skeletal muscle

Question 1

what are muscles

Answer 1

effector organs that respond to nervous stimulation by contracting and so bring about movement

Question 2

what is cardiac muscle

Answer 2

found exclusively in the heart

Question 3

where is smooth muscle found

Answer 3

in wallsof the blood vessels and the gut

Question 4

what is skeletal muscle

Answer 4

makes up the bulk of the body muscle in verterbea and it is attached to bones and control conscious movement

Question 5

what are myofibril

Answer 5

tiny muscles fibres that join together to form an individual muscle

Question 6

why is it joined together

Answer 6

singly its wak and if they were joined end to end cell to cell it would not be able to contract very effectively

Question 7

what has separate cells done

Answer 7

they have fused together into muscle fibres , these fibres share a nuclei and sarcoplasm

Question 8

what within the sarcoplasm

Answer 8

a large concentration of mitochondria and endoplasmic reticulum

Question 9

what is myofibril made from

Answer 9

two types of protein filament, actin and myosin

Question 10

what is actin

Answer 10

the thinner one and consists of two stands twisted around each other

Question 11

what is myosin

Answer 11

thicker and consists of rod shaped like tails with bulbous heads

Question 12

why do myofibrils appear striped

Answer 12

due to their alternating light colored and dark colored bands

Question 13

what are the light bands

Answer 13

they are called the I bands and consistes of of only actin filaments

Question 14

what are the a bands

Answer 14

the overlap of the myosin and actin makes the fibres seem darker

Question 15

what is the h zone

Answer 15

only consists of myosin filament fibres and the m line where myosing join together

Question 16

what is the z line

Answer 16

found in the middle of the I band where the actin join together

Question 17

what is a sarcomere

Answer 17

the distance between two adjacent z lines

Question 18

what are slow twitch fibres

Answer 18

contract more slowly than fast twitch fibrese and provide less powerful contractions but over a long period , adapted for endurance work

Question 19

where are they found

Answer 19

in calf muscleswhich contract continoulsy to keep us upright

Question 20

how are they suited to this role

Answer 20

by being adapted for aerobic respiration in order to avoid the build up of lactic acid which would prevent long time contraction

Question 21

how is it adapted

Answer 21

large store of myoglobin

Question 22

what is myoglobin

Answer 22

a bright red molecule that stores oxygen and accounts for the red color

Question 23

what else is there

Answer 23

a rich supply of blood vesselds to deliver oxygen and glucose for aerobic respiration
numerous mitochondria to produce atp

Question 24

what are fast twitch fibres

Answer 24

these contract more rapidly and produce powerful contractions for a short period of time

Question 25

they are adapted to what

Answer 25

intense exercise such as weight lifting , where there is short burst of intense activity eg biceps

Question 26

how are they adapted to their role

Answer 26

they have thicker and more numerous myosin filaments
higher concentration of glycogen
a high concentration of enzymes involved in aerobic respiration which produce atp rapidly
a store of phosphocreatine

Question 27

what is phosphocreatine

Answer 27

a molecule that can rapidly generate adp from atp in aerobic conditions to provide energy for muscle contractions

Question 28

in slow twitch fibres why are the mitochondria found close to the edge of muscle fibres

Answer 28

so that there is a short diffusion pathway for the oxygen from the blood capillary to the mitochondria

Question 29

what do fast twitch fibres have less of

Answer 29

fewer mitochondria and blood vessels and don’t have much myoglobin so cannot store oxygen