The Heart Flashcards
What protects the cardiac muscle?
cardiac muscle is protected by ribcage, within thoracic cavity - surrounded by a protective fluid-filled sac (pericardium)
What are the 4 chambers of the heart?
- Right atrium (receives deoxygenated systemic venous return).
- Right ventricle (pushes blood to pulmonary circulation for oxygenation)
- Left atrium (receives oxygenated blood from pulmonary circulation)
- Left ventricle (pumps oxygenated blood under high pressure to head and body)
What are the 2 types of atrioventricular valves?
mitral & tricuspid
What side of the heart is the mitral valve on?
left
What side of the heart is the tricuspid valve on?
right
How many flaps does the mitral valve have?
2
How many flaps does the tricuspid valve have?
3
What connects the atrioventricular valves to the cardiac wall?
chordae tendinae & papillary muscles
What are the 2 semilunar valves?
aortic & pulmonary (small fibrous nodules come together
Where are cardiac cells found?
Heart wall: epicardium, myocardium, endocardium
What type of cells are electrically active?
cardiac cells
What are conducting cells?
Rapidly spread action potentials
What are examples of where conducting cells are found?
SAN, atrial intermodal tracts, AVN, bundle of His, Purkinje system
What are contractile cells?
action potentials (AP) lead to contraction - generation of force/pressure
Where are contractile cells?
majority of atrial + ventricular tissue
What links electrical signals & contraction of the myocytes (excitation-contraction coupling)?
Extracellular Ca2+
What is the electrophysiology of myocytes?
excitation - contraction coupling
What is the electrophysiology of myocardium?
extensively branched muscle fibre cell connected by intercalated discs (ID)
What connects myocardium (extensively branched muscle fibre cell)?
intercalated discs (ID)
What is the myocardial cell structure part of?
sarcolemma
How do depolarising current flow from cell to cell?
cell to cell (Electronical coupling) across Gap junctions, in wave-like flows (symcytium)
What is the role of desmosomes?
anchor fibres together
Where does excitation-contraction coupling occur?
T-tubules - sarcolemma forms deep invaginations
What happens when depolarisation is relayed through to the cell core, via the T-tubules?
Ca2+ is released
Where is Ca2+ released from?
Sarcoplasmic reticulum
Where does the electrical signal originate?
in the sinoatrial node (SAN)
What is the action potential intrinsic rate at rest?
60-100/min
What prevents the spread of the electrical excitation into the ventricles?
Fibrous atrioventricular ring
When is it necessary to delay the spread of the electrical excitation into the ventricles?
allows for optimal atrial emptying
What is the 2nd pacemaker in the cardiac cycle?
AVN (atrioventricular node)
What occurs in atrial systole?
atrial depolarisation (which follows SAN stimulation)
- ventricles relaxed & atrioventricular valves open, filled ventricles with blood
What follows atrial systole?
isovolumetric ventricular contraction
What occurs during isovolumetric ventricular contraction?
- Purkinje fibre electrical activation, ventricle contract, increasing pressure, leadingto atrioventricular valves closing, as the ventricular pressure is larger
What follows isovolumetric ventricular contraction?
Rapid ventricular ejection
What occurs during rapid ventricular ejection?
ventricular pressure > aortic pressure
- semilunar valves open, leading to rapid blood ejection.
- this leads to a decrease in ventricular pressure, and an increase in arterial pressure, leading to atrial filling beginning.
What follows rapid ventricular ejection?
Reduced ventricular ejection
What occurs during reduced ventricular ejection?
ventricular depolarisation (decrease in pressure) - semilunar valves still open.
- arterial volume of blood decreases.
What follows reduced ventricular ejection?
Isovolumetric ventricular relaxation
What occurs during Isovolumetric ventricular relaxation?
- begins when ventricles are fully repolarised.
- semilunar valves close (ventricular pressure < atrial pressure
What follows isovolumetric ventricular relaxation?
Rapid ventricular filling
What occurs during rapid ventricular filling?
atrioventricular valves open as ventricular pressure < atrial pressure.
- ventricles begin to fill from atria
What occurs after rapid ventricular filling?
reduced ventricular filling
What happens during reduced ventricular filling?
longest phase of cardiac cycle and included last portion of ventricular filling
What are the stages of the cardiac cycle co-ordinated sequence?
- atrial systole
- isovolumetric ventricular contraction
- rapid ventricular ejection
- reduced ventricular ejection
- isovolumetric ventricular relaxation
- rapid ventricular filling
- reduced ventricular filling
What can be used to identify pathology in the electrical activity of the heart?
electrocardiograms
What can be placed around the heart to measure electrical actvitiy?
electrodes
What 2 types of deflections can be created as a result of the direction of the electrical activity?
positive or negative
How many electrodes are used for a simple analysis of ECG vs a clinical analysis?
simple = 3
clinical = 15
What occurs when there is a Na+ current in the heart?
rapid depolarising phase (largest current in heart)
What occurs when there is a Ca+ current in the heart?
rapid depolarising phase - triggers contraction all cardio myocytes
What occurs when there is a K+ current in the heart?
repolarising phase all cardiomyocytes
What occurs when there is pacemaker currents in the heart?
non-selective cation channels (Na+K+ inward current) - cells of SAN, AVN
What can partially block channels in myocytes?
Drugs
Describe what the current should be between the intracellular & extracellular heart muscle cells
Must be equal and opposite
What channels open when depolarisation occurs?
Sodium (Na+) & Calcium (Ca+), causing cations to enter
What is the P wave on an electrocardiogram?
depolarisation of atria
Why can you not see the repolarisation of the atria?
masked by the QRS wave
What time interval is in the PR INTERVAL?
time between atrial depolarisation & ventricular depolarisation
What occurs during the QRS complex?
depolarisation of ventricles
What is at the ST SEGMENTS?
regions between end of ventricular depolarisation & ventricular repolarisation
What is the T wave?
repolarisation of ventricles
What is atrial tachycardia?
fast electrical excitation
What is atrial fibrillation?
irregular excitation of the atria
What is ventricular fibrillation?
irregular excitation of the ventricles
