muscle physiology 2 Flashcards

Terms Definitions
actin attachment.
sternocleidomastoid contract involuntary
holds muscle to bone
scattered throughout the sacroplasm
provide ATP as an energy source for the contraction of myofibrils
anchors actin to Z disks
*Divides fascicle into individual muscle fibers *arterioles around each fiber*ties adjacent fibers together
increased force
inc'd muscle fiber size
Muscle Spindles are activated by muscle __________ which triggers a _____________. They are located in the ___________.
Thin filaments in myofibrils. Composed of three protein components - actin, tropomyosin and troponin. Tropomyosin wraps around F-actin helix. Troponin attached to tropomosin. Contains binding sites for myosin heads.
Respiration = what type of activity?
*Each Nucleus from myoblast origin *Fused Myoblasts form muscle fiber
white muscle
Glycolytic fibers, which lack myoglobin and this reddish color, are referred to as ______ _______.
a state of sustained maximum contraction
i.e. making a fist
doesn't change length during contraction
I band
threshold stimulus
minimal strength needed to cause contraction
Skeletal Muscle
attaches to bone, skin or fascia
Striated with light and dark bands
Voluntary control of contraction and relaxation
--- motor units are emplyed where maintaining constant precision is important and position or posture is not.
Muscle Hypertrophy
Enlargement of muscle mass from increased amounts of actin and myosin filaments in muscle fibers as well as enzymes linked to energy production. Response from contraction at maximal or near maximal force.
In resting state
Troponin/tropomyosin complex on actin prevents cross bridge formation
Glycolytic fibers
__________ fibers have high cytosolic concentration of glycolytic enzymes and therefore can generate ATP rapidly via glycolysis
Energy is used during muscle contraction to move calcium ions into the sarcoplasmic reticulum and the
T tubules
Shape of fibers
Skeletal muscle - elongated, cylindrical, blunt ends
Smooth muscle - elongated, spindle shaped, pointed ends
Cardiac muscle - elongated, cylindrical fibers that brance
smaller units along the length of myofibrils
each about 2 micrometers in length
Functional unit of skeletal muscle
Gives muscle striated pattern
1. Latent Period (2msec)--Ca2+ is released from SR--slack is being removed from elastic components2) Contraction Period (10-100 msec) filaments slide past each other3) Relaxation Period (10-100 msec) active transport of Ca2+ back into SR4) Refractory Peri
wave summation
15. What is released from the myocin head AFTER it attaches to the active site on actin?
Know skeletal muscle microscopic structures. Be able to recognize structures and know major functions of each:
I Band
Isotropic, to turn equally
When the work increases but oxygen uptake doesn't is called _____  _________.
VO2 Max
Gap Junction (nexus)
Allows for exchange of cytoplasmic solutes. Permits electrical coupling of cardiac muscle cells in longitudinal section.
Sarcoplasmic reticulum
*Similar to ER, connected to TT *Surrounds myofibrils*Contains extracellular fluid high in Ca-(2+)
cardiac muscle
_______ ________ cells are similar to smooth muscle cells in that they are extensively connected by gap junctions, such that an action potential, once initiated, travels throughout the entire cell network.
When ATP is broken down in muscle cells, the two end products are phosphate groups and
antagonistic muscles
muscles that move body parts in different directions
i.e. flexor and extensor muscles
theory that muscle fatigue may be the result of calcium leaking out of the SR (then calcium isnt there for contraction)
38. What is the term for a sustained contraction due to maximal frequency of stimuli?
Define or explain:
minimal stimuli needed to give a measurable response
Which kind of muscle fiber generates ATP through aerobic respiration, is called a red muscle and needs blood for O2 is somewhat resistant to fatigue?
Fast Twitch Oxidative
Type 1 Myosin
Slow oxidative. Slow rate of ATP Hydrolysis. Primarily dependent on oxidative phosphorylation for ATP needs. Blood glucose and free fatty acids are major energy source. Muscle glycogen is slowly depleted.
latent period
the delay of a few milliseconds tha occurs btwn the action potential in a muscle cell and the start of contraction, when the cell first begins to generate force.
Position of nuclei in cell
Skeletal muscle - peripheral
Smooth muscle - central
Cardiac muscle - central
stores Ca2+ in relaxed muscle, release of Ca2+ triggers muscle contraction
transverse (t) tubule
shin splints
sorness of foront of lower leg, kue to straining, often as result of walking up and down hills
56. What happens to muscle tone with upper motor neuron damage?
tone is increased
what force production occurs during #4
Muscle length
impacts cross bridge interaction (more interaction=more force)
Muscle and connective tissue have elastic properties
What is a Monosynaptic Reflex?
A reflex with only one synapse.
SN synapses in S.C. with MN and innervates a muscle
Aerobic metabolism
*required for use of ATP and CP as energy source*Uses glucose, glycogen, oxygen, (myoglobin helps)*At rest, fatty acids used for ATP to make more glycogen, ATP and CP
-attached to hair follicles in skin-in walls of hollow organs (BVs and GI tract)-nonstriated in appearance-small, involuntary cells; tapering @ ends-single, oval-shaped, centrally located nucleus
contraction of smooth muscle
84. What type of muscle fibers are suited for power movements and contract rapidly (fast myosin)?
white, fast twitch fibers
What are the four functional characteristics of muscle tissue?
- excitability (be able to receive/respond to internal/external stimuli)- contractility (shorten forcibly)- extensibility (stretch or extend)- elasticity (recoil; resume original resting length)
Explain the two kinds of Excitation-Contraction Coupling Fatigue

