Skeletal Muscle Flashcards
Which is the largest organ in the body by mass?
skeletal muscle
What is skeletal m uscle responsible for?
locomotion, metabolic activity
What are the three types of muscle?
skletal smooth cardiac
What are the five different jobs that the three types of muscle perform?
movement, stabilization, storage, moving substances, generating heat
What is the largest metabolic organ?
skletal muscle
How do you change metaoblism?
stress muscles
When heart rate increases, this means muscles are ____
activated
What controls skeletal muscle contraction?
peripheral nerves
Where do peripheral nerve axons originate from?
motor neuron cell bodies in the spinal cord, somatic
Skeletal muscle contraction accounts for all what?
all voluntary body movement
What are two terms for muscle cells?
fibres or myocytes
Myocytes are filled with what?
myofibrils
What are sacromeres in series?
myofibrils
What are myocybrils?
sacromeres in series
What is the basic contraction unit of the muscle?
sacromere
One sacromere is identified?
btw 2 z lines
Myosin is what
thick filament
actin is what
thin filamenet
Order muscle components from smallest to largest
actin and myosin < sacromere < series of sacromeres = myofibrils , fibres/myocytes (wrapped in edomysium) , fasicle wrapped in perimysium < muscle wrapped in epimysium FORMs tendon ATTACHES to bone
What are fibres wrapped in?
endomysium
What are fasicles wrapped in?
perimysium
What are muscles wrapped in?
epimysium
Order perimysium, endomysium, epimysium
endomysium < perimysium < epimysium
What is an H zone?
space btw thin filaments when muscle is resting
What is the 1/2 I band?
space btw 2 lines and thick filament
Which spaces get smol during contraction?
H zone and 1/2 I band, therefore sarcomere shortens
What shortens in muscle contraction?
sarcomere
What is the structure in the middle of a sarcomere?
M line
What is an A band?
the width of the thick filament
Describe sliding filament theory
Thick filament doesnt move, filaments slide past one another to shorten
What decreases in atrophy?
filaments and sarcomeres, therfore fibers
Why is there atrophy?
when muscle isnt used it atrophys bc muscles are metabolically demanding and costs too much energy to maintain
What causes atrophy?
casts, going to space, denervation
Give an example of denervation
spinal cord injury
In sliding filament theory, how many actins does myosin interact with?
6
In sliding filament theory, how many myosins does actin interact with?
3
The three types of muscle differ in: (4 items)
morphology, location, function, method of activation
Skeletal muscle is wrapped in what type of tissue?
connective tissue
What are the three types of connective tissue involved in skeletal muscles?
endomysium, perimysium, epimysium
Endomysium surrounds what
individual muscle fibres
perimysium surrounds what
bundle of muscle fibres
epimysium surrounds what
entire muscles
What is the periosteum of the bone
lining of the bone
what is continous with the periosteum of the bone
tendon
What is aponeurosis?
broad flat tendon
What do you call a broad flat tendon
aponeurosis
How is the muscle connected tot he bone?
through the matrix around it which joins together to form a tendon and the tendon attches to the bone
Define muscle dystrophy
erros in the interface btw connective tissue and tendons
Examples of muscle dystrophy?
mutation in matrix protein or in muscle (where proteins connect to matrix) which causes rip in muscles
Pathology of muscle dystrophy? Who is affected?
duchenne syndrome, lil boys
What is hypertrophy
increased number of filaments (actin and myosin), more sarcomeres expands fibres which causes muscle enlargement and efinition
What happens to the # of muscle cells is muscle hypertrophY?
of myocytes font increase, rather the fibre diameter gets bigger which means stronger
What features of myosin allow it to cross bridge?
2 globular heads and long hinged tail
What is a thick filament
lots of myosin
What does myosin atpase do? What does this allow myosin to do?
breaks atp to harness energy which allows myosin to pull actin
What are the diff features of myosin
tail, hinge, myosin heads (2), actin binding sites, myosin ATPase
describe architecture of thin filament
actin molecules form 2 coiled chains
Describe actin
a series of lil globuals with binding sites
What does tropomyosin do
tropomyosin molecules run along actin and block cross bridge binding sites
What substance blocks cross bridge binding sites?
tropomyosin
What substance holds tropomyosin in place?
troponin
What does troponin do?
hold tropomyosin in place
What can bind to troponin? What happens when this substance binds?
