Download Ch8-Muscular

Chapter 8 – Muscular System
I.
II.
A.
Introduction
A.
All movements require muscles to contract
using ATP (chemical energy)
- moving blood, urine, & sweat
- producing heat to warm the body
B.
C.
Each muscle is an organ made of blood &
tissues (muscle, connective, & nervous)
Pg. 190
D.
B.
Cardiac
1.
involuntary muscle of the heart
2.
doesn’t fatigue
3.
have striations & intercalated disks –
join cells & transmit contraction from
cell to cell heart cells beat spontaneously
* This arrangement allows
parts to move
independently
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C.
Pg. 192
There are 3 layers of connective tissue within
each muscle
1.
epimysium: closely surrounds a
skeletal muscle
2.
perimysium: separates muscle into
bundles called fascicles
3.
endomysium: surrounds each muscle
fiber (cell)
Pg. 190
8-2
III. Structure of a
Muscle Fiber (cell)
Cell Membrane = Sarcolemma
Cytoplasm = Sarcoplasm, containing:
1.
many nuclei & mitochondria
2.
thin proteins called myofibrils, which
are responsible for muscle contraction
a) thin one is actin
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b) thick one is myosin
A layer of fibrous
connective tissue
called fascia
surrounds &
separates each
muscle
- it extends beyond
muscles to form
tendons that are
fused to the
periosteum of bones
Three types of muscle exist skeletal, smooth, & cardiac
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A.
B.
B.
Connective Tissue
Sarcoplasmic Reticulum – channels
surrounding each myofibril that
transport chemicals
Transverse (T) Tubules – channels
that pass through the core of a
muscle fiber to transport calcium &
ATP
IV.
Types of Muscle
A.
Smooth
Pg. 122-123
1.
2.
Pg. 192
3.
* SR
8 - 5 & T-tubules activate muscle contraction
when the fiber is stimulated
C.
Skeletal
1.
voluntary muscles used for movement
that are attached to bones
2.
do fatigue
3.
have striations
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V.
involuntary muscles lining organs
(stomach, bladder, uterus, blood
vessels)
do peristalsis (wavelike contractions) to
move substances through the lumen
these muscles surround
fibers are slower to contract & relax,
but resistant to fatigue
Skeletal Muscles of the Human Body
A.
Muscles attach to bones at 2 sites
1.
Origin = immovable end of a muscle
2.
Insertion = movable end of a muscle
* Contraction always occurs
to move point of insertion
towards point of origin *
Pg. 122-123
Pg. 122-123
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8-8
8-9
Pg. 204
1
B.
C.
Interaction of Skeletal Muscles
1.
In a group of muscles, the one doing
the majority of the work is the prime
mover or agonist
2.
Muscles that resist the action of the
prime mover are antagonists
3.
Assisting the prime mover are
muscles called synergists
Skeletal Muscles to know (pg. 205)
1.
Facial Expressions
a)
Epicranius (Frontalis & Occipitalis) –
elevates eyebrows
b)
Orbicularis oris – closes & protrudes lips
c)
Orbicularis oculi – closes eyes
d)
Platysma – depresses lower lip (pg 207)
e)
Zygomaticus – “smile” muscle; elevates
corner of mouth
2.
Mastication
a)
Masseter – elevates & protracts mandible
b)
Temporalis – elevates & retracts mandible
Prime
Mover
Synergists
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3.
Neck
Sternocleidomastoid – Each flexes & rotates the
head and neck forward & laterally
4.
Trunk
a)
Trapezius – elevates & depresses scapula
b)
Latissimus dorsi – extends arm at
shoulder, adducts & medially rotates arm
c)
Pectoralis major – flexes arm at shoulder,
adducts and medially rotates arm
d)
Rectus abdominis – Compresses abdomen,
flexes vertebral column
e)
External oblique – Compresses abdomen,
flexes and rotates vertebral column
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VI. Muscles & The Nervous System
A.
Neuromuscular Junction - site where a motor
neuron (nerve cell) and a muscle fiber
functionally, but not physically connect
5.
Arm
a)
Deltoid – Flexes arm at shoulder, adducts
and medially rotates arm
b)
Biceps brachii – Flexes forearm at elbow,
laterally rotates (supinates) forearm and
hand
c)
Triceps brachii – Extends forearm at elbow
6.
Lower Leg
a)
Tibialis anterior – dorsiflexion
b)
Soleus – plantar flexion
c)
Gastrocnemius – plantar flexion & flexion
8 - 14 of leg at knee
B.
Pg. 193
8 - 16
1.
The end of the
muscle fiber forms
a motor end plate
2.
The motor neuron
stores chemicals
called
neurotransmitters
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C.
