A&P Muscle Unit
Thin filament has ___ chains of G actin
2
Incurable patients of DMD rarely live beyond age ____
30
Tropomyosin
A protein of muscle that forms a complex with troponin regulating the interaction of actin and myosin in muscular contraction
Botulism prevents release of _____ at synaptic knobs
ACh
What is the importance of regulating elimination of materials?
Allows our bodies to get rid of waste; circular sphincters control; passage of material at orifices
Dystrophin
Anchors some myofibrils to sarcolemma proteins
superficial fascia
Areolar and adipose CT superficial to deep fascia
Endomysium
Areolar connective tissue wrapping individual fiber; Delicate layer for electrical insulation, capillary support, binding of neighboring cells
terminal cisternae
Blind sacs of the sarcoplasmic reticulum
What are the five main functions of skeletal muscle?
Body movement, maintenance of posture, protection and support, regulating elimination of materials, heat production
Botulism
Caused by clostridium botulinum, commonly known as food poisoning
A bands make up _______ region of sarcomere
Central
Muscular Dystrophy
Collective term for hereditary diseases where skeletal muscles degenerate
Thin
Consists of bundles of many myosin protein molecules
Perimysium
Dense irregular connective tissue wrapping fascicle; houses many blood vessels and nerves
Abnormalities of _______ cause muscular dystrophy
Dystrophin protein
What are the three components of connective tissue?
Epimysium, Perimysium, and Endomysium
What are the five characteristics of Skeletal Muscle tissue?
Excitability, Conductivity, Contractility, Extensibility, Elasticity
Connectin
Extends from Z disc to M line
_________ is stored for when fuel is needed quickly
Glycogen
A bands contain __ zone and ___ line
H, M
Sarcolemma (plasma membrane)
Has T-tubules (transverse tubules) that extend deep into the cell;Sarcolemma and its T-tubules have voltage-gated ion channels that allow for conduction of electrical signals
Sarcoplasm (cytoplasm)
Has typical organelles plus contractile proteins and other specializations
What is the importance of heat production?
Helps maintain body temperature
Bisected by Z discs
I bands
Get smaller when muscle contracts (can disappear with maximal contraction)
I bands
The positions of thin and thick filaments give rise to alternating _____ and _______.
I-bands, A-bands
Incomplete tetany and tetany
If frequency is increased further, myogram exhibits incomplete tetany
Why is each skeletal muscle considered an organ?
It is multiple types of tissues working together: skeletal muscle fibers, connective tissue, blood vessels, and nerves
Protein meshwork structure
M Line
Example of direct (fleshy) attatchment
Margins of brachialis, lateral head of triceps brachii
Sarcomeres
Myofilaments arranged in repeating units
Each skeletal muscle is an ________.
Organ
What is the importance of protection and support?
Package internal organs and hold them into place
Specialized proteins are ________ to myofilaments
Perpendicular
What does the deep fascia do?
Separates individual muscles and binds muscles with similar functions
What does superficial fascia do?
Separates muscles from skin
What does maintenance of posture do?
Stabilize joints, maintain body position
indirect attatchment
Tendons bridge the gap between muscle ends and bony attachment
Twisted strands of F-actin; each F-actin composed of G-actin monomers
Thin filaments
Latent period
Time after stimulus but before contraction begins No change in tension
Relaxation period
Time when tension is decreasing to baseline Generally lasts a little longer than contraction period
Contraction period
Time when tension is increasing Begins as power strokes pull thin filaments
What is the one major purpose of muscle in the human body?
To convert chemical energy into mechanical energy
calcium release channels
Triggered by electrical signal traveling down T-tubule; calcium released into sarcoplasm
Skeletal is ______, has extensive blood vessels
Vascularized
What does DMD cause?
Walking difficulties, muscle atrophy, postural issues
Sarcomeres are delineated at both ends by
Z discs
Troponin
a smaller calcium-binding protein attached to the tropomyosin
Tetanus
a sustained muscular contraction resulting from a rapid series of nerve impulses
Extensibility
ability to be stretched
Excitability
ability to respond to a stimulus by changing electrical membrane potential
Elasticity
ability to return to original length following a lengthening or shortening
Muscle fibers have __________ mitochondria for ______ _____ production
abundant; aerobic ATP
Electrical excitation of a muscle fiber follows _______________ law
all-or-none
Myoglobin
allow for storage of oxygen used for aerobic ATP production within cells
Z discsZ disc are ______ for thin filaments
anchors
Where is skeletal muscle found?
