Lecture 6: Neuromuscular Aspects of Movement I

Question 1

Muscles and motion

Answer 1

Muscles produce a motion when it creates tension and tries to shorten

Question 2

Skeletal muscle

Answer 2

• overlap over each other
• striated (tells which way it will pull)

Question 3

Origin

Answer 3

Proximal attachment of a muscle
- closer to axial skeleton

Question 4

Distal

Answer 4

Distal attachment of a muscle

Question 5

Wrapping points/retinacula

Answer 5

redirect muscle pull btwn origin and insertion

Wrapping points change direction (can be negative or positive)

Negative angle is held down by retinacula

Question 6

Aponeuroses

Answer 6

Wide bands of connective tissue (wide tendon)

Attach muscle to bones like tendons

Question 7

Layers of muscle

Answer 7

myofirbils (smallest unit) –> muscle fibres –> fascicle –> muscle (biggest)

Question 8

Endomysium

Answer 8

covers muscle fibres

Question 9

Fascicles

Answer 9

bundles of muscle fibres

covered by perimysium

Question 10

Perimysium

Answer 10

covers fascicles

Question 11

Epimysium

Answer 11

covers whole muscle AND tendon
- like cling flim

Question 12

Sarcomere

Answer 12

Smallest contractile unit of muscle
- connected together in series
- Z-disc to Z-disc
Has actin and myosin

When stimulated by motor nerve, the sarcomere shortens

Question 13

Actin

Answer 13

thin filament

Question 14

Myosin

Answer 14

thick filament

Question 15

Muscle contraction

Answer 15

Z-Discs get closer and I-band gets narrower
- A-band does NOT change

Question 16

Light/dark bands and muscle

Answer 16

Myosin (thick) = dark band (absorbs lots of light)

Light bands - I band
Dark bands - A band

Question 17

Rigor mortis

Answer 17

NO ATP
- can’t hydrolyze to form ADP and disconnect crossbridges

Small muscles go into rigor first and big muscles last (big muscles have higher ATP stores)

Question 18

Length-tension curve

Answer 18

Best scenario (2): 2.20-2.25 microns
- produces 100% of tension (ideal)

worst case (1): longest sarcomere (no actin for crossbridges to connect) = no contraction

1 (longest) –> 6 (shortest)

shortest sarcomere = overlap in actin = decrease in tension

Question 19

Pennation angle

Answer 19

Angle btwn muscle fibres and the line of pull of the muscle

Smaller angle = more direct pull = LESS force and more excursion
- fatigues easily

Larger angle = less direct pull = greater force and smaller excursion (small movement)
- force multiplier = can put more muscle fibres in parallel

Question 20

Small pennation

Answer 20

Large excursion, small force, easily fatigued, quick rxn. time

Ex. Tibialis anterior (small angle)
- only needed for dorsiflexion when walking (small excursion)

Fusiform muscle

Question 21

Fusiform muscle

Answer 21

Little to no pennation angle

Question 22

Large pennation

Answer 22

Small excursion, large force (can stack more in parallel), goof endurance, slower rxn. time

Ex. Gastrocnemius

Question 23

Pennation arrangements

Answer 23

Longitudinal
Unipennate
Bipennate
Multipennate

Question 24

Longitudinal pennation

Answer 24

Fusiform muscle
- little to no pennation angle

Muscle fibres travel in direction of muscle pull

Ex. sartorius and tib ant.

Question 25

Unipennate

Answer 25

single pennation angle btwn muscle fibres and direction of pull pulls in one direction more likely to see aponeuroses

Question 26

Bipennate

Answer 26

pulls equally both ways tracks to one side b/c there are 2 slightly different pennation angles Ex. vastus intermedius

Question 27

Multipennate

Answer 27

pulls in multiple directions jack of many trades, master of none - likely to pull or tear b/c it doesn't do any one thing well Ex. rotator cuff

Question 28

CHARACTERISTICS OF A MUSCLE

Answer 28

1. Flexibility: how much ROM does the muscle allow at the jt 2. Strength: maximum FORCE that can be created 3. Power: how FAST can the muscle produce force (force x velocity) - explosive starts 4. Endurance: how LONG can the muscle produce force? - fusiform muscles tire out quickly

Question 29

Knee extensor group

Answer 29

Quads (anterior) - vastus lateralis - vastus intermedius - vastus medialis - rectus femoris (also a hip flexor)

Question 30

Elbow flexor group

Answer 30

Anterior - biceps brachii - brachialis - brachioradialis Brachialis and brachioradialis fill in ROM to allow usable power when biceps are too short/long

Question 31

Uniarticulate muscle

Answer 31

One-joint muscle only cross one joint = only affect one joint when they contract Ex. soleus in calf group (only crosses ankle)

Question 32

Multiarticulate muscles

Answer 32

Multi-joint muscles Cross two or more joints = affect several jts SIMULTANEOUSLY when they contract Ex. gastrocenemius in calf (crosses ankle and knee)

Question 33

Drawback of multi-joint muscles

Answer 33

They can't get full ROM at both joints simultaneously Active and passive insufficiency Ex. semimembranosus and semitendinosus are vulnerable b/c they cross hip and knee - both thrown into passive insufficiency = too long = tear

Question 34

Active insufficiency

Answer 34

muscle CAN'T SHORTEN enough too short = active part in making it too short (you do action)

Question 35

Passive insufficiency

Answer 35

muscle CAN'T LENGTHEN enough

Question 36

Steps of movement

Answer 36

1. Agonist starts moving 2. Antagonist stops moving 3. Co-contraction (slow and fix mistakes)

Question 37

Agonists

Answer 37

Muscles that pull together to produce the DESIRED motion at a joint Ex. trying to lift a glass of water to mouth: elbow flexors are agonists

Question 38

Antagonists

Answer 38

Muscles that pull in OPPOSITE DIRECTION at a joint Ex. elbow extensors

Question 39

Agonist-antagonist relationship

Answer 39

When agonists are active, antagonist group is inhibited to allow motion In some situations, there is CO-CONTRACTION (both groups are active) - used to stabilize of slow the jt.

Question 40

What happens when a muscle is activated by a motor nerve?

Answer 40

The sarcomeres ATTEMPT to shorten (not always able to)

Question 41

Concentric contraction

Answer 41

Muscle is activated and SHORTENS External loading is insufficient

Question 42

Isometric contraction

Answer 42

Muscle is activated and REMAINS THE SAME LENGTH External loading exactly balances internal force produced by muscle Ex. planks, holding yoga pose

Question 43

Eccentric contraction

Answer 43

Muscle is activated and LENGTHENES Produces more force than other ways

Question 44

FACTORS THAT DETERMINE AMOUNT OF TENSION FROM MUSCLE ACTIVATION

Answer 44

1. The AMOUNT of activation (does the brain want full or partial power) 2. LENGTH of muscle (muscle has an 'ideal length' for max tension. Tension drops off if longer or shorter) 3. SPEED of muscle (as muscle shortens faster, its tension drops quickly) - lengthening muscle (eccentric) = tension goes up

Question 45

Velocity-Tension Curve

Answer 45

Power is a parabolic function In concentric phase, force drops off exponentially as velocity increases (force stays below 1) At isometric contraction, force is at 1 At eccentric contraction, force goes above 1 then plateaus at max - some fusiform muscles can go up to 180% with external load - external load is needed to lengthen

Question 46

Velocity and force

Answer 46

Inverse relationship As velocity increases, force decreases