Unit 3 Lecture Flashcards
The ability of muscular tissue to stretch, within limits without being damages is called
extensibility
The ability of muscular tissue to return to its original length and shape after contraction or extension is called
elasticity
What is the dark middle part of the sarcomere? How long does it extend?
Dar middle part of sarcomere - A band
A band extends entire length of THICK myosin filaments
What are the 4 steps of muscle contraction in order?
- ATP hydrolysis by myosin
- attachment of actin to myosin - cross bridge
- power stroke - myosin head pivots, pulls thin past thick towards center of sarcomere
- detachment of actin from myosin
What are the neurons that stimulate skeletal muscles to contract?
somatic motor neurons
How do the muscles contribute to homeostasis?
producing heat, body movement, moving substances
What zone in the middle of the A band contains only thick filaments?
H zone
When connective tissue elements extend as broad, flat sheet, its called
aponeurosis
Define Transverse tubules
tiny invaginations in the sarcolemma of a muscle cell that tunnel in from the surface toward the center of each muscle fiber
when an AP goes down a T tubule, it stimulates the voltage gated Ca channels that stimulate the Ca release channel of the sarcoplasmic reticulum
a dense sheet or broadband or irregular connective tissue that lines the body wall and limbs, supports and surrounds muscles and other organs of the body is called
fascia
Threadlike contractile elements within sarcoplasm of muscle fibers that extend the entire length of the fiber, composed of filaments are
myofibrils
List the 3 connective tissues surrounding the muscle fibers in order from outer to inner most layer
epimysium
perimysium
endomysium
What does the M line do?
supporting protein in the middle of the sarcomere
Long cylindrical cell covered by endomysium and sarcolemma are called
muscle fibers
What are the contractile proteins os muscles?
Actin (thin) and myosin (thick)
Describe skeletal muscle. What are its 4 functions?
surrounds skeleton, multi nucleated and striated, Voluntary
producing movement, stabilizing body parts, storing/mobilizing substances, generating heat
What are the 4 properties of muscular tissue?
- electrical excitability - ability to respond to AP
- contractibility - ability to contract forcefully when stimulated bu an AP
- Extensibility - agility of muscular tissue to stretch
- Elasticity - returns to original shape after being stretched
Describe the following: epimysium, perimysium, endomysium
epimysium - dense irregular CT that encircles entire muscle
perimysium - dense irregular CT that surrounds 10-100 muscle fibers, separates them into FASCICLES
endomysium - reticular fibers that separate individual fibers from each other
What are the regulatory muscle proteins?
troponin - binds with Ca and changes shape to move tropomyosin away from myosin binding site
tropomyosin - covers actin to prevent myosin from binding
What are Titian, nebulin, alpha actin, myomesin and dystrophin?
structural muscle protein
tinning - connects Z to M, helps with elasticity and extensibility
alpha actin - part of Z disc that attaches to actin
nebulin - wraps around filament
dystrophin - links actin to membrane proteins in sarcolemma
What happens to the Z discs, H zone and I band when a muscle contracts? A band?
Z discs - come closer together
H and I - get smaller/disappear bc of actin/myosin overlap
A - size stays the same, actin and myosin overlap more depending on strength of contraction
What does a triad consist of?
one transverse tubule and two terminal cistern of 2 different SR
What is the length-tension relationship?
the force of a muscle contraction depends on the length of sarcomeres in a muscle prior to contraction
under stretched < 1.8 um-2.2 um < overstretched
How does creatine phosphate help derive ATP necessary for the contraction cycle?
Creatine kinase transfers the P from creatine P to ADP
Describe anaerobic glyolysis
When CP stores are depleted, glucose is covered into pyretic acid to generate ATP
Describe cellular respiration
under aerobic conditions, pyruvic acid can enter the mitochondria and go through the Krebs cycle to generate large amounts of ATP
What are the two sources of oxygen in muscle tissue?
oxygen that diffuses into muscle fibers from the blood
oxygen released by myoglobin within muscle fibers
What is muscle fatigue? What causes it?
inability to maintain force of contraction after prolonged activity
caused: inadequate release of Ca from SR depletion of CP, oxygen and nutrients build top of lactic acid and ADP insufficient release of ACh at NMJ
What is central fatigue?
central fatigue occurs due to changes in CNS and generally results in cessation of exercise
- feeling of tiredness, desire to cease activity
What’s oxygen debt?
the added oxygen, over and above the resting oxygen consumption that is taken into the body after exercise
breathing heavily to get extra oxygen for:
- replenishing CP stores
- converting lactate into pyruvate
- reloading O2 onto myoglobin
What happens to most of the lactic acid after exercise?
it gets converted back into pyruvic acid and used to ATP production via aerobic cellular respiration
What are the three reasons for oxygen consumption after exercise?
- elevated body temperature causes faster reactions and more ATP use, need more O2 for more ATP
- the heart and muscles used for breathing still working hard - consume more ATP
- tissue repair occurs more quickly
What is a motor unit? How does it affect the strength of a muscle contraction?
