Studied by 15 peopleThree types of muscles tissue include
skeletal, cardiac , & smooth
Three prefixes used to refer to muscle
myo, mys, sacro
Define sarcoplasm
the cytoplasm of a muscle cell
Define sarcolemma
the cell membrane of a muscle cell
Why is it called "skeletal" muscle tissue?
Because it forms muscles that attach to the skeleton
Skeletal muscles cells have obvious stripes called
striations
Why is skeletal muscle tissue called voluntary muscle
Because it is the only type subject to conscious control
Describe skeletal muscle
long, cylindrical cells ; each cell is multinucleated with the nuclei just deep to the cell membrane
Skeletal muscle is....
striated and voluntary
Cardiac Muscle is .....
striated and involuntary
_____ forms the middle, muscular layer of the heart wall called myocardium
Cardiac muscle tissue
Describe cardiac muscle tissue
branched cells with one central nucleus
In cardiac muscle tissue- The cells are joined end to end to fit together tightly at unique junctions is called __________
Intercalated discs
Why are intercalated discs important (2)
Strengthen the cardiac muscle tissue and hold the cells together during contractions
Allow conduction of cardiac muscle action potentials (impulses) to spread quickly throughout the heart
Smooth muscle tissue is ...
Not striated & involuntary
Where is smooth muscle tissue found
in the walls of hollow visceral organs
Examples of where smooth muscle tissue is found in
Stomach, urinary bladder, respiratory passages
What is the role of smooth muscle tissue
To force fluids and other substances through internal body channels
Smooth muscle forms
valves, dilates, and constricts the pupils, and forms arrector pili muscles
Describe smooth muscle tissue
spindle shape and each cell has an elongated, central nucleus
Contraction of smooth muscle is regulated by
hormones and the autonomic division of the nervous system
The 4 special characteristics of muscle tissue is
Excitability, contractility, extensibility, elasticity
The four important functions of muscle
Produce movement
Maintain posture & body position
Stabilize joints
Generate heat
Produce movement described
Skeletal muscles are responsible for all locomotion & manipulation
Maintain posture & body position described
tiny adjustments to counteract the downward pull of gravity
Stabilize joints described
Strengthen and stabilize the joints of the skeleton
Generate heat described
As they contract muscles generate heat which plays into maintaining normal body temperature
Special characteristic excitability described
"responsiveness", ability of a cell to receive, and respond to a stimulus by changing its membrane potential, stimulus is usually a chemical
Special characteristic contractility described
Ability to shorten forcibly when adequately stimulated. Sets muscles apart from all other tissue types
Special characteristic extensibility described
Ability to extend or stretch; when relaxed muscles can extend beyond their resting length
Special characteristic elasticity described
ability of a muscle cell to recoil and resume its resting length after stretching
A skeletal muscle is made up of
muscle fibers, blood vessels, and connective tissue
Define skeletal muscle
is an organ because it is formed by two or more types of tissue
Each muscle is served by
1 nerve, 1 artery, & 1 or more veins
Skeletal muscle is said to be
well innervated and well vascularized
_____ is associated with skeletal muscles
connective tissue sheaths
Superficial fascia
is loose connective tissue that separates muscles from skin ; provides a pathway for vessels and nerves to and from muscles
Deep fascia
is dense irregular connective tissue that fills spaces between muscles and holds muscles with similar functions together ; it allows free movement of muscles and carries vessels and nerves
Three layers of connective tissue
epimysium, perimysium, edomysium
The three connective tissue do what
Extend from the deep fascia to protect and strengthen skeletal muscle
epimysium
dense irregular connective tissue that encircles the entire skeletal muscle
perimysium
dense irregular connective tissue that surrounds groups of 10 to 100 muscle cells, grouping them into bundles called fascicles
edomysium
areolar connective tissue within each fascicle that surrounds individual muscle cells
Describe a direct ( fleshy) muscle attachment
The epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage
Describe indirect muscle attachment
the muscle connective tissue wrapping extend beyond the muscle either tendon, or aponeurosis ; The T or A anchors the muscle to the connective tissue covering of a skeletal element or to the fascia of other muscles
Tendon
ropelike, cordlike ; formed of dense regular CT
Aponeurosis
sheetlike, a broad flat sheet of dense regular CT
Skeletal muscle fibers contain
calcium-regulated molecular motors
Sacrolemma
the cell membrane of a muscle cell
What is the skeletal muscle range in diameter
10-100 ; up to 30 cm
Define sarcoplasm
the cytoplasm of a muscle fiber
The sarcoplasm contains what
glycosomes and myoglobin
Define glycosomes
granules of stored glycogen that provide glucose during muscle cell activity for ATP production
Define myoglobin
