Download B20 C10 Muscles notes

B20 C10 The Muscular System and Homeostasis p. 330
Overview of the Muscular system
 Watch Crash course muscles: https://www.youtube.com/watch?v=jqy0i1KXUO4
 Read pg. 330, including the chapter concepts.
Functions of the muscular system
• movement (voluntary and involuntary)
• maintain body temperature (contracting muscles produce heat)
• body support (posture, stabilizes joints, protects internal organs)
• regulation of blood pressure (vasoconstriction)
• guards body exits and entrances (sphincter muscles)
Muscles Cooperate!
• Muscles can only contract (pull), they cannot push, so muscles that move your body
(skeleton) occur in opposing pairs – one pulls the bone one way, one the other way.
 Check out your bicep/tricep pair (pg. 331)
There are 3 types of muscle cells: skeletal, smooth, cardiac
p. 332-333
 Fill in the illustrated guide to the 3 types of muscle cells below. You can use digital or hand
drawn illustrations.
 Make a dichotomous key that separates the 3 types by visible features
 Try someone else’s dichotomous key.
Properties of the 3 muscle tissue types
MUSCLE
TYPE
SKELETAL
SMOOTH
Striations
Voluntary or
involuntary
Location
Cells
Diagram
 See if you can identify the 3 types of muscle cells using the microscope!
CARDIAC
Skeletal Muscle
Muscle  Muscle-fibre bundle  muscle fibre  myofibrils  myofilaments
 Read pg. 335-336. Make a line drawing of a muscle showing the hierarchy of a muscle
structure. Label or color code each part of the hierarchy, as well as blood vessels, nerves, and
nuclei. Which part of the hierarchy is an individual muscle cell?
 What cellular organelles are particularly abundant in muscles? Hint: Muscles need lots
of energy (ATP) and are made of lots of protein.
How do muscles contract? the sliding filament model
There are 2 different myofilaments: actin (thin) and myosin (thick with the golf club heads). (see
pg. 337).
In contraction, the myosin heads bind to the actin myofilament, then the myosin golf club heads flex
and pull the actin myofilament, sliding the actin myofilaments connected to Z-lines towards the center
of the muscle fibre unit (sarcomere). This shortens (contracts) the sarcomeres in the muscle fibres, all
along the muscle, causing the muscle to contract and move the bone it is attached to.
Role of calcium ions, troponin and tropomyosin in the sliding filament model of muscle
contraction
What happens when muscles are relaxed? : In
a relaxed muscle the myosin heads are raised and
ready to bind to the actin, owing to the splitting
of an ATP molecule. However,
TROPOMYOSIN, a long protein “rope” blocks
the sites where myosin heads bind to actin,
keeping the muscle relaxed, Fig. a.
What happens to tropomyosin when muscles
contract? Nerve impulses to the muscles release
Ca2+ which is stored in the sarcoplasmic
reticulum. Calcium binds to troponin. The
troponin-Ca2+ complex pulls the tropomyosin
away, exposing the myosin binding sites on the
actin myofilament. The golf club heads of
myosin can now bind to the muscle and slide the
actin filaments towards the M-line, contracting
the muscle.
What is the role of Ca2+ (calcium) in muscle
relaxation? When the nerve stimulation stops Ca2+ is returned to sarcoplasmic reticulum by active
transport, the tropomyosin “rope” moves back and inhibits the myosin binding sites, and the muscle
relaxes. See Fig. 10.7 pg 339.
 Watch these clips on the sliding filament model:
https://www.youtube.com/watch?v=7O_ZHyPeIIA
https://www.youtube.com/watch?v=BVcgO4p88AA
https://www.youtube.com/watch?v=Ktv-CaOt6UQ Crash Course review
http://highered.mheducation.com/olc/dl/120104/bio_b.swf
https://www.youtube.com/watch?v=0kFmbrRJq4w
 Using the information in these clips and the figures and information on pg. 336 – 339, make a
working model explaining the sliding filament model of muscle contraction. Include:
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•
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actin
myosin
ATP
ADP + P
troponin
tropomyosin
Ca2+
Z – line
M - line
You will be marked on:
• Creative, neat, realistic, functional working model
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• Accurate and detailed explanation of the process
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• Presentable to the Boss: all structures listed
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are included in the model, evidence of excellent
effort, NOT A RUSH JOB
___________________________________________________________
TOTAL /15 = %
 Learning Check! Put the steps involved in muscle contraction below in order starting with 1.
1. The muscle is at rest.
2. The myosin head reattaches to actin farther along the fibre, and move the fibre one more
“step” closer to the center.
3. Calcium binds to the protein troponin.
4. Nerve impulses to the muscle stop, Ca2+ ions are removed from the myofilaments,
a long filament made of the protein tropomyosin blocks the binding sites on the
actin molecule.