7.
Upper Leg
a)
Gluteus maximus – Extends thigh at hip
b)
Gluteus medius – Abducts thigh, rotates
thigh medially
c)
Sartorius – Flexes leg at knee, flexes thigh
at hip, abducts thigh, rotates thigh
laterally, rotates leg medially
d)
Gracilis – Abducts & medially rotates thigh
e)
Quadriceps – extends leg at knee:
Rectus femoris, Vastus medialis,
Vastus lateralis, Vastus intermedius
f)
Hamstrings – flexes leg at knee:
8 - 15 Biceps femoris, Semitendinosus,
Semimembranosus
Muscular Responses
1.
Threshold Stimulus – a muscle fiber
remains unresponsive until a certain
strength of stimulation is applied
2.
Calcium ions cause Actin and Myosin
to slide together, causing a
contraction called a twitch.
3.
During a twitch, a fiber pulls at its
attachment, followed by relaxation
Motor Units
1.
A whole muscle can create more
force if more muscle fibers are
8 - 17
involved in the contraction
8 - 18
Pg. 201
2
1.
2.
3.
4.
5.
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C.
Motor Units are 1 motor neuron and
the 2-3 muscle fibers it controls
These are functional units, because an
impulse to the motor neuron will cause
all fibers in the unit to contract at the
same time (“All or None Response”)
Some units are more sensitive to
stimulation than others, and thus have
a lower threshold stimulus
At lower thresholds, fewer sensitive
units contract; At higher intensities of
stimulation, more motor units cause
contraction
Recruitment: increase in # of motor
units activated during a contraction
Relaxation – the lengthening of a muscle
from its point of origin
1. Acetylcholine is decomposed
by Acetylcholinesterase
(ATP needed)
2. Calcium ions leave muscle
fiber thru T-tubules
3. ACTIN and MYOSIN
slide apart
VII. Skeletal Muscle Contraction
*Letters Origin
A.
Actin & Myosin create Striation Patterns
1.
Sarcomere = area from Z line to Z line
2.
I bands – light bands composed of
actin attached to Z lines
3.
A bands – dark bands w/ myosin in
middle, actin on edges
Pg. 191
a)
H zone of only myosin w/ an M
line holding myosin in place
2.
Fast Fibers
 forceful exercise
(weight lifting) causes muscles to contract more
 new actin and myosin develop, increasing the
diameter of muscle fiber
8 - 25
 muscle enlarges (no new fiber made)
Contraction - the pulling of a muscle against
its attachments
1.
2.
3.
4.
8 - 20
8 - 21
Pg. 195
VIII. Fatigue
A.
During rest or moderate activity, enough O2
is present in muscle cells to do aerobic
respiration
B.
Oxygen debt develops during strenuous
exercise - Muscles lose their ability to
contract & become fatigued
C.
Lactic acid (feeling of pain or of muscles
burning) builds up as an end product of
anaerobic respiration
1.
A muscle cramp can occur due to a
lack of ATP required to get rid of
calcium ions so muscle fibers can relax
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IX. Muscle Conditions
A.
Muscle Tone - achieved by sustained contraction
within muscles, & is needed for normal posture
1.
Slow Fibers – fatigue-resistant muscle fibers
 use (distance running, swimming) develop
more mitochondria
B.
D.
E.
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B.
Muscle Use & Disuse
1.
Muscular Atrophy
 Decrease in size & strength of
muscles due to disuse (accidents,
space travel)
 less mitochondria, actin, &
myosin
2. Muscular Hypertrophy –
enlarged muscles due
8 - 26
to increased overuse
ATP is needed from
mitochondria
The neurotransmitter,
acetylcholine, is released at
the neuromuscular junction
Calcium (Ca) ions are
released into muscle fibers
thru T tubules
ACTIN and MYOSIN slide
together
Sarcomere animation
“Repaying” oxygen debt may take
several hours
Factors that may lead to muscle fatigue:
- Accumulation of lactic acid
- Loss/decrease in blood supply (less O2)
- Loss of acetylcholine supply
- Malnutrition (lack of glucose)
- Respiratory problems (less O2)
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C.
Muscle Injuries
1.
Mild Strain – few fibers injured, fascia
intact, little loss of function
2.
Severe Strain – many fibers & fascia
torn, loss of function, pain,
discoloration, swelling of tissues
3.
Tetanic Contraction – sustained,
forceful contraction that lacks
relaxation (i.e. tetanus bacteria, drugs)
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D.
Rigor Mortis – muscle contraction at
time of death
 muscles run out of ATP & Ca can’t be
removed
 constant state of contraction after 72 hrs
 Actin and Myosin remain linked until
muscle cells decompose
8 - 28
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