Muscle Tissue for Final EXAM Flashcards
attach the muscle to the bone
tendons
plasma membrane of a muscle fiber
Sarcolemma
cytoplasm of a muscle fiber
Sarcoplasm
long protein cords occupying most of sarcoplasm
Myofibrils
packed into spaces between myofibrils
Mitochondria
smooth ER that forms a network around each myofibril
Sarcoplasmic reticulum (SR)
tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side
T tubules
a T tubule and two terminal cisterns associated with it
Triad
made of several hundred myosin molecules, each molecule shaped like a golf club. Two chains intertwined to form a shaft-like tail and a double globular head. The heads are directed outward in a helical array around the bundle. The heads on one half of the thick filament angle to the left, while heads on other half angle to the right. The bare zone is the area in the middle with no heads.
Thick filaments
two intertwined strands made up of string of globular (G) actin subunits each with an active site that can bind to head of myosin molecule.
Thin filaments
segment from Z disc to Z disc
Sarcomere
Darkest part is where thick filaments overlap a hexagonal array of thin filaments
A band
not as dark; middle of A band; thick filaments only
H band
middle of H band
M line
means light
I band
provides anchorage for thin filaments and elastic filaments
Z disc
A segment of myofibril from one Z disc to the next in the fiber’s striation pattern.
Sarcomere
Fibrous protein strands that carry out the contraction process.
Myofilaments
one nerve fiber and all the muscle fibers innervated by it
Motor unit
have about three to six muscle fibers per neuron which allows for
fine degree of control.
Small motor units
have hundreds of fibers allowing for more strength than control. Leads to powerful contractions.
Large motor units
Small motor units examples
Eye and hand muscles
Large motor units examples
Quadriceps femoris and gastrocnemius
point where a nerve fiber meets its target cell.
synapse
gap between axon terminal and sarcolemma
Synaptic cleft
a terminal branch at the end of the part of synpatic neuron
synaptic knob
Four major phases of contraction and relaxation
Excitation
Excitation–contraction
Contraction
Relaxation
a process in which nerve action potentials lead to muscle action potentials
excitation
events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract
Excitation–contraction coupling
the step in which the muscle fiber develops tension and may shorten
Contraction
when stimulation ends, a muscle fiber relaxes and returns to its resting length
Relaxation
the amount of tension generated by a muscle depends on how stretched or shortened it was before it was stimulated
Length–tension relationship
a quick cycle of contraction and relaxation when stimulus is at threshold or higher.
Twitch
very brief delay between stimulus and contraction
Latent period
time when muscle generates external tension
Contraction phase
time when tension declines to baseline
Relaxation phase
an increase in tension that occurs when each successive stimuli is delivered after the relaxation phase of the preceding twitch.
Treppe
higher frequency stimuli produce what
temporal (wave) summation
Each new twitch rides on the previous one generating higher tension with only partial relaxation between stimuli.
wave summation
Higher frequency stimuli with each new twitch riding on the previous twitch. Only partial relaxation between stimuli till it reaches maximum level of tension.
Incomplete Tetanus
Unnaturally high stimulus frequencies (in lab experiments) cause a steady, contraction and muscle never begins to relax.
Complete (fused) Tetanus
Muscle produces internal tension but external resistance causes it to stay the same length.
Isometric muscle contraction
Muscle changes in length with no change in tension.
Isotonic muscle contraction
muscle shortens as it maintains tension
Concentric contraction
example of concentric contraction
lifting weights
muscle lengthens as it maintains tension
Eccentric contraction
example of eccentric contraction
slowly lowering weight
Two main pathways of ATP synthesis
Anaerobic fermentation
Aerobic respiration
enables cells to produce ATP in the absence of oxygen; yields little ATP and lactate, which needs to be disposed of by the liver.
Anaerobic fermentation
produces far more ATP; does not generate lactate; requires a continual supply of oxygen.
Aerobic respiration
supply oxygen to the cells in your muscles
myoglobin
transfers Pi from one ADP to another, converting the latter to ATP
Myokinase
the combination of ATP and CP which provides nearly all energy for short bursts of activity. Enough energy for 6 s of sprinting.
Phosphagen system
uses carbohydrates (glucose) stored in the muscles as Glycogen
Glycogen lactic acid system
what type of breathing is Short-Term Energy
Anaerobic Fermentation
what type of breathing is Long-Term Energy
Aerobic Respiration
Three major types of skeletal muscle fibers
- fast glycolytic
- slow oxidative
- Intermediate fibers
what type of twitch is well adapted for endurance; resist fatigue by oxidative (aerobic) ATP production
slow oxidative
what kind of muscles has slow-twitches (slow oxidative)
muscles that maintain posture
(ex: erector spinae of the back, soleus of calf)
white, or type II fibers
Fast glycolytic
what kind of muscles has fast-twitches (Fast glycolytic)
quick and powerful muscles
(ex: eye and hand muscles, gastrocnemius of calf and biceps brachii)
what type of twitch is well adapted for quick responses
Fast-twitch (Fast glycolytic)
Properties of cardiac muscle
- Contracts with regular rhythm
- works at anytime
- resistant to fatigue
- cells contract in unison
can contract without need for nervous stimulation
Cardiac muscle
Uses aerobic respiration almost exclusively, rich in myoglobin and glycogen.
cardiac muscle
named for its lack of striations
smooth muscle
lack nerve supply; others receive input from autonomic fibers with many varicosities containing synaptic vesicles
smooth muscle
what type of twitch does cardiac muscles exhibit
slow
Takes longer to contract but can remain contracted for a long time without fatigue
smooth muscle
how does smooth muscle contract
is always triggered by Ca2+, energized by ATP, and achieved by sliding filaments
how does smooth muscle get excited
- Autonomic activity
- Hormones, carbon dioxide, oxygen, and pH
- Temperature
- Stretch
- Audtorhythmicity
