Exam 4: Muscular System Pt. 2 Innervations and Contractions Flashcards
one neuron may innervate _____ fiber/s
many
is every skeletal muscle individually innervated?
yes
all skeletal muscle is depolarized in response to _______
acetylcholine
what muscle types use gap junctions instead of being individually innervated
cardiac and smooth
Raynaud’s syndrome
overreaction to cold
constriction of blood vessels to extreme degrees
- blockage of Ca would decrease vasoconstriction
- Ca channel blockers
Why do you think Ca blockers would effect heart, but not have an effect on skeletal muscle?
skeletal muscle relies on intracellular Ca
- the heart is all from external
why do Ca blockers not have same level of effect on digestive system even though you get digestive effects?
digestive system has smooth muscle - smooth is dependent on extracellular
why would it hit Ca channels in cardiac but not digestive if both smooth?
cardiac slightly diff than digestive
- Ca targets diff families
neuromuscular blocking agents - anesthesiology
what does it target?
acetylcholine receptors
resistant to acetylcholinesterase - muscles relaxes
do you think neuromuscular blocking agents can effect the diaphragm?
yes
- you can temporarily stop it - intubate them
what is a motor unit composed of?
one neuron and all the muscle fibers it innervates
- only one type of fiber
as a stimulus increases are more or less units recruited?
more increasing tension
where can you find smaller motor units
in the hand because it requires precision
the number of motor units active at rest
muscle tone
muscles with higher degree of muscle tone respond ____ and use more ____ at rest
quickly
energy
why are warm ups beneficial?
- result in heat production
- less prone to damage and have inc recruitment
3 types of muscle fibers
type I, type IIA, type II B
type I fibers
- endurance fibers - slow oxidative - slow twitch
- dependent on aerobic respiration
- high myoglobin content: lots of stored O2
- muscle fibers a darker red, wales have black bc underwater so long
- many mitochondria
- highly vascular
- slow to fatigue: do not fatigue easily
- slower contraction compared to others
- small fibers
- maintaining posture
Type II B
- burst of strength- fast glycolytic fibers- fast twitch
- fast contractions
- anaerobic respiration: do not need as much O2, lower myoglobin
- store lots of glycogen
- not many mitochondria
- not many capillaries compared to type I
- large fibers
- last to recruit but do so quickly
- short intense movements - hitting baseball
Type II A
intermediate - you can train one way or another
- mainly aerobic but larger store for anaerobic
- high myoglobin: less than type I
- red to pink color
- sprinting, walking
Which type of muscle fiber predominates in pectoralis major muscle?
type II B - fast twitch
which muscle fiber type predominates gastrocnemius
type I - endurance
3 stages of a muscle twitch
latent, contraction, relaxation
myogram
shows time vs force of contraction
latent stage of muscle twitch
time tat stimulus is being communicated to sarcomere
- depolarization of membrane , releasing Ca
contraction stage of muscle twitch
- increase in tension, hen work is being done
- troponin can bind Ca
relaxation of muscle twitch
recovery period for muscle cell
- put Ca back into storage - sarcomere back to original shape, relaxed
increase in stimulus strength results in _____
increased tension
what causes an increase in muscle tension?
recruitment of more motor units
tension in lifting notebook vs heavy back pack
more tension in backpack
Treppe
stimulus is applied immediately after relaxation
tension “steps up” with stimuli
gets bigger and bigger until max tension to handle frequency
- not the same at the beginning bc you are warming up - easier to recruit as you warm up
- max not as high bc allowing them to fully rest
wave summation
- higher frequency than treppe
- stimulus applied before relaxation complete
- tension increases, does not reach baseline until stimulus stopped
- waves look piled on top of eachother
- more recruitment of motor units since incomplete relaxation
incomplete tetanus
wave summation nears max tension
- still allows partial relaxation
- it is the max you can get with wave summation
tetanus
frequency of stimuli no longer allows for relaxation
- max tension reached
- NO relaxation
- eventually hit fatigue
stimulus frequency and tension types (4)
treppe, wave summation, incomplete tetanus, tetanus
isometric muscle contractions
- develops tension without changing length
ex: lifting something heavy and you cannot budge it - no change in muscle length
isotonic muscle contraction (2 types)
concentric and eccentric
isotonic concentric muscle contraction
tension development while shortening
isotonic eccentric muscle contraction
tension development while lengthening
ex: slow curls in gym - slowly lowering the weigh - muscle gets longer and you feel tension increase
when does muscle fatigue occur (3)
- high energy demand is placed on muscles
- dramatic variations in muscle recruitment
- insufficient O2 - oxygen debt
blood flow to muscles but the demand is higher than you reach with aerobic respiration - so you take on anaerobic respiration
oxygen debt
results of muscle fatigue (3)
- inc glycolysis - accumulation of lactic acid
- acidosis in cell dec enzymes involved in ADP rephosphorylation
- muscles do not preform as well
organ to recover from the lactic acid build up - cori cycle
liver
glycolysis dependent tissues
skeletal muscle blood cells bone marrow renal medulla peripheral nerves hypoxic tissues
cori cycle, what does the liver do?
gluconeogenesis: takes it backwards which costs liver energy, it invests ATP to take lactate to make glucose - releases glucose to bloodstream so cells that need glucose can have it
cycle between cells producing lactic acid and liver clearing it out and providing sugar
Rhabdomyolysis
breakdown/degeneration of skeletal muscle cell
- cell contents released into blood stream (potassium K)
life threatening due to effects on heart, kidney, liver
3 ways to damage kidneys
direct toxicity - iron in myoglobin
obstruction of tube- myoglobin interacts with glycprotein in kidneys and precipitates out
vasoconstriction - due to inflammation
hyperkalemia
too high K in blood
- throws off balance of ions - balance for nerves and muscles - can send someone into heart attack
lactic acidosis
too acidic
- pH change, can get hypoxic
uremia
wastes remaining in blood instead of being excreted in urine - kidney not filtering
- clogged - vasoconstriction - back up of toxic material
Myoglobinuria
myoglobin in urine
ex: casts
best diagnostic marker for Rhabdomyolysis
serum CK (CPK)
