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27 Cards in this Set

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Briefly describe the ANATOMICAL location of the heart
Midsternal line
2nd rib
2/3 lies to left of centre
Apex points to the left hip
Explain the FUNCTION of the LAYERS of the heart wall
3 layers
Epicardium - sisceral layers of serous pericardium
Myocardium - Cardiac muscle & connective tissue
Endocardium - endothelium (squamous epithelium)
Explain the FUNCTION of the COVERINGS of the heart
Fibrous Pericardium - tough dense connective tissue / anchors, protects & prevents from overfilling with blood
Serous Pericardium - Deep to fibrous pericardium / double layer membrane / serous fluid in cavity / allows frictionless movement
Describe the FOUR main chambers of the heart
2 Atria (left & right)
Receiving chamber / thin walled
2 Ventricle (left & right)
Discharging chambers / thick, muscular wall
Describe the heart valves
Ensure 1 way flow through the heart
2 Artrioventricular Valves (AV) sound LUB : prevent retrograde flow from ventricles to atria : Rights = tricuspid / Left = Bicuspid (mitral)
2 Semilunar valves (SL)
Prevent backflow from vessels onto ventricles, sound DUB : Aortic semilunar + Pulmonary semilunar
Describe the movement of blood through the heart
Heart actually 2 pumps side by side
Right side (ventricle) of the heart pumps blood to the lungs PULMONARY CIRCUIT PUMS - gas exchange
Left side (ventricle) of the heart pumps blood to all body tissue = SYSTEMIC CIRCUIT PUMP functional blood
Describe blood flow to, from & through the heart
Blood returning from the body is relatively oxygen poor & carbon dioxide rich
It enters the RIGHT ATRIUM and passes into the R Ventricle, which pumps it to the lungs via the PULMONARY trunk.
In the lungs the blood off loads carbon dioxide & picks up oxygen.
Freshly oxygenated blood is carried by the Pulmonary veins back to the Left side of the heart (left Atrium) and passes into the Left Ventricle, which pumps it into the Aorta.
From there the blood is transported via smaller systemic arteries to the body tissues, where gases & nutrients are exchanged across the capillary walls.
Briefly describe the STRUCTURE of CARDIAC MUSCLE
- 30% of cell volume is mitochondria (controls release of energy fm foods / forms ATP)
- all or nothing contraction of heart
- some cardiac muscle cells are self-excitable, eg: pacemaker (specialized cardiac cells)
- have long absolute refractory period, cant produce tetanic contraction
- specialized conduction system
- cardiac muscle conducts electricity
Relate the STRUCTURE of cardiac muscles to its FUNCTION
Length of absolute refractory period (in-excitable period when Na+ channels are still open or inactivated) lasts approximately 250ms, nearly as long as the contraction.
1 - DEPOLARIZATION
2 - PLATEAU PHASE
3 - REPOLARIZATION
Briefly describe the SEQUENCE of the ELECTRICAL conduction system
Sinoatrial (SA) node - determines heart rate
Atrioventricular (AV) node - delays impulse allowing atria to contract
AV bundle - conduction between atria & ventricles
R & L bundle branches
Purkinje Fibres - distribute impulse throughout ventricle wall
What determines the heart rate?
SA node (sinoatrial)
Name the IONS involved in controlling the electrical conduction system
Ca2+ influx **** very important for heart function, but too much could cause an irregular heart beat
K+ channels open
What is electrocardiography (ECG)?
Measuring the electrical currents generated in the heart that spread through the body
Name the 3 main waves (ECG)
P - depolarisation of Atria (1st wave)
QRS - ventricular depolarisation
T - ventricular repolarisation
what happens during the Cardiac Cycle?
Electrical activity to muscle contraction to pressure changes to valves opening & closing
Systole = contracting
Diastole = relaxing
Define Cardiac OUTPUT
Amount of blood pumped by each ventricle per minute
Product of heart rate (HR) & stroke volume (SV)
CO (cardiac output) = HR x SV
During exercise CO = how much?
20-25 litres per minute
True of False
The lower the heart rate the better the heart is working?
True, the heart has more time to fill & contract.
How can CO be regulated?
by altering either the HR or SV
Define Stroke Volume Regulation
Normally SV = EDV - ESV
SV - stroke volume
EDV - end diastolic volume
ESV - end systolic volume
How can EDV be increased?
by increasing venous return
How can ESV be decreased?
by increasing the force of cardiac contraction
increase preload / increase sympathetic stimulation
What is Pre-load?
- cardiac muscle will contract more strongly when stretched
- increase venous return = increased contractile force
what is after-load dependent on?
Blood pressure
- the higher the blood pressure, the less blood is ejected from the ventricle
- effects of stress & hypertension
Explain the heart sounds
2 sounds
1st - LUB, as the AV valves close
lounder & longer than the 2nd sound
2nd - DUB, as SL valves close
What is end diastolic volume?
end-diastolic volume (EDV) is the volume of blood in a ventricle at the end of filling (diastole)
What is end systolic volume?
End-systolic volume (ESV) is the volume of blood in a ventricle at the end of contraction