Chpt. 49

1
Chpt. 49
Muscles Motor Locomotion
Why Do We Need All That ATP?
2
Function of Muscles

• To convert chemical energy of ATP into mechanical
  work,
• To get around
• To get your food
• To digest your food
• To pump your heart so that oxygen can get
  to that mitochondria

3
Types of Muscle Tissue

• 1) Cardiac
• rapid contraction
• 2) Skeletal
• rapid contraction
• 3) Smooth
• slow sustained contraction

4
involuntary, striatedauto-rhythmic
voluntary, striated
heart
moves bone
multi-nucleated
involuntary, non-striated
digestive systemarteries, veins
evolved first
5
As a side

• Insect flight muscles contract more rapidly than
  ANY OTHER
• 1,000 contractions/second
• Highest metabolic rate
• Contain more mitochondria than any other tissue
• HOW get oxygen???

6
HOW DO WE MOVE THESE 206 BONES?
7
SKELETAL MUSCLE
8
skeletal muscles move bones by pullingnot
pushing, therefore they come in antagonistic
pairs
9
So in other words, in order to flex, you must
contract your flexor muscles and in order to,
relax, you must contract the antagonistic muscle
flexor vs. extensor
10
Extensor (quadracep)
Notice the TENDON connects the muscle to the
bone. One bone is pulled towards another bone
upon contraction.
11

• Vertebrate Skeletal Muscle
• Structure

composed of smaller smaller smaller units
plasma membrane
skeletal muscle
nuclei
tendon
muscle fiber (cell)
myofibrils
myofilaments
12
Vertebrate Skeletal Muscle
each muscle fiber one long, cylindrical,
multinucleated cell
13
Vertebrate Skeletal Muscle
Bundle of fibers
Muscle fiber cells composed of bundles of
myofibrils (threadlike structures)
14
Myofibrils are basically parallel contractile
units
15
Myofibrils consist of even smaller structures
thick filaments thin filaments
16
myofibrils have a regular arrangement regular
arrangement regular arrangement regular
arrangement regular arrangement
17
sarcomere basic unit of a myofibril - hundreds
are connected end to end make up the myofibril
18
sarcomeres are made of these proteins
thick filaments thin filaments
19
Thin filaments actin

• Complex (bunch) of proteins
• braid of actin molecules tropomyosin fibers
• tropomyosin fibers secured with troponin complex
• these are proteins

