Topic 7: Muscles Flashcards
Tendon
Connects muscle to bone
Describe the structure of a skeletal muscle fibre
Long, thin
Surrounded by a sarcolemma (cell surface membrane)
Inside is sarcoplasm (cytoplasm) containing many shared nuclei,
many mitochondria and other cell organelles (ER, Golgi)
Many myofibrils run lengthwise through the cytoplasm
Myofibrils are composed of repeated contractile units called sarcomeres – they contain overlapping myofilaments - thin filaments contain actin, thick filaments contain myosin
Ligament
Connects bones to bones
Describe 2 structural differences between slow and fast twitch muscle fibres
- Fast twitch has fewer mitochondria than slow twitch
- Fast twitch has fewer capillaries that slow twitch
Thick filament
Myosin
Thin filament
Actin
H zone
Myosin only
A band
Actin & Myosin
I band
Actin only
Describe how the tertiary structure of myosin is related to its function (3)
- (part) folded into a specific shape with a globular head (1)
- that can bind to actin (1)
- (myosin) has a site that can bind with ATP (1)
State the importance of calcium ions in sliding filament theory
- Calcium ions bind to troponin
- Causing troponin to change shape/move
- This causes tropomyosin to move, exposing actin-myosin binding sites
- Allowing myosin head to bind
Describe what happens in rigor mortis, using sliding filament theory
- After death, ATP production stops
- In absence of ATP, the myosin heads remain attached to the actin (actin-myosin cross bridges remain intact)
- The muscle is unable to relax and remains rigid
Explain why too much exercise could be harmful to the human body (3)
▪︎ increases exercise results in increased wear and tear of joints/ligaments/tendons
▪︎ (therefore leading to) joint damage
▪︎ suppression of immune system
▪︎ (therefore leading to) increased risk of infection/contracting illness
Describe what happens to the energy that is not converted to useable energy in a muscle cell?
- Lost as heat
- Used to increase body temperature
