Preview Chapter 10
In groups we will define the following terms
1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle
4. Sarcomere
5. Myofibril
6. Myofilament
7. Sarcoplasmic reticulum
8. Motor neurons
9. Neuromuscular junction (aka synapse)
10. Neurotransmitter
Copyright 2009, John Wiley & Sons, Inc.
Copyright 2009, John Wiley & Sons, Inc.
Overview of Muscular Tissue Types of Muscular Tissue
The three types of muscular tissue Skeletal
Cardiac
Smooth
Copyright 2009, John Wiley & Sons, Inc.
Skeletal Muscle Tissue So named because most skeletal muscles move
bones
Skeletal muscle tissue is striated: Alternating light and dark bands (striations) as seen when
examined with a microscope
Skeletal muscle tissue works mainly in a voluntarymanner
Copyright 2009, John Wiley & Sons, Inc.
Cardiac Muscle Tissue
Found only in the walls of the heart
Striated like skeletal muscle
Action is involuntary
Copyright 2009, John Wiley & Sons, Inc.
Smooth Muscle Tissue
Located in the walls of hollow internal structures Blood vessels, airways, and many organs
Lacks the striations of skeletal and cardiac muscle tissue
involuntary
Copyright 2009, John Wiley & Sons, Inc.
Overview of Muscular Tissue Functions of Muscular Tissue
Producing Body Movements
Walking and running
Stabilizing Body Positions
Posture
Moving Substances Within the Body
Heart muscle pumping blood
Moving substances in the digestive tract
Generating heat
Shivering increases heat production
Copyright 2009, John Wiley & Sons, Inc.
Overview of Muscular Tissue
Properties of Muscular Tissue Excitability
Ability to respond to stimuli
Contractility Ability to contract forcefully
Extensibility Ability to stretch
Elasticity Ability to return to an original length
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Skeletal Muscle Tissue Connective Tissue
Components
Fascia Dense sheet of
irregular connective tissue that surrounds muscles
Epimysium Separates muscle
fibers into bundles called fascicles
Perimysium Surrounds numerous
bundles of fascicles
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Skeletal Muscle Tissue Endomysium
Separates individual muscle fibers from one another
Tendon Cord that attach a
muscle to a bone
Aponeurosis Broad, flattened
tendon
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Skeletal Muscle Tissue Nerve and Blood
Supply
Neurons that stimulate skeletal muscle to contract are somatic motor neurons
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Skeletal Muscle Tissue Microscopic Anatomy The number of skeletal muscle fibers is set before you
are born Most of these cells last a lifetime
Muscle growth occurs by hypertrophy An enlargement of existing muscle fibers
Testosterone and human growth hormone stimulate hypertrophy
Copyright 2009, John Wiley & Sons, Inc.
Skeletal Muscle Tissue Sarcolemma
The plasma membrane of a muscle cell
Transverse (T tubules) Tunnel in from the plasma membrane
Muscle action potentials travel through the T tubules
Sarcoplasm, the cytoplasm of a muscle fiber
Copyright 2009, John Wiley & Sons, Inc.
Skeletal Muscle Tissue Myofibrils
Thread like structures which contract.
Sarcoplasmic reticulum (SR) Membranous sacs which encircles each myofibril
Stores calcium ions (Ca++)
Release of Ca++ triggers muscle contraction
Filaments Function in the contractile process
Two types of filaments (Thick and Thin)
Sarcomeres Compartments of arranged filaments
Basic functional unit of a myofibril
Copyright 2009, John Wiley & Sons, Inc.
Skeletal Muscle Tissue Z discs
Separate one sarcomere from the next
A band Thick and thin filaments overlap
I band Lighter, contains thin filaments but no thick filaments
H zone Center of each A band which contains thick but no thin filaments
M line Supporting proteins that hold the thick filaments together in the H
zone
Copyright 2009, John Wiley & Sons, Inc.
Skeletal Muscle Tissue Contractile Proteins
Myosin Thick filaments
Functions as a motor protein which can achieve motion
Convert ATP to energy of motion
Actin Thin filaments
Actin molecules provide a site where a myosin head can attach
Tropomyosin and troponin are also part of the thin filament
Structural Proteins Titin
Stabilize the position of myosin
Dystrophin Links thin filaments to the sarcolemma
Copyright 2009, John Wiley & Sons, Inc.
