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Chapter 10
Muscles Exam III
83
Anatomy
Undergraduate 2
10/24/2011

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Term
Number of muscles
Definition
40% of body weight, Almost 600 muscles (around 3 muscles per bone)
Term
Muscle composition
Definition
70% H2O, Mostly protein (actin & myosin), small amount of CHO( stored as glycogen), small amount of lipid(stored)
Term
Muscle excitability (or irritability)
Definition
Muscle tissue contracts in response to nervous stimuli (electrical current is ion movement)
Term
Muscle contractility
Definition
Muscle tissues responds to electrical stimuli by contracting, muscles only pull they don't push.
Term
Muscle extensibility
Definition
Once muscle fibers relax they can be stretched beyond their resting length by contraction of opposing muscle
Term
Muscle elasticity
Definition
Muscle fibers recoil to original length after stretching
Term
Muscle functions
Definition
Movement, thermogenesis, posture/support.
Term
Function: Movement
Definition
Move the body (and/or parts of the body)
Term
Function: Thermogenesis
Definition
Heat production, are in a continuous state of fiber activity.
Term
Function: Posture/Support
Definition
Maintain posture, stabilize joints, support viscera, many times you don’t even notice that postural muscles are working.
Term
Myokymia
Definition
Twitching of muscle segments.
Term
Skeletal muscle
Definition
Striated, voluntary, cells are called fibers
Term
Cardiac muscle
Definition
Striated, involuntary
Term
Smooth muscle
Definition
No striations, involuntary. cells are called fibers
Term
What does muscle contraction depend on?
Definition
Myofilaments(located in cytoplasm)
Term
Plasmalemma
Definition
sarcolemma
Term
Cytoplasm
Definition
sarcoplasm
Term
Skeletal Muscle CT: Endomysium
Definition
Surrounds individual muscle cells, binds adjacent fibers together and supports capillaries and nerve endings that serve the muscle fibers
Term
Skeletal muscle CT: Perimysium
Definition
Binds group of muscle cells (fascicle), supports blood vessels and nerve fibers
Term
Skeletal muscle CT: Epimysium
Definition
Binds fascicles together (dense irregular CT) and surrounds entire muscle, is continuous with tendon.
Term
Fascicle
Definition
Smallest unit that can be seen with naked eye
Term
Skeletal muscle CT
Definition
All 3 layers of CT are continuous with the tendons of mm
Term
Fascia
Definition
Fibrous CT that covers muscle and attaches it to skin.
Term
Blood vessels in Skeletal muscle
Definition
Generally, each skeletal muscle is supplied by one nerve, one artery, and one or more veins
Term
Nerves in Skeletal muscle
Definition
Each muscle fiber is contracted by one nerve ending – Contact point is neuromuscular junction (aka motor endplate)
Term
Motor unit
Definition
one motor neuron and all the muscle fibers it stimulates.
Term
Innervation ratios
Definition
LARGE ratio 1:1000 = strong motor unit (ex: quads)
SMALL ratio 1:10 = fine, precise control (ex: eyeball)
Within each muscle of the body there are MANY motor units, ranging from small to large ratios
Term
Electromyogram(EMG)
Definition
detects electrical currents of activation process
Term
Muscle attachments
Definition
Skeletal muscles cross at least one joint, extend from one bone to another, muscles attach to origins and insertions via CT that extends into periosteum.
Term
Muscle attachments: Origin
Definition
less movable muscle attachment
Term
Muscle attachments: Insertion
Definition
more movable muscle attachment, insertion is pulled toward origin
Term
Biarticular
Definition
muscles span 2+ joints
Term
Muscle attachments: Direct attachment
Definition
short CT strands
Term
Muscle attachments: Indirect attachment
Definition
CT extends beyond muscle to form tendon OR aponeurosis (flat sheet) A few tendons or aponeroses attach to skin, cartilage, sheets of fascia, or raphe
Term
Raphe
Definition
Seam of fibrous tissue.
Term
Retinaculum
Definition
Strong band of CT that binds a group of tendons.
Term
Macroscopic to microscopic
Definition
Muscle, Fasciculus, Muscle cell, myofibrils, sarcomeres.
Term
Myofibrils
Definition
Strand of regularly arranged threadlike fibers that extend entire length of muscle, densely packed, contain myofilaments (actin and myosin), basically a chain of sarcomeres.
Term
Sarcomeres
Definition
Found in striated muscle (skeletal and cardiac)- due to arrangement of myofilaments. The basic unit of structure and function in muscle.
Term
Actin
Definition
Thin filaments, a protein that is 6 nm in diameter.
Term
Myosin
Definition
Thick filaments, a protein that is 16 nm in diameter.
