Chapter 9 - Muscles Flashcards
There are 3 types of muscle tissue in the muscular system. What are they?
Skeletal muscle, cardiac muscle, smooth muscle
Skeletal Muscle
Attached to bones of skeleton
voluntary (consciously controlled)
Cardiac Muscle
makes up most of the wall of the heart
involuntary (non-consciously controlled)
responsible for pumping action of the heart
Smooth Muscle
found in walls of internal organs, such as those of digestive tract
Involuntary (non-consciously controlled)
Skeletal Muscles facts
Over 600 skeletal muscles in the body
Attached to bones, and skin of face
Under conscious control
(voluntary)
Are organs of the muscular system
Skeletal muscles are composed of:
Skeletal muscle tissue
Nervous tissue
Blood
Connective tissues
Connective tissue coverings over skeletal muscles:
F.A.T.
Fascia, Tendon, Aponeurosis
Fascia
Thin covering of connective tissue around a muscle
Tendon
Cord-like mass of connective tissue that connects muscle to a bone
Aponeurosis
Sheet-like mass of connective tissue that connects a muscle to bone, skin, or another muscle
Connective tissue in and closely surrounding a muscle:
Epimysium: surrounds whole muscle; lies beneath fascia
Perimysium: surrounds fascicles within a muscle.
Endomysium: surrounds muscle fibers (cells) within a fascicle
Skeletal muscle fiber (cell):
(I don’t really know how to break this slide up)
Multinucleated
Sarcolemma: Cell membrane of muscle fiber
Sarcoplasm: Cytoplasm of muscle fiber
Many myofibrils:
Long, parallel structures that run down fiber
Consist of thin actin filaments and thick myosin filaments
Sarcomeres: Units that connect end-to-end, to make up myofibrils
Sarcoplasmic reticulum (SR): Endoplasmic reticulum of muscle; stores calcium
Transverse (“T”) tubule: Relays electrical impulses to the SR
Triad: Unit consisting of 1 T tubule and 2 SR cisternae
Myofibrils consist of…?
Sarcomeres connected end to end
Striation Pattern is made by…?
arrangement of myofilaments in myofibrils
A sarcomere consists of these structures:
I band: Light band; composed of thin actin filaments
A band: Dark band; composed of thick myosin filaments with portions overlapped with thin actin filaments
H zone: Center of A band; composed of thick myosin filaments
Z line (Z disc): Sarcomere boundary; in center of I band anchors filaments in place
M line: Center of sarcomere and A band; anchors thick filaments
I Band
Light band; composed of thin actin filaments
A Band
Dark band; composed of thick myosin filaments with portions overlapped with thin actin filaments
H Zone
center of A band; composed of thick myosin filaments
Z Line (Z Disc)
sarcomere boundary; in center of I band anchors filaments in place
M Line
center of sarcomere and A band; anchors thick filaments
Thick filaments:
Composed of myosin protein
Heads form cross-bridges with thin filaments
Thin Filaments
Composed of actin protein
Associated with troponin and tropomyosin, which prevent cross-bridge formation when muscle is not contracting
Contraction of a skeletal muscle fiber:
Requires interaction from several chemical and cellular components
Results from a movement within the myofibrils, in which the actin and myosin filaments slide past each other, shortening the sarcomeres
Muscle fiber shortens and pulls on attachment points
Neuromuscular Junction (NMJ):
A type of synapse
Also called a myoneural junction
Site where an axon of motor neuron and skeletal muscle fiber interact
Skeletal muscle fibers contract only when stimulated by a motor neuron
Parts of a Neuromuscular Junction:
Motor neuron: Neuron that controls skeletal muscle fiber
Motor end plate: Specialized folded portion of skeletal muscle fiber, where fiber binds to neurotransmitter
Synaptic cleft: Space between neuron and muscle fiber, across which neurotransmitter travels
Synaptic vesicles: Membrane-bound sacs containing neurotransmitters
Neurotransmitters: Chemicals released by motor neuron to deliver message to muscle fiber
Acetylcholine (ACh) is…?
…the neurotransmitter
Nerve impulse causes release of ACh from synaptic vesicles
ACh binds to ACh receptors on motor end plate
ACh causes changes in membrane permeability to sodium and potassium ions, which generates a muscle impulse (action potential)
Impulse causes release of calcium ions from SR, which leads to muscle contractio
Order of events in Cross-bridge Cycling:
Myosin head attaches to actin binding site, forming cross-bridge
Myosin cross-bridge pulls thin filament toward center of sarcomere
ADP and phosphate are released from myosin
New ATP binds to myosin
Linkage between actin and myosin cross-bridge break
ATP splits
Myosin cross-bridge goes back to original position, ready to bind to another binding site on actin
When neural stimulation of muscle fiber stops, what happens?
