Muscle tissue
Eccentric and concentric
2 types of isotonic contraction
Isometric contraction
A muscle contracts but does not change in length.
Weak muscle contraction
Activation of few motor units
Strong muscle contraction
Activation of many motor units
alpha-actinin
(structural protein of Z disc)
anaerobic glycolysis, 2 mins
Breakdown of muscle glycogen into glucose that is converted into pyruvic acid to generate ATP. And what duration of energy does it provide?
Synaptic end bulbs
Axon terminal divides into a cluster of?
Mitochondria, 10-15 x
Cardiac muscle cells have more? Their contractions last for how longer?
ATP, carbon dioxide, water, heat
Cellular Respiration produces?
Muscle fiber (cell)
Contains sarcoplasm, myofibrils, peripherally located nuclei, mitochondria, transverse tubules, sarcoplasmic reticulum, and terminal cisterns
Actin
Contractile protein that is the main component of a thin filament; each actin molecule has a myosin-binding site where the myosin head of a thick filament binds during muscle contraction
Myosin
Contractile protein that makes up a thick filament; molecule consists of a tail and 2 myosin heads, which bind to myosin-binding sites on actin molecules of a thin filament during muscle contraction
A band
Dark, middle part of the sarcomere that extends for the entire length of the thick filaments and includes those parts of the thin filament that overlap them
relaxation period
During the third phase, also lasting 10-100 msec, Ca2+ is actively transported back into the sarcoplasmic reticulum, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases.
Muscle Tone
Even when at rest, a skeletal muscle exhibits a small amount of tension, called tone. Tone is established by the alternating, involuntary action of small groups of motor units in a muscle.
Motor units
It consists of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates
I band
Lighter, less dense area of the sarcomere that contains the remainder of the thin filaments but no thick ones. A Z disc passes through the center of each such band.
Fast oxidative-glycolytic fibers
Has periods where more energy and periods of rest are ne eded, with slower cellular respiration
muscle fiber (cell)
Long, cylindrical cell covered by endomysium and sarcolemma
28 34 ATP molecules
Mitochondria contains how many ATP molecules?
aerobic respiration
If sufficient oxygen is present, the pyruvic acid formed by glycolysis enters the mitochondria, where it undergoes aerobic respiration, a series of oxygen-requiring reactions (the Krebs cycle and the electron transport chain) that produce ATP, carbon dioxide, water, and heat
1) From creatine phosphate 2) By anaerobic glycolysis 3) By cellular respiration
Muscle fibers have three ways to produce ATP
H zone
Narrow region in the center of each A band that contains thick filaments but no thin filaments
Z discs
Narrow, plate-shaped regions of dense material that separate one sarcomere from the next
fast glycolytic fibers
Ne eds short bursts of energy
Chemical stimuli
Neurotransmitters released by neurons, hormones distributed by the blood or even local changes in pH
skeletal muscle
Organ made up of fascicles that contain muscle fibers (cells), blood vessels, and nerves; wrapped in epimysium
Pyruvic acid
This can enter the mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of ATP.
excitation-contraction coupling
This concept connects the events of a muscle action potential with the sliding filament mechanism.
wave summation
This phenomenon, in which stimuli arriving at different times cause larger contractions
Myofibrils
Threadlike contractile elements within the sarcoplasm of muscle fiber that extend for the entire length of the fiber. Composed of filaments
contactile proteins
Proteins that generate force during muscle contractions
regulatory proteins
Proteins that help switch the muscle contraction process on and off
Structural proteins
Proteins that ke ep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility, and link myofibrils to the sarcolemma and the extracellular matrix
M line
Region in the center of the H zone that contains proteins that hold thick filaments together at the center of the sarcomere
Troponin
Regulatory protein that is a component of thin filament; when calcium ions (Ca2+) bind to this, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin.
Tropomyosin
Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin.
