mammalian cardiac cycle Flashcards

1
Q

outline the movement of blood through the heart

A
  • deoxygenated blood enters RA through vena cava
  • goes to RV through tricuspid valves
  • goes to pulmonary artery through semi-lunar valves to lungs
  • from lungs oxygenated blood enters LA of heart through pulmonary vein
  • goes to LV through bicuspid valves
  • goes to aorta through aortic valve to rest of body
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2
Q

what is the heart made out of

A

cardiac muscle

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3
Q

function of coronary arteries

A

supply heart muscle with oxygen and glucose in order to keep it contracting and relaxing continuously

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4
Q

what are the pericardial membranes + their function

A

a protective, fluid-filled sac that surrounds the heart

it helps to prevent the heart from over distending / swelling with blood

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5
Q

which side of the heart is thicker + why

A

left side, because there is a thicker layer of muscle in left ventricle wall as it must pump blood around whole body and all extremities

this means it must provide sufficient force to overcome resistance of aorta and arterial systems of whole body

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6
Q

systole definition

A

the state of contracting

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7
Q

diastole definition

A

the state of relaxing

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8
Q

outline the cardiac cycle with pressure differences and systole/diastole

A
  • blood flows into atria through veins, increasing atrial pressure
  • atrial pressure > ventricular pressure
  • this causes atrio-ventricular valves to open so blood flows into ventricles
  • atrium walls contract - ATRIAL SYSTOLE
  • this pushes all blood out of atria into ventricles, increasing ventricular pressure
  • ventricular pressure > atrial pressure
  • this causes atrio-ventricular valves to close and semi-lunar valves to open
  • ventricle walls contract - VENTRICULAR SYSTOLE
  • atrium walls relax - ATRIAL DIASTOLE
  • blood is pumped out of ventricles into arteries, increasing arterial pressure
  • pressure in blood vessels > ventricular pressure
  • this causes semi-lunar valves to close
  • ventricles relax - VENTRICULAR DISATOLE
  • cycle starts again
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9
Q

myogenic definition

A

muscle is intrinsically able to produce its own stimulus/rhythm

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10
Q

outline the process by which the heart generates its own heart beat, which reference to atrial + ventricular systole

A
  • cells in SAN depolarise/become electrically excited
  • this triggers a wave of excitation to spread across atria - ATRIAL SYSTOLE
  • this wave cannot pass to ventricles due to non-conducting tissues separating them
  • this means the AVN detects the wave of excitation after a short delay
  • AVN transmits wave of excitation down purkyne fibres - VENTRICULAR SYSTOLE
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11
Q

SAN definition

A

sinoatrial node
located in the right atrium wall

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12
Q

what is the purpose of the SAN

A

it acts as a pacemaker
also known as the pacemaker region

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13
Q

AVN definition

A

atrioventricular node
located in between atria and connected to purkyne fibres

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14
Q

purkyne fibres definition

A

conducting fibres
initially bundled together in the Bundle of His, then they branch out as the fibres run down septum to the apex of the heart, then up ventricle walls

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15
Q

why is the short delay imposed by AVN important

A

this delay ensures the atria have contracted

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16
Q

what does a P-wave show on an ECG

A

electrical activity in atrial systole

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17
Q

what does the QRS complex show on an ECG

A

electrical activity in ventricular systole

18
Q

what does the Q-T interval represent in an ECG

A

ventricles contracting

19
Q

what does the T-wave show on an ECG

A

the recovery of the ventricles

20
Q

what does the T-P interval represent on an ECG

A

the heart is relaxed and filling with blood

21
Q

8 examples of heart conditions

A
  • tachycardia
  • bradycardia
  • heart block
  • hypertrophy
  • fibrillation
  • flat line
  • arrhythmia
  • ectopic heart beat
22
Q

what is tachycardia

A

elevated heart rate for no reason
- can sometimes be so high that little blood is pumped as filling time is too short
treatment - relaxation therapy, beta blockers

23
Q

what is bradycardia

A

reduced heart rate for no reason
- could indicate good aerobic fitness, or drug use
- leads to increased risk of blood clots + stagnation
treatment - lifestyle changes or pacemakers

24
Q

what is heart block

A

a delay in conduction between atria and ventricles, appears on an ECG as the separation of P-wave and QRS complex
treatment - pacemaker

25
what is hypertrophy
when 1 side of the heart is enlarged, causes QRS complex to be distorted - cause of enlargement could be high blood pressure that ends up thickening left ventricle treatment - beta blockers
26
what is fibrillation
cardiac muscle contraction is not coordinated, ECG will appear distorted - little blood is pumped as a result
27
what is flat line
no electrical activity within heart - only 2% of people with a flatline leave the hospital alive
28
what is the length of 1 cardiac cycle in humans
approx 0.8 seconds
29
how to work out beats per minute
no. beats x 60/time time = time that no. of beats was counted in
30
function of the septum in heart
prevents the mixing of oxygenated and deoxygenated blood
31
what is the function of valves in the heart
prevents backflow of blood and ensure efficient movement of blood
32
why do ventricles contract from the apex up
blood needs to be moved upwards + ensures complete emptying of ventricles
33
what does an ECG show
the spread of electrical excitation through the heart as a way of recording what is happening as it contracts x axis = time y axis = electrical potential mV
34
what does ECG stand for
electrocardiogram
35
how can heart rate be measured using an ECG
using the time between R peaks
36
cardiac cycle definition
the sequence of events that occur in the heart during 1 heartbeat
37
what causes the sounds of a heart beat
blood hitting the heart valves
38
what causes the lub sound
blood hitting atrioventricular valves as ventricles contract - occurs during ventricular systole
39
what causes the dub sound
backflow of blood hitting semilunar valves - occurs during ventricular diastole
40
what is arrythmia
when the heart has an abnormal rhythm treatment - pacemakers
41
what is an ectopic heartbeat
when there are extra heartbeats outside of the normal rhythm treatment - beta blockers
42
how are ECGs measured
electrodes are stuck on skin which can measure electrical differences in the skin this signal is fed into a machine which produces an ECG