muscle physiology Flashcards
what are three characteristics of muscle tissue
excitable, contractile, elastic
what are the three types of muscle tissue
smooth, cardiac, skeletal
what are the parts of skeletal muscle
belly, origin, insertion
what is the belly of skeletal muscle
the thickest part of the muscle
what is the origin of skeletal muscle
proximal/less moveable end
what is the insertion of skeletal muscle
proximal/less moveable end
what is the endomysium
the connective tissue that is around each muscle cell/fiber
what is the periomysium
the connective tissue that is around each fasicle (grouping)
what is the epimysium
the connective tissue that is around the entire muscle
where is internal tension
within cells
where is external tension and what does it do
on the bones to move something
what do muscles move
the skeleton, skin
what does muscle tone maintain
posture, support joints
what produces heat
muscle metabolism
how much of the body’s heat is produced from muscle metabolism
80%
what is sarcolemma
the muscle membrane
what are transverse (T) tubules
pits that go deep off the membrane
what is the sarcoplasm
muscle cytoplasm
what are myofibrils
cylindrical subunits of contractile protein filaments
what is a terminal cisternae
“end containers”
the widening of sacroplasmic reticulum near the t tubule
what does the sarcoplasmic reticulum contain
smooth er, terminal cisternae, calcium ions
what is glycogen
starch, chains of glucose
what does myoglobin do
transfers oxygen
do muscle cells have lots of mitochondria
yes
where are muscle cell nuclei located
at/near the sarcolemma
what is in thick myofilaments
myosin
what are myofilaments made of
proteins
what is in thin myofilaments
actin, tropomyosin, troponin
what are the three parts of troponin
I, T, C (all polypeptides)
what does the I polypeptide bind to
actin
what does the T polypeptide bind to
tropomyosin
what does the C polypeptide bind to
calcium
what are A bands dark from
thick (myosin) filaments
why is the H zone in A bands pale
there are no thin filaments
why are I bands pale
there are no thick (myosin) filaments
what is the Z disc/line
where thin filaments are connected to each other
what is the sarcomere
the distancebetween adjacent Z disks
what happens to I bands when there is contraction
they get smaller
what happens to the H zone when there is contraction
it disappears
what happens to A bands when there is contraction
they stay the same because it is the length of the thick filaments
what happens to the sarcomere when there is contraction
it shortens
what does the alpha motor neuron do
stimulates muscle fibers
what is a motor unit
1 alpha motor neuron and all muscle fivers that it innerves
how many and what type of motor neurons does fine control require
many small motor units
how many and what type of motor neurons does gross control require
few large motor units
what is the synaptic knob
a widened neuron ending
where is acetylcholine (ACh) found
in membrane bound vesicles
what is acetylchlinesterase (AChE)
an enzyme that breaks apart ACh
where is the motor end plate
on muscle membranes (sarcolemma)
what do junctional folds do
increase surface area
where are ACh receptors
ACh gated ion channels
what is the resting potential of muscle
-90 mV
what is the resting potential of neurons
-70 mV
why is there a membrane potential
because of the sodium-potassium pumps and gradient
what is an action potential
a change in the membrane charge
how does a muscle get stimulated by a neuron (8 steps)
1.) action potential from neuron reaches the synaptic knob
2.) the action potential in a neuron opens the voltage gates calcium channels in the neuron knob
3.) calcium diffuses into the neuron
4.) the increase in calcium induces exocytosis of ACh from neuron
5.) ACh diffuses to the ACh receptor on the sarcolemma
6.) ACh receptors allow sodium to diffuse into the cell and potassium to diffuse out of the cell
7.) the muscle cells creates an action potential
8.) the process stops by ACh being broken apart by AChE
what are the steps to excitation-contraction coupling (8)
1.) action potential is recreated along the sarcolemma and down T tubules
2.) an action potential opens the voltage-gated calcium channels in the sarcoplasmic reticulum
3.) Calcium diffuses out of the sarcoplasmic reticulum, binding to troponin, and moving through tropomyosin, exposing binding sites on the actin filament
4.) myosin heads bind to actin
5.) myosin heads bend and release previously attached ADP and phosphate
6.) ATP attached to myosin head to release cross bridge
7.) the myosin head recocks
8.) the process continues as the action potential is releasing calcium around myofilaments and ATP is available
what happens during rigor mortis
there is a lack of ATP causing the calcium pumps to stop working, calcium to increase around actin and myosin, exposing binding sites, and not releasing
what is nerve gas
AChE is no longer working so ACh stays at the neurotransmitter junction, keeping the muscle contracted
what is a muscle twitch
a rapid “jerk” response to a single stimulus
what causes the muscle to twitch
a stimulus above the threshold
what happens during the latent period of a muscle twitch
calcium releases from the sarcoplasmic reticulum, exposing binding sites at crossbridges
what happens during the contraction period of a muscle twitch
actin and myosin interact and the muscle shortens
what happens during the relaxation phase of a muscle twitch
there is no muscle action potential –> there is a decrease in calcium through the calcium pump –> cover binding sites and ATP is released –> the muscle stops contracting
when does wave summation happen
when the stimulus frequency is changed
what is tetanus
a sustained contraction
why do contractions continue to grow
because calcium is maintained
what is recruitment
multiple motor unit summation
