Lecture 13 - Musculoskeletal system 3: Muscle Flashcards
What are 3 types of muscle tissue
- skeletal (striated, voluntary) aprox 40% body mass
- cardiac (striated, involuntary)
- smooth (visceral)(non-striated, involuntary)
What are 4 functions of muscles
- Movement: locomotion, manipulation, circulation)
- Stabilization of body position: gravity
- Regulation of organ volume: stomach, bladder
- Release of heat: during contraction
What are 4 characteristics of muscles
- Excitability or irritability: can transmit, produce & react to a stimulus (electric current, neurotransmitter)
- Contractility: shortening & widening of the cells ( force production, generated by an action potential)
- Extensibility: can be stretched
- Elasticity: retakes its form either after the contraction or the extension.
What is fascia
Connective tissue layer that covers muscles and organs
What is superficial fascia
(Under the skin)
Loose areolar CT and adipose tissue
What is Deep fascia
- dense CT
- surrounds deeper organs, including muscles
- makes strong fibrous framework
- bound to capsules, tendons, ligaments
What are other names for superficial fascia
Subcutaneous layer or hypodermis
What is subserous fascia
- betwn serous membrane and deep fascia
- areolar tissue
What are 3 layers of skeletal muscle
- Epimysium: envelopes all of the muscle
- Perimysium: surrounds the fascicles of myocytes 10-100
- Endomysium: isolate each myocyte
The epimysium and perimysium fuse and elongate to form
Part of the tendons
What is a tendon
- extension of CT
- interfaces with bone to produce strong anchor for contraction
What is aponeurosis
- broad flat sheet of CT
- typically merges with fibrous tissue from nearby muscle
What is tendon sheath
- double-walled tube that encloses tendons
- contains synovial membrane, reduces friction
What are the 6 type of muscle arrangements
- Parallel
- Fusiform
- Convergent
- Circular
- Spiral
- Pennate
Describe parallel muscle fibres arrangement
- long axis of the fascicles are oriented parallel to the long axis of the muscle
- straplike (ex. Sartorius / thigh muscle)
Describe fusiform muscle fibres arrangement
- long axis of the fascicles are oriented parallel to the long axis of the muscle but have expanded belly
- ex. Biceps brachii
Describe convergent muscle fibres arrangement
- broad origin (fixed point)
- fascicles leading to a single tendon at the insertion end (mobile point)
- ex. Pectoral
Describe circular muscle fibres arrangement
- fascicles in concentric circles
- ex. Orbicularis occuli or oris (eye or mouth), sphincter
Describe spiral muscle fiber arrangement
- fascicles twist btw points of attachment
- ex. Lassimus dorsi
Describe pennate muscle fibre arrangement
- shorter fascicles, attach diagonally on the central tendon on the axis of the muscle
- resemble feathers
What are the 3 types of pennate muscle fibre arrangement
- 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
When muscle contraction occurs what usually happens to the two attached bones and what is the origin and insertion
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
What are 4 main muscle action groups
- Prime mover
- Antagonist
- Synergist
- Fixator
what is muscle action prime mover (agonist)
- 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
What is antagonist muscle action
muscles that oppose prime movers while relaxed
What is synergist muscle action
Contract at same time as agonists to stabilize action
What is fixator muscle action
Joint stabilizers, subtype of synergists
What are the 3 components of the lever system (bone+muscle)
- Fulcrum: fixed point (articulation)
- Effort or applied force: Work provided against a resistance (contraction of a muscle)
- Load: Displacement
Depending on the placement of the 3 components in the lever system what are the 3 kinds of lever systems
1st class 2nd class 3rd class
What is 1st class lever
- 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
What is 2nd class lever
- 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
What is 3rd class levers
- 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
How are skeletal muscles named (7)
- 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)
