MUSCLE I

Question 1

what is the purpose of structural proteins in muscle

Answer 1

to transmit movement or force outside of the cell

Question 2

name the 4 structural proteins discussed

Answer 2

titin, nebulin, a-actin and dystrophin

Question 3

describe the structure of titin

Answer 3

large, elastic protein

2 titin molecules running parallel to myosin

Question 4

what is the function of titin?

Answer 4

anchors thick filament to Z-disc (main)

also acts as molecular ruler during myogenesis, helps with passive length tension and prevents overstretching

Question 5

what is the structure of nebulin?

Answer 5

long inelastic protein with 2 strands for each actin, running the length of each actin

Question 6

what is the function of nebulin?

Answer 6

anchors thin filament to Z disc

Question 7

what is another (secondary) function of nebulin?

Answer 7

can be used to determine the length of the actin filament

Question 8

what is the purpose of alpha-actinin?

Answer 8

attachment point for actin filaments to z-disc

Question 9

what are dystrophins?

Answer 9

focal contact points between sarcomere and membrane/extracellular matrix

Question 10

what type of myosin is in muscle?

Answer 10

myosin II

Question 11

what is the structure of myosin II?

Answer 11

hexameric protein with 2 heavy chains and 2 light chains

Question 12

when is myosin “bent”?

Answer 12

when bound to ADP and Pi

Question 13

when is myosin “straight”?

Answer 13

when bound to ADP only

Question 14

function of troponin T

Answer 14

binds to tropomyosin, positions actin and exposes myosin binding sites

Question 15

function of troponin I

Answer 15

binds to actin, prevents myosin from binding actin

Question 16

function of troponin C

Answer 16

calcium binds causing a conformational change that disrupts actin-TnI interaction

Question 17

function of caldesmon

Answer 17

acts similar to TnT in smooth muscles

Question 18

function of calponin

Answer 18

acts similar to TnI in smooth muscle

Question 19

A-band

Answer 19

entire length of thick filament

Question 20

H-zone

Answer 20

thick only

Question 21

I-band

Answer 21

thin only

Question 22

what happens to the A-band, H-zone and I-band during muslce contraction?

Answer 22

H and I shorten, A is stable

Question 23

what is the consequence of increased muscle fiber length?

Answer 23

decreased cross linkages, decreased force of contraction

Question 24

what is the consequence of decreased muscle fiber length?

Answer 24

thick filament clashes with z-disc, less lesion and less force of contraction

Question 25

describe the steps in muscle contraction (5)

Answer 25

1-ATP binds to actomyosin and disrupts bond between them 2- myosin hydrolyzes ATP to ADP and Pi 3- Pi is released from myosin and power stroke occurs 4- ADP released from myosin, causing myosin to rotate further 5- ATP free to bind and start cycle over

Question 26

what is the power stroke in muscle contraction?

Answer 26

dissociation of Pi is the power stroke

Question 27

what controls the rate of muscle contraction?

Answer 27

dissociation of ADP controls the rate of contraction

Question 28

describe slow twitch type I muscle (6)

Answer 28

small, fatigue resistant, red myoglobin, lots of mitochondria, Ox metabolism and low glycogen

Question 29

describe fast twitch type IIA (6)

Answer 29

intermediate, fatigue resistant, red myoglobin, lots of mitochondria, Ox metabolism and high glycogen

Question 30

describe fast twitch IIB/IIX (6)

Answer 30

large, fatiguable, white myoglobin, few mitochondria, glycolytic metabolism and high glycogen

Question 31

what does endurance training change regarding muscle fibers? (4)

Answer 31

increases type IIA, increases mitochondria, increases myoglobin, decreases type IIX

Question 32

what neurotransmitter is involved with skeletal muscle contraction?

Answer 32

acetylcholine

Question 33

describe the interaction between DHP receptors and RyR-1 receptors in skeletal mm

Answer 33

there is a physical interaction between DHP receptors and RyR-1 receptors in skeletal mm that leads to Ca release from sarcoplasmic reticulum

Question 34

what is the role of calcium in skeletal muscle contraction?

Answer 34

binds troponin C to increase Pi dissociation and allow power stroke to occur

Question 35

what neurotransmitter is involved with cardiac muscle contraction? what receptors?

Answer 35

norepinephrine, beta-adrengeric receptors

Question 36

discuss RyR-2 receptors

Answer 36

found in cardiac muscle, involved in calcium induced calcium release

Question 37

what is chronotrophy?

Answer 37

heart rate

Question 38

what is inotrophy?

Answer 38

heart contractility

Question 39

what is lusitrophy?

Answer 39

heart relaxation (rate)

Question 40

which receptors are responsible for calcium-induced calcium release in smooth muscle cells?

Answer 40

IP3 receptors on sarcoplasmic reticulum

Question 41

what does calcium bind in smooth muscle cells?

Answer 41

calmodulin, Rho-A kinase, caldesmon and calponin

Question 42

what is the function of calcium-calmodulin?

Answer 42

activation of myosin light chain kinase (MLCK) to phosphorylate myosin and allow it to interact with actin

Question 43

what is the function of Rho-A Kinase?

Answer 43

Rho-A Kinase inhibits myosin light chain phosphatase (MLCP) so that the light chains can remain phosphorylated for a prolonged period

Question 44

what causes myosin to return to the the relaxes state in smooth muscle?

Answer 44

MLCP (dephosphorylates)

Question 45

what can activate MLCP?

Answer 45

cGMP

Question 46

what are the functions of caldesmon and calponin in smooth muscle?

Answer 46

expose tropomyosin and allow MLC to bind

Question 47

what causes muscular dystrophy?

Answer 47

defective focal adhesion proteins leading to weak contraction, disruption of membranes

Question 48

what is malignant hyperthermia?

Answer 48

autosomal, myopathy secondary to defect in RyR-1 causing uncontrolled mm contraction and hyperthermia

Question 49

what causes familial hypertrophic cardiomyopathy?

Answer 49

single amino acid mutation in the myosin heavy chain that changes ATP hydrolysis and decreases contractile force leading to wall hypertrophy

Question 50

what receptors are reduced in the setting of heart failure?

Answer 50

RyR-2

Question 51

how doe viagra work?

Answer 51

inhibits breakdown of cGMP (through inhibition of PDE5) that enhances the relaxation of smooth mm allowing blood to collection for erection