Muscles

Question 1

What are muscles?

Answer 1

Bundles of fibres wrapped in connective tissue sheaths

Question 2

What are skeletal muscles?

Answer 2

Multi nucleated striated fibres that contain sarcomeres that are made in utero by myoblasts

Question 3

How are skeletal muscles classified?

Answer 3

According to their speed and wether or not they are oxidative or glycosidic

Question 4

What are oxidative fibres?

Answer 4

Red fibres that have a small diameter and contain many mitochondria, contain myoglobin and are more vascular

Question 5

What are the benefits of being vascular?

Answer 5

Enhanced delivery of oxygen and nutrients

Question 6

What is the function of myoglobin?

Answer 6

Enhances the delivery of oxygen

Question 7

Where is mitochondria used?

Answer 7

Oxidative phosphorylation

Question 8

What is the function of slow oxidative fibres?

Answer 8

Resistance of fatigue

Question 9

What is the function of fast oxidative fibres?

Answer 9

Intermediate resistance of fatigue

Question 10

What are glycolytic fibres?

Answer 10

White fibres with a large diameter and contain few mitochondria. They have a decreased blood supply but a high concentration of glycolytic enzymes and glycogen

Question 11

What happens to fast glycolytic fibres

Answer 11

They fatigue quickly

Question 12

What is fatigue?

Answer 12

Prevents a lot of ATP from being used in breaking/reforming cross bridges in order to sustain contractions

Question 13

What causes fatigue?

Answer 13

Repeated muscle stimulation

Question 14

What is tetanus?

Answer 14

State of extended contraction due to the summation of APs which prevents Ca from returning to the sarcoplasmic reticulum so tropomyosin remains in it’s unblocked state, so cross bridges are not broken

Question 15

Why can Ca not re-enter the sarcoplasmic reticulum due to tetanus?

Answer 15

Tetanic tension > twitch tension

Question 16

What is the process of recruitment?

Answer 16

As load increases, more motor fibres are needed to compensate so more muscles can be involved in the movement

Question 17

What is an isotonic twitch?

Answer 17

Contraction with shortening length

Question 18

What is another name for isotonic twitches?

Answer 18

Concentric

Question 19

What is an isometric twitch?

Answer 19

Contraction with constant length

Question 20

What is an eccentric twitch?

Answer 20

Contraction with increasing length

Question 21

What is the process of excitation-coupling contraction?

Answer 21

Muscle fires APs, Ca ions are released from the SR, Ca ions bind to troponin on actin filaments, tropomyosin is removed, binding sites are exposed, myosin binds to actin, cross-bridges form, contraction occurs, Ca ions return to the SR, tropomyosin returns to its original shape, cross-bridges break, contraction ends

Question 22

What does contraction cause?

Answer 22

Various changes in the sarcomere

Question 23

What happens when filaments slide over each other?

Answer 23

A band and H zone decrease

Question 24

What is the A band?

Answer 24

Myosin

Question 25

What is the I band?

Answer 25

Actin

Question 26

What is the H zone?

Answer 26

Space between opposite actin filaments

Question 27

What is a Z line?

Answer 27

Dark line that separates each sarcomere

Question 28

What is smooth muscle?

Answer 28

Involuntary, mono nucleated muscles that is supplied by the ANS and contains no striation but contains myosin and actin

Question 29

How are myosin and actin arranged in smooth muscle?

Answer 29

Diagonally, anchored to membranes and cell structures by dense bodies

Question 30

Where does smooth muscle exist?

Answer 30

Hollow organs

Question 31

What are examples of hollow organs?

Answer 31

GI tract, bladder and airways

Question 32

How do smooth muscles operate?

Answer 32

By forming cross-bridges between myosin and actin but by a different mechanism than skeletal muscle

Question 33

What type of muscle can sustain contractions for longer?

Answer 33

Smooth muscle

Question 34

Why is smooth muscle useful in BVs?

Answer 34

Smooth muscle can sustain contractions for longer so they can stay open for longer periods of time

Question 35

How do contractions occur in smooth muscle?

Answer 35

APs released from muscle, Ca ions released from SR, Ca ions bind to calmodulin, calmodulin binds to light chain kinase, myosin to phosphorylated by ATP, cross-bridges form with actin, contraction occurs

Question 36

How does relaxation occur in smooth muscle?

Answer 36

Myosin light chain phosphatase dephosphorlyates the cross bridges