Muscle Tissue Flashcards
What is motor unit recruitment?
Is the process whereby the number of active motor units is increased according to need.
The more neurons that are activated (in the spinal cord) the more motor units will be?
Stimulated and the more muscle tension will be produced.
The larger the motor units recruits, the more?
muscle tension will be produced
Are all motor units recruited simultaneously?
No, only the number of motor units needed are recruited
Which motor unit is recruited first?
The smallest, weakest motor units.
Larger, stronger motor units are recruited if?
They are required by the task.
In response to AP, what contracts longer, Cardiac muscle or skeletal muscle?
Cardiac muscle
It contracts 10-15 times longer than skeletal muscle and must continue to do so, without rest, for the life of the individual.
What does cardiac muscle use to respond to each AP?
The rich supply of O2 delivered by the extensive coronary circulation to generate ATP through aerobic respiration,
Muscle fibers of cardiac muscle exhibit
Autorhythmicity
What of the cardiac muscle tissue fibers results in synchronous contraction?
The interconnectedness of fibers
What alters the autorhythmicity of the cardiac muscle tissue?
Autonomic nervous system
Endocrine system
Why is the mitochondria larger and more numerous in the cardiac muscle compared to the skeletal muscle?
In accordance with a greater dependency on aerobic respiration to generate ATP.
True or False
Smooth Muscle is autorhythmic
True
How does smooth muscle generate ATP?
Through anaerobic respiration (glycolysis)
True or False
Smooth Muscle has a high capacity for generating ATP.
False
Has a low capacity
In addition to thick and thin filaments, which filaments are also present in smooth muscle?
Intermediate Filaments
Where do intermediate filaments attach?
Intermediate filaments,
which are functionally similar to Z discs found in striated muscle and found in both the sarcoplasm and the sarcolemma
What generates tension on the intermediate filaments?
Contraction of the thick and thin filaments.
It pulls the dense bodies and causes shortening of muscle fiber.
What are the two types of smooth muscle?
Single-unit smooth muscle tissue (AKA Visceral smooth muscle tissue)
Multiunit smooth muscle tissue
Which type of smooth muscle- fibers connect to one another by gap junctions and contract as a single unit?
Single-Unit (Visceral smooth muscle)
Which type of smooth muscle- fibers lack gap junctions and contract independently?
Multiunit smooth muscle
Electron microscopy has show that _____ can cause damage, including torn sarcolemma’s, damaged myofibrils, and disrupted Z discs.
Intense Exercise
Chemical analysis after exercise has also shown increases in blood levels of?
Myoglobin and creatine kinase, both of which are normally confined within muscle.
What is DOMS?
Delayed onset muscle soreness that follows strenuous exercise by about 12-48 hours
Functions of Muscular Tissue
What are some characteristics of muscular tissue?
Muscles are excitable
Contractible
Extensible
Elastic
Functions of Muscular Tissue
What are the main functions of muscular tissue?
Create Motion
Stabilize body positions and maintain posture
Store substances within the body using sphincters
Move substances by peristaltic contractions
Generate heat through thermogenesis
What are the three types of muscular tissue?
Skeletal
Cardiac
Visceral (smooth muscle)
What is the function of skeletal muscle?
Movement, heat, posture
Where is visceral (smooth muscle) located?
G.I. tract, uterus, eye, blood vessels
What is the function of visceral (smooth muscle) ?
Peristalsis
Blood pressure
Pupil size
Erects hairs
What is the appearance of skeletal muscle?
Striated, multi-nucleated (eccentric)
Fibers parallel
What is the appearance of cardiac muscle?
Striated, one central nucleus
What is the appearance of visceral (smooth muscle)?
No striations, one central nucleus
Which of the three muscular types are voluntary?
Skeletal
Skeletal muscle
A single muscle cell
Fiber
Skeletal muscle
A bundle of muscle fibers (bundle of muscle cells)
Fascicle
Skeletal muscle
An organelle in a muscle fiber composes of filaments
Myofibril
Skeletal muscle
Fibrous protein molecules within myofibrils (the thick and thin filaments that are the contractile proteins)
Filaments
Skeletal muscle Connective tissue
This surrounds a fiber
Endomysium
Skeletal muscle Connective tissue
This surrounds a fascicle
Perimysium
Skeletal muscle Connective tissue
This surrounds the entire muscle
Epimysium
Skeletal muscle Connective tissue
What all blends together and eventually tie into the tendon?
The endomysium, perimysium, epimysium
What nerve cell supplies a group of muscle fibers?
Somatic motor neuron
Each muscle fiber is supplied by how many neurons?
Only one
What is the site where the neuron contacts the muscle fiber called?
Neuromuscular junction
Why are skeletal muscle fibers multinucleated?
