MUSCULAR SYSTEM (muscles, tendons)

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Ch. 6 The Muscular System
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Case Study Investigation
You are selected for an internship at the
National Space Biomedical Research Institute in
Houston, Texas. Part of your job is to monitor
the health of the astronauts for the National
Aeronautics and Space Administration (NASA)
before, during, and after a space mission. By
chance, your time in the lab corresponds with the
return of an American astronaut from the
International Space Station. She just spent 171
days in the space station and is now getting back
to her research studies on earth. Unfortunately,
it was discovered that she would have to go
through at least 3 weeks of physical therapy.
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You learned from reading her physical health
report that she lost 30 of her skeletal muscle
mass. Most of it occurred within the last 2
months of the mission in space. The normal
muscle loss during a space mission is less than
20. A majority of muscle atrophy results from
disuse, yet she followed all the exercise
programs NASA requires. Your job is to assist
the research team in investigating her problem.
By the end of this chapter, you will
be asked to determine the most likely cause
of her accelerated loss of muscle mass.
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Applied Learning Outcomes

• Use the terminology associated with the
  musculature system
• Learn about the following
• Different types of muscle cells
• Muscle tissue development
• Gross and fine muscle structure
• Gross muscle function
• Muscle cell physiology
• Muscle types and actions
• Muscle development and growth
• Understand the aging and pathology of the
  musculature

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Overview
Muscle cells change their shape by shortening or
contracting. They are composed of specialized
contractile cells. Over half the bodys mass is
composed of muscle tissue, and over 90 of this
muscle tissue is involved in skeletal
movement. Muscles require glucose, oxygen,
calcium and electrolytes and release metabolic
wastes.
Chapter 6 The Muscular System
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Muscle
Three types of muscle are found in the human
body a) Cardiac muscle (slightly striated
involuntary b) Skeletal muscle
(striated voluntary) c) Smooth muscle
(non-striated involuntary)

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Skeletal Muscle Function 1. Skeletal
Movements pulling on bone (relaxation /
contraction)
Prime mover muscle responsible for the movement
Synergist muscles that help the prime mover
Antagonist muscle that produces the opposite
movement as prime mover
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2. Posture / Muscle Tone balance weight
distribution and hold muscles in
position a. tonic
contraction
only a few
muscles
contract at a time
NO shortening and NO movement
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• Regulate Organ Volume
• a. sphincters bands of smooth muscle that
  prevent outflow of fluids from hollow organs

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• Move substances within the body
• a. cardiac muscle pumps blood
• smooth muscle moves food through digestive sys.
  (peristalsis)

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• Heat Production when muscles contract they
  produce heat
• Hypothermia decrease in
• body temp below normal
• b. Hyperthermia increase in
• body temp above normal

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raises eyebrow
closes jaw
closes eyes
smile muscle
closes jaw
closes lips
yes/no muscle
extends head / neck
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Muscles of the Trunk
deltoid
adducts arm
abducts arm
adducts upper arm
flex trunk
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MUSCLES of the ARM
flexes elbow
extends elbow
flexes forearm pronates supinates
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flexes thigh lower leg
(middle quadricep)
Quadriceps extend the leg
(lateral quadricep)
(medial quadricep)
Vastus intermedius
(inner quadricep)
plantar-flexes ankles
dorsi-flexes ankles
plantar-flexes ankles
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extends thigh
Hamstrings flex the leg
adducts thigh
(lateral hamstring
(middle hamstring)
(medial hamistring)
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1. Origin stationary bone the muscle attaches
to (zygomatic arch)
MusculatureGross Anatomy
2. Body rest of the muscle (masseter)
3. Insertion moveable bone the muscle attaches
to (mandible)
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Origin Scapula / Humerus
Sacs of synovial fluid btwn tendon bone for
lubrication
Body Biceps Brachii
Insertion Radius
Tendon attachs muscle to bone
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Concept Check 1