oxygen-binding pigment in muscle ~ red pigment that stores oxygen
Define myofibrils
tiny rod like structures that are packed in the cytoplasm and run the length of the cell
How many myofibrils are in a single muscle cell
hundreds to thousands
Myofibrils are made of a chain of what
sacromeres
Define striations
a repeating series of dark and light bands; are evident along the length of each myofibril
Myofibrils contains _____ and _____
thick myofilaments & thin myofilaments
Thick and thin myofilaments are
very orderly arranged by forming bands
The forming bands of thick and thin myofilaments include
A band, I band, H zone, & Z discs
A band
a region that extends the entire length of the thick filaments and it contains thick filaments and overlapping thin filaments
I band
area on each side of an A band that contains the rest of the thin filaments but no thick filaments`
H zone
an area in the center of the A band that contains only thick filaments
Z discs
proteins to which thin filaments attach
Sarcomere
is the unit of a myofibril that extends from one Z disc to the next Z disc
What is the smallest contractile unit of a muscle cell; the functional unit of contraction
sacrcomere
The two main contractile proteins in muscle that form the myofilaments are
actin and myosin
Myosin
thick filaments are formed by it; shaped like a golf club with two heads
Two heads of myosin is called
globular heads
The myosin heads have _____ and _________ and contain _____
actin-binding sites & binding sites for ATP; contain ATPase enzymes that split ATP
Actin
thin filaments form it; has polypeptide subunits
Globular Actin (G actin)
polypeptide subunits, kidney shaped
The G actin molecules are polymerized into what
long actin filaments called filamentous or F actin
The backbone of each filament is formed by two intertwined F actin filaments that look like what?
Twisted double strand of pearls
Each G actin of the actin filament has a ___________ to which the myosin heads attach during contraction
myosin binding site
In relaxed muscles, the myosin binding sites on actin are blocked by a rod-shaped protein called
tropomyosin
Does the distance between successive Z discs shorten
Yes
As a muscle cell shortens ; do the I bands shorten?
Yes
Do the H zones disappear
yes
What happens to the A bands within a sarcomere
Move closer together but their length does not change
Motor neurons ________ skeletal muscle fibers to contract
stimulate
The four steps that must occur for a skeletal muscle cell to contract
The cell must be activated, that is, stimulated by a neuron ~ nerve cell
It must generate an electrical current called an action potential or impulse in its sarcolemma
The action potential is automatically propagated along the sarcolemma
Intracellular calcium ion levels must rise briefly, providing the final trigger for contraction
The motor neurons that activate skeletal muscle cells is called
somatic motor neurons; motor neurons of the somatic, voluntary, nervous system
Neuromuscular junction
is the synapse between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell
Action potentials
electrical currents, are conducted along axons of motor neurons to the neuromuscular junction
As a rule, each muscle has only ____________ located about midway along it's length
one neuromuscular junction
The neuromuscular junction is formed by three main parts
Axon terminal
Synaptic cleft
Junctional holds of the sarcolemma
Axon terminal
the end of the axon of the motor neuron, within are synaptic vessels
Synaptic vessels
within axon terminal; and contain neurotransmitteracetylcholine
Synaptic cleft
space filled with gel-like extracellular substance between an axon terminal and the sarcolemma of the skeletal muscle cell
Junctional folds of the sarcolemma
the folded part of the sarcolemma that is associated with the axon terminal
The receptors associated within junctional folds of the sarcolemma is called
ACh receptors
Events at the neuromuscular junction that lead to the transmission of an impluse from the motor neuron to the skeletal muscle cell includes these steps
Release of acetylcholine (ACh)
Activation of ACh receptors
Production of a muscle action potential
Termination of ACh activity
Release of acetylcholine (ACh)
A nerve impulse along the axon of the motor neuron reaches the axon terminal. This triggers the release of the neurotransmitter acetylcholine (ACh) from the synaptic vesicles by exocytosis into the synaptic cleft
Activation of ACh receptors
Acetylcholine diffuses across the synaptic cleft and binds to ACh receptors on the junctional folds of the sarcolemma. This opens ion channels in the sarcolemma.
Production of a muscle action potential
The inflow of ions generates a muscle action potential (impulse) in the junctional folds of the sarcolemma of the muscle cells
Termination of ACh activity
Acetylcholine that is bound to ACh receptors of the junctional folds is then rapidly broken down in the synaptic cleft by acetylcholinesterase
Acetylcholinesterase
is an enzyme in the synaptic cleft near the sarcolemma of the junctional folds
The destruction of ACh prevents
continued contraction of the muscle cell
Note
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