Muscles

Question 1

what are muscles?

Answer 1

-specialized effectors which bring about movement through contraction

Question 2

what is the main type of muscle in the body and it is voluntary or involuntary?

Answer 2

-skeletal
-voluntary

Question 3

how does skeletal muscle vary throughout the body?

Answer 3

-it varies in size

Question 4

what is skeletal muscle made up of?

Answer 4

-muscle fibers bunched together

Question 5

what is each fiber surrouned with?

Answer 5

-a cell surface membrane which is called the sarcolemma

Question 6

are muscle fibers multinucleate?

Answer 6

-yes

Question 7

what type of organelle is the muscle fibers particularly rich in?

Answer 7

-mitochondria

Question 8

what does the sarcolemma do at intervals along the muscle fiber?

Answer 8

-fold inward to form T tubules

Question 9

what is the name of the substance that is found inside the muscle fibers?

Answer 9

-myofibrils which is a highly specialised contractile unit

Question 10

what are the two types of proteins that are found in the myofibrils?

Answer 10

-actin
-myosin

Question 11

what type of thickness of filaments do both actin and myosin produce?

Answer 11

-myosin forms thick filaments 15nm
-actin forms thin filaments 7nm

Question 12

where do the myosin filaments lie in the myofibrils? what is the m line?

Answer 12

-towards their central region
-linked by a thin disc called the m line that runs perpendicular to the filaments

Question 13

where do the actin filaments lie in the myofibrils? what is the z line?

Answer 13

-towards the outer edges of the myosin filaments
-they are held together by a thin disc known as the z line

Question 14

what is a section called between two z lines? what is contained in these sections?

Answer 14

-a sarcomere
-in this is the first z line then the myosin filaments and the m line and then this ends at the second z line

Question 15

what type of pattern are the myosin and actin arranged in the myofibril? what is the term used to describe this?

Answer 15

-in an alternating pattern which forms the striated banded pattern

Question 16

what is the name given to the part of the myofibril which contains myosin? what else is included in this section?

Answer 16

-the A band
-it also includes thinner actin which penetrates between the myosin filaments

Question 17

what is the name given to the part of the myofibril that contains actin only?

Answer 17

-the I band

Question 18

what is the H zone?

Answer 18

-the part of the A band that contains myosin only

Question 19

how many actin filaments surround every myosin filament?

Answer 19

-each is surrounded by 6 actin filaments that form a regular hexagonal pattern