Cardiac Muscle

Question 1

Cellular Anatomy

Answer 1

form a highly branched cellular network in the heart

Question 2

AP in Contractile Cardiac Muscle

Answer 2

Na+ increases rapidly, Ca2+ comes in slowly, and K+ comes out fast

Question 3

Cardiac AP Steps

Answer 3

Na+ influx through voltage gated Na+ 
channels.
• Plateau caused by voltage gated (L-Type) 
Ca2+ channels and....
– Decrease K+ permeability
• End of AP caused by K+ efflux.
• Entire AP lasts ~ 200 msec.

Question 4

Cardiac Muscle Contraction

Answer 4

occurs due to the the binding of the myosin head to adenosine triphosphate ( ATP ), which then pulls the actin filaments to the center of the sarcomere, the mechanical force of contraction.

Question 5

Pacemaker Cells

Answer 5

Autorhythmic Cells
• Non-contractile
• No resting membrane potential
• Pacemaker potential………

Question 6

Pacemaker Potentials

Answer 6

the slow, positive increase in voltage across the cell’s membrane (the membrane potential) that occurs between the end of one action potential and the beginning of the next action potential.

Question 7

ec coupling in cardiac muscle

Answer 7

the process from electrical excitation of the myocyte to contraction of the heart