Week 2 - Muscle Tissue Flashcards
List types of muscle fiber and state:
- whether or not they are striated in appearance
- how many nuclei each muscle cell contains
- voluntary/involuntary control
skeletal muscle - striated, multiple nuclei, voluntary
smooth muscle - non-striated, single nucleus, involuntary
cardiac muscle - striated, usually single nucleus, involuntary
Skeletal muscle attaches to _______
Smooth muscle attaches to ________
- bone, skin, fascia
- hair follicles in skin, walls of hollow organs – blood vessels, GI tract
Cardiac muscle cells are branched cylinders usually w/ one central nucleus; intercalated discs made up of _____ and ______ join neighboring cells
gap junctions
desmosomes
Gap junctions allow action potentials to spread between cardiac cells by ___________
permitting the passage of ions between cells, producing depolarization of the heart muscle
When muscle fibers contract, in what direction(s) do they shorten?
skeletal muscle - linear
cardiac muscle - linear
smooth muscle - all directions
List functions of muscle tissue
- Producing body movements
- Stabilizing body positions
- Regulating organ volumes - sphincters
- Movement of substances w/in body - blood, lymph, urine, air, food, fluids, sperm
- Producing heat (thermogenesis) - shivering
List properties of muscle tissue
- Excitability
- Conductivity
- Contractility
- Extensibility
- Elasticity
Superficial fascia is _______
Deep fascia is _________
- loose connective tissue & fat underlying the skin
- dense irregular connective tissue around muscle - epimysium, perimysium, endomysium
All deep fascia extend beyond the muscle belly to form _______
the tendon
Each skeletal muscle is supplied by ______. Each motor neuron supplies ____ muscle cell(s).
- a nerve, artery, and two veins
- multiple
Nerve fibers and capillaries are found in the _______ between individual muscle cells
endomysium
Sarcolemma is ______
Sarcoplasm is red due to _________
Transverse Tubules are _____
- plasma membrane of a muscle cell
- presence of myoglobin
- tiny invaginations from surface toward the center of each muscle fiber. Allows the action potential to travel from the sarcolemma throughout muscle fiber
Define sarcoplasmic reticulum. In relaxed muscles it stores ______
- A fluid filled system of tubules that surround each myofibril
- calcium
Myofibrils are ______. They contain three smaller structures called _______
- contractile elements of skeletal muscle
- thin filament (actin), thick filament (myosin), elastic filament (titin)
_______ are considered to be the contractile unit of the skeletal muscle. They are defined as _____
- Sarcomeres
- arrangement of myofilaments into compartments w/in muscle fiber
List the different types of protein present in a sarcomere, give examples for each type
contractile - actin, myosin
structural - titin, nebulin
regulatory - troponin, tropomyosin
During muscle contraction describe how the length of each area below changes: A band Zone of overlap H zone I band
- no change
- increases
- decreases
- decreases
The number of cross bridges (overlap of thick & thin filaments) determines ____. What will decrease the number of cross bridges?
- the amount of force that the muscle fiber can produce
- muscle stretching past optimal, muscle shortened past optimal
Describe the process of muscle contraction/relaxation
- Nerve impulse reaches synaptic end bulbs, stimulating release of acetylcholine
- Acetylcholine bind to receptors on muscle cell, stimulating opening of gated ion channels
- Na+ travels down its electrochemical gradient into the cell, causing depolarization
- depolarization causes an action potential to travel across the cell, opening Ca2+ channel to open on the sarcoplasmic reticulum
- Ca2+ binds to and activates troponin, which moves tropomyosin away from binding site on actin molecules
- myosin binds to actin, hydrolyzes ATP and uses the energy from hydrolysis to ratchet towards the Z disc
- Action potential stops
- Acetylcholine is broken down, Ca2+ channels in sarcoplasmic reticulum close
- Ca2+ is pumped back into sarcoplasmic reticulum via active transport
- troponin/tropomyosin covers actin binding site
- muscle relaxes
A single motor neuron makes contact w/ an average of ______ muscle fibers
150
The neuromuscular junction is usually located near ______ of the muscle fiber since _______
the midpoint
skeletal muscle fibers often are vey long
List structures of the neuromuscular junction
synaptic end bulbs
synaptic cleft
motor end plate
List 3 sources of ATP production w/in muscle cells
creatine phosphate
anaerobic respiration
aerobic respiration
Muscle contraction requires huge amounts of ATP for _______
- powering contraction
- pumping Ca2+ into SR
- other metabolic reactions
In anaerobic respiration:
one glucose molecule yields __ ATP (net)
glucose is broken down into _____ which is then coverted into ______ which diffuses into the blood then to ______
2
2 pyruvic acid
lactic acid
liver for conversion back to glucose
In aerobic respiration:
one glucose molecule yields __ ATP (net)
a typical fatty acid molecule yields ___ ATP
36
>100
Muscle has 2 sources of oxygen, which are _____
oxygen diffused from blood
oxygen released from myoglobin w/in muscle
What factors are thought to contribute to muscle fatigue?
