Lecture 8 - Skeletal Muscle Flashcards
4 Functions of Skeletal Muscle
Movement
Posture
Storage/Movement of Substances
Heat Generation
Gross Muscle Anatomy (3 points)
Force produced by muscle
Force transmitted to skeleton via tendon
Movement occurs/joint stabilizes
Sarcomere Definition
Moving Parts of Muscle
Epimysium Definition
Outer Connective Tissue
Holds Fascicals in place
Endomysium Definition
Connective Tissue holding muscle fibres together
Perimysium Definition
Inner Connective Tissue holding fascicals in place
6 Components of a Muscle Fibres
Multiple Nuclei
Light I Band
Dark A Band
Myofibril
Sarcolemma
Mitochondria
Number of Sarcomeres in a Myofibril
Thousands joined in series/parallel to one another
Components of Sarcomere
Z Line
H Zone
M Line
Light I Band
Dark A Band
2 types of Myofilaments
Thick Myosin Filament
Thin Actin Filament
2 Features of Actin Filaments
Double Helical Structure
Tropomyosin covers binding sites on Actin units
Features of Myosin Filaments
300 Myosin Units long
Two subunits - S1/S2
2 Subunits in Myosin Filaments
S1 - Globular Head
S2 - Flexible Region and Tail
Why are binding sites in thin filament covered?
Stops unwanted contraction
3 Structural Proteins in Sarcomere
Titin
Nebulin
Desmin
Titin Function
Springlike protein responsible for returning sarcomere to original structure
Nebulin Function
Maintaining Overall Structure
Desmin Function
Maintains Z Line
Sliding Filament Mechanism (5 points)
During Contraction:
H Zone decreases in length
I Band decreases in length
A Band stays the same
Overall change in muscle length
Sarcoplasmic Reticulum Definition
Interconnecting tubules surrounding myofibrils
2 Functions of Sarcoplasmic Reticulum
Regulates intracellular levels of Ca2+
Stores Ca2+ and releases on stimulation to allow contraction
Cross Bridge Cycle (7 points)
Action Potential Arrives
Ca2+ binds to Troponin
Causes conformational change in Tropomyosin
Exposes binding site of actin
Myosin Globular head binds to actin binding site using ATP
Pi released from Myosin Globular Head
ATP used to break Actin/Myosin Bond
Length/Tension Relationship in Muscle (3 points)
When filaments overlapped, no tension
As muscle stretches, tension increases as Z Line is not there
Once actin and myosin aren’t overlapped, tension decreases
Force/Velocity Relationship in Muscle (3 points)
Force during shortening < isometric force
Faster the movement, less time myosin heads have to attach to binding site
Force during lengthening > isometric force
3 types of Muscle Fibres
Type I
Type IIA
Type IIX
Features of Type I Fibres
Small Cross Sectional Area
Red
High Endurance Capacity
Low Max Force
Features of Type IIA Fibres
Medium Cross Sectional Area
Pink
Intermediate Endurance Capacity
Intermediate Max Force
Features of Type IIX Fibres
Large Cross Sectional Area
White
Low Endurance Capacity
High Max Force
6 Parts to Motor Neuron
Cell Body
Myelin Sheath
Axon
Dendrites
Node of Ranvier
Axon Terminal
Node of Ranvier Definition
Gap in Myelin Sheath where axon is exposed
Components of Node of Ranvier
Sodium and Potassium Channels in Membrane
Neuromuscular Junction Definition
Where motor neuron meets muscle fibre
Muscle Spindle Function
Prevents Overstretching of Muscles due to changes in muscle length
Mechanism of Overstretch Prevention
Afferent Neuron wraps around muscle spindle
Efferent Neuron causes muscle spindle to contrat
