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ELAINE N. MARIEB
EIGHTH EDITION
6
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALSOF HUMANANATOMY
& PHYSIOLOGY
PART A
The Muscular System
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The Muscular System Muscles are responsible for all types of body
movement
Three basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle
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Characteristics of Muscles Muscle cells are elongated
(muscle cell = muscle fiber)
Contraction of muscles is due to the movement of microfilaments
All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh
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Skeletal Muscle Characteristics Most are attached by tendons to bones
Cells are multinucleate
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded and bundled by connective tissue
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Smooth Muscle Characteristics Has no striations
Spindle-shaped cells
Single nucleus
Involuntary – no conscious control
Found mainly in the walls of hollow organs
Figure 6.2a
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Cardiac Muscle Characteristics Has striations
Usually has a single nucleus
Joined to another muscle cell at an intercalated disc
Involuntary
Found only in the heart
Figure 6.2b
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Function of Muscles Produce movement
Maintain posture
Stabilize joints
Generate heat
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Energy storage in muscles At rest the muscle fibers produce more ATP
than they need.
Some of the excess ATP is used to make creatine phosphate, a energy-rich molecule that is unique to muscle fibers.
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Microscopic Anatomy of Skeletal Muscle Cells are multinucleate (which is different
from most of the cells in your body)
Nuclei are just beneath the sarcolemma
Figure 6.3a
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Microscopic Anatomy of Skeletal Muscle Sarcolemma – specialized plasma membrane
Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum
Figure 6.3a
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Fascia – a broad band of fibrous connective tissue beneath the skin or around muscles and other organs.
Superficial fascia - The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together.
Deep fascia – dense, irregular connective tissue that holds muscles together and separates them into functional groups
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HW Compare and contrast the three different
types of muscles.
What is the purpose of the sarcolemma and what does it incase?
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 6.3b
Microscopic Anatomy of Skeletal Muscle Myofibril
Bundles of myofilaments
Myofibrils are aligned to give distinct bands
I band =
light band (thin fibers)
A band = dark band (thick fibers)
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Microscopic Anatomy of Skeletal Muscle Sarcomere
Contractile unit of a muscle fiber
Figure 6.3b
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Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere
Thick filaments = myosin filaments
Composed of the protein myosin
Has ATPase enzymes
Figure 6.3c
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Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere
Thin filaments = actin filaments
Composed of the protein actin
Figure 6.3c
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Microscopic Anatomy of Skeletal Muscle Myosin filaments have heads (extensions, or
cross bridges)
Myosin and actin overlap somewhat
Figure 6.3d
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Microscopic Anatomy of Skeletal Muscle At rest, there is a bare zone that lacks actin
filaments
Sarcoplasmic reticulum (SR) – for storage of calcium
Calcium is one of the minerals needed to aid contraction of muscles, when released, muscle is able to contract.
Figure 6.3d
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Properties of Skeletal Muscle Activity Irritability – ability to receive and respond to
a stimulus
Contractility – ability to shorten when an adequate stimulus is received
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Nerve Stimulus to Muscles Skeletal muscles
must be stimulated by a nerve to contract
Motor unit
One neuron
Muscle cells stimulated by that neuron
Figure 6.4a
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Nerve Stimulus to Muscles Neuromuscular junctions – association site of
nerve and muscle
Figure 6.5b
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Nerve Stimulus to Muscles Synaptic cleft – gap
between nerve and muscle
Nerve and muscle do not make contact
Area between nerve and muscle is filled with interstitial fluid
Figure 6.5b
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Transmission of Nerve Impulse to Muscle Neurotransmitter – chemical released by nerve upon
arrival of nerve impulse
The neurotransmitter for skeletal muscle is acetylcholine which prevents continuous movement of muscle because it has to be present to start movement. (aCh is destroyed so another action potential does not arise unless aCh is released from the motor neuron)
Neurotransmitter attaches to receptors on the sarcolemma
Sarcolemma becomes permeable to sodium once aCh binds to its protein receptor.
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Receptor Proteins Proteins that need a binding agent (ligand) to
allow channel to open so contents can go inside or outside the cell.
http://getbodysmart.com/ap/muscletissue/nervesupply/receptor/animation.html
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Transmission of Nerve Impulse to Muscle Sodium rushing into the cell generates an
action potential
Once started, muscle contraction cannot be stopped
Action potential is the start of a reaction
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The Sliding Filament Theory of Muscle Contraction Activation by nerve
causes myosin heads (crossbridges) to attach to binding sites on the thin filament
Myosin heads then bind to the next site of the thin filament
Figure 6.7
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The Sliding Filament Theory of Muscle Contraction This continued action
causes a sliding of the myosin along the actin
The result is that the muscle is shortened (contracted)
Figure 6.7
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http://www.blackwellpublishing.com/matthews/myosin.html
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1. What is the sliding filament theory?
2. How does aCh play a role in muscle contraction?