L13 The Heart Flashcards
What is the pericardium?
Pericardium is a protective, fluid-filled sac that surrounds heart
Acts like a protective bubble for your heart. Reduces friction as it beats
How many chambers are within the heart?
4 chambers
What does the right atrium (RA) receive?
Deoxygenated systemtic venous return
Where does the right ventricle (RV) push blood to?
Pushes blood to pulmonary circulation for oxygenation
Where does the left atrium (LA) receive oxygenated blood from?
From pulmonary circulation
Where does the left ventricle (LV) pump oxygenated blood to?
Pushes blood to head and body under high pressure
What does the work pulmonary refer to?
Refers to anything related to lungs
How many circulations are there within the heart?
Pulmonary and systemic circulation
Pulmonary ( between heart and lungs)
Systemic ( between heart and body)
What do valves do?
Valves control unidirectional blood flow in cardiac cycle
What are the two atrioventricular valves called?
Mitral and tricuspid
What are the two semilunar valves called?
Aortic valve
Pulmonary valve
What is chordae tendinae?
They are thin, strong cords of fibrous connective tissue
What connects the atrioventricular valves to the cardiac walls?
Chordae tendinae and papillary muscles
What is the heart wall made of?
Endocardium - outermost
Myocardium
Epicardium
What are conducting cells?
They are a group of cells that are responsible for rapidly spreading action potentials (AP)
Specialised cardiac cells
What are contractile cells?
They are responsible for contraction of the heart via action potentials (AP)
What is the link between the electrical signals and contraction of the myocytes (excitation - contraction coupling)?
Calcium ion release
Give me a structural property of the myocardium
Has extensively branched muscle fibre cell - connected by intercalated discs (ID)
What do gap junctions (GJ) do?
They facilitate the depolarisation current flow from cell to cell
What do Desmosomes do?
They act as strong anchoring points between the cells
anchor fibres together
How does excitation - contraction coupling happen?
Action potential triggered in sarcolemma which spreads to the T tubules which releases calcium ions which binds the actin adn myosin together creating a large instantaneous force
Where do electrical signals originate from ?
The sinoatrial node (SAN)
What is the body’s natural pacemaker called? (The 1st pacemaker)
Sinoatrial node
What is Action potential (AP) propagation?
It’s the process by which electrical signals, or nerve impulses, travel along the axon of a neuron
What two ways can AP propogate?
Cell to cell via gap junctions
Conduting pathways
AP - action potential
What is the atrioventricular (AV) node?
Acts as a secondary pacemaker
Located in the right atrium
Why is the atrioventricular node 0.1s delayed compared to the SA node?
It allows the atria to fully contract and empy their blood into the ventricles before the venctricles contract.
Maximises efficiency of blood pumping
What does the atrioventricular ring do?
It prevents the direct spread of electrical impulses from the atria to the ventricles
What is the secondary (backup) pacekmaker?
AVN - atriovenventricular node
What is the ‘His- Purkinje fibre system’?
Specialised network of cells in the heart that rapidly conducts electrical impulses throughout the ventricles
What are the average bpm of each pacemaker?
1st - 60-100/min
2nd - 40bpm
3rd - 20bpm
What happens during atrial systole?
Atrial depolarisation
Contraction of atrium, increases pressure
What happens during isovolumentric ventricular contraction?
Purkinje fibre electrical activation causes ventricles to contract (systole), which increases pressure
When AV close, ventricular has more pressure than atrial chamber
What are the two AV valves?
Mitral and tricupsid valves
What are the two semilunar valves called?
Pulmonary and aortic valves
What happens during rapid ventricular ejection?
- Semi lunar valves (SLV) open and rapid blood ejection
- Ventricular volume decreases
What happens during reduced ventricular ejection?
- SLV still open - blood still ejected
- Arterial volume decreases
- Blood transfered to ‘arterial tree’ by elastic recoil
What happens during isovolumetric ventricular relaxation?
- Begins after ventricles fully repolarised
- Ventricles relaxed - pressure decreases
- SLV close
What happens during rapid ventricular filling?
- Ventricular pressure is greater than atrial pressure
- Mitral and tricuspid valves open
What happens during ventricular filling?
Longest phase of cardiac cycle and includes last portion of ventricular filling
List the order of the sequence of how blood flows through the heart (7)
-Atrial systole
-Isovolumetric ventricular contraction
-Rapid ventricular ejection
- Reduced ventricular ejection
- Isovolumetric ventricular relaxation
- Rapid ventricular filling
- Reduced ventricular filling
How do myocytes vary in anatomy and channels?
They have time dependent + voltage gated (VG) currents
Ion channels open and close in response to changes in membrane voltage and time
What does ECG stand for?
Electrocardiogram
Are the IC and EC currents in the heart muscle cells equal and opposite?
Yes.
What is ‘sum of vectors’?
Refers to the collective electrical activity generated by millions of individual cells as they depolraise and repolarise
What detects the sum of vectors?
By electrodes on the body’s surface
Why are electrodes measured in planes?
Electrodes measure in planes because they capture the electrical activity of the heart from different angles
Can cause a positive or a negative deflection
What does the P wave stand for?
Depolarisation of atria
What does the QRS complex mean?
Depolarisation of ventricles
What does the T wave stand for?
Repolarisation of ventricles
