Muscle 7

Question 1

Long action potential duration prevents….

Answer 1

summation of contraction

Question 2

How is e-c coupling achieved in cardiac muscles?

Answer 2

ca2+ induced ca2+ release

Question 3

An increase in calcium conc. triggers contraction by..

Answer 3

removing the inhibition of cross bridge cycling

Question 4

In cardiac muscle the SERCA pump is regulated by

Answer 4

phospholamban

Question 5

phosphorylated phospholamban

Answer 5

Ca2+-pump inhibition is removed, enhancing relaxation rates and contractility

Question 6

dephosphorylated phospholamban

Answer 6

inhibits SERCA

Question 7

how to enhance contractile force in cardiac muscle

Answer 7

• an increase in intracellular Ca2+

- length tension relationship (greater force when stretched)

Question 8

The heart is innervated by..

Answer 8

the autonomic nervous system

Question 9

sympathetic and the heart

Answer 9

increases heart rate/conduction and contractility (autorythmic and contractile)

Question 10

parasympathetic and the heart

Answer 10

decreases heart rate/conduction (autorythmic)

Question 11

phosphorylation of Ca2+ channels

Answer 11

causes calcium channels to remain open longer during APs

Question 12

phosphorylation of ryanodine receptors

Answer 12

increases release of Ca2+ from the sarcoplasmic reticulum

Question 13

phosphorylation of SERCA

Answer 13

increase the speed of Ca2+ re-uptake which increases Ca2+ storage

Question 14

a stretched sarcomere

Answer 14

• decreased diameter reduces distance that Ca2+ needs to diffuse, increasing probability of cross-bridge cycling
• increases Ca2+ induced Ca2+ release

Question 15

heart rate is under…

Answer 15

tonic control

Question 16

stimulation by parasympathetic nerves….

Answer 16

decreases heart rate (below 90 bpm)

Question 17

stimulation by sympathetic nerves…

Answer 17

increases heart rate (above 90 bpm)

Question 18

resting heart rate

Answer 18

70-72 bpm

Question 19

Without autonomic stimulation, autorythmic cells have a firing rate of…

Answer 19

90 APs per minute

Question 20

parasympathetic neurons containing ACh mainly innervates…

Answer 20

the SA and AV node

Question 21

ACh acts on…

Answer 21

muscarinic cholinergic receptors, opening K+ channels and closing T-type Ca2+ and HCN channels

Question 22

sympathetic neurons releases NE, which activates

Answer 22

Beta1 adrenergic receptors

Question 23

Beta1 adrenergic receptors increase Na+ conductance through HCN channels and T-type Ca2+ causing….

Answer 23

cells to reach threshold more rapidly and a decreased level of repolarization

Question 24

Smooth muscle is __________ than skeletal

Answer 24

more variable

Question 25

smooth muscle is ……. in length

Answer 25

50 to 400 um

Question 26

smooth muscle is …… shaped and __nucleated

Answer 26

spindle, uni

Question 27

smooth muscle does not have…

Answer 27

troponin and t-tubules

Question 28

thin filaments in smooth muscles are anchored to..

Answer 28

cell membrane or to cytoplasmic structures known as dense bodies (similar to z-lines)

Question 29

in smooth muscle, what forms the cytoskeleton?

Answer 29

intermediate filaments