Download MUSCULAR SYSTEM (muscles, tendons)

Ch. 6
The Muscular
System
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.
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.
Determine the most likely cause of her accelerated loss of muscle mass.
Overview
Muscle cells are composed of
specialized contractile cells that
allow them to change shape and
shorten or contract.
Over half the body’s 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
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)
Musculature:
Gross Anatomy
2. Body: rest of the muscle
(masseter)
3. Insertion:
moveable bone the
muscle attaches to
(mandible)
1. Origin: stationary bone the
muscle attaches to
(zygomatic arch)
Origin:
Scapula /
Humerus
Sacs of synovial fluid btwn
tendon & bone for lubrication
Body
Biceps
Brachii
Insertion:
Radius
Tendon
attachs muscle
to bone
raises eyebrow
closes jaw
closes eyes
smile muscle
closes jaw
extends head / neck
closes lips
yes/no muscle
Muscles of the Trunk
adducts
arm
deltoid
abducts
arm
adducts
upper
arm
flex trunk
flexes
elbow
MUSCLES of the
ARM
extends
elbow
flexes forearm
pronates & supinates
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
extends thigh
Hamstrings
flex the leg
adducts thigh
(middle hamstring)
(medial hamistring)
(lateral hamstring
Basic 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
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
3. Regulate Organ Volume
a. sphincters: bands of smooth muscle that prevent outflow of fluids
from hollow organs
4. Move substances within the body:
a. cardiac muscle – pumps blood
b. smooth muscle – moves food through digestive sys. (peristalsis)
5. Heat Production: when muscles contract they produce
heat
a. Hypothermia – decrease in
body temp below normal
b. Hyperthermia – increase in
body temp above normal
Concept Check #1
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. If I were to flex my elbow which muscle would be the prime
mover, synergist, and antagonist?
Prime mover – main muscle responsible for movement (bicep)
Synergist – other muscles that help PM (brachioradialis)
Anatogonist – produces opposite movement (tricep)
Concept Check #2
4. 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;
sphincters)
5. How does the origin and insertion of a muscle differ?
Origin – immovable bone that muscle attaches to
Insertion – movable bone that muscle attaches to
The insertion bone moves towards the origin bone
6. Research the origin and insertion for the following muscles:
Gastrocnemius: Origin: femur
Insertion: calcaneous
Pectoralis major: Origin: clavicle /sternum Insertion: humerus
Skeletal Muscle Structure
surrounds fassicles
surrounds each
surrounds entire
muscle
bundle of muscle cells
http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP13904 Muscle Structure Animation
Microcopic Muscle Cell Structure
 skeletal muscle cells are long, cylindrical cells covered with an
excitable (can transmit) membrane called the sarcolemma
 proteins in sarcolemma responds to and transmits info to muscle
cells causing them to contract
 cytoskeleton of
muscle cells contain
myofilaments made
up of protein
a) thick: myosin
b) thin:
1) actin
2) troponin
3) tropomyosin
 contractile unit of muscle is called a sarcomere (thousands/muscle cell)
which is surrounded by a sarcoplasmic reticulum (stores/transports
Ca for contraction)
 Thick & thin
myofilaments
overlap within
sarcomere 
gives muscle its
striated
appearance &
carries out
contraction
 chains of
sarcomeres form
myofibrils
Sarcomere Chain Structure
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html# - Sarcomere shortening bio book animation
 1 sarcomere 
How Do Muscles Contract
 contraction occurs when sarcomeres shorten simultaneously
1. Nerve Stimulation at the neuromuscular junction (motor
neuron meets muscle fiber)
 Nerve cells release neurotransmitter acetylcholine which binds to
sarcolemma and allows Na+ /K to cross membrane
 Flow of ions causes Ca to be released from SR; travels to
sarcomere and initiates contraction phase
http://www.galaxygoo.org/biochem/ne
o/nmj_flash.html
(basic neuromuscular
junction animation)
2. Muscle Contraction – takes place inside muscle cell
 Ca binds to troponin; moves it off the actin-binding site on
tropomyosin so myosin can attach to actin
 ATP provides energy for myosin head to pull thick m.f across
thin m.f. (shortening Z-lines of sarcomere)
https://www.youtube.com/wat
ch?v=CepeYFvqmk4 - How a
muscle cell is signaled
https://www.youtube.com/wat
ch?v=jqy0i1KXUO4 - Crash
Course in Contraction
http://highered.mcgrawhill.com/sites/0072495855/student_view0/cha
pter10/animation__action_potentials_and_mu
scle_contraction.html - action potential and
muscle contraction
http://highered.mheducation.com/sites/0072495855/student_view
0/chapter10/animation__breakdown_of_atp_and_crossbridge_movement_during_muscle_contraction.html - good video
3. Muscle Relaxation
starts when neural
stimulation stops

