Cardiac Muscle

Question 1

Product of Cardiac Pump Function = Pressure on a volume of blood

Answer 1

Events involved in the generation of that pressure and effects on that volume:

In the vasculature, the regulation of pressure and distribution of flow of that volume and then the return of that volume of blood to begin a new cycle again

Right heart pumps blood through the lungs, left heart pumps blood thru the peripheral prgans (systemic circulation)

Pulmonary System= low pressure, low resistance

Systematic system= high pressure, high resistance

Tricuspid mitral valves prevent back bulge during ventricular contraction

Aortic/ pulmonic valve : prevents back flow

Question 2

Heart= Sophisticated electrical System

Answer 2

Atrial syncytium- connects the SA to AV node thru three tracts (Ant: Bachman, Mid: Wenckelbach, Post: Thornel)

Atrial bundle (AV node)= special ring that separates the atria and ventricles, allowing the atria to fire first

Bundle of His- spreads current thru the ventricles

Question 3

Heart sounds

Answer 3

S1= beginning of systole closure of mitral and tricuspids

S2= beginning of diastole (closure of aortic and pulmonary valves)

S3/S4= Pathologic, both occur in diastole

Question 4

Cell types

Answer 4

Myocardial muscle- Atria and ventricles- generate force

Conducting- Bundle of his and branches/ purkinje fibers some in atria- coordinate contraction

Pacemaker- SA node + AV- initiate heart-beat control heart rate

Question 5

Key points

Answer 5

1. Gap junctions= low resistance pathways that allow for rapid spread of AP thru intercalated disks (spaces between cardiac muscle) why the heart can act like an electrical syncytium
2. Behaves similarly to skeletal muscle but has a characteristic plataue phase

Question 6

Steps in cardiac muscle activation

Answer 6

1. AP spreads from cell membrane to T tubules
2. This triggers an increase in Ca2+ conductance from the extracellular fluid through L type calcium channels (in plateau phase)
3. The external calcium influx- triggers most CA to be released from SR ( amount of Ca dependent on Ca stored in SR and inward Ca2+ current during the plataue phase of AP)
4. Intracellular Ca binds troponin C and tropomyosin moves out of the way
5. Actin and Myosin can bind, causing the thin and thick filaments to slide against each other magnitude of tension depends on proportion of intracellular Ca2+
6. Relaxation occurs then Ca2+ is pumped back into the SR

Question 7

Wiggers diagram

Answer 7

S1= isovolumic contraction