PHY2011 Lecture Notes - Lecture 24: Skeletal Muscle, Endoplasmic Reticulum, Relaxed Muscle
20 Jun 2018
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Week 9 L2 (T5AL1) -muscle types, functional structure and cross-
bridges
1. Describe the functional substructure of muscles
2. Identify different types of muscles
3. Describe the process of cross-bridge cycling
Movement
oExternal (walking, throwing, smiling)
oInternal (circulation of blood, movement of food and gas through gut)
Muscle causes movement
oCaused by muscle contraction
Muscle cells- specialised cells
oGenerate force
oShorten
Muscle types
oSkeletal
Striated -longitudinal
Voluntary
Multi nucleated
oCardiac -heart
Striated -branched
Voluntary
One nucleus per fibre
oSmooth -gut
Involuntary
Longitudinal
No striations
Striated muscle
oCan only contract in one axis
oBut cardiac muscle is branched, meaning there is not one single direction of
contraction
find more resources at oneclass.com
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Functional structure of skeletal muscle
oWhole muscle – attached to bone by a tendon
oMuscle fibre = single muscle cell
oMicrofibril -make up a muscle cell (1-2μm in diameter)
oSarcomere -make up a microfibril (the sections of overlapping myofilaments -split at
z-disks)
oMyofilaments -Make up a sarcomere = thick and thin filaments
Whole muscle (Organ)
oMuscle Fibre (single muscle cell)
Myofibril (specialised intracellular structure)
- Thick and think filaments (Cytoskeletal elements)
Myosin and actin (Protein molecules thank make up thick
and thin filaments respectively)
The sarcomere
oBasic contractile unit of skeletal muscle
oResponsible for the striated appearance of skeletal muscle
oExtremely ordered geometry – repeating pattern
oHexagonal arrangements of the thick and thin filaments in the overlap region
Each thick filament is surrounded by 6 thin filaments
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Week 9 l2 (t5al1) -muscle types, functional structure and cross- bridges: describe the functional substructure of muscles. Identify different types of muscles: describe the process of cross-bridge cycling. Movement: external (walking, throwing, smiling, internal (circulation of blood, movement of food and gas through gut) Muscle causes movement: caused by muscle contraction. Muscle cells- specialised cells: generate force, shorten. One nucleus per fibre: smooth -gut. Striated muscle: can only contract in one axis, but cardiac muscle is branched, meaning there is not one single direction of contraction. Whole muscle (organ: muscle fibre (single muscle cell) Myosin and actin (protein molecules thank make up thick and thin filaments respectively) The sarcomere: basic contractile unit of skeletal muscle, responsible for the striated appearance of skeletal muscle, extremely ordered geometry repeating pattern, hexagonal arrangements of the thick and thin filaments in the overlap region. Each thick filament is surrounded by 6 thin filaments.
