Muscular System Flashcards
Muscular System Overview
- Refers to skeletal muscular system
- Primarily attached to bone
- Produce movement by contracting (byproduct - heat)
Skeletal Muscle General Information
- Cells called fibers
- Fascicles = group of fibers (bundle)
- Whole muscle = group of fascicles
CT Components of Skeletal Muscle
1) Fascia
2) Tendons and Aponeuroses
Fascia
- CT components of skeletal muscle
- =CT
1) Epimysium - surrounds entire muscle
2) Perimysium - surrounds fascicles
3) Endomysium - surrounds each muscle fiber
Tendons and Aponeuroses
- CT components of skeletal muscle
- extensions of Epi-, peri-, and endomysium
- Anchors to bone (periosteum), cartilage, skin, or fascia
- Tendon = rope-like ( Achilles Tendon)
- Aponeurosis = sheet- like (Epicranial Aponeurosis)
Skeletal Muscle Fiber Structure
- Large multinucleate cells
- Parts:
1) Sarcolemma
2) Sarcoplasm
3) Myofibrils
4) T- tubules
5) Sarcoplasmic Reticulum
Sacrolemma
- Fiber structure
- Cell membrane of a muscle cell
Sarcoplasm
- Fiber structure
- Cytoplasm
Myofibrils (intercellular structures)
- within each fibre there are several hundreds to thousands
- Composed of sarcomeres (they’re little sections)
- sarcomere made of 2 types of myofilaments
1) Thin Filaments
2) Thick Filaments - the myofilaments create dark and light bands (striations) of the sarcomere (banding pattern in other slides)
Thin Filaments
- Composed of:
1) Actin
2) Tropomyosin
3) Troponin - regulate contraction (regulatory proteins)
Thick Filaments
- Composed of:
1) myosin - functions in contraction - Attached to Z discs by Titin
- Has rod-like tail with 2 globular heads - head extends toward actin and attaches to it forming a crossbridge
A Band
- Banding pattern
- dark = length of thick filament - myosin and actin (with troponin and tropomyosin)
H Zone
- Banding pattern
- lighter band at center of A Band - myosin ONLY
I Band
- Banding Pattern
- light = actin (with troponin and tropomyosin) and titin
Z Discs
- Banding pattern
- Center of I band
- actin and titin attach
- Connect sarcomeres: between 2 Z- discs = 1 sarcomere
- Sarcomeres join end to end (at Z-discs) to form Myofibrils
M Line
- Banding pattern
- Where myosin tails (thick myofilament) attach to each other (Center of sarcomere)
T- tubules
- Fiber structure
- Continuations of sarcolemma that extend deep into Fiber (cell)
- Directly encircle myofilaments of Myofibrils at junction of A and I bands (2/sarcomere)
Sarcoplasmic Reticulum
- Fiber structure
- = smooth ER
- triad= 2 enlarged areas of SR (terminal cisternae) and T-tubule
How muscles produce movement (overview)
1) Pulling on bones when they contract
2) Using group action
3) lever systems
Pulling in bones when they contract
1) Origin = attachment of tendon to stationary bone
2) Insertion = attachment of tendon to movable bone
Using Group Action
1) Agonist = major muscle producing the movement
2) Synergists = help the agonist action and prevent undesirable motions caused by the agonist
3) Anagonist = produces opposite action of agonist (contraction inhibited when agonist contracts)
Lever Systems
- Bone/muscle interaction at a joint
- Parts:
1) Levers = bone
2) Fulcrum = joint - Effort = contraction of agonist
- Resistance = opposes movement
- Effort must be greater than resistance to get movement
- Examples: Flexion of Forearm and Extension of forearm
Naming of Skeletal Muscles
1) Action they perform (in anatomical position)
2) Shape of muscle
3) Origin and Insertion
4) Location
5) Relative Size
6) Direction of Fibers
7) Number of origins
Flexors
- Decrease angle between 2 bones
- Biceps Brachii
Extensors
- Increase angle (back to anatomical position after flexion)
- Triceps Brachii
Abductors
Move limb away from midline
Adductors
Move limb toward midline
Shape of Muscle
Example 1: Deltoid - triangular shape
Example 2: Trapezius - Trapezoid Shape
Origin and insertion
Example: Sternocleidomastoid -Origin: Sterno = sternum Cleido = clavicle -Insertion: Mastoid = mastoid process of temporal bone
Location
Tibialis Anterior
Relative Size
Example: Gluteus
- Maximus
- Medius
- Minimus
Direction of Fibers
Example 1: Rectus Abdominis (rectus = straight ||)
Example 2: External Obliques \ or //
Number of Origins
Example 1: Biceps Brachii- 2 origins on scapula
Example 2: Triceps Brachii - 3 origins on scapula and humerus
Example 3: Quadriceps Femoris - 4 origins on os coxa and femur
