Download Monday Oct

19 October 2011
This Week in Physiology:
Lab: Visual System Part 2,
Somatosensory Data Collection
Vestibulocochlear system PPT
Lectures: Ch. 9 Muscle Physiology
Next Week in Physiology:
Lab: Frog muscle physiology
Lectures: Ch. 10 Control of Body
Movement
Abstracts due Friday
Instructions on Website!
About midterm grades…..
About Take Home portion of Test 1
1QQ # 19
Write a question that you were prepared to
answer today and provide the answer to that
question.
A more challenging/sophisticated/thoughtprovoking question with its correct answer
earns more points than a simple
memorization-type question.
S1
Muscle kinetics
Link to cytosolic calcium
concentration, release, and
reuptake?
S2
Fig. 09.16
S3
Fig. 09.20
Why does this plateau?
So….. Tension produced by a single myofiber varies depending on frequency of Action Potentials.
S4
Muscle Metabolism
• Classification of Myofiber types
– Speed of myosin ATPase
– Metabolic sources of ATP
– Fatigability
S5
Classes of Myofibers based on Twitch Duration
Each muscle fiber express only one of two
different myosins isozymes:
• Fast twitch = rapid hydrolysis of ATP means
crossbridges cycle faster
• Slow twitch = slower hydrolysis, isozyme
catalyzes the reaction slower
Myosin isozymes not modified by athletic training!
S6
Classes of Myofibers based on
Metabolic and Enzyme profiles
• Oxidative: at peak activity rely on full aerobic
cellular respiration
– many mitochondria, enzymes for oxidative
phosphorylation, numerous capillaries, lots of
myoglobin (red)
• Glycolytic: at peak activity rely on glycolysis
– few mitochondria, many glycolytic enzymes, large
store of glycogen, fewer capillaries, little
myoglobin (white)
Metabolic profiles CAN BE modified by athletic training!
S7
3 Sources of ATP in muscle
Powerstroking &
Disconnecting crossbridges
Creatine phosphate, then oxidative phosphorylation (OP) from
glycogen, then OP from blood glucose, then blood fatty acids. If
intense, switch to glycolysis… then take a breather… oxygen debt
S8
A 1998 Review on the
Use of Creatine as a
Nutritional Supplement
S9
Type I
Type II A
Fig. 09.03
Type II B
S 10
S 11
Type I
What are the causes of
fatigue?
Type IIA
Depends on the type of
activity…
Type IIB
S 12
Causes of fatigue
• High intensity, short duration exercise
– Conduction failure in t-tubules
– Lactic acid accumulation
– Accumulation of ADP and inorganic phosphate
• Low intensity, long duration exercise
–
–
–
–
As above, and
Depletion of muscle glycogen
Low plasma glucose (hypoglycemia)
Dehydration
• Control pathways: “willpower”
– Common in couch potatoes
S 13
So what are the ways a muscle
(consisting of many myofibers)
increases tension?
S 14
Fig. 09.13
Motor unit = a single somatic motor neuron
and all the muscle fibers in innervates
S 15
But each motor unit
has myofibers of the
same type: I or IIA or
IIB.
S 16
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
– Level of fatigue (state of activity)
S 17
Fig. 09.26
Relationship between
recruitment and
motor unit type
The Size Principle
Size of somatic
motoneuron cell
body