Unit 11 - Muscular System Flashcards
What does the muscular system refer to
Skeletal muscle system
What are muscles in the muscular system primarily attached to
Bone
How do muscles produce movement
By contracting
What are muscles important for
- locomotion
- maintaining body posture
What are skeletal muscle cells called
Fibers
Fasicle
Group of fibres
Whole muscle
Group of fascicles
CT components of skeletal muscle
- Fascia
- Tendons and aponeuroses
What is fascia
CT surrounding muscles or other organs
Epimysium of fascia
Surrounds entire skeletal muscle
Perimysium of fascia
Surrounds fascicles within skeletal muscle
Endomysium of fascia
Surrounds each muscle fiber (cell) within skeletal muscle
What are tendons and aponeuroses
Extensions of epimysium, perimysium and endomysium
What do tendons and aponeuroses anchor
Muscle to bone (periosteum), cartilage, fascia
Tendon
Rope like bundle of dense regular CT
- ex. Calcaneal (Achilles) tendon
Aponeurosis
Flat sheet of dense regular CT
- ex. Epicranial aponeurosis (scalp)
What kind of cells is skeletal muscle fiber made of
Large, cylindrical and multinucleate cells
Parts of skeletal muscle fibres
- Sarcolemma
- T-tubules
- Sarcoplasm
- Myofibrils
- Sarcoplasmic reticulum
Sarcolemma
Cell membrane
T-tubules
Continuations of Sarcolemma that extend deep into fibre (cell)
Myofibrils
- intracellular structures
- within each fibre there are several hundreds to thousands
- composed of sarcomeres
Sarcomere structure
- composed of proteins
- made of 2 types of myofilaments
1. Thin myofilaments
2. Thick myofilaments
Thin myofilaments
- formed by 3 proteins involved in contraction
1. Actin
2. Tropomyosin
3. Troponin
Thick myofilaments
- formed by a protein called myosin
- attached to Z discs by titin
- create dark and light bands (striations) of the sarcomere
Myosin
- has rod-like tail with 2 globular heads
What does myosin do at rest
Head extends towards actin
What does myosin do during contraction
Head attaches to actin to shorten the sarcomere
What does the banding pattern of thick myofilaments consist of
- A band
- H zone
- I band
- Z discs
- M line
A band
Dark band that is length of thick myofilament
H zone
Lighter area at center of A band
I band
Light band consisting of thin myofilaments
Z discs
- in center of I band
- connected to thick myofilaments (via titin) and thin myofilaments
- connection point between adjacent sarcomeres
- sarcomeres join end to end (at Z discs) to form a Myofibril
Sarcoplasmic reticulum
- is smooth endoplasmic reticulum
- triad is formed from 2 enlarged areas of Sarcoplasmic reticulum (terminal cisternae), and a T-tubule that runs in between them
Ways muscle produce movement
- Leverage system
- Pulling on bones when they contract
- Using group action
Lever system
- bone/muscle interaction at a joint
Parts of lever system
- Levers = bone
- Fulcrum = joint
Effort
Contraction of agonist
Resistance
opposes movement
What needs to happen for movement to occur
Effort has to be greater than resistance
Origin
Attachment of tendon to stationary bone
Insertion
Attachment of tendon to moveable bone
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
Agonist= biceps brachii
Antagonist= triceps brachii
Synergist= brachialis, brachioradialis
Lever= radius (insertion of agonist)
Fulcrum= elbow joint
Effort= muscle contraction
Resistance= weight of object + forearm
Extension of forearm
Agonist= triceps brachii
Antagonist= biceps brachii
