Muscle Flashcards
describe the main function of muscle
contraction, which leads to a lot more functions
list and describe the 4 functional properties of muscle
- contractility: the ability of muscles to shorten forcefully
- excitability: the ability of muscles to respond to a stimulus
- extensibility: the ability of muscle to stretch beyond its normal resting point and can still contract
- elasticity: the ability of muscle to recoil to its original resting length after being stretched
list the 3 muscle types
- skeletal muscle
- cardiac muscle
- smooth muscle
describe skeletal muscle
striated, multi-nucleated= much longer cells that run the length of the muscle, voluntary muscle contraction
describe cardiac muscle
also striated, found only in the heart, mono-/di/nucleated cells that are connected via intercalated disks, involuntary muscle contraction
describe smooth muscle
nonstriated, mononucleated, shorter cells, involuntary muscle contraction
what tissue are the tendons of skeletal muscle made of?
dense regular connective tissue
what is the origin and its location in skeletal muscle tendons?
the less mobile, fixed attachment, usually on the proximal end of the muscle
what is the insertion and its location in skeletal muscle tendons?
the more mobile attachment, usually on the distal end of the muscle
what is the epimysium of skeletal muscle?
dense regular connective tissue that surrounds the entire muscle and is continuous with the tendons of that muscle
what is the perimysium of skeletal muscle?
dense regular connective tissue that surrounds bundles of muscle fibers
what is the endomysium of skeletal muscle?
dense regular connective tissue that surrounds individual muscle fibers, allows for smoother movement and contraction
describe the sarcolemma of skeletal muscle fibers
the cell membrane
describe the sarcoplasm of skeletal muscle fibers
the cytoplasm
describe the sarcoplasmic reticulum of skeletal muscle fibers
specialized endoplasmic reticulum
describe the terminal cisterns of skeletal muscle fibers
contained in sarcoplasmic reticulum, have voltage-gated Ca2+ channels
describe transverse (T) tubules of skeletal muscle fibers
tubes that run from sarcolemma into cell
describe triads in skeletal muscle fibers
one T tubule plus two terminal cisterns
describe myofibrils of skeletal muscle fibers
bundles of proteins called myofilaments
list the 2 components of myofilaments of skeletal muscle fibers
- thick filaments
2. thin filaments
what are thick filaments composed of?
myosin
what are the two components of myosin?
a tail and a head
what do myosin heads contain? (2)
an actin binding site and and ATP binding site
what 3 proteins make up thin filaments?
- actin
- tropomyosin
- troponin
describe the structure of actin proteins
2 strands spiraled around each other
describe the location and function of tropomyosin
spirals around actin, covers myosin head binding sites on actin
describe the location and function of troponin
attached to tropomyosin along thin filament, has Ca2+ binding sites
what is a sarcomere? where is it found?
the basic unit of contraction, found within myofibrils, runs from one Z disc to another
during a contraction, what moves, what shortens, and what remains the same in the sarcomere?
myosin pulls actin toward M-line, and the entire sarcomere shortens, the I band and the H zone also shorten, and the A band remains the same
what is a motor unit?
one motor neuron and all the muscle fibers it innervates
how do the muscle fibers of the same motor unit contract?
simultaneously
how many muscle fibers does a typical motor neuron innervate?
150
list the first 5 steps of muscle contraction
- motor neuron releases a neurotransmitter (ACh) at neuromuscular junction
- ACh binds to receptor on sarcolemma of muscle fiber
- Na+ channels open on sarcolemma, resulting in depolarization, leading to an action potential along sarcolemma
- (happening at the same time as 3) excess ACh at neuromuscular junction is broken down by Acetylycholinesterase on sarcolemma
- action potential travels along sarcolemma and down the Transverse tubules
list steps 6-12 of muscle contraction (beginning after the action potential travels along sarcolemma and down T tubules)
- when action potential reaches voltage-gated Ca2+ channels on T tubules, those channels are pulled away from Ca2+ release channels on terminal cisterns of sarcoplasmic reticulum
- Ca2+ leaves sarcoplasmic reticulum via Ca2+ release channels and enters sarcoplasm
- Ca2+ diffuses into myofibrils
- Ca2+ binds to troponin on thin filament
- a conformation change in the troponin/tropomyosin complex will expose myosin head binding sites on actin
- myosin head will bind to ATP and hydrolyze it to ADP and a phosphate group
- myosin head orients itself to bind to actin (getting to the ready position)
list steps 13-17 of muscle contraction (beginning after the myosin head orients itself to bind to actin)
- myosin head binds to actin
- myosin head pivots toward center of sarcomere and pulls actin toward center of sarcomere with it = power stroke
- ADP is released from myosin head and a new ATP binds, and myosin head releases from actin
- myosin head will hydrolyze ATP and orient itself to bind to a new myosin head binding site on actin, process repeats
- myosin head walks along actin, shortening sarcomere
when does muscle relaxation occur?
