U2- Muscular System (Histology/ Contraction/ Metabolism) Flashcards
three universal chara. of muscles
excitability
contractility
elasticity
functions
support/ posture
temp homeostasis
regulation of dig. passage
protection of soft tissue
skeletal muscle
striated + voluntary
connected to bones
composed of muscular tissue + fibrous CT
muscular tissue
actin and myosin
Protective layers in muscle CT
endomysium
perimysium
epimysium
endomysium
surr. e/ fiber
perimysium
bundles fibers into fasicles
epimysium
surr. entire muscle
myofilaments
have actin + cross-bridging binding sites
3 types, thick, thin and elastic
thick myofilaments
made of myosin (golf club head structure)
intertwined shaft tail
thin myofilaments
made of fibrous + globular actin
G binds to head of mysoin
when relaxed tropomyosin blocks active site
(allows sliding)
tropomyosin
binds to actin
elastic myofilament
made of protein titin
stabilizes thick fila.
prevents overstretching
striations
A + I bands
A bands
dark
where thick and think myofil. overlap
middle = H Band
ONLY thick
I bands
light
located by Z disk
anchor point
when shrink together they shorted muscle during contra.
sarcolemma
plasma mem. of muscle fibers
polarized
sarcoplasm
cytoplasm in btw muscle fibers
satellite cells
unspecialized cells
btw muscle fibers and endomysium
myofibril
arranged area of musc. fibers
section from z disk to z disk
myoblast
stem cell for muscl
divide + connect
nerve stim. and muscle contraction relationship
nerve stim= musc. contrac.
motor neurons
located in spinal cord and brain stem
axons lead to musc.
1 neuron= 1 motor fiber
motor unit
neuron and motor fiber
neuromuscular junction
type of synapse
nerve fiber meets muscle cell (myocyte)
synapse
nerve fiber meets receptor cell
synaptic cleft
separates axon terminal + musc. fiber
axon term.
end of e/ nerve fiber
contains synaptic vesicle
synaptic vesicle
filled w/ neurotrans. chem.
excrete w/ exocytosis
electrical potential
“voltage”
diff in charge btw 2 points
voltage
resting mem. potential
maintained by Na- k pump
phases of muscle behavior
1-excitation
2- excitation-contraction coupling
3- contraction
4- relaxation
muscle tone
partial contraction
prepares musc. for action
endpoint of contraction
contraction stops when thick filam. reach z disks
brief and weak
endpoint of relaxation
stretching stops when no overlap btw thick and thin filaments.
myosin heads unable to attach to anything
myogram
chart for timing and strength of musc. contraction
threshold
min voltage necessary generate action pot. in fiber
latent period
delay btw threshold and twitch
contraction phase
musc. produces tension + moves object
only when at max elongation (rubber band)
factors affecting strength of twitch
temp
intensity of stim.
frequency of stim.
twitch temp
if warm, enzymes wrk faster
twitch stim frequency
fast frequency- strong and quick
slow frequency- weak and long
twitch stim intensity
higher volt- more excitability- more motor units involved
recruitment
chain of motor units are involved
temporal summation
stimulus’ piggyback on e/o
causes incomplete tetanus
inc. intensity of twitch
complete tetanus
not normal in bio functions
twitches fuse into single contraction
isometric contraction
muscle tension changes w/ same length
contraction at cellular lvl
energy absorb. by elastic
NO MVMNT
isotonic contraction types
eccentric and concentric
isotonic contraction
contraction w/ change in length w/ same tension
object lifiting has opposite force
eccentric contraction
isotonic
lengthens + maintains tension
concentric contraction
shortens and maintains tension
anaerobic fermentation
short term energy
cell produces ATP w/out O2
generates lactic acid
aerobic respiration
long term energy
cell produces ATP w/ continual O2
fast-twitch muscles
white color
energy from anaerobic (produces ATP faster)
fast absorption and releasement of Ca
slow-twitch muscles
red color
energy from aerobic respir.
slow Ca absorption and releasement
cardiac muscle functions
contract w/ reg rhythm
involuntary
resistant to fatigue (aerboic respir.)
long contractions
cardiac muscle structure
striated and branched (intercalated discs)
larger T-tubules
enlarged mitochondria
no need for outside nervous stim.
smooth muscle function
drives food through dig. system (peristalsis)
dilate + constrict blood vessels
maintains BP
smooth muscle structure
no striations
ATP from aerobic respir.
latch bridge mechanism
involuntary
visceral muscle
“single-unit smooth muscl”
cells connected w/ gap junction
directly stim e/o and act as one unit
smooth musc. ways of excitation
autonomic nerve fibers
neurotransmitters
contraction / relaxation (slow!!)
smooth muscle contraction process
Ca binds to calmodulin
activates myosin light chain kinase
adds ph grp to regul. protein
hydrolases ATP
pwr/ recovery strokes occurskeletal muscle phase 1- excitation
1-nerve signal reaches neuro-m junction,
opens Ca voltage-gated channel, Ca enters cell
2- Ca stim. release ACh into synaptic cleft
3- Ach diffuses and binds receptors on sarcolemma
4- Na flows into cell making sarcolem. less negative (depolarization) and K flows out changing sarclem. to higher negative again (repolarization)
5- change in charge of resting mem. poten. = Action. poten.
skeletal muscle phase 2- excitation-contraction coupling
1- Action potential charge reaches t tubules + travels down
2- action pot. opens gated channels in t tubules, which opens Ca channels
3- Ca binds to troponin of thin filam
4- tropomysoin/troponin changes shape, exposes active site on actin filam. for bonding
5- can now connet to myosin heads of thick filam.
