Muscle Physiology Flashcards
general characteristics of muscle fibers
excitable, extensible, tightly packed. flexible, have action potentials
is smooth muscle striated
no
where is smooth muscle found
blood vessels, respiratory tracts, visceral linings, gastrointestinal tract
is smooth muscle voluntary or involuntary contraction?
voluntary
is smooth muscle myogenically active
yes
Nuclei of smooth muscle
uninucleated, central nuclei
organization of smooth muscle
lacks organized sarcomeres, have adhesion plates, sarcolemma, nucleus, actin, myosin and gap junctions
form of smooth muscle
form circular and longituidnal layers. If going around its circular muscle and circular closes the tube. If it goes along the muscle its longitudinal which shortens and lengthens the tube
myogenic activity
ability of muscle tissue to contract on its own without requiring external nervous stimulation
is cardiac muscle striated/
yes
is cardiac voluntary or involuntary contraction
involuntary
how does cardiac muscle contract
similar to slow twitch, have a long refractory period to ensure a single beat and no tetanus
how is cardiac muscle stimulated
cardiac muscle stimulates other cardiac muscle
is cardiac muscle myogenically active
yes
nuclei structure in cardiac muscle
uninucliated, central nuclei
how is calcium released from the SR of cardiac muscle
calcium entry triggers the release of Ca from the SR
is skeletal muscle striated
yes
is skeletal muscle control voluntary or involuntary
voluntary
how is skeletal muscle stimulated
neurotransmitters stimulate skeletal muscle
is skeletal muscle myogenically active
no
structure of nuclei in skeletal muscle
multinulicated, peripheral nuclei
what are the two types of skeletal muscle
fast twitch and slow twitch
Fast twitch skeletal muscle
known as white fibers because have lower concentration of myoglobin which makes them paler. faster depolarization, shorter latent period.
Slow Twitch muscle
red muscle fiber bc high myoglobin concentration, high amts of mitochondira, slower depolarization, longer latent period
what type of respiration do fast twitch muscle use
predominantly anaerobic
skeletal muscle contraction
initiation of muscle action potential, excitation contraction/coupling, relaxation
Sarcomere
Fundamental unit of muscle contraction, goes from Z line to Z line
Thick filament
made of myosin
thin filament
made of actin
does myosin need a motor protein
no
does action need motor protein
actin itself does not generate movement but works in conjuction with motor proteins (myosin) to produce movement
important proteins for actin
troponin, and tropomyosin
Where is there no overlapping myosin
the H zone which is located in the center of the A band is where this is no overlap of the thick and thin filaments
what determines the specific properties of myosin
The essential light chains and the regulatory light chain
what is the structure of myosin
head that bind actin, the light chain and the tail
step 1 of the sliding filament model
ATP binds which causes myosin to detach
step 2 of sliding filament model
detachment of myosin causes ATP to hydrolyze during which ATP becomes ADP and phosphate which remain bound to myosin
step 3 of sliding filament model
hydrolysis causes myosin to attach to actin
step 4 of sliding filament model
phosphate is released which promotes power stroke, actin moves
step 5 of sliding filament model
adp is released opening up binding site for ATP to then bind agin starting the cycle over agin
how is the binding of myosin to actin regulated?
ability of myosin to bind actin is regulated by Ca and thin filament proteins troponin and tropomyosin
where are the thin filaments of the sarcomere anchored?
to the Z line
what does the I band represent
distance between myosin filaments
what does the Z disk split
the I band
Myofibers
also known as muscle fibers, they are specialized elongated cells that are the fundamental units of skeletal muscle tissues
Network of Sarcoplasm Reticulum in myofibers
myofibers have an extensive network of SR which is important for the storage and release of calcium
where are T tubules located and what do they do
contained in the myofibers, t tubules help propagate the action potential deep into the fiber, ensuring a coordinated contraction
Terminal cisternae
part of the SR and are responsible for storing and releasing calcium ions which are essential for muscle contractions.
what part of muscle is most impacted if there is not adequate calcium
the terminal cisternae, it would not function properly leading to impaired muscle contraction
DHPR calcium channels
also known as L type voltage gated calcium channels. they are located in the T tubules of muscle cell membrane
Function of DHPR channels
act as voltage sensors playing a large role in process of excitation-contraction coupling by triggering release of calcium from sarcoplasmic reticulum
Tropomyosin
located along actin filaments, helps to regulate muscle contraction by blocking binding sites on actin filaments
what is the result of actin and myosin working together
allows for movements of cells, movement of vesicles, and movement of muscles
Myosin 1
monomeric motor protein that binds to actin and hydrolyzes ATP to generate force, plays a large role in intracellular movements (endo/exocytosis) nromally found in cytoplasm
Myosin II
dimeric, composed of two heavy chains each with head, neck and tail region. The tails intertwine allowing them to form thick filaments. Their function is muscle contraction in smooth, muscle, and cardiac muscle
Myosin V
dimeric motor protein, the tail domains contain cargo that binds regions that mediate attachment to various organelles or vesicles. Transport things over longer distances with the cell. Can also move progressively along actin filaments meaning it can take multiple steps without detaching from actin filament
unitary displacement in myosin
myosin movement displays unitary displacement (proceeds in steps) the length of the step is determined by the length of the myosin isoform neck. it refers to how far along the actin filament the myosin can move in one cycle
Troponin
complex of three regulatory proteins that are integral to muscle contraction is skeletal and cardiac muscle ( not present in smooth muscle)
Troponin when muscle is at rest
when at rest calcium concentration is sarcoplasm is low , in this state TnCis not bound to calcium, TnI binds to actin inhibiting the interaction between actin and myosin, tropomyosin is head in place by troponin complex which covers the myosin binding sites on actin preventing contraction.
Troponin when a stimulus for contraction is recieved
Ca ions bind to TnC which induces confirmational change in the TnC and as a result TnC interacts strongly with TnI pulling it away from actin which pulls TnI away from myosin binding sites on actin revealing these sites for myosin binding. Myosin can then bind to actin initiating cross bridge cycling which leads to muscle contraction
Troponin C
calcium binding component, when Ca ions bind to it TnC undergoes confirmational change that is essential for muscle contraction
TnI
inhibitory component of troponin complex in the absence of calcium TnI binds to actin in thin filament and holds the troponin-tropomyosin complex in place preventing interaction btw actin and myosin preventing muscle contraction
TnT
binds entire troponin complex to tropomyosin. helps anchor the troponin complex
funny channels
involved in pacemaker cell potentials in the heart depend on sodium potassium flux
calmodium
calcium binding messanger protein. in smooth muscle contraction calmodulin is important in smooth muscle cells where it binds to calcium and activates myosin light chain kinases which is then phosphorylated leading to contraction of smooth muscle (important note is that it works in smooth muscle)
RyR
calcium release channel on SR releases calcium into cytoplasm during muscle contraction, does not pump calcium back into the SR
SERCA Pump
specifically responsible for pumping Ca back into the SR which is essential for muscle relaxation by reducing cytoplasmic calcium levels after contraction
rapid changes in sarcoplasmic Ca level
necessary for contraction, in the absence of excitation sarcoplasmic calcium is kept very low by the Ca ATPase in the sarcolemma and by SERCA
where are the SERCA located
in the sarcolemma and the sarcoplasmic reticulum