- inadequate release of Ca2+ from SR
- decline of Ca2+ concentration in SR
- depletion of creatine phosphate
- O2 depletion
- lactic acid/ADP buildup
Increasing strength requires ____
increasing motor unit recruitment
______ is a sheath of connective tissue that groups muscle fibers into bundles (anywhere between 10 to 100 or more) or fascicles
perimysium
List the various periods of muscle tension in sequential order
latent period
contraction period
relaxation period
refractory period
Describe wave summation of muscle tension/stimulation
If 2nd stimuli occurs after refractory period but before muscle has relaxed, the second contraction will be stronger than the first
Describe unfused tetanus of muscle tension/stimulation
sustained but wavering contraction when skeletal muscle is stimulated at rate of 20-30x/second
Describe fused tetanus of muscle tension/stimulation
sustained contraction in which individual twitches cannot be discerned when skeletal muscle is stimulated at rate higher than 80-100x/second
Describe the 2 types of isotonic contraction
concentric isotonic contraction - muscle shortens and pulls on another structure
eccentric isotonic contraction - muscle length increases during contraction
Describe isometric contraction
myosin cross-bridges generate tension but muscle doesn’t shorten because force of load equals muscle tension
What is muscle tone?
the small amount of tautness or tension in muscle due to weak involuntary contraction of motor units
Skeletal muscle fibers can be categorized into __ main types: namely ______. List applications of each type
3
slow oxidative fibers - posture, endurance activities
fast oxidative-glycolytic fibers - walking, sprinting
fast glycolytic fibers - short-duration/intense strength
Describe slow oxidative skeletal muscle fibers
smallest in diameter
large myoglobin content
many large mitochondria
create ATP mainly via aerobic cellular respiration
very fatigue resistant
capable of prolonged, sustained contractions for many hours
Describe fast oxidative-glycolytic skeletal muscle fibers
intermediate diameter
large myoglobin content & high glycogen content
create ATP via aerobic cellular respiration/glycolysis (anaerobic)
moderately fatigue resistant
Describe fast glycolytic skeletal muscle fibers
largest diameter generate most powerful contractions low myoglobin & few capillaries high glycogen content create ATP via anaerobic cellular respiration fatigue quickly
Compared to skeletal muscle, cardiac muscle has:
more sarcoplasm, mitochondria larger t-tubules at Z-discs less well-developed SR limited intracellular Ca2+ reserves prolonged delivery of Ca2+ to sarcoplasm
Cardiac muscle contains ______ which contract w/o stimulation
autorhythmic cells
Describe visceral smooth muscle
found in walls of hollow viscera & small blood vessels
autorhythmic
contains gap juctions which cause fibers to contractin unison
Describe multiunit smooth muscle
individual fibers w/ own motor neuron ending
found in large arteries, large airways, errector pili muscles, iris ciliary body
In smooth muscle, troponin is replaced by ______
calmodulin
Can skeletal, cardiac and smooth muscle undergo hypertrophy and/or hyperplasia?
skeletal - hypertrophy
cardiac - hypertrophy
smooth - hypertrophy, hyperplasia
Sarcomeres are separated from each other by _______
Z discs
Movement in a sagittal plane which decreases the angle of a joint usually taking the body foward is ______
Flexion