Contraction and Relaxation of Skeletal Muscle
Myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere
Progressively pulling the thin filaments toward the center of the sarcomere
Leading to shortening of the entire muscle
https://youtu.be/hr1M4SaF1D4
Contraction and Relaxation of Skeletal Muscle
Copyright 2009, John Wiley & Sons, Inc.
Contraction and Relaxation of Skeletal Muscle
The onset of contraction begins with the SR releasing calcium ions into the muscle cell
Where they bind to actin opening the myosin binding sites
Copyright 2009, John Wiley & Sons, Inc.
Contraction and Relaxation of Skeletal Muscle
Botulinum toxin Blocks release of ACh from synaptic vesicles
May be found in improperly canned foods A tiny amount can cause death by paralyzing respiratory
muscles
Used as a medicine (Botox®) Strabismus (crossed eyes)
Blepharospasm (uncontrollable blinking)
Spasms of the vocal cords that interfere with speech
Cosmetic treatment to relax muscles that cause facial wrinkles
Alleviate chronic back pain due to muscle spasms in the lumbar region
Copyright 2009, John Wiley & Sons, Inc.
Contraction and Relaxation of Skeletal Muscle
Curare A plant poison used by South American Indians on
arrows and blowgun darts
Causes muscle paralysis by blocking ACh receptors inhibiting Na+ ion channels
Derivatives of curare are used during surgery to relax skeletal muscles
Anticholinesterase Slow actions of acetylcholinesterase and removal of
ACh
Can strengthen weak muscle contractions Ex: Neostigmine
Treatment for myasthenia gravis
Antidote for curare poisoning
Terminate the effects of curare after surgery
Copyright 2009, John Wiley & Sons, Inc.
Types of Skeletal Muscle Fibers
Slow Oxidative Fibers (SO fibers) Smallest in diameter
Least powerful type of muscle fibers
Appear dark red (more myoglobin)
Generate ATP mainly by aerobic cellular respiration
Have a slow speed of contraction
Very resistant to fatigue
Adapted for endurance-type activities such as running a marathon
Copyright 2009, John Wiley & Sons, Inc.
Types of Skeletal Muscle Fibers
Fast Glycolytic Fibers (FG fibers) Largest in diameter
Generate the most powerful contractions
Have low myoglobin content
Few mitochondria
Appear white in color
Generate ATP mainly by glycolysis
Fatigue quickly
Adapted for intense anaerobic movements of short duration Weight lifting
Copyright 2009, John Wiley & Sons, Inc.
Types of Skeletal Muscle Fibers
Fast Oxidative–Glycolytic Fibers (FOG fibers) Intermediate in diameter
between the other two types of fibers
Have a dark red appearance
Generate considerable ATP by aerobic cellular respiration
Moderately high resistance to fatigue
Generate some ATP by anaerobic glycolysis
Contribute to activities such as walking and sprinting
Copyright 2009, John Wiley & Sons, Inc.
Smooth Muscle Tissue Physiology of Smooth Muscle
Contraction lasts longer than skeletal muscle contraction
Contractions are initiated by Ca++ flow primarily from the interstitial fluid
Ca++ move slowly out of the muscle fiber delaying relaxation
Able to sustain long-term muscle tone Prolonged presence of Ca++ in the cell provides for a state of
continued partial contraction
Important in the: Gastrointestinal tract where a steady pressure is maintained on
the contents of the tract
In the walls of blood vessels which maintain a steady pressure on blood
Copyright 2009, John Wiley & Sons, Inc.
Regeneration of Muscular Tissue Hyperplasia
An increase in the number of fibers
Skeletal muscle has limited regenerative abilities Growth of skeletal muscle after birth is due mainly to
hypertrophy
Satellite cells divide slowly and fuse with existing fibers Assist in muscle growth
Repair of damaged fibers
Cardiac muscle can undergo hypertrophy in response to increased workload Many athletes have enlarged hearts
Smooth muscle in the uterus retain their capacity for division
Online Quiz
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Look for this website: http://highered.mcgraw-hill.com/
Go to Chapter 9
Copy and answer #1-20 (skip 5, 10, 11, 16)
ONLY COPY THE CORRECT ANSWER!
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Videos
Muscle Contraction: https://youtu.be/hr1M4SaF1D4
NMJ animation: http://youtu.be/7wM5_aUn2qs
Crash course: https://youtu.be/Ktv-CaOt6UQ
Copyright 2009, John Wiley & Sons, Inc.