Muscle I

Front 1

Functions of skeletal muscle

Back 1

skeletal movement
maintain body position
support soft tissue
guard openings
maintain body temperature
store nutrient reserves

Front 2

Thin filaments

Back 2

- directly attached to Z-line
- Made of 3 Proteins:
Actin, troponin, tropomyosin

Front 3

Thick filaments

Back 3

made of protein: myosin

Front 4

Titin

Back 4

connects myosin in thick filament to z-line
- keeps thick filaments centered within sarcomere
- depicted as a spring on a drawing since it is source of elasticity within muscle

Front 5

I band

Back 5

"isotropic band"
there thin filaments are (includes z-line)

Front 6

A band

Back 6

"an-iotropic band)
contains thick AND thin filaments
NO H-zone

Front 7

H-band

Back 7

no overlap of thick and thin filaments on sasrcomere

Front 8

Thick filament 3D structure (myosin)

Back 8

- head of myosin = ratchet
- long tail + two heads
- each myosin interacts with 6 actin (thin) filaments
- tail points center
- only ONE head can be bound to form cross-bridge
- each head has 2 binding sites: actin and ATP

Front 9

Thin filaments 3D structure (actin)

Back 9

- made of 3 proteins
- globular actin = pearl strand
- actin molecules covered by tropomyosin - boxs myosin binding site on actin
- troponin (T, C, I) attached to tropomyosin

Front 10

Troponin

Back 10

attached to tropomyosin on thin filament
- has 3 subunits:
~ Troponin T - bound to tropmyosin
~ Troponin C - bound to Ca2+
~ Troponin I

Front 11

Low cytosolic calcium

Back 11

... is a relaxed muscle
tropomyosin blocks cross-bridge bind site on actin (the "pearl beads")

Front 12

High cytosolic calcium

Back 12

... activated muscle = contraction!

is when calcium binds to troponin. this moved tropomyosin away from cross-bridge binding site;
- this complex then pulls tropomyosin away from cross-bridge binding site to myosin bind with actin

Contraction = calcium binds to troponin; this complex

Front 13

Sliding Filament Theory

Back 13

Thin filaments slides towards CENTER of sarcomere
length does NOT change

Front 14

Roles of ATP in skeletal muscle contraction

Back 14

1. breaks bond between myosin and action
2. resets myosin head to go through another cross-bridge cycle
3. provides energy for "power stroke" = movement of myosin (ratchet)

Front 15

Motor unit

Back 15

... is the motor nerve PLUS ALL fibers it innervates

one motor nerve can innervate many muscular fibers

Front 16

What is a neuromuscular junction?

Back 16

the point of synaptic contact between axon terminal of a motor neuron and the muscle fiber it controls

Front 17

SINGLE fiber Force production in skeletal muscle depends on...

Back 17

(Tension of a single muscle fiber depends on...)
1. Number of cross-bridges at given time
2. Length -- resting length at time of stimulation; how long is the fiber
3. Frequency - how rapidly you stimulate that muscle fiber; how rapidly you cause it to fire AP

Front 18

How can you increase WHOLE muscle force?

Back 18

active MORE motor UNITS

-- force is directly proportional to cross-sectional area: larger CSA = more force produced
- more motor units = increased CSA

Front 19

How does length affect force?

Back 19

Thick and thin filament overlap, hence it affects the number of cross-bridges you can produce

sarcomere length-tension curve

Front 20

unfused tetanus in skeletal muscle

Back 20

stimulation as muscle is relaxing because you can see the relaxation on the graph

type of how frequency affects force production

Front 21

Frequency effects on force production

Back 21

if you stimulate muscle BEFORE it gets a chance to relax, more ca2+ will be released from SR, more cross-bridges will develop, thus MORE force because you're adding more Ca within cellular space

Front 22

Fused tetanus

Back 22

stimulus is so closed together that force will go up and then it will level off because ALL cross bridges that can form are going to be active

Front 23

WHOLE muscle force production is affected by ...

Back 23

1. Contraction type
2. Velocity
3. Muscle fiber type
4. Muscle architecture

Front 24

4 Types of Muscle Contraction

Back 24

1. Isotonic contraction
2. Isometric contraction
3. Eccentric contraction
4. Concentric contraction

Front 25

Isotonic contraction

Back 25

- only done in lab
- can't do it in moving joint because as you move you move in a range of motion to the forces change and "isotonic" means "same force" which isn't literally possible
- force remains same
- muscle contracting

Front 26

Isometric contraction

Back 26

- muscle contracts but for NOT shorten
- length does NOT change
---- so if weight is too heavy for muscle to lift, then force will go up and stay up but muscle isn't producing enough force that it will be able to lift weight, so it doesn't change in length

Front 27

Eccentric Contraction

Back 27

active WHILE lengthening
- is when muscles tend to be least stable - why muscles can injure
- ie: downward motion of bicep curl

Front 28

Concentric Contraction

Back 28

- muscle active AND shorten
(muscle shortening and movement at joint)
- ie: upward motion of bicep curl

Front 29

How does Velocity Affect Force production?

