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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
Where is the san located
Near the opening of svc on the superior lateral wall of RA
26
What is ohms law
Voltage = current x resistance
27
Normal timing for p wave
80-100ms
28
Normal timing of QT interval
Men 350-440 | Women 350-460
29
How many bipolar , unipolar chest and limb leads
Three bipolar | Three unipolar limb six unipolar chest leads
30
Where do all the six chest electrodes go
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
Names of the 4 steps of cardiac cycle
Diastole Isovolumetric contraction Systole Isovolumetric relaxation
32
Describe the 4 steps of cardiac cycle with valves
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
Define contractile the in terms of myocardial work
The state of the heart which enables it to increase its contraction to achieve higher pressures
34
Components of the myocardium
Contractile tissue Connective tissue Fibrous frame Specialised conduction system
35
Function of plasma membrane in cardiac myocyte
Regulates excitation contraction coupling | Spreads the cytosol from extra cellular space and sarcoplasmic reticulum
36
Structure of myosin
2 heavy chains 4 light chains Heads are perpendicular on the thick filament at rest
37
Structure of actin
Globular protein | Double stranded macromolecule helix
38
Three parts of troponin protein and function
I- inhibit actin and myosin interaction T- binds troponin complex to tropomyosin C- high affinity to ca2+ so it binds
39
Describe actin
Globular protein Single polypeptide Polymerises with actin to make double helix
40
what does preload mean
the stretch of myocardium or end-diastolic volume of the ventricles
41
what is your pulse pressure
upper and lower numbers of your blood pressure
42
Define cardiac output
Blood ejected by each ventricle per minute
43
Define stroke volume
Volume of blood ejected per beat
44
Physiological factors that can affect cardiac output
``` Exercise Emotion Pregnancy Posture Sweating Age Gender ```
45
Another term for end diastolic volume
Preload
46
Starlings law of the heart basics
More heart chambers filled with blood Increased ventricular pressure Stronger force of contraction Increased sv
47
Why does frank starling law work
Increased stretch of muscle fibres Increase formation of actin myosin cross bridge Increased force of contraction
48
Blood pressure differences between systemic and pulmonary circulation
Systemic 120/80 | Pulmonary 20/8
49
What is the ejection fraction
Sv/ edv
50
Factors that affect preload
``` Atrial contractility Venous return Ventricular compliance Valvular resistance Heart rate ```
51
What is afterload
Resistance left ventricle must overcome to circulate blood | Indirectly proportional to SV
52
Define blood flow
The volume of blood that flows through the systemic circulation
53
Location of baroreceptors
Present in carotid sinus and aortic arch
54
Mechanism of Parasympathetic control of heart rate
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
Mechanism of Sympathetic control of heart rate
Via postganglionic fibres from sympathetic trunk which innervate the SAN and AVN fibres release noradrenaline which acts on b1 adrenoreceptors to increase HR
56
Baroreceptor reflex for increase in bp
``` Increase bp Increase receptor activity Increase afferent impulses to cardiovascular centre Increase psns and decrease sns . Decrease in CO and vasodilation ```
57
Examples of vasoconstrictors and vasodilators
Con- endothelin 1 and internal pressure | Dilate - adenosine , prostacyclin , hypoxia
58
Role and location of chemoreceptors
Detect changes in o2 and co2 | In aortic arch and carotid sinus same as baroreceptors
59
Action potential in cardiac myocytes 5 steps
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
What is a relative refractory period
When a greater than normal stimulus can depolarise the cell
61
How long is the pr and qrs interval
Pr 120-200 ms | Qrs - 0.06-0.1 ms
62
What does the st segment represent
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
Where do the three unipolar leads go
Avr right wrist Avf left wrist Avf left foot
64
How to work out heart rate from an ecg
Differences between two qrs complexes
65
Difference between cardiac and skeletal muscle
Cardiac muscle is involuntary | Skeletal is voluntary
66
How to conduct a heartbeat
``` San Bachmann bundles Avn delayed Bundle of his Purkyne fibres Contraction from the base upwards ```
67
how long does cardiac cycle last
0.8 secs
68
what causes a dicrotic notch
caused by an increase in aortic pressure upon closure of the | aortic valve- this happens due to the blood rebounding against the valve
69
In which layer do action potentials occur in the heart
Myocardium
70
What does a q wave show
Interventricular septum depolarisation
71
Where is av node located
Bottom of right atrium

cardiology and respiratory (10 decks)

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