Na+ and K+
ion levels
completely
recover

SR retrieves
most of its Ca

Myosin heads
release actin

Troponin covers
actin-binding
site on
tropomyosin
https://www.youtube.com/
watch?v=mO6a9UZmtag –
rigor mortis animation
Rigor Mortis  muscle stiffness caused by Ca leakage out of SR into
sarcomere after death
Creatine phosphate, glycogen, & myoglobin (red chemical)  all serve as
energy or oxygen reserves for muscle contraction
Types of Skeletal Muscle Fibers
unique muscle composition is genetically determined
https://www.23andme.com/health/Muscle-Performance/ - 23 and Me genetic testing
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)
Rapid, intense movements of short
duraction (i.e. sprinters, throwing a
ball or weight lifting)
Muscle: soleus
Muscle: gastrocnemius / vastus lateralis
Concept Check #3
7. List the three membranes of muscle in order from superficial to
deep then explain how they each differ.
epimysium – membrane that surrounds the entire muscle
perimysium – membrane that surrounds each fascicle
endomysium – membrane that surrounds each fiber (cell)
8. What is the name given to the membrane that surrounds a muscle
cell and why is it important?
sarcolemma; responds to signals from other cells/environment and
transmits the information to the muscle cells causing them contract
9. Why is the sarcoplasmic reticulum that surrounds the sarcolemma
so important?
Stores the calcium needed to unlock/move the troponin/tropomyosin
cover on the myosin binding sites.
Concept Check #4
10. Draw a picture of a sarcomere and label the two different
myofilaments and explain how it relates to the sliding filament theory.
Myosin binds to actin and pulls on it. The myofilaments overlap each
other causing the distance between each Z-line to shorten. With
hundreds of sarcomeres within a muscle cell it causes the cell to
shorten.
11. Why is Ca necessary for starting a muscle contraction.
Attaches to troponin which holds the tropomyosin on top of the
myosin-binding sites on actin. This unlocks/changes it’s shape in
order to remove it and allow myosin to bind to actin.
Skeletal Muscle Action
 skeletal muscle structure responds to the amount of work it must do
1. irregular use or lack of neural stimulation causes
 a loss of sarcomere proteins
 decrease in muscle strength
 decrease in muscle size = hypotrophy or atrophy
2. regular use & increased blood flow causes
 increase in muscle strength
 increase in muscle size = hypertrophy
 Increased blood flow = enlarges muscle diameter = muscle strength
 Heavy muscle use = sarcomere density = muscle diameter
 Some ppl can increase sarcomere density and strength w/o a significant increase in
diameter……genetic differences and variations in blood flow
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;
It’s the difference in picking up 1 textbook or 25 textbooks.
http://study.com/academy/lesson/how-motor-unit-summation-develops-muscle-tension.html - study. Com (partial)
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)
Skeletal Muscle Action
 isotonic contractions: when a muscle is actively shortening
or lengthening
ex. lifting weights
 isometric contractions: no movement but muscle is
contracted and tension is building ex. pushing against an
immovable object
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 can’t 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
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 muscle’s 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 ligament, muscle, or tendon and
damage to nearby blood vessels
 requires time for tissue and protein replacement
 To keep swelling down apply cold 1st
followed by continuous warmth to speed
healing
• contusions – related to sprains; direct hit(s) to a muscle
Myopathy / Neuromuscular disorders

inability of the nervous system to communicate properly to muscles
1. mitochondrial myopathies – group of neuromuscular diseases caused
by genetic abnormalities of the mitochondria; muscles can’t produce energy
from food; muscles become easily cramped
2. myosistis ossificans (2 types – 1st non-hereditary; 2nd
hereditary) – caused by damage to soft tissues @ muscle; bone
growing within muscle tissue; pain during contraction
3. muscular dystrophy- involves progressive weakness in the
voluntary muscles; inability of nervous system to stimulate
muscle action; results in atrophy and wasting
Affect of Steroids on Muscles
 boost body’s 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)
Aging of the Muscular System
 sarcopenia (natural muscle loss due to aging process)
 cachexia (muscle loss usually associated with AIDS, cancer, starvation,
anorexia, bulimia); slower form reduces bodies ability to rebuild muscle
structure
 decrease in neural stimulation -> 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 (IGF1); needed for muscle cell growth, maintenance, & repair
 physical therapies 
1) artificial up-regulation with electrical pulses (causes muscles to
retain protein)
2) muscle massages
Concept Check #5
12. List 2 things that can happen when muscles are used irregularly.
Regularly?
Irregulary
Regularly?
1- cells lose sarcomere protein
1. muscle size increases
2- contraction strength decreases
2. muscle strength increases
3- muscle size decreases
13. How do hypertrophy and hypotrophy (atrophy) differ?
Hypertrophy – increase in muscle size
Hypotrophy (atrophy) – decrease in muscle size
14. 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.
Muscle fibers (cells) have different threshold stimuli. Picking up a pencil
won’t meet every fibers threshold requirement so not all will contract .
If they are, they will contract full as per the all or none theory.
Concept Check #8
15. How do strains, sprains, and contusions differ?
strains  overworked muscles, joints, tendons, ligaments
sprains suddent/violent stress on a muscle, joint, tendon, ligament
contusion  very deep bruise
16. Name and describe 2 different types of myopathies.
muscular dystrophy – progressive weakness of muscles
myosistis ossificans – bone develops w/in muscle
17. What is cachexia in terms of muscle aging.
Quickened muscle loss due to the inability to rebuild muscle
18. Describe 4 factors that contribute to muscle aging.
neural stimulation, decrease in sex hormones,
poor nutrition, natural causes
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:
1. 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 American’s muscle
loss?