when ACh is no longer released at neuromuscular junction
list the 4 steps of muscle relaxation
- cessation of action potential results in voltage-gated Ca2+ channels covering Ca2+ release channels
- Ca2+ that was released returns to sarcoplasmic reticulum via Ca2+ ATPase pump (which requires energy)
- Ca2+ diffuses away from troponin, tropomyosin covers myosin head binding sites on actin
- sarcomere returns to resting length
list the 3 ways muscles can obtain ATP
- from creatine phosphate
- from anaerobic glycolysis
- from aerobic respiration
when does muscle obtain energy from creatine phosphate and how long does it last?
when contraction begins, lasts about 15 seconds
in what form can muscle store glucose and how is it released when needed?
as glycogen, glucose is released from glycogen during contraction and that glucose is broken down to create ATP
where else can muscle get glucose to break down to form ATP?
from the bloodstream
what are the products of anaerobic respiration?
ATP and lactate
how long does the energy provided from anaerobic respiration (glycolysis) last?
2 minutes
where does aerobic respiration occur and what does it require?
only in the mitochondria, requires oxygen
list 3 substrates that can be used to produce ATP via the Krebs cycle/citric acid cycle in aerobic respiration?
- pyruvate
- fatty acids
- amino acids
how are the 3 muscle fiber types classified?
based on respiration type
list the 3 muscle fiber types
- slow oxidative fibers
- fast glycolytic fibers
- fast oxidative-glycolytic fibers
what are slow oxidative muscle fibers also called?
slow twitch fibers/type I
how does the myosin head hydrolyze ATP in slow oxidative muscle fibers?
slowly
why do slow oxidative muscle fibers appear red/dark?
they contain a lot of myoglobin, which stores oxygen
what type of respiration do slow oxidative muscle fibers perform?
aerobic respiration
what type of movements are slow oxidative muscle fibers good for?
movements that happen over a long period of time, like posture maintenance and endurance
where can slow oxidative muscle fibers be found in chicken, and in what type of horse are these most predominant?
dark meat in chicken, Arabian horses
what are fast glycolytic muscle fibers also called?
fast twitch/type IIA
how does the myosin head hydrolyze ATP in fast glycolytic muscle fibers?
quickly
what do fast glycolytic muscle fibers lack and what does this mean for their color and respiration type?
they lack myoglobin = no oxygen = rely on anaerobic respiration = appear white
what are fast glycolytic muscle fibers good for?
short bursts of activity
what are fast oxidative-glycolytic muscle fibers also called?
fast twitch/type IIB
do fast oxidative-glycolytic muscle fibers have any myoglobin? what does this mean?
they have SOME myoglobin, which means they can utilize some aerobic respiration
where are fast oxidative-glycolytic muscle fibers found in chickens and in what type of horse are they predominant?
chicken breasts, white meat, in Quarter Horses
what color are fast oxidative-glycolytic muscle fibers?
slightly pink
what is summation? what does it determine?
adding things together, determines contraction strength
list the 2 types of summation
- motor unit summation
2. temporal summation
describe motor unit summation
when multiple motor units contract at the same time, the contraction is stronger
describe temporal summation
when the frequency of the stimulus to contract increases, the contraction is stronger
what is tetany?
when further increases in the frequency of the stimulus to contract will not result in a stronger contraction, the contraction has reached a steady state
does tetany always occur as a result of pathology?
no not always
what is tetanus?
when clostridium tetani produces a neurotoxin that results in tetany of muscles, prevents inhibitory signals, so only activating signals are released, neurotoxin can get through blood-brain barrier
what is fatigue?
decrease in work capacity caused by work itself
what causes muscular fatigue?
caused by decrease in available ATP and a buildup of metabolites in muscle such as lactate or phosphate
what is muscle rigor?
when ATP is depleted, the myosin head cannot detach from actin and stays in a painful contracted state
what is rigor mortis? how does is affect meat?
muscle rigor that occurs after death, has a negative effect on meat tenderness after slaughter
what is Hyperkalemic Periodic Paralysis (HYPP)
high blood potassium (K+), caused by defective Na+ channels in muscle that randomly open, leading to depolarization, causing random muscle contraction, can be mild or severe, linked to Impressive’s genes
list 3 drugs that effect muscle contraction
- anticholinesterase
- curariform
- botulinum toxin
how does anticholinesterase effect muscle contraction?
inhibits acetylcholinesterase so acetylcholine will not be broken down, prolonging muscle contraction due to no removal of stimulus to contract
what is anticholinesterase used in and why is that bad?
insecticides, if animals get into it can lead to asphyxiation and death
how does curariform effect muscle contraction?
binds to acetylcholine receptors, keeping acetylcholine from binding, inhibiting contraction, leading to asphyxiation
how is curariform used in a good way?
in small doses during surgery to prevent certain muscles from contracting and fucking things up
what is botulinum toxin produced by and where is it found?
clostridium botulinum, found in some soils
how does botulinum toxin effect muscle contraction?
inhibits release of acetylcholine from motor neuron, inhibiting contractions and can lead to asphyxiation