Muscle Structure

Question 1

Describe skeletal muscle tissue.

Answer 1

• considered an organ
• muscle fibres are striated (possessing stripes) when observed under a microscope
• there are over 700 skeletal muscles and together they form the muscular system

Question 2

What are the 3 types of muscles in the body?

Answer 2

• skeletal
• cardiac
• smooth

Question 3

What are the 5 functions of skeletal muscle tissue?

Answer 3

• body movement
• maintenance of posture
• temperature regulation
• storage and movement of materials
• support

Question 4

What 7 things are taken into account when naming muscles?

Answer 4

• shape
• location
• attachment
• size
• orientation
• position
• function

Question 5

What are fascicles?

Answer 5

a bundle of muscle fibres separated from other bundles of fibres by a dense irregular connective tissue covering

Question 6

What do muscle fibers contain?

Answer 6

myofibrils

Question 7

What are myofibrils composed of?

Answer 7

myofilaments

Question 8

Name the organizational levels of skeletal muscle.

Answer 8

• muscle
• fascicle
• muscle fiber (muscle cell)
• myofibril
• myofilaments

Question 9

What are muscle fibres (muscle cells)?

Answer 9

• elongated, multinucleated cylindrical finer (cell)
• contains myofibrils, separated from other fibres by delicate layer of areolar connective tissue
• has striations

Question 10

What is a myofibril?

Answer 10

• long, cylindrical contractile element within muscle fibre
• as long as the muscle fibre itself
• composed of myofilaments
• has striations

Question 11

What are myofilaments?

Answer 11

short contractile proteins of 2 types: thick (composed of myosin) and thin (composed of actin, tropomyosin, and troponin)

Question 12

What are the 3 concentric layers of connective tissue composed of?

Answer 12

• collagen

- elastic fibres

Question 13

What function do the 3 concentric layers of connective tissue serve?

Answer 13

• protection
• sites for blood vessel and nerve distribution
• attachment of the muscle to the skeleton

Question 14

What are the 3 connective tissue layers?

Answer 14

• endomysium
• perimysium
• epimysium

Question 15

Describe the endomysium.

Answer 15

innermost layer that surrounds and electrically insulates each muscle fibre

Question 16

Describe the perimysium.

Answer 16

surrounds the fascicles

Question 17

Describe the epimysium.

Answer 17

• surround the entire muscle
• deep fascia surrounds each muscle and separates muscles from each other
• superficial fascial separates muscle from skin

Question 18

Connective tissue merges to form a _____. Define this.

Answer 18

• tendon

- attachment to the muscle to bone, skin, or another muscle

Question 19

What is a aponeurosis?

Answer 19

sometimes, the tendon forms a thin, flattened sheet

Question 20

Most muscles extend over a ______ and have attachments to both articulating bones.

Answer 20

joint

Question 21

What happens upon contraction of the muscle in a muscle that extends over a joint?

Answer 21

one of the articulating bones moves and the other one does not

Question 22

The point of attachment to the bone that does not move is called the _____.

Answer 22

origin

Question 23

The point of attachment to the bone that does move is called the _____.

Answer 23

insertion

Question 24

Describe the contraction of skeletal muscle fibres.

Answer 24

• muscle fibres shorten by myofilaments filament interaction within each functional unit of a muscle
• generates tension

Question 25

The mechanism for contraction is explained by _______________.

Answer 25

the sliding filament theory

Question 26

The neuromuscular junction = _____+______

Answer 26

neuron+muscle

Question 27

How does muscle contraction begin?

Answer 27

a neuron impulse stimulates an impulse in a muscle fibre

Question 28

Skeletal muscles are comprised of a mixture of 3 different types of muscle fibres. What are they?

Answer 28

• slow oxidative (SO) fibres (type I)
• fast oxidative (FO) fibres (type IIa)
• fast glycolytic (FG) fibres (type IIx or IIb)

Question 29

Describe the ATP use of each type of skeletal muscle fibre.

Answer 29

type I: slow
type IIa: fast
type IIx: fast

Question 30

Describe the capacity to make ATP for each type of skeletal muscle fibre.

Answer 30

type I: high, aerobic
type IIa: moderate, aerobic
type IIx: limited, anaerobic

Question 31

Describe the concentration of capillaries in each type of skeletal muscle fibre.

Answer 31

type I: extensive
type IIa: moderately extensive
type IIx: sparse

Question 32

Describe the colour of each type of skeletal muscle fibre.

Answer 32

type I: dark red
type IIa: lighter red
type IIx: white (pale)

Question 33

Describe the contraction velocity of each type of skeletal muscle fibre.

Answer 33

type I: slow
type IIa: fast
type IIx: fast

Question 34

Describe the resistance to fatigue of each type of skeletal muscle fibre.

Answer 34

type I: highest
type IIa: high
type IIx: low

Question 35

Describe the distribution of each type of skeletal muscle fibre.

Answer 35

type I: found in greatest abundance in muscles of the trunk, especially postural muscles
type IIa: found in greatest abundance in muscles of the lower limbs
type IIx: found in greatest abundance in muscles of the upper limbs

Question 36

Describe the diameter of each type of skeletal muscle fibre.

Answer 36

type I: smallest
type IIa: intermediate
type IIx: largest

Question 37

Describe the number of mitochondria in each type of skeletal muscle fibre.

Answer 37

type I: many
type IIa: many
type IIx: few

Question 38

Describe the amount of myoglobin in each type of skeletal muscle fibre.

Answer 38

type I: large
type IIa: medium
type IIx: small

Question 39

Describe the primary function of each type of skeletal muscle fibre.

Answer 39

type I: endurance (ex. marathon running), maintaining posture
type IIa: medium duration, moderate movement (ex. walking, biking)
type IIx: short duration, intense movement (ex. sprinting, lifting weights)