Motor unit - consists of a somatic motor neuron and the muscle fibers it innervates
more activated = stronger contraction
What are the variables that affect muscle tension?
frequency of stimulation - number of impulses a second
amount of stretch before contraction
nutrient/oxygen availability
number of muscle fibers that are contracting in unison
How are motor units are recruited?
weakest first, followed by stronger motor units
motor units contract alternately to sustain contractions for longer periods of time
What are the periods of contraction for a muscle fiber?
latent - AP sweeps over sarcolemma and Ca ions released
contraction - Ca binds troponin, myosin binding sites on actin are exposed, cross bridges form
relaxation - Ca actively transported back to SR, myosin binding sites covered by tropomyosin, myosin detaches from actin, tension decreases
refractory - period of lost excitability - if two stimuli are applied immediately after the other, the muscle will not respond to 2nd stimulus
what is wave summation
when an action potential triggers muscle contraction before the first contraction has finished
- stimuli arrive at different times
- results in a stronger contraction
What is unfused and fused tetanus?
unfused - sustained but wavering contraction
- stimulated at a rate of 20-30/sec
fused - sustained contraction in which individual twitches cannot be detected
- stimulated at 80-100 - does not relax at all
both have larger peals because of the buildup of Ca
- tautness/partial contraction enables force of another contraction to be greater than one before
What is tone
small amount of tension of muscles at rest
- established by alternating, involuntary activation of small group of motor units in a muscle
Describe isotonic vs isometric contraction
isotonic - tension is constant while muscle length changes
- concentric: becomes shorter
- eccentric: becomes longer
isometric - muscle contracts but does not change length
- tension generated is not enough to exceed the resistance of the object to be moved
Describe the slow oxidative muscle fibers. Where are they found? What are their functions?
deep color
- large amount of myoglobin, mitochondria, capillaries
- high capacity for generating ATP via aerobic respiration
- slow rate of ATP hydrolysis and contraction velocity
- high fatigue resistance
- recruited first
- low glucose and creatine
postural muscles (neck)
maintains posture and aerobic endurance activities
Describe the fast oxidative glycolytic fibers. Where are they found? What are their functions?
medium color
- large amount of mitochondria, myoglobin and capillaries
- perfumes aerobic and anaerobic
- fast ATP hydrolysis and contraction
- intermediate fatigue
location: lower limb muscles
walking, sprinting
Describe the fast glycolytic fibers
white
- smallest amount of myoglobin, mitochondria and capillaries
- anaerobic glycolysis
- fast ATP hydrolysis, contraction, fatigues quickly
- highest amount of creatine and glycogen
- 3rd in recruitment
location - extraocular muscles function - rapid, intense movements of short duration
What affects the distribution of the three different muscle fibers?
- action of the muscle
- person’s training
- genetics
most muscle is a mix of all 3, about half of typical skeletal muscle fiber are SLOW OXIDATIVE
what is the order for recruitment for the different motor units?
- slow oxidative - weak contractions
- fast oxidative glycolytic - more force
- fast glycolytic - max force
activation of motor units is controlled by the brain and the spinal cord
What determines the relative radiation of fast glycolic and slow oxidative fibers in each muscle?
determined genetically - accounts for individual differences in physical performance
What is hypertrophy and how is it affected by endurance exercises?
increased thickened of muscle due to increased synthesis of thick and thin filaments
- cardiovascular changes: cause skeletal muscles to receive better oxygen and nutrients
greater elasticity contributes to a greater degree of flexibility, increasing range of motion
What are characteristics of cardiac muscle?
striated, central nucleus, branched
INTERCALATED DISCS - contain desmosomes and gap junctions that allow muscle AP’s to spread from one muscle fiber to another
have more mitochondria and contractions lats 15x longer than skeletal
What makes smooth muscle weird?
can shorten and lengthen to greater extent - get smaller in response to stretch
contain thin, thick, and intermediate filaments that are not arranged orderly
- thin and intermediate attach to dense bodies
lack transverse tubules
caveolae - small spaces that contain extracellular Ca that help with small SR storage of Ca
when it contracts, it rotates like a corkscrew
- starts more slowly and lasts much longer
no contractile proteins
contains gap junctions
What are things that cause smooth muscle to relax?
autonomic nervous system,
stretching
hormones like epi
- pH, oxygen, Co2 levels, ion concentration
What are the connective tissue that surrounds the three muscular tissues?
skeletal - endomysium, permimysium, epimysium
cardiac - enodmysium, perimyseum
smooth - endomysium
what are the regulatory proteins for smooth muscle tissue?
calmodulin and myosin light chain kinase
Describe the first class lever, second class lever, and third class lever
first class - fulcrum in the middle
second class - load in the middle
third class - effort in the middle
Inside the SR, molecules of a calcium-binding protein called _____ bind to the Ca, enabling more Ca to be sequestered or stored within the SR
calsequestrin
What are the regulatory proteins that switch contraction process off?
troponin, tropomyosin
What are myofibrils?
contractile organelles of skeletal muscles that extend the entire length of the muscle fiber
What are the 4 elastic components of muscle?
titin molecules
Titin
connective tissue around muscle fibers
tendons that attach to muscle to bone
All three connective tissue layer surrounding muscle fibers may extend beyond the muscle fibers to form a roselike structure called ______ that attaches the periosteum to the bone
tendon
What is the cytoplasm of the sarcolemma?
sarcoplasm
The sarcoplasm contains large glucose molecule called ____ and a red color protein called ____
glycogen
myoglobin
What is the basic functional unit of a myofibril?
sarcomere
Muscle contraction cycle starts when the SR releases ____ ions into the sarcoplasm and binds to _____.
Calcium
Troponin
What are the 4 functions of muscular tissue
movement
stabilizing structure
storing and mobilizing energy
generating heat
What is a fascicle?
bundles of muscle fibers wrapped in perimysium
The force of a muscle contraction depends on the _____ in a muscle prior to contraction
length of sarcomeres
what are the 2 functions of the fascia?
allows free movement of muscles
fills spaces between muscles