skeletal muscle phase 3- Contraction
“sliding filament model”
1- ADP + Ph energize head into high energy position
2- head binds active site on thin fila.
forms cross-bridge btw myosin and actin
3- myosin releases ADP + Ph upon binding, moves into low energy position, bringing thin filam. along w/
“power stroke”
stays bound to actin until released by ATP
4- ATP binds to myosin, head releases from actin, and returns to recovery stroke in high energy position to rebind farther down thin filament
skeletal muscle phase 4- Relaxation
1- nerve signals stop reaching neuro-musc. junction
ACh not released
2- stimulation of fiber ceases bc ACh broken down
3- Ca dissociated from troponin not replaced
4- tropomyosin blocks active site on thin filament,
muscle loses tension
muscle tone
partial contraction
prepares musc. for action
consumes contin. energy
myogram
chart displays timing and strength of musc. contraction
threshold
minim. voltage necessary generate action pot. in fiber
maximum threshold
twitch occurs
contraction phase
musc. produces tension + moves object (load)
factors that affect strength of twitch
how stretched before stim.
temp of muscl. (if warm enzymes wrk faster)
stim frequency
together= strong and quick
apart= weak and long
intensity of stim
higher volt= mre excitability= mre motor units involved
recruitment
multiple motor units involved in excitation
temporal summation
stimulus overlap e/o before muscle can recover
causes incomplete tetanus
inc. intensity of twitch
incomplete tetanus
caused by temporal summation
complete tetanus
twitch turns into single contraction
not normal human process
isometric contraction
musc. changes tenses
length is constant
maintains joint stability and acts as structure
Ex. wall sit
isotonic contraction
muscle tense constant
length changes
Ex. lift barbell
eccentric v. concentric
eccentric contraction
lengths w/ same tension
concentric contraction
shortens w/ same tension
anaerobic fermentation
ATP source without O2 generates lactic acid short term energy used ATP + phosphate
aerobic respiration
uses O2
long term energy
produces more ATP
uses glucose + fatty acids
Activity level- Rest
fatty acids carboxylized
ATP + Glycogen made
Activity level- Moderate
glycogen consumed
makes lots of ATP
aerobic
Activity level- Strenuous
lactic acid produced
demand for O2 greater than supply
makes little ATP
anaerobic
fatigue factors
K plus accumulation
fuel depletion
electrolyte loss
fuel depletion
no mol. to synthesize ATP
energy demand> energy supply
K plus accumulation
lowers mem. potential
makes less excitable
excess postexercise O2 consumption (EPOC)
diff. btw elevated heart rate at end of exercise and normal heart rate
O2 needed regen. ATP aerobically
convert lactic acid to glucose
slow twitch
red color "slow oxidative" maintain posture fatigue resistant aerobic resp.
slow twitch composition
blood capillaries
myoglobin
mitochondria
fast twitch
anaerobic ferm. white color "fast glycolytic" fast ATP hydrolysis fatigue quick
fast twitch composition
high con. of glycogen + phosphate
cardiac muscle function
invol.
contract w/ reg rhythm
resistant to fatigue (aerobic resp.)
cardiac muscle structure
striated, branched (intercalated discs)
not need outside nervous stim.
enlarged mitochon.
smooth musc. structure
no striations
not always innervated
if so- are involuntary
few T-tubules
smooth muscle functions
peristalsis
dilate/ contract blood vessels + airway
maintain BP
hypertrophy
cells divide and grow
opposite of hypo trophy
latch-bridge mechanism
in smooth musc.
maintains tonic concentration (muscle tone)
smooth muscle- visceral muscle
single unit smooth muscle
cells connect w/ gap junction
directly stim e/ o/ -act as one unit
smooth muscle-ways of excitation
autonomic nerve fibers
neurotransmitters
Smooth musc- contraction and relaxation
slow process
Ca binds to calmodulin
adds ph grp to 2 proteins
hydrolysis ATP
the accumulation of blank ions during short exercise lowers mem. potential of the muscles and makes it less excitable
potassium
calcium channel pockets in the sarcolemma of smooth musc. cell pockets
caveolae
thickened notched ends of cardiac musc. cell w/ gap jun.
intercalated discs
swelling along length of nerve fiber, innervates smooth musc.
varicosities
regulatory protein in smooth musc. that binds to Ca and activates myosin light-chain kinase, replaces troponin in smooth musc., binds to Ca
Calmondium
what protein activates myosin light-chain kinase
Calmondium
what protein replaces troponin in smooth muscle
calmondium
binds to calcium in terminal cisternae
calsequestrin
charac. of voluntary relaxation
stop stim.
no calcitrol
Ca transported to sarcoplasmic reticulum
breaks bond w/ troponin
(tropomyosin covers active site)
charac. of involuntary relaxation
lack Ca
no ATP
all of none principle
if at threshold, all fibers contract
tension
position musc. in before contraction
length-tension relat.
optimum overlap of myofilaments
strength varies w/ amnt tension before contraction
contraction switch factors
strength and intensity
contraction strength
happens by motor unit recruitment
contraction intensity
how many motor units are involved
energy currency
ATP
Ph andGTP
required for contraction
glycogen
creatine phosphateATP generation
oxidative or fermentation
glycogen as energy
if not used turns to fat
stores longer in aerobic resp.
creatine phosphate as energy
reversible rxn
ATP needs be constant
made w/ ATP and creatine
strength exercise
anaerobic ferm.
hypertrophy
muscl. cells build more myofilam.
endurance exercise
can convert intermediate fibers
inc. blood supply
aerobic resp.