Depletion Theory- a depletion of glycogen which interferes with Ca++ release from the Sarcoplasmic Reticulum 

Accumulation-Pi build up leads to a decrease in the release of Pi from Myosin meaning it can't power stroke
Graded response to stimulus
Entire muscles do not have all or nothing response
Response is graded depending on number of contracting fibers in a muscle.
distribution & recruitment of dif types of fibers
# of muscle fibers doesn't change
In the expiriment, what did you treat the muscle cells with?
KCl MgCl2 and ATP
47. What does a larger stimulus do during multiple motor unit summation?
more motor units are recruited
What force production occurs during # 2
Type of motor unit Activated
increase fast-twitch motor neurons activated
increase force
Fast Oxidative Fibers = what type of activity?
Aerobic & some Anaerobic Glycolysis
attaches to bone, skin or fascia (connective tissue)
striated w/ light and dark bands
What are the three kinds of Series Elastic Elements found in muscles?

Stretchy Elastic Proteins in tendons (collagen)
Stretchy Elastic Proteins between muscle fibers
Stretchy Elastic Proteins found w/in the sarcomere (elastin)
empties quickly (~15 sec); quick breakdown
1 P from ATP goes to creatine phosphate (waiting to b released quickly); creatine P drops P to produce ATP for contraction
To what does the phrase "power stroke" refer?
The phrase "power stroke" refers to when myosin and actin contact to "pull the trigger." Inorganic phosphate is released during the power stroke.
49. If you have stimulated the maximum number of motor units for a given muscle and get x amount of tension produced, what will happen if you increase the stimulus?
you will still produce the same amount of tension because you have already reached the maximum amount of motor units
Why is ATP needed for the contraction of a muscle
to latch on to form cross bridges and to break the cross bridges
vastus medialis
no partial contraction
Cardiac muscle
heart; involuntary movement
property of muscle tissue
Malignant Hyperthermia
Mutation in Ryanodine Receptor.
*Separates muscle from other tissues/organs
Study Chart on Muscle characteristics (handout)
Myasthenia Gravis
Disease of the neuromusucular junction, where circulating antibodies block ACh receptors at the neuromuscular junction.
Rod-shaped protein that spirals about the actin core helping to stiffen it. More importantly it blocks myosin binding sites on actin.
Step 6
Ca(2+) attaches to troponin*exposing attachment site to actin
a cytosolic protein that regulates many processes in amotst all cells of the body.
Skeletal muscle - attached to skeleton
Smooth muscle - walls of intestines, blood vessels, etc.
Cardiac muscle - walls of heart
voluntary control of contraction & relaxation
110. Is cardiac muscle voluntary/involuntary, and striated/nonstriated?
involuntary and striated
What do smooth muscles not have?
No sarcomeres
Lag Phase
1. Wave of depolerization (action potential)
2. permeability of presynaptic terminal is increased
3. calcuim ions diffuse into presynaptic termainal- acetylcohline is released by exosytosis into synaptic cleft
4. Acetylcholine diffuses across the synaptic cleft and bings to acetylecholine receptor molecules
5. post synaptic membrane becomes more permeable to sodium ions
6. Acetylcholine is turned into acetic acid and choline, limiting the length of time acetylcholine is bound to the rececptor cite; so one presynaptuc action potential produces one postsynaptic action potential in the musle fibers
7. action potential produced is sent into the t tubles
8. electrial changes occur in the t tuble and makes the membrane of the sarcoplasmic reticulum very permible to ca+ ions
9. calcium Ions diffuse fromthe sarcoplasmic reticulum into the sarcoplasm
10. Ions bind to troponin; the troponin-tropomyosin complex changes its position and exposes the active site on the actin myofliaments
isotonic contractions
Muscle length changes (concentric and eccentric).
*Bundles of Thick (myosin) and thin (actin) *Myofilaments (proteins) organized into sarcomere
A fiber's ________ does not affect its force-generating capacity insofar as i reflects the # of sarcomeres in series, ________ in fibers length do influence its ability to generate force.
Sodium ions
in resting cells, concentration is kept low by active transport
ability to respond to stimuli and produce electrical signals