Term
Sarcomere function
Definition
contraction- filaments slide over each other, myosin heads attach to active sites on actin (sliding filament theory)
Term
Sarcomere: Z lines
Definition
At ends of sarcomere (one sarcomere goes z line to z line)
Place where actin is attached
Term
Sarcomere M-line
Definition
Middle of sarcomere
Where myosin is anchored
Term
Sarcomere: H zone
Definition
Has bright appearance
ONLY myosin exists there (no overlap with actin)
Includes M-line
Term
Sarcomere: A bands
Definition
Includes ANYWHERE there is myosin, including where it overlaps with actin
Includes M-line and H zone
Appearance is dark bands
Term
Sarcomere I bands
Definition
ONLY actin exists there (NO myosin)
Term
Muscle contraction: Crossbridge formation
Definition
Myosin binds to actin, requires calcium from SR (sarcoplasmic reticulum)
Trigger for calcium release is (efferent) motor neuron impulse
Term
Muscle contraction: Crossbridge movement
Definition
Z lines are pulled toward M-line
Myosin attaches to actin and pulls actin toward center of sarcomere
Requires ATP hydrolysis
Term
Muscle contraction: Crossbridge release
Definition
Requires binding of fresh ATP
Term
Regional changes during concentric contraction
Definition
Entire sarcomere = shortens
Z lines = shorten, pulled in toward M-line
H zone = shortens
A bands = DOES NOT shorten (myosin’s length itself doesn’t shorten)
I bands = shorten
Term
Fiber length and Contraction force
Definition
Ideal resting length for muscle fibers is that at which they can generate the most force
The greatest force is produced when the fiber starts out slightly stretched
Term
Titan
Definition
protein that prevents overstretching; runs from Z line to M line
Term
Sarcoplasmic reticulum
Definition
smooth ER with interconnecting tubules that surround myofibrils
Stores Ca++, which is released for muscle contraction – diffuses to thin filaments
Ca++ Pumped back into SR after contraction
Term
T tubules: invaginations of sarcolemma
Definition
Reach deepest regions of cell
Conduct nerve impulses
Term
Motor endplate
Definition
Located in region of muscle cell membrane (is a receptor)
Electrical current causes release of neurotransmitter (acetylcholine) from nerve terminals onto muscle
Ach hooks up to the motor endplate on the sarcolemma

Binding of Ach causes another electrical current across muscle cell membrane and into t-tubule, causes calcium release from SR
Term
Motor endplate: What is the type of receptor?
Definition
Nicotinic cholinergic
Term
One motor unit only contains...
Definition
one muscle fiber type
Term
Skeletal muscle fiber types: Overview
Definition
There is actually a wide continuum of fiber types that have various mechanical and enzymatic properties.
Fiber types are often referred to in terms contraction speed (fast vs. slow; Type I vs. Type II) but are also categorized in terms of how they manufacture ATP (oxidative vs. glycolytic)
Term
Skeletal Muscle gender stats
Definition
The average man, woman, child (regardless of race) has about 50  5% slow, and 50  5% fast (equal percentage of IIA, IIB)
There are NO significant gender differences in fiber types that would ALONE account for any gender differences in sport performance
Term
Skeletal Muscle Fiber Types: Individual differences
Definition
There are INTER (among different people)-individual differences in fiber type distribution, so my biceps might have 45% ST and yours might have 55% ST
Term
Cardiac muscle: Overview
Definition
Heart wall muscle, arranged in bundles
Striated and uses sliding filament
Cells are single (not fused like skeletal), separated by endomysium
Term
Cardiac Muscle: Each cell is...called a fiber?
Definition
NOT, fiber is a row of joined cells.
Term
Cardiac Muscle: Typical... are present?
Definition
Sarcomeres
Term
Cardiac Muscle: Myofibrils are...
Definition
difficult to discern because they are branched (many mitochondria)
Term
Cardiac Muscle: Role of Ca++
Definition
Triggered by Ca++ but simpler SR and less T tubules
Ca++ from extracellular fluid triggers Ca++ release – diffusion into sarcomeres
Term
Cardiac Muscle: Each cell can...
Definition
rhythmically contract without innervation
Term
Cardiac muscle: Cells stay slightly...
Definition
shorter than optimal length so that they can stretch due to greater volumes of blood returned to heart (increases contraction force)
Term
Smooth muscle: Overview
Definition
Sliding filament mechanism for contraction (not as well understood)
Spindle-shaped cells, separated by endomysium
Term
Smooth muscle: Locations where found
Definition
Inside eye, walls of circulatory vessels, respiratory tubes, digestive tubes, urinary organs, reproductive organs
Term
Smooth muscle: In walls of hollow viscera...
Definition
fibers are grouped in sheets – often 2 sheets (longitudinal layer and circular layer)
Term
Smooth Muscle: cell info
Definition
No striations, no sarcomeres – but there are thin and thick filaments
Term
Smooth muscle: Myofilaments move muscle by...
Definition
interacting with cytoskeleton elements (intermediate filaments that have dense bodies, which anchor thin filaments)
Term
Smooth Muscle: Ca++ stimulates...
Definition
contraction – different from skeletal (no T tubules)
Term
Smooth Muscle: Contractions are...
Definition
slow, fatigue-resistant
Term
Smooth muscle: Involuntary control
Definition
only a few cells in each sheet are innervated – impulse spreads through adjacent fibers
Term
Muscle disorders: Smooth muscle
Definition
has few problems – mostly due to irritants
Term
Muscular Dystrophy
Definition
Inherited muscle-destroying diseases (group), usually appear in childhood
Muscle fibers degenerate
Term
Fibromyalgia
Definition
Chronic pain of unknown cause
Severe musculoskeletal pain, fatigue, sleep abnormalities, and headache
Term
Development of muscle: Overview
Definition
Most muscle develops from myoblasts
Fuse together to make skeletal muscle
Do not fuse to make cardiac, smooth muscle
Term
Development of muscle: Skeletal muscle...
Definition
strength is generally greater in men, mostly due to testosterone levels
Term
Development of muscle: With age...
Definition
amount of CT in muscle increases, # of muscle fibers decreases, and muscles become stringier
Term
Development of muscle: Body weight...
Definition
declines due to loss of muscle mass, leads to decline in strength (sarcopenia = muscle wasting)
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