Muscle

Question 1

Cardiac muscle

Answer 1

Striated, branched, regular lattice pattern of actin and myosin when cut in cross section. Has larger mitochondria than skeletal muscle, thicker t tubules, slightly less organized. In between t tubule and sarcoplasmic reticulum, lies terminal cysternae. In cardiac muscle, the terminal cysternae and t tubule form a dyad.

Question 2

Cardiac action potential

Answer 2

Longer than other muscle types - 200 to 400ms This is to prevent against tetany/ reentrant arrhythmias Longer absolute refractory period

Question 3

Excitation-contraction coupling

Answer 3

In cardiac muscle, calcium is needed for a contraction to occur. Action potentials triggers the release of calcium which causes contractions.

Question 4

Excitation contraction coupling in cardiac muscle

Answer 4

Action potential sweeps past and goes into t tubule Voltage gated L type Ca channels open and let in small amount of Ca Ryanodine receptors (calcium release channels) on SR membrane get triggered by this calcium and open, causing even more release of calcium. This is called calcium induced calcium release. SR calcium ATPase and Na/Ca exchanger removes calcium from cytoplasm

Question 5

His calcium causes muscle contraction

Answer 5

Binds to troponin which moves tropomyosin out of the way and allows for cross bridge formation of myosin heads to actin

Question 6

Length tension relationship

Answer 6

Check

Question 7

Length tension relationship

Answer 7

Increasing sarcomere lenght causes: Increased cross bridge overlap Increased Ca sensitivity of troponin C So, stronger contractions when muscles are more stretched (I.e. when there is increased blood flow)

Question 8

Force frequency relationship

Answer 8

Increased rate of contraction (frequency) increases force of contraction, Since SR calcium stores also increase. EXCEPT in failing heart, where increase of frequency causes decreases in force of contraction

Question 9

Smooth muscle

Answer 9

Makes up part of the walls of hollow organs Not striated Regulated by ANS, hormones and pacemaker cells in GI tract

Question 10

Smooth muscle structure

Answer 10

Has dense bodies, which anchors actin filaments Has gap junctions p, to allow movement of current and small molecules

Question 11

Regulation of SM in vessels

Answer 11

ANS Autocoids, local hormones, blood born substances

Question 12

Regulation of SM in airways

Answer 12

ANS, autocoid, local hormones

Question 13

Regulation of SM in intestines

Answer 13

Interstitial cells of cajal ANS Autocoid, local hormone

Question 14

Distinguish between Type 1, type 2a and type 2b skeletal muscle fibres

Answer 14

Question 15

Which Part of the sarcolemma passes into the interior of the cell?

Answer 15

Terminal Cisternae

Question 16

2 main mechanisms of calcium release in striated muscle

Question 17

Smooth muscle contraction and dilatation secondary messengers

Answer 17

Contraction: NO mediated and IP3

NO mediated vasodilation: GMP (from endothelial cell)

cAMP mediated vasodilation (from hormone)

Question 18

Contraction of smooth muscle

Answer 18

Myosin light chain kinase binds to calmodulin, and in the presence of calcium this becomes active complex.

Complex phosphorylates myosin which can form cross bridges with actin (contraction)

Question 19

Smooth muscle relaxation

Answer 19

Relaxation only occurs if myosin phosphatase dephosphorylates myosin with cGMP pathway.

Question 20

Mechanism that allows small ATP expenditure in smooth muscle

Answer 20

Latch bridge formation; when even dephosphorilated myosin stays bound to the actin