L11 revised

Question 1

what is the largest single tissue in the human body?

Answer 1

muscle

Question 2

what are the 3 types of muscles present in the human body?

Answer 2

skeletal: striated , under voluntary nervous control
cardiac: striated , involuntary

and smooth : non striated, involuntary

Question 3

describe the structure of striated muscles

Answer 3

a single muscle is composed of thousands of muscle fibers that extend for variable distance along its longitudinal axis

each muscle fiber is a large and complex multinucleated cell

Question 4

what are muscle fibers surrounded by ?

Answer 4

an electrically excitable plasma membrane called the sarcolemma

Question 5

what do individual muscle fibers contain ?

Answer 5

many myofibrils arranged in parallel embedded in intracellular fluid called sarcoplasm

Question 6

what are the parallel structures inside individual muscle fibers called ?

Answer 6

myofibrils

Question 7

what is the intracellular fluid inside individual muscle fibers called ?

Answer 7

sarcoplasm

Question 8

what is the functional unit of muscle called?

Answer 8

sarcomere

Question 9

where do T tubules invaginate from ?

Answer 9

sarcolemma

Question 10

how does myofibril appear under the microscope ?

Answer 10

shows alternating dark(A bands ) and light(I bands ) bands

Question 11

what region of the A band appears slightly lighter than the rest of the band ?

Answer 11

the central region of the A band , Which is also called the H band

Question 12

what is the I band bisected by ?

Answer 12

very dense and narrow z line

Question 13

where can thin filaments be found ?

Answer 13

in the I band . they also extend to the A band but not into the H zone

Question 14

what proteins do thin filaments contain ?

Answer 14

actin , tropomyosin , and troponin

Question 15

how are thin filaments arranged ?

Answer 15

they are arranged around the thick (myosin ) filaments as a hexagonal array

Question 16

where can thick filaments be seen ?

Answer 16

confined to the A band

Question 17

what protein do thick filaments contain ?

Answer 17

myosin

Question 18

how are thick filaments arranged ?

Answer 18

cross section as a hexagonal array

Question 19

what is monomeric actin called ?>

Answer 19

G actin \

it is globular

it makes up to 25% of muscle protein by weight

Question 20

when does F actin form?

Answer 20

when G-actin polymerizes in the presence of Mg2+ to form the insoluble helicat filament called f actin

Question 21

describe the structure of myosin

Answer 21

has a fibrous tail consisting of 2 intertwined helices

each helix has a globular head portion attached at one end

the hexamer consists of 2 heavy (H) chains and 4 light (L) chains

Question 22

what is tropomyosin ?

Answer 22

fibrous molecule that consists of 2 chains , alpha , and beta , that attaches to F actin in the grooves between its filaments

it is present in all muscles and all muscles like structures

Question 23

what is troponin ?

Answer 23

structure unique to skeletal muscles and consists of 3 poly peptides

Question 24

what are the three polypeptides of troponin , briefly describe each ?

Answer 24

Troponin T : bind to tropomyosin as well as the 2 other troponin components

Troponin I:inhibits the F actin- myosin interaction , also binds to other components of troponin

troponin C : is a calcium binding polypeptide .

4 molecules of calcium ion are bound per molecule of troponin C

Question 25

cardiac troponins help in diagnosing _____

Answer 25

myocardial infarction

Question 26

MUSCLE CONTRACTION AND RELAXATION ARE IN THE OTHER DECK AND PPT

Answer 26

..

Question 27

What is malignant hyperthermia ?

Answer 27

body temp rises on exposure to certain anesthetics and skeletal muscle relaxants The reaction consists primarily of rigidity of skeletal muscles, hypermetabolism, and high fever.

Question 28

what is the function of dystrophin ?

Answer 28

it is a cytoskeletal protein that connects F-actin to the DG complex(dystroglycan ) dystrophin complex acts as an anchor connecting each muscle cells cytoskeleton with the frame work of extracellular matrix proteins .Also play a role in cell signalling by interacting with chemical signals.

Question 29

what happens if dystrophin is absent ?

Answer 29

In absence of dystrophin, plasma membrane of muscle cells gets damaged during contractile process leading to muscle cell death.

Question 30

what term is applied to diseases that cause progressive weakness of skeletal muscles ?

Answer 30

muscular dystrophy Mutations in the genes for the various components of the dystrophin–glycoprotein complex are a prominent cause.

Question 31

Duchenne muscular dystrophy is ____?

Answer 31

is a serious form of dystrophy in which the dystrophin protein is absent from muscle

Question 32

Becker muscular dystrophy is ___?

Answer 32

Dystrophin is present but altered or reduced in amount.

Question 33

what is sarcopenia ?

Answer 33

Loss of skeletal muscle mass with age