Fused tetanus (complete)
When a skeletal muscle fiber is stimulated at a higher rate of 80 to 100 times per second, it does not relax at all. A sustained contraction in which individual twitches cannot be detected
unfused tetanus (incomplete)
When a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli. The result is a sustained but wavering contraction called
muscle shortening
Sliding of thin filaments past thick filaments produces
Slow oxidative Fibers
Slow enough pace for cellular respiration to occur. Needs a lot of energy
synaptic vesicles
Suspended in the cytosol within each synaptic end bulb are hundreds of membrane-enclosed sacs called
isotonic contraction
Tension is constant while muscle length changes.
Axon terminal
The end of the motor neurons
contraction period
The second phase, last 10-100 msec, During this time, Ca2+ binds to troponin, myosin-binding sites on actin are exposed, and cross-bridges form
How many units are activated
The strength of a muscle contraction depends on
neuromuscular junction
Where muscle potentials arise at
Creatine phosphate
While muscle fibers are relaxed, they produce more ATP than they need for resting metabolism. Most of the ̄excess ATP is used to synthesize__, an energy-rich molecule that is found in muscle fibers.
To "pay back" their oxygen debt
Why do people continue to breathe heavily for a time after stopping exercise?
Tropomyosin
With active site where myosin head attach to pull the thin filament towards the M Line
cellular respiratory, minutes up to hours
Within mitochondria, pyruvic acid, fatty acids, and amino acids are used to produce ATP via___, an oxygen-requiring set of reactions.
electrical signals
action potential that arises in muscular tissue itself (own)
creatine kinase
catalyzes the transfer of a phosphate group from CP to ADP to rapidly yield ATP.
Cardiac muscle
has the same arrangement as skeletal muscle, but also has intercalated discs.
Contractility
the ability to contract forcefully when stimulated by action potential
Electrical excitability
the ability to respond to certain stimuli by producing electrical signals.
Elasticity
the ability to return to its original length and shape
extensibility
the ability to stretch
Synapse
is a region where com- munication occurs between two neurons, or between a neuron and a target cell—in this case, between a somatic motor neuron and a muscle fiber.
Central fatigue
is the type of fatigue associated with the concentration of neurotransmitters within the central nervous system, which affects muscle function.
excitation-contraction coupling
occurs at the triads of the skeletal muscle fiber
muscle fatigue
the inability to maintain the force of contraction after prolonged activity.
Thick filaments (myosin, dark) and Thin filaments (actin, light)
two types of contractile proteins within myofibril
Neurotransmitter
the first cell communicates with the second by releasing a chemical messenger called
length-tension relationship
The force of a muscle contraction depends on the length of the sarcomeres in a muscle before contraction.
Nebulin
(anchors thin filaments to Z disc)
Titin
(connects Z disc to M line)
Myomesin
(forms M line proteins)
Dystroponin
(links thin filament to integral membrane proteins)
muscle fascicle
Bundle of muscle fibers wrapped in perimysium
Smooth muscle
Found in most visceral organs (e.g., intestines, stomach) Work automatically without you being aware of them Involved in many 'houseke eping' functions
Hyperplasia
Increase in cell number
hypertrophy
Increase in cell size
twitch contraction
Is the brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron.
The sliding filament mechanism
Myosin pulls on actin > Thin filament slides inward > Z discs move toward each other, and the sarcomere shortens > Muscle contraction
latent period
The delay, which lasts about 2 msec, is termed? During this period, the muscle action potential sweeps over the sarcolemma and calcium ions are released from the sarcoplasmic reticulum
a) Replenishing CP stores b) Converting lactate into pyruvate c) Reloading O2 onto myoglobin
The extra oxygen goes toward?
a. Binding of calcium b. Crossbridge formation c. Power stroke d. Crossbridge detachment
What are the 4 contraction cycle?
T - TROPOMYOSIN. I - F ACTIN C - CALCIUM IONS
What are the subunits of Troponin
Creatine phosphate, 15 seconds
What is added to ADP to create a 1 ATP? And what is the duration of energy provided?
Acetylcholine (ACh)
What is inside the synaptic vesicles?
anaerobic glycolysis
When muscle activity continues and the supply of creatine phosphate within the muscle fiber is depleted, glucose is catabolized to generate ATP.
Synaptic cleft
a small gap that separates the two cells, between somatic motor neuron and a muscle fiber.
