Functional Anatomy Flashcards
Skeletal Muscle
Muscle tissue attached to bones
What are the two types of skeletal muscles?
Fast twitch fibres (white) and slow twitch fibres (red)
Structure of skeletal muscle
Skeletal muscle surrounded by epimysium
made up of fascicles surrounded by perimysium
each fascicle contains individual muscle fibres surrounded by endomysium
fibres arranged into myofibrils, running parallel to each other and the length of the muscle fibre
myofibrils contain a chain of sarcomeres, which compose of actin and myosin filaments responsible for creating movement
Three types of connective tissue in the structure of a skeletal muscle
epimysium (surrounds skeletal muscle)
perimysium (surrounds fascicles)
endomysium (surrounds individual muscle fibres)
Define epimysium
connective tissue sheath surrounding each skeletal muscle
Define Perimysium
connective tissue surrounding each fascicle
define endomysium
connective tissue which surrounds each individual muscle fibre
fascicle
a bundle of skeletal muscle fibres surrounded by the perimysium
muscle fibre
a muscle cell composed of numerous myofibrils
myofibril
small, thread like strands that run through each muscle fibre
what is each myofibril made up of?
many sarcomeres joined end to end which are seperated by their Z-lines
Sarcomere
comprises the unit between the two Z lines and makes up the functional unit of a muscle fibre
Z lines
found at either end of sarcomeres
actin
the thin protein filament attached to the z line
myosin
the thick protein filament attached to the crossbridges
crossbridges
tiny projections on myosin filaments that attach on the actin filaments, pulling the actin filaments upon contraction
h zone
space between the actin filaments
Sliding filament theory steps
- Calcium released from the sarcoplasmic reticulum enters the sarcomere
- myosin is stimulated to reach for actin
- myosin attaches to actin filaments creating a crossbridge
- breakdown of ATP releases energy to actin filaments creating a crossbridge
- crossbridges/myosin pulls on actin
- sarcomere shortens as actin filaments move closer together
- z lime is pulled closer together, actin and myosin overlap causing I band and H zone disappear
- Calcium leaves the sarcomere
Three fibre types
Type 1
type 2a
type 2b
characteristics of type 2a (roman numerals)
- fast contraction speed
- moderate force of contraction
- moderate fatigue resistance
- generate greater force and more powerful contractions than slow twitch fibres because they are larger
- possess some aerobic characteristics e.g. moderate levels of myoglobin, mitochondria, and blood capillaries
- stimulated by relatively large motor neurons
- stimulated at a moderate frequency
- 800m athlete up to 70% fast twitch
characteristics of type 2b (roman numerals)
- rapid contraction speed
- high force of contraction
- fatigue very quickly
- high capacity for anaerobic ATP production
- possess high anaerobic characteristics such as high levels of glycogen, PCR, and glycolytic enzymes
- stimulated by very large motor neurons and at a high frequency
- sprinter up to 80% fast twitch
Type 1 slow twitch
- slow contraction speed
- low force of contraction
- high capacity for ATP production
- High fatigue resistance
- contracts repeatedly for continuous activity
- possess aerobic characteristics, e.g. myoglobin, mitochondria, blood capillaries
- stimulated by small motor neurons and at low frequency
- endurance cyclist up to 80% slow twitch
concentric contraction summary + example
high velocity = low force
slow velocity = high force
e.g. lifting heavy weight upwards slowly is easier
eccentric contraction summary + example
High velocity = high force
low velocity = low force
e.g. lowering heavy weights quickly is easier
