Isfahan University of Technology
Advance Physiology
(part 4)
By: A. Riasi
(PhD in Animal Nutrition & Physiology)
Muscle physiology

Three muscle types are structurally and functionally
distinct.

The muscle can be classified in two different ways:

Striated or unstraited muscles

Voluntary or involuntary muscles
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle

In this section we turn our attention to the following
topics:

How does cross-bridge interaction between actin and
myosin bring about muscle contractions?

How does a muscle action potential trigger this contractile
process?

What is the source of Ca++ that physically repositions
troponin and tropomyosin to permit cross-bridge binding?
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
 Acetylcholine

(ACh) as neuro-transmiter
Transverse tubule (T tubule)
 Action
potential reach the central portion of the fiber
Skeletal Muscle
Figure 3.25b
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle
Skeletal Muscle

Three pathway supply additional ATP as needed
during muscle contraction:
1. Transfer from a high energy phosphate from a phosphagen
(creatine phosphate and arginine phospahte) to ADP.
2. Oxidative phosphorylation (the citric acid cycle and
electron transport system)
3. Glycolysis
Skeletal Muscle
Skeletal Muscle
The phosphagens contain a high-energy phosphate
group.


Energy and phosphate from ATP can be transferred
to creatine or arginine to form the phosphate.
Creatine phosphate + ADP
Creatine + ATP
Skeletal Muscle
There are cardiovascular limits to the amount of O2
that can be delivered to muscle.
In this situation the muscle fibers rely increasingly on
glycolysis. It has two advantages:
1- Glycolysis can form ATP in absence of O2
2- It can proceed much more rapidly than oxidative
phosphorylation because fewer steps.
Skeletal Muscle
There is a disadvantage of the low efficiency of
glycolysis (2 ATP vs 36 ATP in oxidative phosphorylation).
The end product of anarobic glycolysis is pyruvic acid
that is converted to lactic acid.
Lactic acis leads to acidosis and is believed to play a
role in the onset of muscle fatigue.
Skeletal Muscle
What are the reasons of muscle fatigue?
1. A local increase in inorganic phosphate resulting from the
breakdown of phosphagens;
2. Accumulation of lactic acid, which (via release of H+) may
inhibit key enzymes in the energy-producing pathways or
the excitation contraction coupling process;
3. Depletion of energy reserves.