20
Thick filaments myosin

• Single protein
• myosin molecule
• long protein with globular head

bundle of myosin proteins globular heads aligned
21
Thick thin filaments

• Myosin tails aligned together heads pointed
  away from center of sarcomere

22
sarcomere basic unit of a myofibril - hundreds
are connected end to end make up the myofibril
23
SARCOMERE
24
making up the sarcomere
Z-lines the borders of the sarcomere
(actin)
25
at rest, the thick myosin thin actin filaments
in the sarcomere do not overlap completely
26
area inwhich only thick myosin filaments H zone
27
Area inwhich only thin actin filaments I band
28
Area in which both thin actin filaments
thick myosin filaments A band
29
More muscle anatomy SARCOLEMMA plasma membrane
30
More muscle anatomy T tubule inward extension
of the plasma membrane
31
More muscle anatomy mitochondrion ohh, there
are plenty!
32
More muscle anatomy sarcoplasmic reticulum
another name for endoplasmic reticulum
33
How does the Muscle Contract?
34
Sliding Filament Model
35
Motor Unit
(Usually hundreds of muscle fibers)
36
NEUROMUSCULAR JUNCTION
37
NEUROTRANSMITTOR ACETYLCHOLINE released as
action potential moves to synaptic terminal
of muscle fiber
38
The acetylcholine causes the action potential to
continue in the muscle fiber
39
The action potential spreads into T-Tubules
(invaginations in the membrane of the muscle
fibers)
40
The a.p. opens Ca2 channels in the sarcoplasmic
reticulum (e.r.)
41
The special type of smooth endoplasmic reticulum
found in smooth and striated muscle fibers whose
function is to store and release calcium ions.
42
Ca2 flows binds to a protein in the actin
filament
43
Sliding Filament Model
Thin actin filament has myosin binding sites
At rest myosin binding sites are blocked (with
trypomyosin)
44
Sliding Filament Model
Thin actin filament has myosin binding sites
myosin binding sites are opened when Ca2 binds
to the troponin. (Ca2 is released as a result
of acetylcholein rushing through the T-tubules)
45
Sliding Filament Model
At rest, myosin head is bound to an ATP --
ATP
46
Sliding Filament Model
when Ca2 floods into the cell, Myosin head
hydrolyzes (breaks) ATP to ADP and P --.
47
Sliding Filament Model
Myosin binds to Actin --
??????????????????????????????????????????????????
??????????????????????? this forms a
cross-bridge When this occurs, the myosin head
changes shape and releases the ADP P
48
Sliding Filament Model
the myosin head changes shape and releases the
ADP P
49
Sliding Filament Model
The thin actin filament is pulled toward the
center of the sarcomere
50
Sliding Filament Model
SLIDING
51
Sliding Filament Model
ATP
cross-bridge broken when ATP binds back to the
myosin head
52
Cleaving ATP ? ADP P allows myosin head to bind
to actin filament
ADP
1
ATP
2
4
3
53
What is the Stimulus that causes muscle to
contract?
54
Synapse with Neuron Muscle
Synaptic Terminal of neuron releases acetylcholine
55
Synapse with Neuron Muscle
Ca released
Binding sites on actin are now exposed.
Myosin head now binds to the actin
56
Synapse with Neuron Muscle
Muscles do not relax until the Ca is pumped
back into the sarcoplasmic reticulum
ATP
57
Put it all together
Acetylcholine released
1
2
Action potential travels
3
a.p, travels through T-Tubules
ATP
7
Ca2 pumped back into s.r. / ATP required
4
Ca2 released binds to troponin complex
6
Ca2 depleates cross bridge broken/ ATP back on
myosin head
Cross bridge formed
ATP
5
58
Put it all together
1
2
3
ATP
7
4
6
ATP
5
59
Muscle limits

• Muscle fatigue
• lack of sugar
• lack of ATP to restore Ca2 gradient
• low O2
• lactic acidcauses pH drop which interferes with
  protein function
• synaptic fatigue
• loss of acetylcholine
• Muscle cramps
• build up of lactic acid
• ATP depletion
• ion imbalance
• massage or stretching increases circulation

60
Rigor mortis

• So why are dead people stiffs?
• no life, no breathing
• no breathing, no O2
• no O2, no aerobic respiration
• no aerobic respiration, no ATP
• no ATP, no Ca2 pumps
• Ca2 stays in muscle cytoplasm
• muscle fibers continually contract
• tetany or rigor mortis
• eventually tissues breakdown relax
• measurement for time of death

61
Money for Beauty

• What is Botox?
• Toxin derived from Closteridium botulinum
• blocks the release of acetylcholine
• Muscles relax which takes away the wrinkle

62
(No Transcript)
63
The transmission of an impulse from a nerve to
the surface of a resting muscle initiates a
contraction in that muscle. Biochemical and
biophysical studies of muscle tissue have
resulted in an explanation for muscle contraction
known as the sliding-filament theory. a.
Describe the chemical changes that occur when a
nerve impulse is transmitted to the surface of a
resting muscle cell. b. Describe the
internal structure of a muscle fiber as revealed
by electron microscopy. c. On the basis of this
structure, explain the sliding- filament theory.
64
7. Discuss the mechanism by which a muscle cell
contracts or a nerve cell transmits an impulse.
Include in your discussion the relationship
between cell structure and function.
65
This is it!!

• Action potential causes Ca2 release from SR
• Ca2 binds to troponin
• Troponin moves tropomyosin uncovering myosin
  binding site on actin
• Myosin binds actin
• uses ATP to "ratchet" each time
• releases, "unratchets" binds to next actin
• Myosin pulls actin chain along
• Sarcomere shortens
• Z discs move closer together
• Whole fiber shortens ? contraction!
• Ca2 pumps restore Ca2 to SR ? relaxation!
• pumps use ATP

ATP
ATP