Lecture 11: Muscle - Structure & Function Flashcards
What’re the three different types of muscle?
- Skeletal, Smooth, and Cardiac
What are the functions of skeletal muscle?
- Movement
- Heat production
- Posture (maintaining posture for long periods of time)
- Communication (diaphragm needs to contract in a certain way to make sounds)
What happens when we want to conserve heat?
- We shiver
What does myo / sarco mean?
- Muscle (in Latin & Greek)
Transverse leg picture includes:
- Fascia, Fat, Skin, Blood Vessels, Nerves, Muscles
How is connective tissue arranged?
- Epimysium → Fascicle → Covered in perimysium → Muscle Fibre → Wrapped by endomysium
How is muscle tissue arranged?
- Muscle Fibre → Sarcoplasmic Reticulum → T Tubule → Myofibrils → Myofilaments (in sarcomere)
How big is a skeletal muscle fibre?
- Up to 40cm, parallel, cylindrical, multi-nuclear
What does a skeletal muscle fibre look like?
- Striated, protein arrangement
Myofilaments are made of…
- Thick and thin proteins
The thin filaments attached to the sarcomere are made up of…
- Mostly Actin (Some Troponin, and Tropomyosin)
The thick filaments are made up of…
- Myosin heads
What is the sarcolemma?
- Phospholipid bilayer (membrane)
What triggers muscle contraction?
- Calcium
What is a sarcomere?
- A contractile unit
- End-on-end along myofibril length
How big is a sarcomere?
- 2 micrometers
How does a muscle actually contract?
- Thin draws towards each other over thick
- Z lines move closer together
- Individual lengths stay the same
- Energy is consumed
- Calcium is essential
If you want a large ROM do you want long or short muscle cells?
- Long
- Means it can shorten more
What determines thickness of muscle?
- Number of muscle fibres
- Greater number of fibres = greater CSA
- And tension
Why is the angled arrangement of muscle fibres important?
- More tension is developed
- Because there are more fibres in a smaller space
- Not so great ROM
Are relaxed muscles active?
- Slightly
How’re we maintaining posture?
- Nerve impulses go down from spinal chord and activate muscle fibres
- No movement produced but keeps muscles firm and healthy
- Helps stabilize joints and maintain posture
