isovolumetric relaxation

32
Q

Describe the 4 steps of cardiac cycle with valves

A

Diastole - blood enters the atrium through pv veins and svc
Av valves open blood can enter ventricle with gravity
Ap>vp

Iso- vp> ap
Av valve shuts
Sml valve also closed
Ventricle contracts but not enough pressure to Open sl valve

Systole - enough pressure
Slv opens
Blood leaves through aorta and pulmonary artery

33
Q

Define contractile the in terms of myocardial work

A

The state of the heart which enables it to increase its contraction to achieve higher pressures

34
Q

Components of the myocardium

A

Contractile tissue
Connective tissue
Fibrous frame
Specialised conduction system

35
Q

Function of plasma membrane in cardiac myocyte

A

Regulates excitation contraction coupling

Spreads the cytosol from extra cellular space and sarcoplasmic reticulum

36
Q

Structure of myosin

A

2 heavy chains
4 light chains
Heads are perpendicular on the thick filament at rest

37
Q

Structure of actin

A

Globular protein

Double stranded macromolecule helix

38
Q

Three parts of troponin protein and function

A

I- inhibit actin and myosin interaction
T- binds troponin complex to tropomyosin
C- high affinity to ca2+ so it binds

39
Q

Describe actin

A

Globular protein
Single polypeptide
Polymerises with actin to make double helix

40
Q

what does preload mean

A

the stretch of myocardium or end-diastolic volume of the ventricles

41
Q

what is your pulse pressure

A

upper and lower numbers of your blood pressure

42
Q

Define cardiac output

A

Blood ejected by each ventricle per minute

43
Q

Define stroke volume

A

Volume of blood ejected per beat

44
Q

Physiological factors that can affect cardiac output

A 
Exercise 
Emotion
Pregnancy 
Posture 
Sweating 
Age 
Gender
45
Q

Another term for end diastolic volume

A

Preload

46
Q

Starlings law of the heart basics

A

More heart chambers filled with blood
Increased ventricular pressure
Stronger force of contraction
Increased sv

47
Q

Why does frank starling law work

A

Increased stretch of muscle fibres
Increase formation of actin myosin cross bridge
Increased force of contraction

48
Q

Blood pressure differences between systemic and pulmonary circulation

A

Systemic 120/80

Pulmonary 20/8

49
Q

What is the ejection fraction

A

Sv/ edv

50
Q

Factors that affect preload

A 
Atrial contractility 
Venous return 
Ventricular compliance 
Valvular resistance 
Heart rate
51
Q

What is afterload

A

Resistance left ventricle must overcome to circulate blood

Indirectly proportional to SV

52
Q

Define blood flow

A

The volume of blood that flows through the systemic circulation

53
Q

Location of baroreceptors

A

Present in carotid sinus and aortic arch

54
Q

Mechanism of Parasympathetic control of heart rate

A

Via vagus nerve which synapses with post ganglionic cells in san and avn
When stimulated ach binds to m2 receptors which act to decrease hr

55
Q

Mechanism of Sympathetic control of heart rate

A

Via postganglionic fibres from sympathetic trunk which innervate the SAN and AVN
fibres release noradrenaline which acts on b1 adrenoreceptors to increase HR

56
Q

Baroreceptor reflex for increase in bp

A 
Increase bp
Increase receptor activity 
Increase afferent impulses to cardiovascular centre
Increase psns and decrease sns .
Decrease in CO and vasodilation
57
Q

Examples of vasoconstrictors and vasodilators

A

Con- endothelin 1 and internal pressure

Dilate - adenosine , prostacyclin , hypoxia

58
Q

Role and location of chemoreceptors

A

Detect changes in o2 and co2

In aortic arch and carotid sinus same as baroreceptors

59
Q

Action potential in cardiac myocytes 5 steps

A

Phase 4 resting potential -90
Phase 0- action potential arrives at myocytes , if threshold is reached na channels open
Phase 1- partial depolarisation , k channels open the outflix decreases membrane potential
Phase 2- ca channels open allow influx of ca to balance k outflux
Phase. 3 depolarisation ca shut k remain open

60
Q

What is a relative refractory period

A

When a greater than normal stimulus can depolarise the cell

61
Q

How long is the pr and qrs interval

A

Pr 120-200 ms

Qrs - 0.06-0.1 ms

62
Q

What does the st segment represent

A

Starts at the end of S wave and ends at the start of t wave

An isoelectric line that represents the time between depolarisation and depolarisation of the ventricles

63
Q

Where do the three unipolar leads go

A

Avr right wrist
Avf left wrist
Avf left foot

64
Q

How to work out heart rate from an ecg

A

Differences between two qrs complexes

65
Q

Difference between cardiac and skeletal muscle

A

Cardiac muscle is involuntary

Skeletal is voluntary

66
Q

How to conduct a heartbeat

A 
San
Bachmann bundles 
Avn delayed 
Bundle of his 
Purkyne fibres 
Contraction from the base upwards
67
Q

how long does cardiac cycle last

A

0.8 secs

68
Q

what causes a dicrotic notch

A

caused by an increase in aortic pressure upon closure of the

aortic valve- this happens due to the blood rebounding against the valve

69
Q

In which layer do action potentials occur in the heart

A

Myocardium

70
Q

What does a q wave show

A

Interventricular septum depolarisation

71
Q

Where is av node located

A

Bottom of right atrium

cardiology and respiratory (10 decks)

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