Locomotor - Muscles Flashcards
What is the order of skeletal muscles? (smallest to largest)
Myofilaments > Sarcomeres > Myofibril > Muscle fibres > Fascicle > Muscle belly
What is the epimysium?
Surrounds whole muscle belly
What is the perimysium?
Surrounds whole muscle fascicle
What is the endomysium?
Surrounds muscle fibres
What is the sarcolemma?
Surrounds myofibrils
What is the appearance of skeletal muscle?
Multiple peripheral nuclei
Appears striated with regular parallel bundles
Under voluntary control
Highest sarcoplasmic reticulum development
What is the appearance of cardiac muscle?
Striated
Single nucleus
Irregular arrangement of intercalated discs
What are the features of cardiac muscle?
Involuntary control
High mitochondrial density (high metabolic demand)
Low electric resistance
What are the types of cell junctions in cardiac muscles?
Joined at Z line
Desmosome - joins together and stops separation
Gap junction - allows AP to flow
Fascia adherens - provides an anchorage for actin
Transitional junction - where myocytes join
What are the features/appearance of smooth muscle?
No striations
Single nucleus
Longer contractions
Involuntary
What is the equation for muscle strength?
Work = force x distance
Power = work/ time
What are the features of parallel muscles?
Fibres run parallel with line of the pull.
Longer fibres = more sarcomeres = greater shortening ability aka distance increases
e.g. Sartorius and Semitendinous and Latissimus dorsi
What are the features of pennate muscles?
Shorter muscle fibres at angle to internal tendon.
Allows more sarcomeres in smaller space = increase cross sectional area = increase force created
More economical and linked to stabilisation
e.g. Serratus ventralis
Which is better, pennate or parallel?
If pennate and parallel are same length, pennate produces more force, but parallel produces more power
Whats the all or nothing system?
One nerve per muscle fibre with all or nothing, once AP threshold is met all fibres innervated will contract
What makes up a sarcomere?
Between Z discs are actin myofilaments surrounding a myosin filament, joined by cross bridges. The middle is the M line.
What is the sliding filament theory?
- AP travels down T-tubule opening Ca2+. Ca2+ interacts with DHP and ryanodine receptors inducing the SR to release Ca2+
- Ca2+ binds to Troponin C on the actin filament, exposing the myosin binding site
- Myosin head forms a cross bridge and performs a power stroke pulling actin closer
- Myosin head previously had ADP + Pi attached, which is hydrolysed and becomes ATP
- ATP binds back to the head and the power stroke will continue until ATP is depleted and/or Ca2+ is decreaased.
- Ca2+ is removed by Ca-ATPase pump
What are type I muscle fibres?
Slow oxidative
Uses oxidative phosphorylation in mitochondria to produce ATP
Slow and fatigue resistant
Lots of capillaries and smaller in diameter, darker looking
What are type IIa?
Glycotic oxidative fibres
Works via glycolytic phosphorylation of ADP via creatine but limited supply
What are type IIb?
Glycolytic fibres
Uses glycolytic phosphorylation of ADP in cytosol and requires glycogen store. Produces lactic acid as bproduct
Short lived and large amount of force but fatigue quickly
Large in diameter and less capillaries, appear lighter
