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Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
The Muscular System
part 2b
Muscle Physiology
Modified by S. Mendoza 1/2015
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Muscle Metabolism
 ATP is the ONLY energy source used to
power muscles
 Must be generated continuously
 Only 4-6 seconds worth of ATP is stored by
muscles
 After this initial time, other pathways
must be utilized to produce ATP
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.23
Instructions
• Please read the following slides carefully!
• You are responsible for filling in the chart
BUT also for knowing all the info already
typed into the chart.
• You need to be able compare/contract the 3
main pathways that the muscles have to
generate ATP
Direct Phosphorylation of CP
 Muscle cells contain creatine
phosphate (CP)
 CP is a high-energy
molecule found only in
muscle fibers
 After ATP is depleted, ADP is
left
 CP transfers energy to ADP,
to regenerate ATP
 CP supplies are exhausted in
about 15-20 seconds
 CREATINE
SUPPLEMENTATION
Figure 6.10a
Slide 6.24
Direct Phosphorylation
• Used for activities that require brief yet
massive power surges
• Weightlifting, sprinting, diving, etc.
• VERY fast since CP is already in the
muscle
• Very reversible SO is easily & quickly
replenished when muscles are inactive
Anaerobic Respiration
 Glycolysis with lactic
acid fermentation
 Reaction that breaks
down glucose without
oxygen
 Glucose is broken down
to pyruvic acid to
produce 2 ATP
 Pyruvic acid is
converted to lactic acid
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10b
Slide
Anaerobic Respiration
 This reaction is used for
activities that are more
sustained.
 Duration of energy
production is 30-60
seconds
 Activities become
less vigorous as the
O2 depletes and
anaerobic respiration
must be used.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10b
Slide
Anaerobic Respiration
 Anaerobic respiration is
2 ½ times faster that
aerobic respiration so
can be utilized quickly
by the muscle.
 BUT, it is very inefficient
- Huge amounts of
glucose are needed to
produce small amounts
of ATP
 Lactic acid produces
muscle fatigue
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10b
Slide
Aerobic Respiration
 Series of metabolic
pathways that occur in the
mitochondria
 Resting/slowly contracting
muscles use glucose or
fatty acids - Glucose is
broken down to carbon
dioxide and water,
releasing energy
 If these are not available –
amino acids may be used
but produce wastes that
can change body pH
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10c
Slide 6.25
Aerobic Respiration
• Glucose + oxygen are required produce 3638 ATP + carbon dioxide + water
• Duration of energy produced can be hours
• This type of energy production is used for
activities that require endurance rather than
power
– Jogging, marathon running, walking, etc
Summary
DONE WITH CHART – STUDY
THE INFO CONTAINED IN IT
Muscle Fatigue & Oxygen Debt
Cellular Respiration
• 3 main factors affect your
cellular respiration type:
–Your nutrition
–Your respiratory efficiency
–Your cardiovascular fitness
Aerobic Respiration
• Is the most efficient type of
respiration – producing the most
ATP per glucose molecule (36-38
ATP /1 glucose)
• It is slower and requires continuous
delivery of oxygen & nutrients to
the muscle
• Used for endurance activities
Anaerobic Respiration
•
•
Circulatory and respiratory system cannot
deliver oxygen as fast as muscles are
using it up.
leads to lactic acid buildup - when oxygen
is again available – lactic acid is converted
to pyruvic acid and oxidized
Anaerobic Respiration
•
For muscle to be restored to resting state:
• Oxygen stores must be replenished
• Lactic acid converted to pyruvic acid
• Glycogen stores replaced
• ATP & creatine phosphate reserves
replenished
• Liver must reconvert the lactic acid
produced to glucose or glycogen
• ALL of these processes require oxygen
Oxygen Debt
•
•
Oxygen debt is the extra amount of
oxygen that must be taken into the body to
provide for these restorative processes
Difference between amount of oxygen
needed for totally aerobic respiration
during muscle activity and the amount that
is actually used.
Oxygen Debt
•
•
All nonaerobic sources of ATP used
during muscle activity contribute to this
debt
Repaid by rapid, deep breathing (triggered
by change in pH from lactic acid) after
exertion is ended
Oxygen
• Breathing pure oxygen does not help to
repay this debt in the short term!
• Oxygen must have some time to get to the
muscles.
• There are limitations due to your
circulatory/cardiovascular system and your
respiratory system.
