Lecture 6 - Intro to the Muscular System

Question 1

what is muscle tissue?

Answer 1

specialized cells with contractile and conducting properties

Question 2

all muscle cells have these four basic properties:

Answer 2

1) excitability: respond to stimulation
2) contractility: shorten in response to action potential
3) extensibility: ability to contract over different lengths
4) elasticity: ability to regain original length after contraction

Question 3

• somatic structures (under voluntar control though not always conscious)
• innervated by spinal nerves and cranial nerves
• contractily organs that attach directly or indirectly onto bones
• contractions produce motion of the body
  these are all characteristics of what type of muscle tissue?

Answer 3

skeletal muscle

Question 4

list the six major functions of skeletal muscle

Answer 4

1) produce movement at various joints
2) maintain posture and body position
3) support soft tissues
4) regulate entering and exit of materials
5) maintain body temperature
6) communication

Question 5

a skeletal muscle is surrounded by a _____ which becomes coninuous with the periosteum and separates one muscle from another

Answer 5

epimysium

Question 6

the muscle belly is composed of bundles of:

Answer 6

muscle fascicles

Question 7

a muscle fascicle is surrounded by a _____ which protects from damage and contains capillaries and nerve fibres

Answer 7

perimysium

Question 8

each muscle fascicle is composed of bundles of:

Answer 8

muscle fibres (cells)

Question 9

a muscle fibre is surrounded by an _____

Answer 9

endomysium

Question 10

each muscle fibre is composed of bundles of:

Answer 10

myofibrils

Question 11

tiny fibres in the muscle cells which run the full length of the cell

Answer 11

myofibrils

Question 12

each myofibril is composed of bundles of:

Answer 12

myofilaments

Question 13

proteins responsible for muscle contraction

Answer 13

myofilaments

Question 14

why are muscle cells multinucleate?

Answer 14

during fetal development, myoblasts fuse together to form one muscle cell

Question 15

the stem cells of the muscles

Answer 15

myosatellite cells

Question 16

parts of the muscle cells that are essential for energy storage and production

Answer 16

mitochondria, glycogen, and myoglobin

Question 17

wraps around the myofibrils and stores Ca++ to promote muscle contraction

Answer 17

sarcoplasmic reticulum

Question 18

conducts electrical impulses into the muscle cell for muscle fibre contraction

Answer 18

transverse (T) tubules

Question 19

the basic contractile unit of a muscle

Answer 19

sarcomere

Question 20

protein discs which form the boundaries of a sarcomere

Answer 20

Z-lines

Question 21

the centre of a sarcomere which stabilizes the position of myosin (thick filaments)

Answer 21

M-line

Question 22

elastic protein that connects myosin to the Z-line

Answer 22

titin

Question 23

part of the sarcomere which contains thick filaments only

Answer 23

H-band

Question 24

part of the sarcomere which contains thin filaments only

Answer 24

I-band

Question 25

part of the sarcomere that contains both thin and thick filaments, and the zone of overlap

Answer 25

A-band

Question 26

what is the role of ATP in muscle contraction?

Answer 26

required for both the power stroke and release of the myosin head

Question 27

during contraction, which myofilament does the moving?

Answer 27

actin filaments slide toward one another

Question 28

muscle fibres are innervated by _____ which penetrates the epimysium, then perimysium, and ends at a _____ through the ednomysium

Answer 28

somatic motor neurons, muscle fibre

Question 29

the axon terminal is located at the _____ where it releases the chemical _____ for deoplarization

Answer 29

neuromuscular junction (NMJ), acetylcholine (Ach)

Question 30

the action potential changes the membrane potential of the _____ stimulating it to release _____

Answer 30

sarcoplasmic reticulum, Ca++

Question 31

true or false: muscular contraction is an all or none phenomenon

Answer 31

true

Question 32

switch it up: go review the steps of muscle contraction

Answer 32

then treat yourself to a snack

Question 33

all the muscle cells controlled by a single motor neuron constitute a:

Answer 33

motor unit

Question 34

the amount of muscle tension depends on:

Answer 34

the number of motor units that are stimulated, the frequency, the size of the fibres, and the ability to form cross bridges

Question 35

smaller motor neurons control the contraction of _____, therefore creating _____

Answer 35

a smaller number of fibres, smaller and more precise contractions

Question 36

why are motor units activated on a rotating basis?

Answer 36

to avoid fatigue

Question 37

• red fibres due to numerous mitochondria and myoglobin
• usually narrower diameter of each fibre
• slow to contract
• resistant to fatigue
• less powerful contractions
• ATP produced by aerobic metabolism
• more extensive capillary network
• associated with large muscles (ex: glutes)
  these are all characteristics of what type of skeletal muscle fibres?

Answer 37

slow twitch

Question 38

• white fibres
• larger diameter, densely packed myofibrils, large glycogen reserve, few mitochondria
• rapid contraction
• powerful contractions, but fatigure rapidly
• ATP generated by anaerobic glycolysis
• associated with eye and hand muscles
  these are all characteristics of what type of skeletal muscle fibres?

Answer 38

fast twitch

Question 39

some motor units are always active, but tension is not enough to cause movement

Answer 39

muscle tone

Question 40

the tension produced is greater than or equal to the resistance/load, resulting in a movement

Answer 40

isotonic contraction

Question 41

shortening of an active muscle

Answer 41

concentric

Question 42

lengthening of an active muscle

Answer 42

eccentric

Question 43

tension never exceeds the resistance/load, the active muscle does not change in length with contraction

Answer 43

isometric contraction (think of a plank)

Question 44

muscle attachment to moveable bone

Answer 44

insertion

Question 45

muscle attachment to stationary bone

Answer 45

origin

Question 46

what are the four primary muscle actions?

Answer 46

• agonist
• synergist
• antagonist
• fixators

Question 47

a contraction that produces a movement

Answer 47

agonist (prime mover)

Question 48

assists prime mover in performing and action

Answer 48

synergist

Question 49

opposes the movement

Answer 49

antagonist

Question 50

agonist and antagonist muscles contracting at the same time to stabilize a joint

Answer 50

fixators

Question 51

• fascicles are parallel to long axis of muscle
• most common
• muscle either flat band or spindle shaped
• during contractiong, muscle gets shorter and belly gets wider
• exert great force
• ex: biceps brachii, rectus abdominus
  these are all characteristics of what type of muscle fascicle organization?

Answer 51

parallel muscles

Question 52

• fan shaped
• fascicles originate over wide area, but converge at common attachment site
• direction of pull can be changed by varying which fascicles contract
• do not exert as much force
• ex: trapezius
  these are all characteristics of what type of muscle fascicle organization?

Answer 52

convergent muscles

Question 53

• tendons run through body of muscle (like a feather)
• fascicles form oblique angle relative to tendon
• contain lots of muscle fibres
• most powerful contraction
• can be uni, bi, or multi
• ex: rectus femoris, deltoid
  these are all characteristics of what type of muscle fascicle organization?

Answer 53

pennate muscles

Question 54

• fibres concentrically around opening or recess (form sphincters)
• contraction of muscle reduces diameter of opening
• ex: orbicularis oculi
  these are all characteristics of what type of muscle fascicle organization?

Answer 54

circular muscles