During embryonic development, a number of myoblasts fuse to form one skeletal muscle fiber.
T or F
The muscle fibers of skeletal muscle can undergo mitosis?
F
Where is the plasma membrane AKA the sarcolemma found in a individual skeletal muscle fiber?
Beneath the connective tissue (beneath the endomysium).
What is the cytoplasm of the skeletal muscle fiber called/ what is it chocked full of?
Sarcoplasm
Chocked full of contractile proteins arranged in myofibrils
Which way does the T-tubule of the skeletal muscle fiber face?
Opens from the outside fiber toward the interior of the fiber ) like a cul-de-sac)
What are openings that invaginate from the sarcolemma and extend toward the interior of the cell?
T-tubules
What are T-tubules filled with?
Interstitial fluid
What are T-tubules important in the propagation of?
Action potentials
What is the sarcoplasmic reticulum of the skeletal muscle? What does it store?
Smooth endoplasmic reticulum of a muscle fiber
Stores calcium ions, and releases them when the muscle fiber is stimulated.
What is calsequestrin?
A calcium-binding protein inside the sarcoplasmic reticulum, enabling the Ca++ concentration in a relaxed muscle to be 10,000 times higher than in the cytosol
Microscopic organization of skeletal muscle
What is terminal cisterns?
Dilated regions that flank the T-tubules
Microscopic organization of skeletal muscle
What is a triad?
Two terminal cisterns flanking one T-tubule
The basic functional unit of a myofibril is the?
Sarcomere
An arrangement of thick and thin filaments sandwiched between two Z discs.
Sarcomere
What are Myofibrils made of?
Filaments
What are the two types of filaments?
Thin
Thick
What proteins are thin filaments made up of?
Actin
Troponin
Tropomyosin
What is the contractile protein of the thin filament?
Actin
What are the regulatory proteins of the thin filament?
Troponin
Tropomyosin
How many thin filaments are there for every thick filaments?
Two thin filaments
Filaments inside a myofibril are arranged in compartments called?
Sarcomeres
What creates the striations that are seen both in single myofibrils and in whole muscle fibers?
Thick and thin filaments
What are the zones and bands gives rise to a pattern of overlap?
A band I band Z line H zone M line
What is the center of an I band?
Z discs
What is the darker zone, which comprises the length of the thick filaments and a varying overlap of thin filaments?
A band
Where do adjacent sarcomeres abut?
Z discs
What are only thin filaments; consist of parts of 2 adjacent sarcomeres?
I band
What is the center of an A band; only thick filaments?
H zone
What is the midline of a sarcomere?
M line
The tails of what are bound together to form the thick filament?
Myosin molecules
What do the heads (cross bridges) of the myosin molecules bind to?
Bind and hydrolyze ATP; also bind the products of ATP hydrolysis (ADP and phosphate)
Change shape (move toward or away from an M line)
Bind reversibly to actin
In muscle proteins, which proteins are strung together like a bead of pearls?
the Actin proteins of the thin filaments
What looks like golf clubs bound together?
Myosin proteins of the thick filaments
What are the myosin binding sites on the actin protein covered by?
Troponin
Tropomyosin
What fine structures of the skeletal muscle fiber allows for contraction to begin?
Movement of the troponin-tropomyosin complex
Muscle fiber proteins comprise of these three categories?
Contractile proteins
Regulatory proteins
Structural proteins
What are the structural proteins?
Titin
Myomesin
Dystrophin
Sarcolemmal proteins
In this protein each molecule spans half a sarcomere, from a Z disc to an M line, and attaches thick filaments to Z discs and M lines?
Titin
What is very elastic and probably helps sarcomere return to its resting length?
Titin
What links the thin filaments of the sarcomeres to integral membrane proteins in the sarcolemmas, transmitting the tensive forces of the sarcomeres?
Dystrophin
What refers to a group of inherited muscle-destroying diseases causing progressive skeletal muscle fiber degeneration?
Duchenne muscular dystrophy
In DMD, the gene that codes for the protein dystrophin is mutated, resulting in?
Little or no dystrophin in the sarcolemma.
The sarcolemma tears easily during muscle contraction, causing muscle fibers to rupture and die.
The muscle action potential travels along the entire sarcolemma and down the?
T-tubules to the interior of the fiber
What is the synapse between a somatic motor neuron and a skeletal muscle fiber?
A neuromuscular junction (NMJ)
What contains synaptic vesicles filled with ACh, that carries the impulse across the cleft?
Synaptic end bulbs at the tips of axon terminals
Where is the motor end plate located?
What does it comprise?
the region of the sarcolemma opposite the synaptic end bulb.
Comprises the muscle fiber part of the NMJ
What binds to ACh in the sarcomlemma?
Acetylcholine receptors
