Flashcards in Chapter 9 Deck (72):
What are the three types of muscle tissue in the body?
Skeletal, Cardiac and Smooth
Which types of muscle cells are referred to as muscle "fibers"?
Long muscle cells of skeletal and smooth muscle tissue
What characteristics of long muscle cells of skeletal and smooth muscle tissue cause them to be referred to as muscle "fibers"?
Because they are very long cells compared to other cells in the body
What are the two types of myo-filaments?
Actin (thin filament) and Myosin (thick filaments)
Plasma membrane of a muscle cell.
Cytoplasm of a muscle cell.
What does the sarcoplasm contain?
unusually large amounts of glycosomes and myoglobin
What are "glycosomes"?
granules of stored glycogen that provide glucose during muscle cell activity
What is "myoglobin"?
A red pigment that stores oxygen
What prefixes always refer to "muscle" in anatomy?
Myo- and Mys (and sarco- is used as well, but not exclusively for muscle)
What are the characteristics of "skeletal" muscle?
-longest muscle cells
What is the function of "skeletal" muscle?
Responsible for overall body mobility. It can contract rapidly, but it tires easily and must rest after short periods of activity. Nevertheless, it can exert tremendous power.
What are the characteristics of "smooth" muscle?
-one central nucleus
What is the function of "smooth" muscle?
Its role is to force fluids and other substances through internal body channels. Its contractions are slow and sustained.
Where is "smooth" muscle located?
It is found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages.
What are the characteristics of "cardiac" muscle?
-short, fat, and branched cells
-lots of mitochondria
What is the function of "cardiac" muscle?
body's blood pump
Where is "cardiac" muscle located?
Only in the heart
What are the four special characteristics of muscle tissue?
Excitability, Contractility, Extensibility and Elasticity.
What is "excitability"?
Also termed "responsiveness".
Is the ability to receive and respond to stimulus, that is, any change in the environment either inside or outside the body.
What is "contractility"?
Is the ability to shorten forcibly when adequately stimulated. This ability sets muscle apart from all other tissue types
What is "extensibility"?
Is the ability to extend or stretch beyond resting length, when relaxed.
What is "elasticity"?
is the ability of a muscle cell sot recoil and resume its resting length after stretching.
What are the four important functions of muscle?
It produces movement, maintains posture, stabilizes joints and generates heat.
What tissues make up "skeletal" muscle?
Skeletal muscle fibers predominately, blood vessels, nerve fibers, and substantial amounts of connective tissues
What are the three connective tissue sheaths?
Epimysium, Perimysium, and Endomysium
What is "epimysium"?
It is an "overcoat" of dense irregular connective tissue that surrounds the whole muscle
What is "perimysium"?
A fibrous connective tissue that surrounds the fascicles (muscle fiber bundles)
What is "endomysium"?
is a wispy sheath of connective tissue that surrounds each individual muscle fiber (fine areolar connective tissue)
Describe the nervous and blood supply to skeletal muscles.
There is one nerve that brings electrical signal to each muscle, one artery bringing blood (oxygen and nutrients) to each muscle and there may be more than one vein taking blood (carbon dioxide and wastes) away from each muscle.
What is the "origin" of skeletal muscle?
The end of the muscle that is on the bone that will move least in the action
What is the "insertion" of skeletal muscle?
The end of the muscle on the bone that will move most in the action. Hint: the insertion will always move toward the origin in the action.
What is the general microscopic anatomy of a muscle fiber?
Multi-nucleated cell with a specialized plasma membrane called a sarcolemma and cytoplasm called sarcoplasm (contains glycosomes and myoblobin).
They are also very long (several centimeters) and not very wide (several micrometers).
Why is a muscle fiber considered a "syncytium"?
Cells fuse together during fetal development to form muscle fibers so they "work together" = Syncitium
What is the cytoplasm of a muscle cell called?
A cylindrical unit packed with myofilaments (actin and myosin) and fill the muscle fibers
What is considered the smallest contractile unit of a muscle?
What is the general structure of a sarcomere?
Defined from z-disc to z-disc and contains overlapping actin and myosin proteins for contraction.
Sheets of protein that span the myofibril and form the boundaries of the sarcomeres
Define "A band".