Calcium can bind to troponin and change its conformation, therefore pulling tropomyosin away from cross bridge binding site
Calcium is considered what?
regulator of cross bridge cycling
what is the regulator of crossbridge cycling
calcium
what allows actin myosin interactions to occur
calcium
what happens when calcium is removed
tropomyosin moves back and blocks cross bridge binding sites again
What is malignant hypothermia
calcium is released uncontrollably and there are painful contractions
what pathology causes calcium to be released uncontrollably?
malignant hypothermia
What type of movement is excitation-contraction coupling
voluntary
What is the excitation part of excitation-contraction coupling?
electrical signals from brbain
what is the contraction part of excitation-contraction coupling?
muscle contraction
An _________ signal causes release of Ca
excitatory
what type of signal causes Calcium relase
excitatory
Define excitation
AP travels to axon terminal, i.e. neuromuscular junction
AP in neuron causes release of what NT at neuromuscular junction?
ACH
ACH-R at neuromuscular junction is classified as what
nicotinic
ACH-R at motor end plate is classified as what
nicotinic
what is a motor end plate
area on muscle fibre
Describe excitation process
Neurotransmission -> AP -> t-tubules -> sarcoplasmic reticulum (spec. terminal cisternae) -> release of Calcium -> contraction
what is a triad
1 tubule and 2 terminal cisternae
T tubules stand for what
transverse
sarcoplasm contain what
myoglobin and glycogen
define sarcolemma
tubular sheath surrounding skeletal muscles fibres
define sarcoplasmic reticulum
a type of endoplasmic reticulum that stores and releases calcium
sarcoplasmic reticulum can be found where?
cardiac muscle and skeletal striated muscle
what are terminal cisternae
enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules
what are t tubulues
invaginations of the membrane
t tubulues are what
membrane
what are the two reeptors in t tubulues
dihydropyridine and ryanodine
Describe process of Ca influx to T tubulues
DHP is voltage sensitive and so it changes shape when an AP arrives and pulls ryanodine plug out of sarcoplasmic reticulum allowing ca influx
how are muscles relaxed in terms of ca
ca is taken up by enzyme calcium atpase
how is ca reuptaked?
enzyme calcium atpase
which is slower atpase ca reuptake or channel release of ca?
atpase reuptake
what two molecules are needed for cross bridge cycling
ATP and Ca
what are the four steps of cross bridge cycling
- energize myosin 2. actin-myosin binding 3. cross bridge movement (power stroke) 4. breaking the cross bridge
what step does power stroke occur
cross bridge movement
what happens in energizing myosin
atp already bound to myosin so myosin atpase dephosphorylates ATP and this energizes myosin
what happens in actin myosin binding
actin will bind to myosin when Ca is available
what is tehr egulator of cross bridge cyclin
ca
what happens in cross bridge movement
energy stored in myosin is used to make the cross bridge move, therefore shorteining the sarcomere and adp&pi is released
What happens in cross bridge breaking
atp binds ot myosin and this breaks the bond btw actin and myosin
what is rigor mortis
dont have atp to let myosin release actin so it looks contracted
why do u look contracted when u die
dont have atp to let myosin release actin
Describe the process of calcium influx into the t tubules
Ap arrives, DHP which is voltage sensitive changes shape and this pulls out the ryanodine receptor out of the sarcoplasmic reticulum allowing ca influx
out of DHP and ryanodine receptor which is voltage sensitive
DHP
out of DHP and ryanodine receptor which is the plug
ryanodine receptor
what is the function of terminal cisternae
ensure rapid release of ca
where is the ryanodine receptor
in the sarcoplasmic reticulum
How do the muscles relax in terms of Calcium?
calcium is taken up by enzymatic calcium atpase
when can twitch contraction occur
due to difference in speed of ca efflux vs influx
what type of contraction do we do?
tetanic contraction
why is max tetanic contraction force 3-5x greater than max twitch contraction force?
max tetanic contraction is so great bc each subsequent AP releases more calcium
what are the three factors regulating force production
muscle length, AP frequency, # of fibres per motor unit and the cross sectional area (SIZE!) of those muscle fibres
define motor unit
one motor neuron and all the muscle fibres it innervates
what is ratio btw neurons and muscle fibres?