• Supplemental Oxygen
Efficiency of Oxygen Use
•
•
•
Athlete: ~10 % greater rate and efficiency
of oxygen use than normal person
Marathon runner: ~45 % greater
Working your muscles, heart, lungs, etc
out on a regular basis increases your
efficiency
–
Things like smoking, poor nutrition, too much
sugar, etc. decreases your efficiency
Physiological Fatigue
 When a muscle is fatigued, it is unable to
contract EVEN when stimulated
 The common reasons for muscle fatigue are:
 Lactic acid buildup
 Lack of oxygen in muscle
 Ionic imbalance
 Contractures will occur when no ATP is
available (no cross bridge detachment)
 Example: writer’s cramp
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.27
Psychological Fatigue
 Psychological fatigue is voluntarily
discontinuing activity when you start to
“feel tired”
 May be caused by a decrease in the
amount of available ATP
Types of fibers
• Force, velocity, and duration of muscle
contraction are affected by several factors.
• A main factor is fiber type
• Muscle fiber types (and ratios) are
genetically determined.
• Muscles are a mixture of fibers but different
muscles will have different ratios of types.
• Article: Fiber types in Mammalian Skeletal
Muscle
Fiber Types
There are now 4 types proposed as
indicated in article on previous slide.
White vs. Dark meat
MISCELLANEOUS
Developmental Aspects
• Muscular development reflects
neuromuscular coordination
• Due to the way neural pathways
are developed in your brain
• Pg 194 of Marieb book
Developmental Aspects
• Progresses superior to inferior
direction
– Baby can lift head before walking
• Progresses proximal to distal
– Baby can move arm before grasping
object
Men vs. women
•
•
•
Women’s skeletal muscles make up 36 %
of body weight
Men’s is 42 % due to effects of
testosterone
Muscle strength per unit mass is equal
MUSCLE STRENGTH, POWER,
& ENDURANCE
See pages 168-169 in G-W book
• Write the definitions of strength, power, &
endurance in your notes.
• Be able to calculate the Muscle force as
shown in Figure 5.13 when provided the
formula
• Read & follow the example calculation.
• Calculate the Fm in the “Now you try” last
paragraph – show all your work so you can
check your calculation! You will have to do
this on your test.
MUSCLE DISORDERS
Muscle Strain
• Factors that contribute to muscle strain are:
– Degree of stretch
– Speed of stretch
• Read about the grades of strains on pages
182-183 of G-W book
• Also fill in the basic information for
contusions, myositis ossificans, muscle
cramps, & DOMS
Disorders
Read about anabolic steroids on page
180 of Marieb book
Muscle Disorders
• Torticollis – a twisting of the neck which causes
rotation and tilting of the head to one side –
caused by injury to one of the sternocleidomastoid
muscles
• Pulled groin muscles – Strain or stretching of
adductor muscles (magnus, longus, brevis)
• Foot drop – paralysis of anterior muscles in lower
leg – caused by injury to the peroneal nerve
Torticollis
Muscle disorders
• Shin splints –
inflammation of the
anterior muscle group
of the lower leg (& the
periosteum they pull
on)– caused by trauma
or strain – usually felt
on the medial &/or
anterior borders of the
tibia
Duchenne Muscular Dystrophy
• Page 194
• Genetic – affects primarily males – X linked
trait
• Dystrophin protein not produced correctly –
leads to muscle fiber degeneration & atrophy
• Progresses from extremities upward
• Generally do not live beyond young adulthood
KNOW THIS: Muscle Disuse
• When a muscle is completely immobilized
from:
– Enforced bed rest
– Loss of neural stimulation
– Injury
• Degeneration and loss of muscle mass
begins
– Can decrease at a rate of 5% per day
KNOW THIS: Disuse Atrophy
• Flaccid
– Muscle loses tone and becomes soft and flabby
• Atrophy
– Loss of muscle mass
– Replaced by fibrous CT making muscle rehabilitation
impossible
– May be delayed by electrical stimulation
• When muscle is totally deprived of neural
stimulation:
– Paralyzed muscle may ultimately atrophy to ¼ of
original mass
Building Muscle Mass
•
•
•
•
Type of joint involved in motions
Direction of muscle fibers (contained in fascicle)
Anatomy of the muscle
Angles of body parts
• In order to work a muscle effectively & to
minimize risk of injury, the above factors must be
considered. Number of reps and amount of weight
depends on purpose of exercise (building vs.
toning).
•