What is the leading killer in the US?
CVD, 50% of all deaths
Describe blood flow through the hearts chambers/valves
1. Blood enters from superior vena cava/Inferior vena cava and enters into the right atrium. 2. Blood travels through the Tricupsid valve into the Right Ventricle. 3. Blood flows from right Ventricle through pulmonary valve to the Pulmonary artery 4. Blood flows from pulmonary artery to Lungs to Pulmonary veins 5. Blood flow from pulmonary veins into Left Atrium 6. Blood flows from left atrium through mitral (bicuspid) valve to the Left Ventricle. 7. Blood flows from Left ventricle through aortic valve into Aorta.
What outer fibrous layer surrounds the pericardial cavity? What is composed of?
The Parietal Pericardium - Areolar tissue - Epithelium - Dense fibrous layer
What is the space inside the parietal pericardium called?
What is the layer deep to the pericardial cavity? What is it composed of?
Epicardium - Epithelium - Areolar tissue
What resides between the Epicardium and Endocardium?
Myocardium (Cardiac muscle tissue)
What is the innermost layer of the heart? What is it composed of?
- Areolar Tissue
What are the fusions between cardiac muscle cells?
What is the role of gap junctions in cardiac muscle?
They allow electrical signals to pass rapidly form cell to cell
What are microfibrils?
Bundle of protein filaments
What fraction of cell volume do mitochondria occupy on a contractile cardiac fiber?
What is the function of Intercalated disks? What components allow them this function?
They allow the synchronized contraction of cardiac cells. They contain desmosomes that transfer force from cell to cell, and fasciae adherens which are ribbon like junctions stabilize the muscle
What two areas of the heart can initiate electrical activity?
What Node begins electrical activity of the heart?
Sinoatrial Node (pace maker)
What transmits electrical signal from SA node to AV node?
The internodal tract
Where can the electrical signal from the SA node also be sent?
To the Atria via Bachmann's bundle, allows simultaneous depolarization of the atrias
What is the role of Purkinje Fibers?
to send nerve impulses to the cells in the ventricles of the heart and cause them to contract and pump blood either to the lungs or the rest of the body.
How is the electrical signal from the AV node directed?
It is directed towards the apex by the bundle branches, before coming back around by the way of the conduction pathways
Channel in which gates randomly alternate between open and closed positions
Channel in which they open in response to change in membrane potential
Voltage gated channels
Channels which open and close in response to specific chemical stimuli
Ligand Gated channels
Channels which open or close in response to mechanical action such as sensory receptors
Mechanically gated channels
Stages of Atrial/Ventricular Action Potential
4 - Resting Membrane (K leaks out)
0 - Threshold reached, Voltage gated Na open and sodium rushes in (Depolarizes)
1 - Sodium channels close, Voltage gated potassium channels open and potassium leaves cell (Repolarizes)
2 - Voltage gated Ca open and keeps the AP from rapidly repolarizing.
3 - Voltage gated Ca close, and cell begins to repolarize back to resting potential
4 - Voltage gated K close, Resting membrane.
What allows the depolarizing current to travel from contractile or autorhythmic cells?
Once a depolarizing current has entered a contractile cell, how does it travel along the cell?
The Plasma Membrane and T tubules
What happens once Ca channels on the plasma membrane and SR open?
The Ca influx induces Ca release from the SR
How do myosin-binding sites become exposed?
Ca binds to troponin, which causes tropomysin to pull and expose the myosin binding sites
Once muscle fiber contraction finishes, what happens to calcium?
Ca is actively transported back into SR and ECF
Once Ca leaves the SR and muscle fibers, what happens to the muscle fiber?
Tropomyosin reblocks myosin binding site and muscle fiber relaxes
Describe the phases of nodal action potential
4 - Spontaenous depolarization of pacemaker potential
0 - Depolarization phase continues, increase of Ca conductance
3 - Repolarization occurs, K channels open and L type Ca channels inactivate, (decline is long lasting)
4 - Spontaneous depolarization of pacemaker potential occurs