Exm 3 (ch 10) Flashcards
The organization of muscles? Smallest to largest
Muscle filaments -> myofibrils -
> muscle fibers -> fascicle ->
muscle organ
Fibrous connective tissue that surrounds the entire muscle organ
Epimysium
Connective tissue that surrounds a fascicle (group of muscle fibers)
Perimysium
Connective tissue that surrounds each muscle fiber
Endomysium
What is responsible for contraction?
Sarcomere
Invagination of sarcoplasm that carry action potential, stimulating the muscle to contract
T Tubules
Is a membrane sac that wraps around each myofibril. Calcium is released here. 
Sarcoplasmic reticulum
Sarcoplasmic reticulum on both sides of the T tubule
Terminal cisterns
Cells between the Endomysium and muscle fiber. provides extra nutrients. Their function is to repair damaged muscles. 
Satellite cells
Connective tissue that extends beyond the muscle and attaches muscle to bone (epimysium)
Tendons
Broad and flat tendons are called
Aponeurosis
Each muscle fiber is made of myofibrils that have
Myofilaments (myosin and actin)
Gives muscle fiber its elasticity. (The squiggly line connected to myosin in a sarcomere)
Titin
Lighter, less dense area of sarcomere that contains remainder of thin filaments, but no thick, filaments. A Z disc passes through the center of each. Only thin filaments.
I band
Dark, middle part of sarcomere that extends entire length of thick filaments, and includes those parts of thin filaments that overlap the thick filaments. Extends the entire length of thick filaments, even where there is no overlap. 
A band
Narrow region in center of each A band that contains thick filaments, but no thin filaments 
H band
Narrow, plate shaped regions of dense material that separate one sarcomere from the next 
Z discs
Has the filament attachments with no cross bridges
M line
Which two change as muscle contracts
I and H band
Muscle proteins. Contractile:
Myosin and actin
Muscle proteins. Regulatory:
Troponin and tropomyosin
Muscle proteins. Structural:
Titin
When calcium is released from ____ it binds specifically to_____.
Sarcoplasmic reticulum. Troponin.
Ca2+ release from sarcoplasmic reticulum -> binds troponin ->troponin/tropomyosin complex exposes actin binding sites -> myosin attaches -> head bends
Powerstroke
Cross-bridge can’t detach since
ATP synthesis has ceased. Calcium leaks out of sarcoplasmic reticulum
Rigor mortis
All fibers stimulated by a single motor neuron 
Motor unit
What controls the strength of the contraction? 
Motor neurons
Axons from these motor fibers secrete what
Acetylcholine
When you stimulate a motor neuron it is a what kind of response 
An all or nothing response
pulls remaining acetylcholine out of the synapse at the
NMJ – depolarization of the postsynaptic membrane stops which causes the
sarcoplasmic reticulum to stop releasing calcium
Acetylcholinesterase
______ in sarcoplasmic reticulum binds calcium and allows for even
more Ca2+ storage. A conditional component of sarcoplasmic reticulum. Activated by Ca2+-ATPase. A way to stop contraction
Calsequestrin
Troponin/tropomyosin falls back over the binding sites from what?
The lack of Ca2+
________:enlargement of existing muscle fibers. Due to increased production of myofibrils, mitochondria, sarcoplasmic reticulum and other organelles
Muscular hypertrophy
______: increase in the number of fibers due to satellite cells, growing slow and helping build muscle 
Muscular hyperplasia 
______: decrease in size of muscle fibers due to loss of myofibrils. Occurs as a result of aging or disuse. Lack of exercise can cause ~flaccid~ muscle that gets flabby and soft – call it ~atrophied~
Muscle atrophy
Muscles have 3 ways to produce ATP:
Creatine phosphate, anaerobic glycolysis, aerobic respiration 
rapid use but runs out quickly
Creatine phosphate
not very effective long-term
Anaerobic glycolysis
longer to make but most effective
Aerobic respiration
Creatine phosphate. Need energy:
creatine phosphate donates
phosphate to ADP making ATP and creatine
At rest: phosphate attached
to creatine
Creatine phosphate
Duration of energy provided for creatine phosphate 
15 seconds
When creatine phosphate stores are depleted, glucose is converted into pyruvic acid to generate ATP via
Anaerobic glycolysis
Producing 2 ATP for every glucose that you feed into this cycle
Anaerobic glycolysis 
Duration of energy provided for anaerobic glycolysis
2 minutes
Under aerobic conditions, pyruvic acid can enter the mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of A T P
Aerobic respiration
Our main source of energy
Aerobic respiration
Our main source of energy
Aerobic respiration
Duration of energy provided for aerobic respiration
Several minutes to hours
Is the inability to maintain force of contraction after prolonged activity
Muscle fatigue
occurs due to changes in the central nervous system and generally results in cessation of exercise
Central fatigue
consists of a somatic motor neuron and the muscle fibers it innervates
A motor unit
Activating only a few motor units will generally result in a
Weak muscle contraction
Motor units contract alternatively, to sustain contractions for longer periods of time 
Motor unit recruitment
The brief contraction of all muscle fibers in a motor unit in response to a single action potential
A single motor unit contraction 
very short, the time period
between threshold stimulus and shortening of muscle. Right when muscle receives impulse
Latent period
shortening of muscle
Contraction period
returns to original length and
Ca2+ returns to sarcoplasmic reticulum
Relaxation period
after contraction when muscle
cannot immediately respond to threshold stimulus
Refractory period
after one complete twitch muscle uses the same stimulus to make the contraction greater than the original
Treppe
is what happens BEFORE completion of the relaxation period
Wave summation
Even when at rest, a skeletal muscle exhibits a small amount of tension called_____ . It is established by the alternating, involuntary activation of small groups of motor units in a muscle
Tone
tension is constant while muscle length changes
Isotonic
(Isotonic) concentric
Muscle length shortens
(Isotonic) eccentric
Muscle length lengthens (while lowering a weight). Sort of like relaxing or being overpowered. 
muscle contracts but does not change length
Isometric
Muscle fibers that bind O2, and don’t fatigue as fast
Myoglobin
lots of myoglobin, red
• Marathon runners
Slow oxidative
glycolytic fibers with lots of myoglobin, red
• 5K runners
Fast oxidative
low myoglobin and white in color
• Sprinters or body builders
Fast glycolytic
The site of aerobic respiration
Mitochondria
centrally- located nucleus, intercalated discs , and desmosomes. Gap junctions allow action potentials to spread from one muscle fiber to another. Branched
Cardiac muscle
muscle cells have more
mitochondria and their contractions
last 10-15 times longer than skeletal
muscle contractions
Cardiac
muscle contractions start more slowly and last longer than the other 2. Stretchy. Dense bodies: scattered throughout cytoplasm and attach to sarcolemma, similar to Z discs. Myofilaments attach to dense bodies and pull when muscle contracts
Smooth muscle
binds calcium NOT troponin
• Activates myosin light chain kinase -> phosphorylation of myosin head -> actin
attaches
Calmodulin
Neuromuscular junction from beginning to end
action potentials trigger voltage gated calcium channels->exocytosis of acetylcholine->Na+ channels on the postsynaptic membrane open-> depolarization of the muscle -> calcium release from the sarcoplasmic reticulum