Back 29

Heavier something is = slower contraction

Front 30

3 Types of skeletal muscle fibers

Back 30

1. Fast Glycolytic (FG)
2. Slow Oxidative (SO)
3. Fast Oxidative Glycolytic (FOG)

Front 31

Fast Glycolytic (FG)

Back 31

- responds quickly AND responds to repetitive stimulation WITHOUT fatigue
- high force
- low mitochondria
- depends on glycolysis for ATP
Examples: walking muscles

Front 32

Slow Oxidative (SO)

Back 32

- responds well to repetitive stimulation without becoming fatigued
- Example: postural muscles
- dark-meat fibers
- low level force
- MANY mitochondria
- high blood supply
- depends on oxidative phosphorylation thus fatigue SLOWLY -- example: latissimus, traps

Front 33

Fast Oxidative Glycolytic (FOG)

Back 33

- used for quick bursts of strong activation
- Example: sprints and jumps
- more force than SO but less than FG
- fairly fatigue-resistant but not as much as SO

Front 34

Slow Fibers

Back 34

- smaller diameter
- dark in color due to myoglobin
- fatigue resistant
- "white" fibers
- more force produced since force is proportional to CSA so this fiber has a larger CSA

Front 35

Fast Fibers

Back 35

- Larger diameter
- paler color
- easily fatigue
- "red" fibers

Front 36

Size Principle of Muscle Recruitment

Back 36

when you want to produce more force you recruit fibers in a particular order:
smaller first (SO) --> FO --> FOG

Front 37

Muscle Hypertrophy

Back 37

- muscle growth from heavy training
- increases DIAMETER of fibers
- increases MYOFIBRILS
- increases # mitochondia and glycogen
- CANT increase # muscle fibers

Front 38

Muscle Atrophy

Back 38

- lack of muscle activity
- reduce muscle size and tone
- decrease power to be produced

Front 39

Physical Conditioning

Back 39

Improves both power and endurance, but it can shift fiber type distribution

Front 40

Anaerobic activities

Back 40

- use more fast fibers that easily fatigue
- FOG fibers
Example: 50-meter dash, weight-lifting

Front 41

Aerobic activities

Back 41

- prolonged activity
- fast oxidative/glycolytic (FO/FG) fibers

Front 42

How can you change CSA?

Back 42

by changing fiber type, thus activating more motor unit

Front 43

Muscle Architecture

Back 43

1. Parallel
2. Fusiform
3. Convergent
4. Unipennate
5. Bipennate
6. Multipennate

Front 44

Parallel

Back 44

-long muscle made up on in-series, parallel fibers
- designed for muscles that undergo shortening contractions that produce work
- muscles that that usually contract over long distances
- Example: Sartorius

Front 45

Fusiform

Back 45

- 2 distinct origin/insertions and a single muscle belly
- Example: Biceps brachii

Front 46

Convergent

Back 46

- muscle fibers converge on a single insertion
- broad origin
- narrow insertion
- increases CSA while still allowing for intermediate length change while still staying stable on the length-tension curve
Example: Pectoralis major

Front 47

Unipennate

Back 47

single muscle fiber coming in on a tendon
Example: extensor digitorum longus

Front 48

Bipennate

Back 48

2 groups of fibers coming into a single tendon
example: Rectus femoris

Front 49

Multipennate

Back 49

MORE than 2 groups of fibers coming into a tendon
Example: Deltoid

Front 50

Pennate

Back 50

- designed to have large CSA
- designed to produce force
- three types: uni, bi, multi
- is when muscles come in onto a tendon: have short murcles coming in at an angle, which increases CSA, which increases force i can produce (ie: deltoid)

Front 51

Ways to Name skeletal Muscle

Back 51

1. Location in Body
2. Origin / Insertion
3. Fascicle organization
4. Relative position
5. structural characteristics
6. Action

Front 52

Action naming

Back 52

1. Movements - flexors, extensors, adductors, abductors
2. Occupations of habit - risers (laughter muscle)
Example: Masseter - involved in mastication

Front 53

Location in the body

Back 53

-IDs body region
Example: temporalis muscle

Front 54

Origin & insertion

Back 54

- first part of name indicates origin
- second part indicates insertion
Example: Supra/infraspinatus; subscapularis; sternoclavomastoid

Front 55

Fascicle Organization

Back 55

- describes fascicle orientation within muscle
Example: obliques - come in at an angle; transverse abdominis - come in transversely

Front 56

Relative Position

Back 56

1. Externus (superficialis) - relative to oblique
2. Internus (profundus) - relative to oblique
3. Extrinsic - muscle outside organ
4. Intrinsic - muscle inside organ

Front 57

Structural characteristics

Back 57

1. Number of tendons
2. Shape - trapezius; deltoid; rhomboid
3. Size

Front 58

Descriptive Terms for Muscle Size

Back 58

Longus, longissimus, teres, brevis - means short; magnus, major, maximus, minor - small, minimus - smallest

Front 59

What do T-Tubules do?

Back 59

They conduct electrical depolarization of the sarcolemma into the muscle cell interior

Front 60

What is "latent period"?

Back 60

time needed to release Ca2+ from SR, move tropomyosin and cycle the cross-bridges