Cardiac and Smooth Muscle

Question 1

What is the mitochondria and vascularity content of cardiac muscle relative to skeletal muscle?

Answer 1

More mitochondria and vascularity in cardiac muscle

Question 2

What structures allow for cell-to-cell propagation of the action potential in cardiac muscle?

Answer 2

Gap junctions

Question 3

What is the length of cardiac muscle’s refractory period relative to skeletal muscle’s?

Answer 3

Cardiac muscle has a longer refractory period

Question 4

What is the physiologic advantage a longer refractory period in cardiac muscle?

Answer 4

The cardiac muscle cannot be excited again, preventing it from contracting again, and giving the heart time to fill

Question 5

What facilitates the re-uptake of Ca++ into the sarcoplasmic reticulum?

Answer 5

Phosphorylation of phospholamban

Question 6

What is the normal action of phospholamban?

Answer 6

Inhibition of Ca uptake into the SR

Question 7

True or false: cardiac muscle cannot be modulated by hormones

Answer 7

False

Question 8

What physiologic event results in the plateau phase of the cardiac muscle action potential?

Answer 8

Slow opening of voltage-gated L-type Ca++ channels [DHP]

Question 9

To what kind of receptor on cardiac tissue will norepinephrine released by the sympathetic nervous bind

Answer 9

Beta 1 adrenergic receptor

Question 10

What serves as regulatory proteins in smooth muscle?

Answer 10

Myosin Light Chain Kinase and Myosin Light Chain Phosphatase

Question 11

What molecules modulate the rate of ATPase activity in smooth muscle?

Answer 11

Calponin and Caldesmon

Question 12

What is the pattern of smooth muscle filament arrangement?

Answer 12

Diagnonal orientation

Question 13

What is the equivalent of Z lines in smooth muscle?

Answer 13

Dense bodies

Question 14

True or false: smooth muscle cells contain T tubules?

Answer 14

False

Question 15

What is the size of smooth muscle sarcoplasmic reticulum relative to skeletal muscle SR? What is the significance of this?

Answer 15

Smooth muscle cells have a smaller volume of SR, which means smaller calcium storage; Smooth muscle relies on extracellular calcium for contraction

Question 16

Which types of muscle contain gap junctions?

Answer 16

Cardiac and smooth muscle

Question 17

What are the two functional types of smooth muscle?

Answer 17

Single unit and multiunit

Question 18

What is the main type of visceral muscle?

Answer 18

Single unit smooth muscle

Question 19

What type of smooth muscle has rich ANS innervation?

Answer 19

Multiunit

Question 20

What is the result of stretching single unit smooth muscle?

Answer 20

Stretch produces tension which leads to contraction

Question 21

What is the relative level of gap junctions in multiunit smooth muscle compared to unitary smooth muscle?

Answer 21

Fewer or no gap junctions in multiunit smooth muscle

Question 22

What type of smooth muscle has a more stable membrane potential?

Answer 22

Multiunit

Question 23

What does the contractile response of multiunit smooth muscle depend on?

Answer 23

Number of muscle fibers activated and frequency of nerve stimulation

Question 24

What mechanisms can stimulate smooth muscle contraction and relaxation?

Answer 24

Electrical depolarization, chemical stimuli, and mechanical stimuli (stretching)

Question 25

True or false: An action potential is required for smooth muscle contraction?

Answer 25

False

Question 26

What are the two types of smooth muscle action potentials?

Answer 26

Spikes and plateaus

Question 27

True or false: an increase in cytosolic calcium is necessary for smooth muscle contraction?

Answer 27

True

Question 28

What are store operated channels in smooth muscle cells?

Answer 28

Channels that sense when the SR stores of Ca++ are insufficient and can activate the influx of additional Ca++

Question 29

What can activate RyR channels in smooth muscle?

Answer 29

Ca++ induced Ca++ release or IP3 activation

Question 30

To what molecule will calcium bind in smooth muscle?

Answer 30

Calmodulin

Question 31

What are the actions of the calcium-calmodulin complex in smooth muscle?

Answer 31

It activates Myosin Light Chain Kinase as well as CaCM-dependent kinase (CAMK)

Question 32

What is the function of activated myosin light chain kinase?

Answer 32

It phosphorylates myosin light chain, activating it and increasing myosin ATPase activity

Question 33

What phosphorylates calponin? What is the effect of this phosphorylation?

Answer 33

CaCM-dependent kinase; blocks inhibition of myosin ATPase

Question 34

What is the activity of Myosin Light Chain Phosphatase?

Answer 34

Continuously decreases MLC phosphorylation

Question 35

What are the two ways to cause smooth muscle relaxation?

Answer 35

Dephosphorylation of myosin light chain through myosin phosphatase or removal of cytosolic calcium

Question 36

What molecule is responsible for the phosphorylation and inactivation of myosin phosphatase?

Answer 36

Rho-Kinase

Question 37

During pregnancy, what is the effect of an increase in estrogen?

Answer 37

Smooth muscle hypertrophy and increase in gap junction expression

Question 38

What is the effect of oxytocin on smooth muscle contraction

Answer 38

Potent stimulator of smooth muscle contraction

Question 39

What is the effect of nitric oxide in smooth muscle? What is the pathway/mechanism of this action?

Answer 39

Nitric oxide activates guanylyl cylcase, increasing the amount of cGMP, and enhancing smooth muscle relaxation

Question 40

What is the effect of Protein Kinase G activation?

Answer 40

Smooth muscle relaxation

Question 41

What is the mechanism of viagra?

Answer 41

Inhibition of cGMP breakdown

Question 42

What is the mechanism of amlodipine?

Answer 42

Calcium channel blocker that blocks calcium influx

Question 43

What is Raynaud's Syndrome?

Answer 43

When exposed to cold temperature, patients' digits become pale and cold because of vasoconstriction of blood vessels