attached to skeleton
Origin
bony attachment at stationary end of muscle
Insertion
bony attachment to mobile end of muscle
Myofibrils
bundles of myofilaments enclosed in sarcoplasmic reticulum
calmodulin
calcium binding protein
Calsequestrin
calcium-binding protein within the sarcoplasmic reticulum which aids in storage of intracellular Ca2+
Creatine Phosphate
can quickly give up its phosphate group to help replenish ATP supply
Although toxin ingestion can be life-threatening, how can we treat spasticity from botulism?
careful injections, can also be used for cosmetic purposes to diminish wrinkles
H Zone
central portion of A band
Dystrophin is a
clinically important protein
Elastic filaments
composed of titin
retinaculum
connective tissue band that tendons from separate muscles pass under
Thick filaments
consist of bundles of many myosin protein molecules, heads point towards ends of the filament
Myofiliments
contractile proteins within myofibrils; two types
Tendon
cordlike structure of dense regular connective tissue
Relaxation period begins with release of:
cross bridges
A band
dark area; contains thick filaments and overlapping thin filaments
deep fascia
dense irregular connective tissue superficial to epimysium
Epimysium
dense irregular connective tissue wrapping whole muscle
DMD causes problems that begin in _______________
early childhood
When sarcolemma is damaged during muscle contraction calcium...
enters the cells and damages proteins
Contractility
exhibited when filaments slide past each other; Enables muscle to cause movement
Muscle fibers bundled within a ______.
fascicle
A whole muscle contains many ________.
fascicles
Lower than normal pH of sarcoplasm weakens contraction and causes:
fatigue
vascularized
good blood supply
Muscles make up about _____ of body weight
half
Thick filament has ______ of myosin molecules
hundreds
How many myofibrils are in each cell?
hundreds to thousands
Multiple nuclei means:
individual cells are multinucleated
Tetanus blocks release of
inhibitory neurotransmitters in spinal cord, resulting in overstimulation of muscles
Skeletal muscle is ______ by somatic neurons
innervated
sarcoplasmic reticulum
internal membrane complex similar to smooth endoplasmic reticulum
Conductivity
involves sending an electrical change down the length of the cell membrane
I bands
light bands that only contain thin filaments
Direct (fleshy) attachment
little separation between muscle and bone;muscle seems to emerge directly from bone
M Line
middle of H zone
Duchenne muscular dystrophy (DMD)
most common form of muscular dystrophy
What does body movement allow us to do?
move bones, make facial expressions, speak, breathe, swallow
A muscle fiber is a ____________.
muscle cell
A fascicle consists of many _________.
muscle fibers
Synergist
muscle that aids a prime mover in a movement and helps prevent rotation
Antagonist
muscle that opposes or reverses a prime mover
Fixator
muscle that prevents movement of bone
Prime mover
muscle with the major responsibility for a certain movement
Do the muscle fiber twitches follow the all-or-none law?
no
Smooth muscle
non-striated, involuntary
fascicle arrangement
pennate are stronger than parallel, and parallel stronger than circular
multiple motor unit summation
recruitment of more motor units as voltage increases
In wave summation if stimulus frequency is set at about 20 per second:
relaxation is not completed between twitches and contractile forces add up to produce higher tensions
Muscle is stimulated ________
repeatedly
Voltage-sensitive calcium channels
responsive to the electrical signals (action potentials)
What do terminal cisternae do?
serve as reservoirs for calcium ions
What are the three kinds of muscle?
skeletal, smooth, cardiac
Recruitment order based on size of motor units:
small first, large last
Temporal summation
stimuli arriving closer together produce stronger twitches
Cardiac muscle
striated, branched, and involuntary
Skeletal muscle
striated, voluntary, multinucleated
innervated
supplied by nerve fibers
wave summation
temporal summation of twitches
Attachment of muscle to bone (or to skin or to another muscle) can be _______ or _______.
tendons, aponeuroses
Z discs are found in
the middle of I bands
Elastic filaments attach _____ filament to the Z disk, and prevent overstretching
thick
M line is an attachment site for _____ filaments
thick
Sarcomeres are composed of overlapping _____ and ______ filaments
thick, thin
Connectin _____ thick filaments and have ______ properties (passive tension)
thick; "springlike"
Belly
thicker, middle region of muscle between origin and insertion
Aponeurosis
thin, flattened sheet of dense irregular tissue
The minimum voltage that triggers a twitch is the:
threshold
Spastic paralysis is caused by:
toxins from clostridium tetani
Two cisternae with T-tubule in between
triad
T tubules
tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side
Incomplete tetany and tetany causes tension to increase and _________ to partially fuse
twitches
How can we prevent tetanus?
vaccination
Where is smooth muscle found?
walls of internal organs and blood vessels
Where is cardiac muscle found?
walls of the heart
Temperature of the muscles
warmed-up muscle contracts more strongly; enzymes work more quickly