Skeletal, Smooth and Cardiac Muscle Flashcards
What are the three types of skeletal muscle fibres ?
I: Slow Oxidative (Resist Fatigue)
IIa: Fast Oxidative (Intermediate resistance to fatigue)
IIb: Fast Glycolytic (Fatigue quickly)
What are four properties of Oxidative muscle fibres ?
High amount of mitochondria
High in oxidative phosphorylation
Contain Myoglobin
Red
What are four properties of Glycolytic muscle fibres ?
Low amount of mitochondria
High in glycolytic enzymes and glycogen
Lower blood supply
White fibres with longer diameter
Describe the structure of skeletal muscle
Striated
Muscle fibre containing many myofibrils
Bundle of fibres encased in connective tissue sheaths
Myofibril has a central sarcomere which conatins myosin and actin filaments
Explain the mechanics of skeletal muscle contraction
1: Ca is released from the sarcoplasmic reticulum
2: Ca binds to the troponin on the thin filaments
3: This causes a conformational change on the trypomyosin which allows new binds sites to be uncovered allowing more Ca to bind.
4: Cross bridge moves
What is occurring in the myosin head of the cross bridge thick filament ?
1: ATP binds to myosin head - limb moves away from actin.
2: ATP hydrolyses to ADP and Pi - Releases energy
3: ADP released
Define Isomentric twitches
A muscle contracts with no resulting movement
Define Isotonic twicthes
Concentric: Muscle shortens when contracts
Eccentric: Muscle contracts as muscle lengthens
What length changes and zone changes occur when a skeletal muscle contracts ?
The size of the H zone (space between filaments) is reduced.
The I band (space between ends of thick filaments) is reduced also.
The A zone is unchanged.
What is a motor unit ?
Motor neurons and muscle fibres
Define the tension of a muscle
Force exerted by a muscle
Define the load of a muscle
Force exerted on a muscle
How does a muscle twitch occur ?
Single AP + Muscle fibre = Twitch
What is the latent period ?
Time before excitation contraction starts
What is the contraction time ?
Occurs between the start of tension and peak tension
What kind of contractions have a shorter latent period but a longer contraction event ?
Isometric contractions
What is occurring during a tetanic contraction ?
They are greater than twitch as the Ca never runs low enough for the typomyosin to re-block troponin binding sites
What is the length-tension relationship ?
Less overlap of filaments = less tension
Define optimal length (Io)
Muscle length for greatest isometric tension
Define fatigue
Repeated muscle stimulation generates muscle fatigue which prevents the muscle from using up cats amounts of ATP/
What are Type II muscle fibres and what are their properties ?
Fast twitch muscle fibres.
Use anaerobic respiration.
Less reliant on Oxygen which allows for quick generation of ATP.
What are type I muscle fibres and what are their properties ?
Slow twitch muscle fibres.
Use aerobic respiration.
Which allows them to generates large amounts of ATP slowly.
The type I muscle contractions are also less likely to fatigue
Describe the structure and functions of smooth muscle
No striations
Innervated by ANS
Exist in hollow organs
Thick and thin filaments
How are the thick and thin filaments arranged in smooth muscles ?
Arranged diagonally across cells and anchored to membranes. They still slide to contract the muscle.
How does a contraction occur in smooth muscle ?
1: Ca is released
2: Ca binds to calmodulin
3: Ca + Calmodulin activates MLCK
4: MLCK adds phosphate to myosinactivating the myosin
5: X-bridge cycle starts
