Muscle Flashcards
What are the two types of striated muscle?
Skeletal and Cardiac
What are the characteristic features of skeletal muscle?
Multiple nuclei
Orderly arrangement of proteins
Nuclei bulge out
What are the characteristic features of cardiac muscle?
One nucleus per cell
Intercalated discs
Gap junctions
What is meant by hypertrophy?
Muscle fibres taking on more protein (actin and myosin) and so bulking up in appearance.
What structure attaches muscle to bone?
Tendon
What type of cells are used to replace skeletal muscle after an injury?
Satellite cells
What two process help skeletal muscle to recover after injury?
- Satellite cells migrating to point of injury to differentiate into new muscle cells
- Hypertrophy of nearby muscle fibres to help take on the load.
NB: The actual damaged skeletal muscle fibres will never recover.
What changes occur to the appearance of the sarcomere when a muscle contracts?
I band reduces in width
H band reduces in width
(A band remains unchanged)
Describe the sliding filament theory of muscle contraction.
Myosin heads bind to binding sites on actin filaments
On contraction, myosin heads flip, causing actin to change arrangement
Actin filaments slide over myosin filaments, moving closer to the M line- Power Stroke
What molecules block actin binding sites and how do they work?
Tropomyosin partially blocks the binding sites and troponin holds it in place via cooperative blocking?
What is required to unblock binding sites blocked by tropomyosin?
Calcium- Binds to troponin causing it to alter shape, pulling tropomyosin away and exposing binding site.
What is the role of the sarcoplasmic reticulum?
Storage of Calcium ions
What is the role of the transverse tubules in muscle fibres?
To allow conduction of signal deep into the muscle tissue
What makes up a motor unit?
Muscle fibre and motor neuron
What is the difference between an isometric and an isotonic muscle contractions?
Isometric contraction involves no change in muscle length.
Isotonic contraction involves muscle shortening
How is a twitch contraction generated?
A single action potential applied to a muscle fibre
What are the two roles of ATP in muscle action?
- ATP used to separate myosin heads from actin binding sites, allowing a new cross- bridge cycle to begin.
- ATP used to pump Calcium ions back into the sarcoplasmic reticulum, allowing contraction to end.
How does fatigue occur due to high intensity/ short duration exercise?
- Depolarisation and subsequent conduction failure due to increased [K+]
- Increased [Lactic Acid] as waste product, acidifying proteins
- [ADP + Pi] too high to allow myosin detachment from actin binding sites
What are the two qualities which skeletal muscle fibres are characterised based on?
Fast/ Slow
Oxidative/ Glycolytic
What quality of muscle fibres makes the ‘fast’ or ‘slow’?
ATPase activity
What are the differences between oxidative and glycolytic muscle fibres?
Oxidative has high mitochondrial activity for oxidative phosphorylation. Glycolytic has low mitochondrial activity.
Oxidative has narrow diameter. Glycolytic has large diameters.
Oxidative has high vascularisation. Glycolytic has low vascularisation.
Oxidative has myoglobin. Glycolytic has glycogen and glycolytic enzymes.
Oxidative fibres are typically red. Glycolytic fibres are typically white.
What 3 types of skeletal muscle fibres exist?
Slow Oxidative- Resist Fatigue
Fast Oxidative- Mild Fatigue
Fast Glycolytic- Fatigue quickly
What nervous system innervates smooth muscle?
Autonomic
How does smooth muscle contract?
Calcium binds to Calmodluin
Calcium-Calmodulin binds to Myosin Light Chain Kinase
This phosphorylates myosin Cross bridges using ATP
Cross bridges can then bind to Actin sites
