1. Applied Exercise Physiology
Muscles

2. Muscle structure muscle fibres Made up of bundles of
Each fibre contains
Inter-connected tubes –
muscle fibres
Myofibrils
Mitochondria
sarcoplasmic reticulum
Nuclei

3. Muscle fibres Simplest unit =
Contains two main proteins – thick filaments -
and thin filaments -
Slide over each other to cause contraction
sarcomere
myosin
actin

5. Muscle fibres Have pattern of light and dark bands Dark bands =
Light band =
Centre of A band =
Centre of I band =
Sarcomere =
A band
I band
H zone
Z line
Z line to Z line

7. Banding A band Myosin produces extends out from each Z line
Actin alone forms
Myosin without overlap of actin forms
A band
Actin
I band
H zone

9. Sliding-filament hypothesis
Nerve impulse arriving at
muscle fibre causes
that spreads through the muscle fibre's
network of
This causes the to
release
The binds to that is
present on the actin-containing thin
filaments of the myofibrils
(action potential)
wave of depolarisation
T-tubules
sarcoplasmic reticulum
calcium
calcium
Troponin

10. Role of Action Potential (AP) in muscle contraction

11. Structure of thin actin filament

12. Sliding-filament hypothesis
Troponin alters the shape of
Normally the blocks the
binding sites for on thin actin
filament
Once calcium binds to troponin and causes
shape change of troponin, the
moves, unblocking the
tropomyosin
tropomyosin
myosin
tropomyosin
binding sites

13. Sliding filament hypothesis
attaches to the newly uncovered binding sites on the thin actin filament
and are released – the changes shape
Thousands of molecules change shape at same time
This pulls the towards each other - shortening the and the I-band
Myosin
ADP
inorganic phosphate
myosin
myosin
Z-bands
sarcomere

15. Sliding-filament hypothesis
ATP binds to the and breaks down -
the is used to move the myosin into
the structure
These actions of myosin binding followed
by a shape change repeat as long as
is available and is present on thin
filament
myosin
energy
"cocked back"
ATP
calcium

17. Sliding-filament hypothesis
Action potential stops - calcium returns to
the
When no is left on the thin filament
moves back and blocks
binding sites again
stops binding to thin filament -
muscle contractions
sarcoplasmic reticulum
calcium
tropomyosin
Myosin
cease