Lecture 13 - Musculoskeletal system 3: Muscle

Question 1

What are 3 types of muscle tissue

Answer 1

• skeletal (striated, voluntary) aprox 40% body mass
• cardiac (striated, involuntary)
• smooth (visceral)(non-striated, involuntary)

Question 2

What are 4 functions of muscles

Answer 2

1. Movement: locomotion, manipulation, circulation)
2. Stabilization of body position: gravity
3. Regulation of organ volume: stomach, bladder
4. Release of heat: during contraction

Question 3

What are 4 characteristics of muscles

Answer 3

1. Excitability or irritability: can transmit, produce & react to a stimulus (electric current, neurotransmitter)
2. Contractility: shortening & widening of the cells ( force production, generated by an action potential)
3. Extensibility: can be stretched
4. Elasticity: retakes its form either after the contraction or the extension.

Question 4

What is fascia

Answer 4

Connective tissue layer that covers muscles and organs

Question 5

What is superficial fascia

Answer 5

(Under the skin)

Loose areolar CT and adipose tissue

Question 6

What is Deep fascia

Answer 6

• dense CT
• surrounds deeper organs, including muscles
• makes strong fibrous framework
• bound to capsules, tendons, ligaments

Question 7

What are other names for superficial fascia

Answer 7

Subcutaneous layer or hypodermis

Question 8

What is subserous fascia

Answer 8

• betwn serous membrane and deep fascia

- areolar tissue

Question 9

What are 3 layers of skeletal muscle

Answer 9

• Epimysium: envelopes all of the muscle
• Perimysium: surrounds the fascicles of myocytes 10-100
• Endomysium: isolate each myocyte

Question 10

The epimysium and perimysium fuse and elongate to form

Answer 10

Part of the tendons

Question 11

What is a tendon

Answer 11

• extension of CT

- interfaces with bone to produce strong anchor for contraction

Question 12

What is aponeurosis

Answer 12

• broad flat sheet of CT

- typically merges with fibrous tissue from nearby muscle

Question 13

What is tendon sheath

Answer 13

• double-walled tube that encloses tendons

- contains synovial membrane, reduces friction

Question 14

What are the 6 type of muscle arrangements

Answer 14

1. Parallel
2. Fusiform
3. Convergent
4. Circular
5. Spiral
6. Pennate

Question 15

Describe parallel muscle fibres arrangement

Answer 15

• long axis of the fascicles are oriented parallel to the long axis of the muscle
• straplike (ex. Sartorius / thigh muscle)

Question 16

Describe fusiform muscle fibres arrangement

Answer 16

• long axis of the fascicles are oriented parallel to the long axis of the muscle but have expanded belly
• ex. Biceps brachii

Question 17

Describe convergent muscle fibres arrangement

Answer 17

• broad origin (fixed point)
• fascicles leading to a single tendon at the insertion end (mobile point)
• ex. Pectoral

Question 18

Describe circular muscle fibres arrangement

Answer 18

• fascicles in concentric circles

- ex. Orbicularis occuli or oris (eye or mouth), sphincter

Question 19

Describe spiral muscle fiber arrangement

Answer 19

• fascicles twist btw points of attachment

- ex. Lassimus dorsi

Question 20

Describe pennate muscle fibre arrangement

Answer 20

• shorter fascicles, attach diagonally on the central tendon on the axis of the muscle
• resemble feathers

Question 21

What are the 3 types of pennate muscle fibre arrangement

Answer 21

• unipennate: single feather like extensor digitorum longus
• bipennate: 2 rows of muscle fibers, facing in opposite directions like rectus femoris
• multipennate: multiple rows of diagonal fibers like deltoid

Question 22

When muscle contraction occurs what usually happens to the two attached bones and what is the origin and insertion

Answer 22

When contraction happens, one bone usually remains fixed while the other moves (not always but usually)
Origin = point of attachment that doesn’t move
insertion = point of attachment the moves when muscle contracts

Question 23

What are 4 main muscle action groups

Answer 23

1. Prime mover
2. Antagonist
3. Synergist
4. Fixator

Question 24

what is muscle action prime mover (agonist)

Answer 24

• Muscle that directly performs a specific movement
• The movement produced is the action
• Agonist can refer to it, or any other muscle directly contributing to the same action

Question 25

What is antagonist muscle action

Answer 25

muscles that oppose prime movers while relaxed

Question 26

What is synergist muscle action

Answer 26

Contract at same time as agonists to stabilize action

Question 27

What is fixator muscle action

Answer 27

Joint stabilizers, subtype of synergists

Question 28

What are the 3 components of the lever system (bone+muscle)

Answer 28

- Fulcrum: fixed point (articulation) - Effort or applied force: Work provided against a resistance (contraction of a muscle) - Load: Displacement

Question 29

Depending on the placement of the 3 components in the lever system what are the 3 kinds of lever systems

Answer 29

``` 1st class 2nd class 3rd class ```

Question 30

What is 1st class lever

Answer 30

- like seesaws, scissors - ex. raise your head - Fulcrum: atlanto-occipital articulation (btw occipital bone and atlas C1) - Applied force: posterior muscle of the neck - Load: face skeleton

Question 31

What is 2nd class lever

Answer 31

- like wheelbarrow - ex. act of standing on your toes - Fulcrum: articulation of the front of the foot - Applied force: calf muscles - Load: weight of the body

Question 32

What is 3rd class levers

Answer 32

- like tweezers - ex. biceps brachii muscle, flexion of the forearm - Fulcrum: elbow articulation - Applied force: biceps brachii (on proximal end of the radius) - Load: hand + distal end of the forearm

Question 33

How are skeletal muscles named (7)

Answer 33

- Based on structural and functional characteristics 1. location (bone or body region) 2. Shape (characteristic form) 3. Relative size (maximus = largest, mimus = smallest, longus = long, brevis= short) 4. Direction (can be ref to midline or longitudinal axis; rectus = straight, oblique, transversus) 5. function (type of movement; adductor = toward midline) 6. number of heads(multiple point of origin triceps= 3 quadriceps= 4) 7. points of attachement(location of origin or insertion like sternocleidomastoid= sternum and clavicle)