• What are muscles composed of that allow them to
  do their jobs?
• specialized contractile cells
• 2. What are 5 functions of the muscular system.
• 1- movement 2- posture 3- regulate organ
  volume
• 4 move substances w/I body 4-
  heat production
• 3. How are the prime mover, synergist, and
  antagonist involved in movement? If I were to
  flex my elbow what muscles would represent the
  PM, S, and A?
• Prime mover main muscle responsible for
  movement (bicep)
• Synergist other muscles that help PM
  (brachioradialis)
• Anatogonist produces opposite movement (tricep)
• 4. What is a tonic contraction and give an
  example of one.
• No movement and no shortening of a muscle
• Ex. pulling up on something heavy

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Concept Check 2
5. How do sphincters regulate organ
volume? Smooth muscle prevents fluid from
flowing out of a hollow cavity 6. Give an
example of how cardiac and smooth muscle move
substances within the body. Cardiac muscle
pumps blood throughout the body Smooth muscle
moves food throughout the body (peristalsis) 7.
How does the origin and insertion of a muscle
differ? How are they involved in muscle
movement? Origin immovable bone that muscle
attaches to Insertion movable bone that muscle
attaches to The insertion bone moves towards the
origin bone 8. Research the origin and insertion
for the following muscles Gastrocnemius
Origin femur Insertion achilles
tendon Pectoralis major Origin clavicle
/sternum Insertion humerus
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Skeletal Muscle Structure
surrounds fassicles
surrounds each
surrounds entire muscle
bundle of muscle cells
http//www.wisc-online.com/objects/ViewObject.aspx
?IDAP13904 Muscle Structure Animation
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Microcopic Muscle Cell Structure

• skeletal muscle cells are LONG, CYLINDRICAL
  cells covered with an excitable membrane called
  the sarcolemma
• sarcolemma contains proteins that respond to
  signals from other cells/environment and
  transmits the information to the muscle cells
  causing them contract

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• contractile unit of muscle is called a sarcomere
  (thousands run the length of a muscle cell)
• chains of sarcomeres form myofibrils
• sarcomere contains
• 2 types of myofilaments
• 1. thick m.f.? contain
• protein myosin
• 2. thin m.f. ? contain
• proteins actin,
• tropomyosin
• troponin
• sarcoplasmic reticulum
• surrounds sarcomeres

Sarcomere
marks boundaries between sarcomeres
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Sarcomere Chain
http//highered.mcgraw-hill.com/sites/0072437316/s
tudent_view0/chapter42/animations.html
Actin (thin)
Myosin (thick)
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Muscle Cell Function

• contraction occurs when sarcomeres shorten
  simultaneously
• Nerve Stimulation takes place at the
  neuromuscular junction (motor neuron meets muscle
  fiber)
• Ca causes nerve cell to release acetylcholine, a
  neurotransmitter, which binds to sarcolemma and
  allows Na /K to cross membrane

http//www.galaxygoo.org/biochem/neuro/nmj_flash.h
tml (basic neuromuscular junction animation)
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• Muscle Contraction takes place inside muscle
  cell
• ion movement causes SR releases Ca which travels
  to sarcomere to start contraction
• Ca binds to troponin removes tropomyosin (
  blocks myosin heads from attaching to actin)
• Myosin attaches pulls on actin ? shortens
  sarcomere ? shortens muscle
  Sliding filament theory animation

http//science.howstuffworks.com/environmental/lif
e/human-biology/muscle2.htm
http//highered.mcgraw-hill.com/sites/0072495855/s
tudent_view0/chapter10/animation__action_potential
s_and_muscle_contraction.html
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Rigor Mortis ? muscle tension caused by Ca
leakage out of SR into sarcomere after
death Creatine phosphate, glycogen, myoglobin
? all serve as energy or oxygen reserves for
muscle contraction
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• Muscle Relaxation when neural stimulations stop
  exciting the sarcolemma
• Na/K levels are completely recovered SR
  regains most Ca
• troponin/tropomyosin covers binding site ? myosin
  releases actin ? sarcomere relaxes ? muscle
  elongates

Sliding Filament Model
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Types of Skeletal Muscle Fibers

• unique muscle composition is genetically
  determined
• https//www.23andme.com/health/Muscle-Performance/
  