"Dark Bands". Contains myosin with overlapping actin.
Define "I band".
"Light Bands". Contain actin only
Define "H zone"
Define "M line"
Formed by myomesin up the center of the sarcomere
What attaches actin and myosin to the z disc?
Actin is attached by "nebulin".
Myosin is attached by "titin".
Actin is also referred to as?
Myosin is also referred to as?
What is the sarcoplasmic reticulum of a muscle cell?
It is a modified smooth endoplasmic reticulum.
What is the function of the sarcoplasmic reticulum in a muscle fiber?
It specifically stores and releases calcium into the sarcoplasm for muscle contraction.
What is "terminal cisternae"?
The ends of the sarcoplasmic reticulum (SR) that are coupled to the t-tubule to form triads. The calcium is released from this part, which is triggered by electricity coming down the t-tubule.
What is a "t-tubule"?
Indentations of the sarcolemma
What is the function of a "t-tubule" in a muscle cell?
It carries the electric signal deep into the muscle fiber and triggers the SR to release its calcium for muscle contraction
What is a "triad"?
2- terminal cisternae and 1-T-tubule between them at the A-I junctions of the myofibrils
How do the components of the triad work together in muscle contraction?
The t-tubule carries the electric signal to the terminal cisternae, which then are triggered to release calcium into the sarcoplasm for muscle contraction.
Describe the "sliding filament model of contraction".
During muscle contraction, actin is pulled by myosin towards the center of the sarcomere, so actin "slides" past myosin.
How do the actin and myosin interact in the sliding filament model?
the myosin heads "grab" actin to form a cross bridge. Then the myosin heads change shape in a way that pulls actin towards the center of the sarcomere. This action is called a power stroke.
What type of neurons stimulate skeletal muscle?
Describe the structure of a neuromuscular junction
The motor neuron ending contains vesicles filled with the neurotransmitter acetylcholine. The portion of the muscle sarcolemma across from the motor neuron ending is called the motor end plate and contains receptors for acetylcholine. The space between the motor end plate and the motor neuron is called the synaptic cleft.
What is a "synaptic vesicle"?
A lipid "bubble" formed by a phospholipid bilayer
What neurotransmitter will always stimulate skeletal muscle?
What is the space between the axonal endings and the motor end plate of the muscle cell called?
What process releases the neurotransmitter from the axonal terminal?
How is the neurotransmitter destroyed?
An enzyme called acetylcholinesterase.
Why does the neurotransmitter need to be destroyed?
As long as it is in the cleft it can bind to the receptors and cause muscle contraction. To be able to relax the muscle the neurotransmitter must be removed.
Define "motor unit".
A motor neuron and all od the muscle fibers that it innervates
What is the general structure of a smooth muscle fiber?
spindle shaped cells with only one nucleus. Not striated even though it still has actin and myosin. The actin and myosin are arranged in a cris-cross pattern. There is only a little bit of endomysium.
Compare and contrast the structure and function of smooth muscle and a skeletal muscle cell.
Skeletal muscle cells are cylindrical and centimeters long whereas smooth muscle cells are spindle and a couple of hundred micrometers long. Skeletal muscle cells contract to move the body and things in the environment whereas smooth muscle cells contract to move substances through hollow organs.
Wave-like contractions of smooth muscle in the walls of hollow organs to move substances through them
How does smooth muscle receive neurotransmitter since they lack a neuromuscular junction?
Bulbous swellings called varicosities release neurotransmitter over many smooth muscle cells at once
How are the actin and myosin arranged in a smooth muscle cell?
In a cris-cross pattern through the cell. This pattern allows the cell to twist and shorten during contraction.
What are the "intermediate filaments" and "dense bodies" in a smooth muscle cell?
Intermediate filaments are actin and myosin and dense bodies hold them together when they cross in the cell.
List and describe the unique characteristics of smooth muscle?
Sarcoplasmic reticulum is less developed.
Indentations called calveoli hold calcium from extracellular fluid for contraction.
There are no Z-discs or sarcomeres.
Smooth muscle responds to stretch by relaxing, thus allowing a hollow organ to fill with a substance, such as in the stomach, urinary bladder or uterus.