Cardiac and Smooth Muscle

Question 1

What property of the heart allows for electrical conductance?

Answer 1

Gap Junctions

Question 2

What property of the heart allows for mechanical synchrony?

Answer 2

Desmosomes and Fascia Adherens

Question 3

Difference between cardiac muscle and skeletal muscle?

Answer 3

Cardiac muscle has less developed SR but more mitochondria than skeletal muscle

Question 4

Contraction of cardiac muscle requires _______ Ca

Answer 4

Extracellular Ca is required for myocardial contraction

Ca influx occurs during plateau phase of AP

Question 5

Pathway of Ca influx and activation of myofilaments

Answer 5

Ca influx via Ca Channels
Ca activtion of Ryr receptor
Release of Ca from SR
Ca activation of muscle
Activation of PKA => Phosphorylation of Phospholambam
Increased activity of Ca pump reuptake into SR

Question 6

Ways to increase force of heart contraction

Answer 6

Increase Ca
Increase blood flow
Stretching cardiac muscle

Question 7

Sympathetic Activation phosphorylates 4 proteins of cardiac muscle to allow increase intracellular Ca

Answer 7

Phospholambam gets phosphorylated to increase SERCA pump
Ryr Receptor gets phosphorylated for increased release of Ca from SR
Ca Voltage Channel gets phosphorylated to allow increased influx of Ca from
Troponin I gets phosphorylated
NB: All done by PKA

Question 8

Thick Filament

Answer 8

Myosin

Question 9

Thin Filament

Answer 9

Actin

Question 10

Muscle Fibers are attached to

Answer 10

Dense Bodies

Question 11

Activation of Muscle Contraction

Answer 11

1. MLCK must be activated via Ca AND phosphorylated
2. Removal of Pi and ADP from distal head of myosin locks in myosin head to actin
3. Rachet motion of myosin on actin requires ATP
4. back to start

Question 12

Contraction of smooth muscle requires?

Answer 12

Ca/Calmodulin-dependent phosphoryation of myosin

Question 13

Hormones/ NTs promote contraction of vascular smooth muscle via

Answer 13

PIP2/IP3 cascade

these contractions occur in ABSENCE of Ca influx and without changing membrane potential

Question 14

Pharmacomechanical coupling

Answer 14

Promoting contraction without changing the membrane potential nor increasing Ca influx

Question 15

Latch State

Answer 15

Transition to slow CROSS-BRIDGE cycling state
dephosphorylation of light chain causes increased attachement of actin and myosin
Allows for maintenance of force