5. Myosin heads can now bind to the exposed binding sites on the actin myofilaments.
6. Powered by ATP, the myosin heads release and unflex.
7.
The myosin heads flex and slide the actin myofilaments one “step” towards the centre of
the sarcomere.
8.
Nerve impulses to the muscle releases Ca2+.
9. Tropomyosin is moved off of the myosin binding sites on the actin molecule.
10. Myosin cannot bind to the actin molecule, and the muscle relaxes.
11. As the sarcomeres contract, the muscle fibers shorten, the muscle contracts and the bone
moves.
_1_ ___ ___ ___ ___ ___ ___ ____ ___ ___ ___
The energy (ATP) needed for muscle contraction is provided in 3 different ways depending on
the availability of oxygen p. 339 - 341
1. The creatine phosphate (phosphagen) system is used first because creatine phosphate, a highenergy compound, is stored right in the midst of the sliding muscle filaments when they are resting. It
is the speediest way to get ATP to initiate muscle contraction and it does not need O2.
creatine phosphate + ADP  creatine + ATP
However, this reaction can generate ATP for only a few seconds because the creatine phosphate is used
up. Then the ATP has to come from fermentation or aerobic cellular respiration.
2. Fermentation (glycogen glucose  lactic acid (lactate)) is used when exercise is so
vigorous that oxygen cannot be delivered to the muscle cells fast enough, since it is also
anaerobic. However, fermentation can only last 2- 3 minutes then the lactic acid causes
cramping and fatigue.
3. Aerobic cellular respiration takes place in the muscles’ mitochondria and provides
most of the ATP (energy) we need for sustained muscle action.
Glucose + O2 + ADP  H2O + CO2 + 36 ATP
 Learning Check! Explain why the three different athletic events in the diagram above
use 3 different systems for generating ATP for muscle action.
Oxygen Deficit p. 342 - 343
If we exercise so vigorously that our
supply of oxygen cannot make
enough ATP for the muscles through
aerobic cellular respiration, we have
to use fermentation to make the extra
ATP. But this causes a build up of
lactate and we have to get rid of it.
During oxygen debt repayment as
oxygen becomes available the lactic
acid is broken down.
 How is the change in your breathing rate from a resting state to during exercise to after exercise
related to the sliding filament model for a muscle contraction?
Muscles, Health and Homeostasis
 Read pg. 344 – 346 and answer the following questions:
1) What conditions cause atrophy? Why is physical therapy so important in preventing
atrophy?
2) Exercise strengthens muscles, and increases their efficiency. Explain how this happens. What
is hypertrophy?
Muscle Twitch p. 346
Myograms give us a visual understanding of muscular contraction. In this way, they are similar to the
electrocardiograms we looked at to determine heart muscle activity.
Fig. 1.
A Single Muscle Twitch
Fig. 2. 4 Different Muscle Contractions
Fig. 1 shows a single muscle twitch (the contraction of one single muscle fiber) and lasts less than a
second. A single muscle twitch has 3 periods – a latent period, a contraction period and a
relaxation period.
Fig. 2 shows how we get increased muscle contraction strength as more and more fibers contract. As a
muscle gets successive nerve stimulations without relaxing in between, summation occurs – the
strength of each successive contraction “piggy-backs” on the previous one. Tetanus is when the
maximum contraction strength is reached, and we can no longer see individual twitches. Tetanus
continues until muscle fatigue sets in when energy reserves are used up.
 1) Using the information on page 346, label each part of the graph (a – d) with stimulus, latent
period, contraction period and relaxation period. Then define summation, tetanus, and fatigue.
 2) Why does a muscle eventually fatigue?
 Check out https://www.youtube.com/watch?v=Uxwh2IIg_Z0
All muscle fibres use aerobic and anaerobic respiration to provide ATP for muscle action. But not all
muscle fibres use these 2 respirations in the same proportion. Using the information on pg. 346-347,
fill in the Table below:
Fibre type
What type of Muscle fibre are you using?
How do they
Color. Why is it Anaerobic What activities use this type of
work?
this color?
or Aerobic muscle fibre?
respiration
used?
Slow Twitch
Fast Twitch
Intermediate
Form
 Label the 3 different muscle
twitch types on this graph.
Extraocular muscles control
eye movement, the
gastrocnemius muscle is the
bulging muscle in your calf, and
the soleus muscle is a broad
muscle in the lower calf, below
the gastrocnemius, that flexes
the foot to point the toes
downward.
 Read the Value of Exercise pg. 348. Summarize the main points. Watch this clip:
http://www.pbslearningmedia.org/asset/oer08_vid_exercise/
 Study Summary on pg. 349 and 351.
 Answer question 8, 10, 12, 13 on pg. 350.