Lecture 6 - Neuromuscular Aspects of Movement I

Question 1

what is musculature?

Answer 1

• the muscles over the skeleton that provide the means to move it
• each muscle produces motion when it creates tension (shortens)
• how muscles look determines how the bones will move

Question 2

what is the structure of superficial muscles compared to deep muscles?

Answer 2

• superficial are bigger but less powerful (less torque)
• deep are smaller but have more specific actions

Question 3

how do the shape and wrapping of muscles affect function?

Answer 3

• muscle fibres run along the striations, and the nuclei of the muscle fibres handle actions locally
• the direction of striations tells you the direction of pull of the muscle
• redirect muscle pull between the origin and insertion

Question 4

what is the ‘origin’?

Answer 4

• proximal attachment of the muscle

Question 5

what is the ‘insertion’?

Answer 5

• distal attachment of the muscle

Question 6

what is aponeurosis?

Answer 6

• wide bands of connective tissue that connect muscle to bone

Question 7

what are the layers of muscle?

Answer 7

• muscle (covered by epimysium)
• fasicles (covered by perimysium)
• muscle fibres (covered by endomysium)
• myofibrils

Question 8

what is a sarcomere?

Answer 8

• the smallest contractile unit of muscle
• hundreds are connected to form a long chain (in parallel) to form a myofibril (several of which then form muscle fibers)

Question 9

how does the number of myofibrils affect the muscle?

Answer 9

• lower number of myofibrils = more accurate actions, but lower power/force (like eyes)
• higher number of myofibrils = less accurate actions, but more power/force (like the glutes)

Question 10

what is the structure of a sarcomere?

Answer 10

• actin = thin filament
• myosin = thick filament
• z disc = where one sarcomere ends and the next starts
• a band = myosin
• i band = contains z line and half actin
• sarcomeres shorten when stimulated by an ATP
• organized into hexagons (each myosin is surrounded by 6 actin)

Question 11

how does rigor occur in the body?

Answer 11

• when the body no longer has ATP, muscles stay contracted
• smaller muscles go into rigor first, large muscles last

Question 12

what is the length-tension relationship?

Answer 12

• tension created by a sarcomere related to its length

Question 13

what is the ideal length-tension relationship? what is not ideal and why?

Answer 13

• ideal = 2 (2.20-2.25 u)
• 1 (>3.65 u) = no connections so slower contraction and movement (0% tension)
• 5 (<1.05 u) = actions will bump into each other and interfere/block with cross bridges (slower contraction)

Question 14

what is the pennation angle? how does it affect muscle function?

Answer 14

• the angle between muscle fibres and the line of pull
• smaller angle = more direct pull (but less force and greater excursion) and vice versa

Question 15

what are the different pennation arrangements?

Answer 15

• longitudinal = fusiform muscle (pulls vertically)
• unipennate = more fibres in parallel, aponeurosis
• bipennate = two directions of pull
• multipennate = weakness in the body, a muscle that is trying to do many things (has multiple directions of pull, slower contraction, weaker pull)

Question 16

what are the 4 important characteristics of a muscle?

Answer 16

1. flexibility - ROM at the joint
2. strength - maximum force that can be produced
3. power - speed the muscle produces force
4. endurance - time te muscle can produce force

Question 17

what are muscle groups?

Answer 17

• grouped together by what they do biomechanically at the joint (ex: knee extensors)

Question 18

what are one-joint muscles/uniarticulate muscles?

Answer 18

• muscles that only cross one joint
• they only affect one joint when contracted

Question 19

what are multiarticulate or multi-joint muscles?

Answer 19

• muscles that cross two or more joints
• affect several joints simultaneously when they contract

Question 20

what is active insufficiency?

Answer 20

• muscle can’t shorten enough
• for example: knee is fully flexed and hip is fully extended, insufficiency in hamstrings

Question 21

what is passive insufficiency?

Answer 21

• muscle can’t lengthen enough
• for example: hip is fully flexed, knee is fully extended, insufficiency in the hamstrings

Question 22

what is co-contraction?

Answer 22

• when both the agonists and antagonists are active, to stabilize a joint
• agonists start movement
• antagonists slow things down
• co-contract to stabilize and for fine control (isometric movement or putting something heavy down)

Question 23

what is concentric contraction?

Answer 23

• when the muscle activated shortens

Question 24

what is eccentric contraction?

Answer 24

• when the muscle activated lengthens
• produces moe force using the same or less energy, the best way to gain muscles quicker

Question 25

what is isometric contraction?

Answer 25

• when the muscle activated stays the same length

Question 26

what 3 factors influence tension?

Answer 26

1. amount of activation
2. length of the muscle
3. speed of the muscle