Acetylcholinesterase (enzyme) rapidly decomposes ACh remaining in the synapse.
Muscle impulse stops when ACh is decomposed.
Stimulus to sarcolemma and muscle fiber membrane ceases.
Calcium pump moves
Troponin-tropomyosin complex again covers binding sites on actin.
Myosin and actin binding are now prevented.
Muscle fiber relaxes.
What are the 2 Phases of Cellular Respiration?
Anaerobic
&
Aerobic
Anaerobic Phase
Glycolysis
Occurs in cytoplasm
Produces little ATP
Aerobic Phase
Citric acid cycle and electron transport system
Occurs in the mitochondria
Produces the most ATP
Myoglobin stores extra oxygen in muscles
Myoglobin stores what?
Extra Oxygen in Muscles
Muscle Fatigue is what?
the Inability to contract muscle
What are common causes of muscle fatigue?
Decreased blood flow
Ion imbalances across the sarcolemma
Loss of desire to continue exercise
Accumulation of lactic acid (controversial)
What is a Muscle Cramp?
Sustained, involuntary muscle contraction
May be caused by changes in electrolyte concentration in extracellular fluids in the area
Heat Production
Heat is a by-product of cellular respiration in active cells
Muscle cells are major source of body heat
More than half the energy released in cellular respiration becomes heat; less than half is transferred to ATP
Blood transports heat throughout body core
Muscle tone (tonus)
Continuous state of partial contraction in resting muscles
What are the 3 types of Contractions?
Concentric
Eccentric
Isometric
Concentric Contraction
muscle contracts with force Greater than resistance and shortens
(curling a dumbbell, pulling it higher)
Eccentric Contraction
Muscle contracts with force less than resistance and lengthen
(lowering the dumbbell after a bicep curl, pulling it lower)
Isometric Contraction
muscle contracts but does not change length
Compared to skeletal muscle fibers, smooth muscle fibers are?
Shorter
Single, centrally located nucleus
Elongated with tapering ends
Myofilaments randomly organized
Lack striations
Lack transverse tubules
Sarcoplasmic reticulum (SR) not well developed
What are the 2 types of smooth muscle?
Multi-Unit smooth muscle
Visceral smooth muscle
Multi-unit Smooth Muscle:
Cells are less organized
Function as separate units
Fibers function independently
Iris of eye, walls of blood vessels
Stimulated by neurons, hormones
Visceral Smooth Muscle
Single-unit smooth muscle; cells respond as a unit
Sheets of spindle-shaped muscle fibers
Fibers held together by gap junctions
Exhibit rhythmicity
Conduct peristalsis
Walls of most hollow organs
More common type of smooth muscle
Smooth muscle contraction resembles skeletal muscle contraction in these ways…
Interaction between actin and myosin
Both use calcium and ATP
Both are triggered by membrane impulses
Smooth Muscle Contraction is different from skeletal muscle contraction in these ways…
Smooth muscle lacks troponin; uses calmodulin instead
Two neurotransmitters affect smooth muscle: Acetylcholine (Ach) and norepinephrine (NE)
Cardiac Muscle:
Located only in the heart
Striated muscle cells
Muscle fibers joined together by intercalated discs
Fibers branch, contain a single nucleus
Network of fibers contracts as a unit (syncytium)
Self-exciting and rhythmic
Longer refractory period than skeletal muscle
No sustained or tetanic contractions
Skeletal muscles generate many different types of body movements
Action of a muscle depends mainly on these factors…?
Type of joint it is associated with
Way muscle is attached on both side of the joint
One end of a skeletal muscle is more _____ and the other end is more _______?
Fixed
&
Movable
Origin means?
less movable end
Insertion means?
more movable end
When a muscle contracts, what happens?
Insertion is pulled toward origin
True or False
A muscle can have more than one origin or insertion
TRUE
Most skeletal muscle function in groups. Roles of muscles in performing certain actions include…?
agonist
prime mover
synergists
antagonist
Agonist
muscle that causes an action
Prime Mover
agonist primarily responsible for movement (in some cases, the terms “agonist” and “prime mover” are used interchangeably)
Synergists
muscles that assist agonist/prime movert
Antagonist
muscles whose contraction causes movement in the opposite direction of the prime mover
Lifespan Changes
Myoglobin, ATP, and creatine phosphate decline, starting in the 40s
Connective tissue and adipose cells replace some muscle tissue
By age 80, almost half of muscle mass has atrophied
Muscle strength decreases, and reflexes become slower
Exercise helps to maintain muscle mass and function
