1. Muscle Anatomy

2. Learning goal I will understand the anatomy of a muscle fibre.
I will understand the components involved in muscle contraction.

3. a single muscle is defined as...a number of muscle fibres:
SKELETAL MUSCLE
a single muscle is defined as...a number of muscle fibres:
bound together by connective tissue and
usually linked to bone via …
Tendons!!

4. MUSCLE CELLS (FIBRES)

5. A single muscle is made up of many cells or fibres
diameter of fibres - varies btw mm and 0.1mm (NOTE: hair is about 0.15mm)
length of fibres - depends on length of muscle (e.g. bicep fibres = 15 cm)
cell organelles - because they are such big cells, they have multiple nuclei & because they use so much NRG, they have many mitochondria

6. Remember, each fibre is a CELL with it’s own set of organelles.

7. A muscle: from the outside in
connective tissue that covers the outside of a muscle: EPIMYSIUM
protects and reduces friction
connective tissue inside actual muscle: PERIMYSIUM
bounds groups of muscle fibres together
the groups of muscle fibres are called FIBRE BUNDLES (fascicle)
individual muscle fibres are surrounded by a sheath of connective tissue, called the ENDOMYSIUM
muscle fibre is an actual muscle cell: MYOFIBER

8. Video

9. Looking inward

10. Sarcolemma muscle cell membrane beneath the endomysium
contains the cell’s cytoplasm – SARCOPLASM
sarcoplasm contains large amounts of glycogen, protein myoglobin, high concentrations of Ca and mitochondria
MITOCHONDRIA – energy production site

11. Within a single MUSCLE FIBRE, are many MYOFIBRILS that run the length of the fibre (# per fibre varies greatly)

12. Each MYOFIBRIL is made up of 1000’s of SARCOMERES that attach end-to-end down the entire length of the MYOFIBRIL (i.e. think bands on a snake)

13. Inside these SARCOMERES are the actual proteins that are responsible for muscle contraction
ACTIN (thin filament) and MYOSIN (thick filament), stacked up on top of each other

15. there are many myosin & actin filaments stacked in both directions
INSIDE MYOFIBRILS...
Within 1 sarcomere,
there are many myosin & actin
filaments stacked in both
directions

16. During muscular contraction…the SARCOMERES are brought closer together (making muscle smaller) due to an overlap between ACTIN and MYOSIN

17. video

18. The sarcomere is often divided up into different zones to show how it behaves during muscle action.

19. Video The Z - line separates each sarcomere.
The H - Zone is the center of the sarcomere.
distance btw. the actin filaments within the same sarcomere (only myosin)

20. The M – Line is where adjacent myosin filaments anchor on to each other.
It is the midpoint of a sarcomere

21. The darker A - Bands are where myosin filaments align
The lighter I – Bands are where actin filaments align.
distance btw. the myosin filaments of 2 neighbouring sarcomeres (only actin)

22. When muscle contracts the H-zone and I-band both shorten as the z-lines are pulled towards each other.
In full contraction the H – zone can disappear.

23. Learning goal I will understand the anatomy of a muscle fibre.
I will understand the components involved in muscle contraction.