Muscular System (EXAM #2) Flashcards
What is the overview of Muscular System?
- Refers to skeletal muscle system
- Primarily attached to bone
- Produce movement by contracting
What is Skeletal Muscle?
- Cells called fibers
- Fascicle = group fibers
- Whole Muscle = group of fascicles
What are the 2 CT Components of Skeletal Muscle?
- Fascia (connective tissue surrounding muscles or other organs)
- Tendons and Aponeuroses
Fascia (connective tissue surrounding muscles or other organs)
- Epimysium
- Surrounds entire skeletal muscle
- Perimysium
- Surrounds fascicles within skeletal muscle
- Endomysium
- Surrounds each muscle fiber (cell) within skeletal muscle
Tendons and Aponeuroses
- Extensions of epimysium, perimysium, and endomysium
- Anchors muscle to bone (periosteum), cartilage, fascia
Tendon
- A rope-like bundle of dense regular connective tissue
- e.g. calcaneal (achilles) tendon
Aponeurosis
- A flat sheet of dense regular connective tissue
- e.g. epicranial aponeurosis (scalp)
What is the Skeletal Muscle Fiber Structure?
Large cylindrical and multinucleate cells
What are the Parts of Skeletal Muscle Fiber Structure?
- Sarcolemma
- T-tubules
- Sarcoplasm
- Myofibrils
- Sarcoplasmic Reticulum
Sarcolemma
Cell Membrane
T-tubules
Continuations of sarcolemma that extend deep into fiber (cell)
Sarcoplasm
Cytoplasm
Myofibrils
- Intracellular Structures
- Within each fibre tthere are several hundreds to thousands
- Composed of Sarcomeres
What are the structures of sarcomere?
- Made of 2 types of myofilaments
- The myofilaments create dark and light bands (striations) of the sarcomere
- Banding Pattern
- Sarcomeres join end to end (at Z discs) to form a myofibril
What are the 2 types of Myofilaments
- Thin Myofilaments
- Thick Myofilaments
Thin Myofilaments
- Formed by 3 proteins involved in contraction:
- Actin
- Tropomyosin
- Troponin
Thick Myofilaments
- Formed by a protein called myosin
- Attached to z discs by titin
- Myosin has rod-like tail with 2 globular heads
- At rest, the heads extend toward actin and during contraction attaches to actin to shorten the sarcomere
Whar are parts of the banding pattern?
- A band
- H zone
- I band
- Z discs (in center of I band)
- M line
A Band
Dark band that is length of thick myofilaments
H Zone
Lighter area at center of A band
I Band
Light band consisting of thin myofilaments
Z Discs
- Connected to thick myofilaments (via titin) and thin myofilaments
- Connection point between adjacent sarcomeres
M Line
WHere myosin tails (thick myofilaments) attach to each other (center of sarcomere)
Sarcoplasmic Reticulum
- Is smooth endoplasmic reticulum
- Triad is a formed from 2 enlarged areas of sarcoplasmic reticulum (terminal cisternae), and a T-tubule that runs in between them
What are the 3 Ways Muscles Produce Movement?
- Lever System
- Pulling on bones when they contract
- Using group action
Lever System
- Bone/muscle interaction at a joint
- Parts:
- Levers = Bone
- Fulcrum = Joint
- Effort = Contraction of agonist
- Resistance = opposes movement
- Effort must be greater than resistance to get movement
Pulling on bones when they contract
- Origin
- Attachment of tendon to stationary bone
- Insertion
- Attachment of tendon to movable bone
Using group action
- Agonist
- Major muscle producing the movement
- Synergists
- Help the agonist action and prevent undesirable motions caused by the agonist
- Antagonist
- Produces opposite action of agonist (contraction inhibited when agonist contracts)
Flexion of Forearm (Example #1)
- Agonist = Biceps brachii
- Antagonist = Triceps brachii
- Synergists = Brachialis, Brachioradialis
- Lever = Radius (insertion of agonist)
- Fulcrum = Elbow joint
- Effort = Muscle contraction
- Resistance = Weight of object plus forearm
Extension of Forearm (Example #2)
- Agonist = Triceps brachii
- Antagonist = Biceps brachii