Feature Slow Red Twitch Fibers (Type I) Fast White Twitch Fibers (Type IIb)
Size Smallest largest
Mitochondria large amount (get ATP through aerobic processes) small amount (get ATP through anaerobic processes)
Color red (high myoglobin content) white (low myoglobin content)
Speed of Contractions Slow Fast
Resistance to Fatigue High (very fatigue resistant) Low (not fatigue resistant)
Activities Maintaining posture, endurance activities (i.e. marathon runners) Muscle soleus Rapid, intense movements of short duraction (i.e. sprinters, throwing a ball or weight lifting) Muscle gastrocnemius / vastus lateralis
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Concept Check 3

• 9. List the three membranes of muscle in order
  from superficial to deep then explain how they
  each differ.
• 10. What is the name given to the membrane that
  surrounds a muscle cell and why is it important?
• What is a sarcomere? And how do the 2
  myofilaments that make up a sarcomere differ?
• 12. Draw a picture of a sarcomere and label the
  two different myofilaments.

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Concept Check 4

• 13. Why is the sarcoplasmic reticulum that
  surrounds the sarcolemma so important?
• 14. Describe the steps that must occur for a
  muscle to contract and then relax.?
• What is the neuromuscular junction and what
  occurs here?
• 16. Why is Ca necessary for starting a muscle
  contraction?

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Concept Check 5

• 17. Explain the sliding filament theory
  (shortening of a sarcomere).
• 19. Why would a leak of Ca from the sarcoplasmic
  reticulum cause rigor mortis.
• When does a muscle relax?
• 21. Why might marathon runners have more red
  twitch fibers and sprinters have more white
  twitch fibers? Include speed of contraction and
  fatigue resistance in your explanation.

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Skeletal Muscle Action

• skeletal muscle structure responds to the amount
  of work it must do
• irregular use or lack of neural stimulation
• ? cells lose sarcomere proteins
• ? contraction strength decreases
• ? muscle size decreases
• (hypotrophy/atrophy)
• regular use increased blood flow
• ? muscle strength increases
• ? muscle size increases (hypertrophy)
• Does your muscle diameter increase OR does your
  sarcomere density strength increase w/o a
  significant increase in overall muscle size ???
• (determined by genetic differences different
  blood flow patterns)

http//visionals.info/MuscleHypertrophy.php
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Skeletal Muscle Action

• shortening of the muscle brings the insertion
  closer to the origin
• threshold stimulus - minimal level of stimulus
  required to cause a fiber to contract
• muscle cells are controlled by different motor
  units with different threshold levels so not all
  muscles contract at the same time
• All or None Theory a fiber contracts
  completely or not at all Its the difference
  in picking up 1 textbook or 25 textbooks.
• http//entochem.tamu.edu/VertInvertContractswf/ind
  ex.html
• Strength contracting more fascicles
• Endurance producing more
• contracting and relaxing groups
• of fascicles.

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Skeletal Muscle Action

• muscles can be categorized by the effect it has
  on joint motion
• abductor muscles that move a bone away from
  the
• midline (deltoid, gluteus
  maximus)
• adductor muscles that move a bone closer to
  the
• midline (gracilis,
  pectoralis major)
• extensor muscles that increase the angle of a
  joint
• (tricep, quadriceps)
• flexor muscles that decrease the angle of a
  joint
• (bicep, hamstrings)
• sphincter muscles that decrease the size of
  an
• opening (esophogeal sphincter,
  rectal spincter)

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Skeletal Muscle Action

• isotonic contractions when a muscle is
  actively shortening or lengthening
  ex. lifting weights
• isometric contractions when a muscle is not
  shortening or lengthening ex. pushing
  against an immovable object

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Fatigue

• during muscular exercise
• b.v. in muscles dilate blood flow and O2
  delivery increases
• muscle fatigue occurs after extended or strong
  muscle contractions and O2 ATP cant supply
  muscle fibers fast enough
• oxygen debt amount of O2 taken in to pay
  back resting metabolic conditions
• if O2 is unavailable, glucose is converted into
  lactate which helps break down glucose for energy
• production of lactic acid in the body causes
  soreness

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Concept Check 6

• 21. List 2 things that can happen when muscles
  are used irregularly.
• 22. List 2 things that can happen when muscles
  are used regularly.
• How do hypertrophy and hypotrophy (atrophy)
  differ?
• 24. Do all the muscle fibers (cells) in my arm
  contract when I pick up a pencil? Use the terms
  threshold stimulus and all or none theory in your
  explanation.

