Transcript Monday Oct

24 October 2011
This Week in Physiology:
Lab: Frog Muscle Physiology
Lectures: Ch. 9 Muscle Physiology
Ch. 10 Control of Body Movement
Next Week in Physiology:
Lab: Human muscle physiology
Abstracts due Monday
Instructions on Website!
Download JMP from on-campus
About midterm grades…..
1QQ # 20 for 8:30 section
Answer one question.
1. Which are characteristics of Slow-Oxidative myofibers?
a) Abundant capillaries nearby
b) ATP is hydrolyzed relatively quickly
c) Abundant glycogen
d) Abundant myoglobin
e) Belong to large motor units.
2. Name the three classes of skeletal myofibers and indicate which type is
best suited to serve as a postural muscle and why.
1QQ # 20 for 9:30 section
Answer one question.
1. Which are characteristics of glycolytic myofibers?
a) Abundant capillaries nearby
b) ATP is hydrolyzed relatively quickly
c) Abundant glycogen
d) Abundant myoglobin
e) Belong to large motor units.
2. Would a marathon runner benefit from supplementing with
creatine? Why or why not?
S1
So what are the ways a muscle
(consisting of many myofibers)
increases tension?
S2
Fig. 09.13
Motor unit = a single somatic motor neuron
and all the muscle fibers in innervates
S3
But each motor unit
has myofibers of the
same type: I or IIA or
IIB.
S4
Increasing tension in a whole muscle
• Frequency of stimulation of motor neuron
• Activate larger motor units
• Recruitment: activate more motor units
• These factors also influence actual tension
– Fiber length (length-tension) relationship
– Fiber diameter (number of cross bridges)
– Level of fatigue (state of activity)
S5
Fig. 09.26
Relationship between
recruitment and
motor unit type
The Size Principle
Size of somatic
motoneuron cell
body
Types of
Contractions
S6
Isotonic =
Same tension
Isometric =
Same length
Aka Lengthening contraction
S7
Response to training
• Resistance training
Type II change enzyme profiles: II A to II B
Type II add more actin and myosin
Type II increase cross-sectional area (hypertrophy)
• Endurance training
– Type I increases vascularity
– Type I increase number of mitochondria
S8
Read section of
King et al., 1999
that deals with
analysis of muscle
biopsy material in
subjects taking
Andro or placebo
while resistance
training.
What changes
were expected?
What changes
were observed?
Fig. 09.24b
S9
Consider blood flow to skeletal muscles during isometric contractions.
Consider blood pressure during isometric contractions.
The benefits of using trekking poles?
S 10
Chapter 9 B Properties of
Smooth Muscle
How does smooth muscle differ from skeletal muscle?
(innervation, membrane potentials, excitation-contraction coupling, twitch
duration, fatigue, etc. (Table 9-6 p.287)
What are the features of membrane potential of smooth muscle?
(pacemakers and slow waves)
What are the differences between single-unit and multi-unit smooth muscle?
(location, spread of excitation)
Who cares about smooth muscles?
S 11
Excitation-contraction coupling in Smooth Muscles
Figure 9.34
from SR and influx during Action Potential or graded potential
Ca++
Graded potentials
result in graded
contractions
Slow twitch of SM
due to slow action
of myosin ATPase.
Lack troponin
Special situation:
Dephosphorylation &
latch bridge
S 12
Comparison of Twitch Duration
Latchbridge =latch state
Thankful for latch state!
Crucial for long-term tension of
sphincters.
S 13
Comparison of Single-Unit and
Multi-Unit Smooth Muscles
Slow waves and pacemaker potentials
Intestinal tract, uterus, small diameter blood vessels
Large airways of lungs, large arteries, ciliary muscle
Often with pacemaker cells
Control of membrane potential by neurotransmitters, hormones, local factors
for some smooth muscles (02, NO, pH, stretch, vasodilators ….)
S 14
Cardiac
Myofibers
Intercalated Discs: mechanical attachments of cardiac myofibers to
each other, with gap junctions (electrical synapses) to conduct AP
Analogy: Falling dominoes
S 15
Plateau phase
S 16
Why no tetanic contractions of cardiac muscle?
S 17
Figure 12.17
ExcitationContraction
Coupling
Calcium-induced calcium release
What ends the twitch?
Ca++ channels blockers:
•How and where do they work?
•When are they used?
S 18
this table p. 287
Fig.Know
09.06