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Exercise Physiology
Ch. 8 Muscle
65
Physiology
Undergraduate 1
10/20/2013

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Term
How many muscles does the human body contain?
Definition
over 400

40-50% of body weight
Term
Function of skeletal muscle (3)
Definition
Force production for locomotion and breathing

Force production for postural support

Heat production during cold stress
Term
Flexors
Definition
decrease joint angle
Term
Extensors
Definition
increase joint angle
Term
Epimysuim
Definition
Surrounds entire muscle
Term
Perimysuim
Definition
Surrounds fascicles (bundles of muscle fibers)
Term
Endomysium
Definition
surrounds individual muscle fibers
Term
Basement membrane
Definition
just below endomysium (bottom layer of connective tissue covering muscle
Term
Sarcolemma
Definition
Muscle cell membrane
Term
Satellite Cells
Definition
Play role in muscle growth and repair

More nuclei allow for greater protein synthesis

Important for adaptations to strength training
Term
Myonuclear domain
Definition
cytoplasm surrounding each nucleus
Term
Myofibrils
Definition
contain contractile proteins (actin and myosin)
Term
Actin
Definition
thin filament
Term
Myosin
Definition
thick filament
Term
Parts of sarcomere (5)
Definition
z line

m line

h zone

a band

I band
Term
Sarcoplasmic reticulum
Definition
storage sites for calcium

terminal cisternae
Term
Transverse tubules
Definition
extend from sarcolemma to sarcoplasmic reticulum
Term
Neuromuscular junction
Definition
Junction between motor neuron and muscle fiber
Term
Motor end plate
Definition
pocket formed around motor neuron by sarcolemma
Term
Neuromuscular cleft
Definition
gap between neuron and muscle fiber
Term
What is released from the motor neuron to the motor end plate and why?
Definition
Ach (acetylcoline)

causes an end-plate potential (EPP)
Term
EPP
Definition
end-plate potential

causes depolarization of muscle fiber
Term
Sliding filament theory
Definition
actin moves over myosin and crossbridges deliver power stroke to shorten muscle
Term
What happens to ATP during a contraction of muscle
Definition
Myosin ATPase breakes down ATP as fiber contracts
Term
Excitation-Contraction Coupling
Definition
Depolarization of motor end plate is coupled to muscular contraction
Term
Muscle Fatigue
Definition
Decline in muscle power output (lower force generation and velocity of muscle shortening)

2 types: high intensity, low intensity
Term
High-intensity exercise muscle fatigue
Definition
about 60 secs

build-up of lactate, H+, ADP, P, and free radicals lowers amount of cross bridges that can bind to actin
Term
Long-duration exercise muscle fatigue
Definition
2-4 hours in length

Build-up of free radicals, electrolyte imbalance, and glycogen depletion
Term
Muscle cramps
Definition
Spasmodic, involuntary muscle contrations

2 theories: Electrolyte depletion and dehydration theory

Altered neuromusular control theory
Term
Electrolyte depletion and dehydration theory
Definition
water and sodium loss from sweating causes spontaneous contractions
Term
Altered neuromusular control theory
Definition
abnormal activity in muscle spindle and golgi tendon organ fires motor neurons
Term
Biochemical properties of muscle fiber types
Definition
oxidative capacity

Type of myosin ATPase
Term
Oxidative Capacity
Definition
how much oxygen the muscle can receive

effected by:

number of cailllaries, mitochondria, and amount of myoglobin
Term
Contractile properties of muscle fiber types
Definition
Maximal force production

Speed of contraction

Muscle fiber efficiency
Term
Maximal force production
Definition
force per unit of cross-sectional area
Term
Speed of contraction
Definition
(Vmax)

Myosin ATPase activity
Term
How can you type muscle fibers?
Definition
Stain them with stain that detects ATPase

Lightest uses least O2, Darkest used most O2
Term
Type I fibers
Definition
slow twitch fibers

slow-oxidative fibers
Term
Type IIa fibers
Definition
Intermediate fibers

fast-oxidative glycolytic fibers
Term
Type IIx fibers
Definition
Fast twitch fibers

fast-glycolytic fibers
Term
Non-atheltes fiber types
Definition
50-50 fast and slow twitch fibers
Term
Power athlete fiber types
Definition
Higher percentage of fast fibers
Term
Endurance athletes fiber types
Definition
Higher percentage of slow twitch fibers
Term
Isometric muscle contration
Definition
Muscle exerts force without changing length

pulling against immovable object

Postural muscles
Term
Isotonic (dynamic) muscle contraction
Definition
2 types:

Concentric

Eccentric
Term
Concentric muscle contraction
Definition
muscle shortens during force production

going against gravity
Term
Eccentric muscle contraction
Definition
Muscle produces force but length increase

going with gravity

associated with mucle fiber injury and soreness
Term
Muscle twitch
Definition
Contraction as the result of a single stimulus
Term
Latent period in muscle twitch
Definition
lasts ~5ms
Term
Contraction period in muscle twitch
Definition
Tension is developed

40 ms
Term
Relaxation period in muscle twitch
Definition
Lasts 50 ms

Release of muscle tension
Term
Why is their more speed of shortening in fast fibers?
Definition
SR releases Ca at a faster rate

Higher ATPase activity
Term
Motor unit recruitment
Definition
More motor units or faster motor units = more force
Term
Initial muscle length
Definition
ideal length for force generation

increased cross-bridge formation
Term
Sarcopenia
Definition
muscle loss from aging

10% muscle mass lost between 25-50yrs

40% lost between 50-80years
Term
What happens to muscle fiber types during aging
Definition
less fast twitch more slow twitch
Term
What can delay age-related muscle loss?
Definition
Resistance Training
Term
Cachexia
Definition
rapid loss of muscle mass

50% of cancer patients
20% of cancer deaths
Term
Muscular dystrophy
Definition
Hereditary defects in muscle protein

loss of muscle fibers and weakness
Term
Duchene muscular dystrophy
Definition
most common in childhood

progression varies based on specific disease type
Term
Force-velocity relationship
Definition
at any absolute force, speed of movement is greater in muscle with higher percent of fast-twitch fibers

Maximum velocity of shortening is greatest at the lowest force (true for fast and slow twitch)
Term
Summation
Definition
addition of muscle twitches
Term
Tetanus
Definition
individual contractions are fused in a sustained contraction
Term
Factors of force generation during muscular contraction
Definition
types and number of motor units recruited

initial muscle length

nature of motor units' neural stimulation
Term
Force-power relationship
Definition
as speed of movement increases, peak force generated decreases.

amount of power generated by a muscle group increases as a function of movement velocity
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