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Concept Check 7
25. Explain the difference between isotonic and
isometric contractions. Give an example of
each. 26. What is the relationship between
muscle fatigue and oxygen debt?
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Aging and Pathology of the Skeletal System

• many disorders of the musculature are due to
  interactions with the skeletal and nervous
  systems
• Strains vs. Sprains
• strains overworking the muscles force on
  joints and tendons
• pain and swelling of fascia, joints, ligaments,
  and tendons
• nerves signal pain when stretched or swollen
  (stiff)
• sprains more severe sudden or violent stress
• on a joint/muscle
• tearing of a ligament, muscle, or tendon and
• damage to nearby blood vessels
• require time for tissue and protein replacement
• To keep swelling down apply cold 1st
• followed by continuous warmth to speed
• healing

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• contusions related to sprains direct hit(s)
  to a muscle

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• Myopathy / Neuromuscular disorders
• inability of the nervous system to communicate
  properly to muscles
• 1. mitochondrial myopathies genetic
  abnormalities of the mitochondria muscles cant
  produce energy from food muscles become easily
  cramped

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2. myosistis ossificans caused by damage to
soft tissues _at_ muscle bone growing within muscle
tissue pain during contraction a.
Nonhereditary b. Herditary (A.D.)
traumatica progressiva
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3. muscular dystrophy- involves progressive
weakness in the voluntary muscles inability of
nervous system to stimulate muscle action
results in atrophy and wasting
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Steroids on Muscles

• boost bodys ability to produce muscle
• prevent muscle breakdown
• decreases recovery time
• resemble chemical structure of
• testosterone
• T directs the body to produce
• more or enhance male
• characteristics (like increased
• muscle mass, etc)

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Aging of the Muscular System

• natural causes ? sarcopenia
• cachexia ? muscle loss usually associated with
  AIDS, cancer, starvation, anorexia, bulimia
• decrease in neural stimulation -gt atrophy
• malnutrition / undernutrition ? decrease in
  carbs and proteins ? less energy and nutrients
  for repair and maintenance
• decline in sex hormones and insulin-like growth
  factor 1 (IGF-1) needed for muscle cell growth,
  maintenance, repair
• physical therapies ?
• electrical stimulation pulses (causes muscles to
  retain protein)
• muscle massages

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Concept Check 8

• 27. What are the differences between strains,
  sprains, and contusions?
• 28. Name and describe 2 different types of
  myopathies.
• 29. What is cachexia in terms of muscle aging.
• 30. Describe 4 factors that contribute to muscle
  aging.

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Case Study Investigation

• Selected for an internship at National Space
  Biomedical Research Ins.
• Required to monitor astronauts for NASA before,
  during, and after a space mission.
• American astronaut spent 171 days in the space
  stations has to go through 3 weeks of physical
  therapy.
• She lost 30 of her skeletal muscle even after
  following all the exercise programs NASA
  required. The average is less than 20.
• Questions
• Why did the American lose 30 of her skeletal
  muscle after her mission to space? Be specific.
• 2. She lost 10 more than the average astronaut.
  What else associated with her mission could have
  contributed to the Americans muscle loss?

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CSI - ANSWER

• much of the muscles actions go into
  counteracting the affects of gravity on the body
  they have to work harder in gravity environments
• regular resistance produces muscle mass and
  strength
• weightlessness of space flight reduces the
  muscles need to work against gravity muscles
  will lose their mass and strength and they atophy
• protein metabolism ? astronauts dont receive
  large amounts of amino acids they need
• sex hormones ? decline in sex hormones from the
  stress of working in space for 6 mo