week 4: muscular production of movement Flashcards
state the heirarchy of structural organisation of a muscle?
myosin and actin filament
sacromere
myofibrils
muscle fibre
muscle fasicles
muscle
skeletal muscle
heirarchy of structural organisation of enwrapping connective tissue?
and its purpose?
enwrapping tissue provides a framework for the concept of series and parralell elements within a muscle
muscle mass = 85% fibres, 15% CT
- epimysium: enwraps muscle
- perimysioum: enwraps fasicle
- endomysium: enwraps muscle fibres
- sacrolema: specialised cell membrane of muscle cells, contains elastin therefore in heirachy
function of epimysium
- it is the outermost CT layer
- enwraps entire muscle
- enables muscle to retain structural integrity when contracting and lengthening
- keeps entire muscle discete from other structures
function of perimysium
- enwraps fasicles
- fasicular organisation allows nervous system to recruit fibres housed within a fasicle with greater specificity
inner CT/ endomysium function
- enwraps individual fibres
- surrounds and supports the cell extracellular matrix, whcih contains important stuctural componenents
sacrolema
- plasma membrane of each muscle cell
- has elastic properties
what is the function of connective tissue as a whole?
permit force transmission to produce movement
- when a muscle contracts it creates tension
- this tension is transferred sequentially to each layer of tendon, concentrated at the MTJ
- via the tendon the force is transferred to the periosteal layer of bone, pulling on bone and moving skeleton
what are the elements of a single muscle fibre that also contribute to muscle contraction?
- General chemical composition
- Nuclei/ ‘Myonuclei’
- Sarcolemma and Basement Membrane/ Basal Lamina
- Sarcoplasm
- Mitochondria
- Sarcoplasmic Reticulum (SR), and its Terminal Cisternae
- T-Tubule Network
- Myofibrils/ Myofibrillar Proteins
how does the general chemical composition of a muscle, specialised for muscle contraction?
- 75% h20
- 20 % protien
- 5% inorganic compounds
how is nuclei specialised in muscle cells for muscle contraction
- muscle cells are multi-nuclear
- ## loacted at the periphery of the muscle fibre/cells between the myofibrils and sacrolemma
how are sarcolemmas (cell membrane) specialised for motor function?
- specialised, extendible cell membrane of fibres
- can be excitied electrically by AP from motor nueron
- it has a layered structure including: phospholipids, membrane bound receptors and transport molecules, structural proteins
how are basement membranes specialised?
- also known as basal lamina
- they are immediatly external to sacrolemma
- extracellular deposition of protiens to form a membrane
- it is an ECM ‘coat’ that anchor the fibre as well as supporting cell development, reintergation, and cell signalling
sarcoplasm (cytoplasm) specialisations?
- specialised cytoplasm of muscle fibres
- suspends myofibular proteins and organelles
- contents: ions, enzymes, ATP, phosphages, glycogen, lipid droplets, metabolic molecules
mitochondria specialisations
- it is the powerhouse of intercellular space
- the density and size of mitochondria in muscles are larger and higher
- there is peroipheral and intermyofibular mitochondria
sarcoplasmic reticulum (ER) and its terminal cisternae
SR:
- specialised smooth ER that stores, releases and retrives calcium ions
- calcium is fundemental for contraction
TC:
- a region of the SR in close proximity to, and surrounding the transverse tubercles
- stores calcium ions
transverse tubules
- invaginations of the sacrolemma that extend inwards towards the centre of the cell
- retain proximity to SR and have key role in excitation-contraction coupling
- communicate iwth outside cell membrane to deep muscle
myofibrils/myofibule protiens
- give structure and function
- suspended by sarcoplasm and run the length of fibre
- myofibrils are made up of connected sarcomeres
sarcomere
- smallest functional unit within a skeletal muscle
- made of specialised contractile, regulatory and structural protiens
as a functional unit:
- contraction leads to individual contraction of muscle fibres, leadig to entire muscle contraction
what is the structure of a sarcomere
- contain thick myosin and thin actin filaments
- the region of a sarcomere is between 2 Z discs
- M line is structural protein myosin, that anchors the thick myosin filaments in the center of the sarcomere
- A band in middle is dark bc of thick myosin overlap
- an I band anchors thin filaments either side of the sarcomere
- I band on either side is light becuase of thin filaments
describe the structure of a thick filament
- made of myosin
2x MHC, 2xMLC
- MHC= tail region, hinge region, head that contains binding sites for ATP and Actin
- MLC: is the regulatory protein located at hinge region
- the globular head on myosin are referred to as “cross bridge” region, which contain myosin and ATPase (related to splitting ATP, speeding and providing energy)
describe the structure of a thin filament?
made of 2x actin chains
- actin filaments are consecutive, linked actin protiens
- each single unit has a binding site for myosin
- troponin and tropomyosin span the actin chain and have a regulatory role determining actin binding availability
what is the role of titin, and where is it?
- each titin molecule extends from z disk to M line
- part of titin molecule is associatied with thick filament
- rest of molecule is springing and changes length with sacromere
- therfore provides elasticity and stabilises myosin
