Week 3 Physiology Flashcards
1
Q
Sarcomere
A
- Functional unit of striated muscle, unit of muscle contraction
- Made up of striations, nucleus, skeletal muscle
2
Q
Sarcomere molecular components
A
- M line
- Actin (thin) filament
- Myosin (thick) filament
- I band
- H band
3
Q
M line
A
Represents the middle of the sarcomere, does not move
4
Q
Actin (thin) filament
A
- Attached to the Z line and will move towards the M line with each contraction
- Made up of actin
- Has myosin binding sites where myosin heads can attach
Regulatory proteins: - Tropomyosin - long, thin protein that weaves around the actin filament, it covers the binding sites when the muscle is at rest - prevents actin from binding with myosin
- Troponin - blue molecule with three binding sites, separate ones for tropomyosin, actin, calcium ions
5
Q
Myosin (thick) filament
A
- Attached to the M line
- Made up of myosin
- Has a series of myosin heads that project at the end of the filament and myosin tails
- Have myosin-actin binding sites
6
Q
I band
A
Region that contains the actin filament
7
Q
H band
A
Region with myosin present, including where myosin overlaps actin
8
Q
Sliding filament theory
A
- Calcium channels on the sarcoplasmic reticulum (SR) open, calcium ions flow into the sarcoplasm
- Calcium ions bind to troponin, shifting tropomyosin away from the myosin binding sites on actin
- Myosin (thick filament) heads bind to actin (thin filament) forming cross bridges
- Myosin heads flex and perform power stroke, generating force and contracting a single sarcomere
- Myosin heads detach from actin and reset, ATP is utilised
- Cross bridge cycling continues (simultaneous contractions of sarcomeres shorten the entire muscle)
9
Q
Sources of energy in the form of ATP
A
ATP is stored in muscle cells and provides energy via three metabolic processes:
* Creatine-phosphate
* Anaerobic glycolysis
* Aerobic respiration
10
Q
Creatine-phosphate
A
- Easy and immediate source of ATP
- Doesn’t last very long (approximately 15 seconds)
- Used when producing energy quickly
- Relaxed muscle - ATP donates the phosphate to produce creatine phosphate
- Muscle contraction - ADP takes a phosphate from creatine to produce ATP
(Graph)
11
Q
Anaerobic glycolysis
A
- Anaerobic = no oxygen present
- Glycolysis = breakdown of glucose
- Uses glucose as energy source
- Longer duration (approximately a few minutes)
- Glucose sources - muscle glycogen, from blood
(Graph)
12
Q
Aerobic respiration
A
- Aerobic = oxygen present
- Respiration = breathing
- Uses oxygen to breakdown glucose, amino acids, and fatty acids to produce ATP
- Can last as long as there is access to nutrients and oxygen (several minutes to hours)
- Nutrients - Glucose, amino acids, fatty acids
- Byproducts - heat, 30-32 ATP, carbon dioxide, water
(Graph)
13
Q
Muscle contraction
A
- Each muscle comprises of a number of muscle fibres
- Not all muscle fibres within a whole muscle are activated at the same time during a contraction (some fibres will contract whilst others relax)
- Motor neurons control force contractions and the necessary changes
- Motor neurons send signals down the axon, branch along the muscle and each terminal supplies a muscle fibre
14
Q
How to vary the force production in each muscle fibre
A
- Frequency of stimulation
- Sarcomere length prior to contraction
15
Q
Twitch contaction
A
- The force of contraction in a single muscle fibre
- Once a muscle is stimulated it cannot stop without going through its contraction and relaxation period
- Graph measures changing force of contraction with different phases of a muscle contraction
