Muscle Physiology

1
Muscle Physiology
2
Muscle Tissue Types
pg. 390
What do all muscle tissues have in common in
terms of their structure and function?
Figure 12-1 Three types of muscles
3
Skeletal Muscle Anatomy
pg. 392
What changes (in structure and function) would
occur in this muscle with anaerobic training?
Can you explain why? See also the concept map on
pg. 392
Figure 12-3a-1 ANATOMY SUMMARY Skeletal Muscle
4
Skeletal Muscle Fiber Structure
Pg. 393
Figure 12-3b ANATOMY SUMMARY Skeletal Muscle
5
Muscle Fiber Structure
Pg. 394
Figure 12-4 T-tubules and the sarcoplasmic
reticulum
6
Myofibrils Site of Contraction
Pg. 393
What are the functions of Troponin and
Tropomyosin? What is myosin ATPase?
Figure 12-3c-f ANATOMY SUMMARY Skeletal Muscle
7
The Functional Unit of Contraction the Sarcomere
Pg. 395
A single power stroke of myosin cross bridges
shortens the muscle cell by only _at_ 1. Why isnt
muscle contraction jerky? Muscles may shorten
up to _at_ 70 of their resting length! Does tension
produced in a muscle cell vary with cell length
during contraction?
Figure 12-5 The two- and three-dimensional
organization of a sarcomere
8
Skeletal Muscle Contraction Mechanism
Pg. 400
Is the DHP receptor sensitive to voltage,
mechanical change, or a ligand?
These figures are also included in your packet,
on page 121.
Figure 12-11a Excitation-contraction coupling
9
Skeletal Muscle Contraction Mechanism
Figure 12-11b Excitation-contraction coupling
10
Contraction Sequence Sliding Filament Theory
Pg. 398
1. This stage is very short-lived.
See also pp. 119-120 in your packet.
2. In other words, a molecule of ATP must bind
to the myosin head in order for it to be locked
and loaded, ready to interact with actin.
Figure 12-9 (steps 1 2) The molecular basis of
contraction
11
Contraction Sequence Sliding Filament Theory
4. Hydrolysis of ATP results in the binding of
the myosin head to the actin filament, but no
movement has occurred yet.
Figure 12-9 (steps 3 4) The molecular basis of
contraction
12
Contraction Sequence Sliding Filament Theory
Of all the energy consumed during muscle
contraction, only _at_ 25 is realized as external
work (i.e. 75 is lost as heat!). Briefly
describe at least 3 processes that require ATP
in the muscle contraction/relaxation mechanism.
6. The end.
5. The release of the phosphate group causes a
conformational change in myosin, pulling the
actin toward the center of the sarcomere.
Figure 12-9 (steps 5 6) The molecular basis of
contraction
13
Energy for Contraction ATP Phosphocreatine
Pg. 401

• Aerobic Respiration
• Oxygen
• Glucose
• Fatty acids
• 30-32 ATPs
• Anaerobic Respiration
• Fast power (but)
• 2 ATP/glucose
• Phosphocreatine (CrP) ?ATP

What is oxygen debt? How does a cell repay its
oxygen debt?
14
Energy for Contraction ATP Phosphocreatine
Pg. 402
This process is referred to as the phosphagen
system. Explain why. What does a kinase do?
How does it apply in this case?
Figure 12-13 Phosphocreatine
15
Cellular Energy Stores in Human Muscle
See page 124 in your course packet.
16
Muscle Power (ATP production) and Different
Substrates
How is it possible that you get more power
(ATP/min) with fermentation, when a cell produces
only 2 ATP per molecule of glucose by this
metabolic pathway?
17
Substrate usage as a function of exercise
intensity and duration
18
Oxygen Consumption and Work
O2 consumption increases 23X!
Explain the changes (or lack there of) in these
organs.
19
Overview Muscle Cell Metabolism
20
Muscle Fiber Types
Pg. 405
Figure 12-15 Fast-twitch glycolytic and
slow-twitch muscle fibers
Would all of the muscle cells in a motor unit be
of the same type, or would a motor neuron
innervate a mix of fiber types?
21
Muscle Fiber Types (1 of 3)
See also Table 12-2 pg. 122 in your packet

• Red (slow) fibers
• (Type I)
• small cells
• many mitochondria
• reduced SR
• many capillaries
• high aerobic rate
• high myoglobin level
• low glycolytic rate
• low buffer level
• small glycogen store
• slow myosin ATPase
• slow rate of contraction

a.k.a. Slow Oxidative 1/4 to 1/3 as large as
white fibers for light moderate work over
prolonged periods of time Why are red fibers
more resistant to fatigue? How do you think the
size of these motor units compare with those
consisting of white fibers? Why?
22
Muscle Fiber Types (2 of 3)

• Intermediate fibers
• (Type IIa)
• intermediate size
• many mitochondria
• intermediate size ER
• many capillaries
• high aerobic rate
• high myoglobin level
• high glycolytic rate
• intermediate buffer level
• inter. glycogen store
• fast myosin ATPase
• fast rate of contraction

• a.k.a. Fast Oxidative
• High capacities for both aerobic and anaerobic
  metabolsim
• How does more actin and myosin relate to tension
  production in a muscle cell?

23
Muscle Fiber Types (3 of 3)

• White (fast) fibers
• (Type IIb)
• very large cells
• few mitochondria
• well developed SR
• few capillaries
• low myoglobin levels
• low aerobic rate
• high glycolytic rate
• high buffer levels
• large glycogen stores
• fast myosin ATPase
• fast rate of contraction

• a.k.a. Fast Glycolytic
• fatigue quickly
• only energy source
• 2-4 X more power!
• Short bursts of intense work with prolonged
  periods of recovery may be called upon when red
  fibers fatigue
• Why cant white fibers convert to red fibers
  easily?

24
Voluntary Muscle Movement

• Describe the three levels of direct control
  over motor neurons that innervate skeletal
  muscles
• Spinal reflexes
• Cortical (pyramidal) pathways
• Subcortical (extrapyramidal pathways)
• Relate this information to the GPSP at these
  motor neurons.

a.k.a. pyramidal pathway
25
Muscle Proprioceptors
See also pg. 123 in your packet
26
Skeletal Muscle Reflex Sensory Receptors
Proprioceptors
Pg. 432
What part of the CNS do these receptors send
information to, regarding position or a change in
position?
Figure 13-3 Sensory receptors in muscle
27
Tonic Activity of the Muscle Spindle (producing
muscle tone in a muscle at rest)
The sensitivity of the muscle spindle depends on?
Pg. 433
List the other inputs to the alpha motor neuron.
28
Muscle Spindle Function in the Stretch Reflex
Pg. 433
Does this reflex change the length of the muscle?
Explain.
29
Coactivation of Alpha and Gamma Motor Neurons
Pg. 434
What would happen to the firing rate of the
primary afferent neuron if the gamma motor neuron
was not functioning?
30
Pyramidal and Extrapyramidal Tracts
Pg. 125 in packet
31
Golgi Tendon Reflex
Pg. 435
32
Preventing Overcontraction
Pg. 126 in packet
33
Integration of Muscle Reflexes