99. In smooth muscle, what anchors actin to the sarcolemma?
dense areas
The human body is about_________% muscle.
40 - 50%
Golgi Tendon Organs respond to muscle _________, which triggers a _____________ and are located where the ____________ meets the ___________.
Relaxation (inhibition)
Synaptic Cleft
Area between nerve and sarcolemma of muscle fiber.
A Band stains dark due to
Thick Myosin filaments
gap junctions
In smooth muscle, ____ ________ allow ions to move from one cell to another, so an electrical signal initiated in one cell spreads to neighboring cells.
All the muscle fibers stimulated by one motor neuron constitute a
motor unit
Smooth muscle is so named because it contains no
at rest, want myosin binding sights on actin covered by tropomyosin
55. What is the state of partial muscle contraction due to nerves continually stimulating motor units?
muscle tone
Define or Explain:
all stimuli which are greater than maximal
Upper Motor Neurons are located in ______ ___________
The Brain
(an interneuron)
Multiunit Smooth Muscle
Smooth Muscle with no Gap Junctions. Fibers are structurally independent. Innervated by a single nerve fiber with many nerve endings. Allows for finer control. Found in airways, ciliar muscle, piloerector muscle.
# of mitochondria
What is the distinction btwn the oxidative and glycolytic fibers?
muscle tone - a condition in which a muscle is kept partially contracted over a long period of time
One set of fibers, then another set is briefly stimulated so some of the muscle is always contracted
acetylcholinesterase (AChE)
enzyme that breaks down ACh within the synaptic cleft in order to relax muscle
42. During a twitch of a MUSCLE FIBER, what genertes tension?
sarcomere length
What are the 3 proteins of myofibrils?
Contractile proteins: Does the contracting (myosin and actin)
Regulatory proteins: Turns contraction on and off (troponin and tropomyosin
Structural proteins: keeps everything aligned (titin, myomesin, nebulin and dystrophin)
What is the Cross-Bridge Power Stroke?
That which allows for sliding.
What kind of energy does cardiac muscle use?
Aerobic metabolism ONLY(myoglobin helps)
length tension curve
at rest we develop the most tension, at about 80-120% of the optimum length
27. What happens to the tension produced if the sarcomere length is less than 2.0 um?
the tension generated is reduced
Which fiber types does the neck, back, leg muscles have?
higher proportions of postural, slow oxidative fibers
What is the optimal length?
2.25 um
Longer- decrease the # of cross-bridges
Shorter- interrupt the cross-bridge formation which can lead to myosin deformation
The Z line, I band, A band, and H zone are all anatomical parts of the
more interaction of cross bridge b/w actin & myosin
equals more force (cross bridge)
What is the function of ATP in muscle contraction?
To provide energy
Muscle cramps occur when? Why?
Muscle cramps are likely to occur when one is fatigued- low ATP so..
Cant break CB-AS bond
Cant pump out Ca++
What are the types of skeletal muscle fibers?
Type l, slow oxidative, slow-twitch
Type lla, fast oxidative-glycolytic, (FOG)
Type llb, fast glycolytic fibers, fast-twitch
What if you run out of ATP?
You Will Die!!! muhahahhaha*Extra ATP converted to CP (creatine phosphate)* When needed CPK (creatine phosphate)*Releases energy from CP to make ATP
1. myosin heads hydrolyze ATP and become reoriented and energized (ready to bind)2. myosin heads bind to actin, forming crossbridges3.myosin crossbridges rotate toward center of the sarcomere (power stroke)4. As myosin heads bind ATP, the crossbridges det
the contraction cycle keeps repeating as long as there is...
Where do we get our ATP from for muscle contraction?
Carbs, Lipids and sometimes Proteins
each muscle cell is supplied by ____ motor neuron terminal branch
each motor neuron supplies _______ muscle cells
What happens in a partially contracted muscle?
Myosin grabs acting and pulls Z disc over. Smaller H zone and I band
72. What can be used as a source of energy in aerobic metabolism?
glucose, fatty acids, or amino acids
Briefly describe the pathway from 1 SN to skeletal muscle.

1 SN synapses w/ 2 SN in S.C.

2 SN synapses w/ 3 SN in Thalamus

3 SN synapses w/ Interneuron in Cortex

Interneuron synapses with Upper MN in 1 Motor Cortex

Upper MN synapses with Lower MN in S.C.

Lower MN innervates a skeletal muscle
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