one neuron for many muscle fibres
what happens if muscle length is too short
actin bump into each other and cross bridge cant form efficiently and cross bridge cant form efficiently
what happens if muscle length is too stretched
number of cross bridges that can form is reduced
What can decrease force production in terms of muscle length
too stretched or too compressed decreases force production
Describe ap frequency in terms of force production
summation of AP: send another AP before calcium is reuptaken
What are the diff types of AP frequencies
single twitch, wave summation, unfused tetanus, fused tetanus
describe unfused tetanus
some discipation of force
describe fused tetanus
swamped with AP, no discipation of forcel every possible cross bridge is formed
which type of ap summation involves every cross bridge forming
fused tetanus
Describe the factor of # of fibres per motor unit in terms of fore production
3 types of motor units exist based on muscle fibre type
how do muscle fibre types differ
size and ease of activation
how does size of muscle fibres in context of motor units affect force production
size of cross sectional area of muscle fibres determines amount of force produced -> if more muscle is innervated by one neuron, more force is produced
how are skeletal muscle fibre types classified
contraction speed and metabolic profile
what are the two types of fibres in terms of contraction speed
slow and fast
what does contraction speed depend on
myosin atpase action rate
What are the pros and cons of slow fibres
they contract slow (duH) but theyre fatigue resistant
what are the two types of fibres in terms of metabolic profile
oxidative and glycolytic
describe oxidative fibres
primarily use oxygen for atp production
what type of metabolism do oxidative fibres use
aerobic
what type of metabolism do glycolytic fibres use
anaerobic
describe glycolytic fibres
high capcity for ATP production with oxygen
Which muscle fibre types are fatigue resistant?
slow oxidative and fast oxidative glycolytic
what are the 3 types of motor units?
slow oxidative, fast oxidative flycolytic, fast glycolytic
describe order of reqcruitment of motor units
slow oxidative then fast oxidative flycolytic then fast glycolytic
Describe slow oxidative fibres
smol diameter, rich blood supply, aerobic respiration
slow oxidative is used for what activity
posture and endurance
describe fast oxifative glycolytic
intermediate diameter, rich blood supply, aerobic and anerobic respiration
fast oxidative glycolytic is used for what activity
walking and sprinting
walking and sprinting requires what motor units
fast oxidative glycolytic and slow oxidative
posture and endurance uses what motor units
slow oxidative
Which motor unit muscle fibre type has rich blood supply
fast oxidative glycolytic and slow oxidative
what is the size principle
the order of requirtment of motor units is SAME for all activities
describe fast glycolytic
large diameter, few capillaries, anaerobic respiration
what activity uses fast glycolytic
power movements
What are the two contraction types
isometric and isotonic
describe isometric contraction
no load movement, where muscle force = load
describe isotonic contraction
muscle force does not equal load, load is moved
what are the two types of isotonic contraction
concentric and eccentric
describe force load equation for isotonic concentric movement
force > load; load is up
describe force load equation for isotonic eccentric movement
force < load; load is down
which muscle types use actin and myosin
smooth and skeletal muscle
smooth muscle can be electrically coupled by what
gap junctions
actin and myosin are organized how in smooth muscle in comparison to skeltal muscle
less organized
which muscle types have striations
cardiac and skeletal
why do smooth muscles not have striations
filaments are anchored to desnce bodies on interfilament network in cytosol
describe smooth muscle contractions
involvuntary
smooth muscle contraction speed?
v slow!
how do u get toned muscle
smooth muscle, maintains prolonged tension
where do cardiomyocytes connect
intercalated discs
what composes intercalated disks
desosomes and gap junctions
which muscles contain gap junctions
smooth and cardiac muscle
what do desomosomes do
stabilize cell to cell contact
what do gap junctions do
allow direct communication btw adjacent cells via ion passage
where can smooth muscle be found?
arteries, digestion, reproduction, respiration and urination
what is the location of skeletal muscle
MSK system
what is the location of smooth muscle
hollow organs
relative size of diff muscle types
skeletal -> v large, cardiac -> large, smooth -> smol
describe nucleus count in diff muscle types
skeletal is multinucleated, cardiac has 1-2 nuclei, smooth muscle has single nuclei
which muscle types are multinucleated
skeletal and cardiac
which muscle types are striated
skeletala and cardiac
cardiac muscle morphology is
branched
smooth muscle morphology is
spindle shapped
which muscle type is autorhythymic
cardiac and smooth
list contraction speed of muscle types fastest to slowest
skletal is fastest, cardiac is moderate, smooth is slow
what regulates skeletal muscle
somatic NS
what regultes cardiac muscle
ANS, pacemaker cells, intrinsic conduction system, hormones
what regulates smooth muscle
ANS, pacemaker cells, hormones, stretching, nitric oxide
