Chapter 8: Using Muscles and Glands Flashcards
many individual muscle fibers are bundled into ____
fasicles
why are adult muscle cells multinucleated?
because they develop from the fusing of myoblasts in embryo
membrane surrounding each muscle fiber
sarcolemma
muscle fiber’s endoplasmic reticulum
sarcoplasmic reticulum
why does a skeletal muscle look striped?
because of the parallel myofibrils that are aligned in such a way to give a striped appearance.
myofibrils contain arrangements of ___ and ___ that repeat by regular units called ____
myofibrils contain arrangements of ACTIN and MYOSIN that repeat by regular units called SARCOMERES
each muscle fiber contains numerous ___
myofibrils.
each myofibril contains numerous ____
myofilaments (actin and myosin), arranged in sarcomere units.
each sarcomere is separated by a ____
Z line.
in the sliding filament model, the myosin-free bands ___ and the myosin-containing bands stay ____
in the sliding filament model, the myosin-free bands SHORTEN and the myosin-containing bands stay CONSTANT IN WIDTH.
In order for the myosin head to DETACH from actin, what must be present? what happens if it is not present/
you need ATP for myosin head to detach. If there is no ATP, it will not detach and rigor mortis will set in.
The energy to generate a myosin bending force comes from the release of a phosphate from ATP creating ADP.
To release the myosin head from the actin binding site, the ADP on the myosin head must be replaced by a new molecule of ATP.
2 things needed for cross bridge cycling to occur
Ca2+ and ATp
if the end of the muscles are fixed, then further actin-myosin interactions result in an ___ ___ , which is:
isometric contraction: the muscle pulls on its attachment site but does not change in length. (ex/ balling your hands in a fist. There is no movement happening but you are clenching your muscles).
Briefly explain the need for a neuromuscular junction
Motor neurons release acetylcholine at neuromuscular junctions. Acetylcholine depolarizes the sarcolemma, triggering an action potential that spreads through the T-tubule system into the muscle fiber’s interior where it triggers calcium release from the sarcoplasmic reticulum.
___ twitch fibers predominate in small muscles that require intricate but weak movements
FAST twitch. ex/ iris or vocal cords.
___ twitch fibers predominate in large muscles that tend to stay contracted for long periods of time
SLOW twitch.
Describe how myoglobin content affects muscle contraction ability
large amount of myoglobin = darker meat = lots of mito = oxidative phosphorylation = probably slow twitch fibers that are strong and can remain contracted for a long period of time.
individual muscle fibers are innervated by the axons of ___ neurons whose cell bodies are located either in the ___ horn of the spinal cord or in the ___
individual muscle fibers are innervated by the axons of MOTOR neurons whose cell bodies are located either in the VENTRAL horn of the spinal cord or in the MEDULLA (reflex)
the synapse between a motor axon and skeletal muscle fiber is called a
neuromuscular junction
Each muscle fiber is innervated by only one axon, but each axon innervates multiple muscle fibers (top right). ONE axon and all the muscle fiber cells it innervates is called a
motor unit
T Tubules extend from small openings in the ____ deep into the muscle fiber so they can adequately contact the ___ ___
T Tubules extend from small openings in the SARCOLEMMA deep into the muscle fiber so they can adequately contact the SARCOPLASMIC RETICULUM
acetylcholine is released from the ___ ___, floats through the neuromuscular junction and diffuses to the post synaptic side of the synapse called the ___ ___ ___
acetylcholine is released from the MOTOR NEURON, floats through the neuromuscular junction and diffuses to the post synaptic side of the synapse called the NEUROMUSCULAR JUNCTION
When acetylcholine binds to cholinergic receptors on the muscle fiber, it allows an influx of ____, depolarizing the ____, triggering an ___ ___ ___.
When acetylcholine binds to cholinergic receptors on the muscle fiber, it allows an influx of Na+ depolarizing the SARCOLEMMA, triggering an END PLATE POTENTIAL.
This end plate potential opens VOLTAGE GATED Na+ channels, which let even more sodium into the muscle fiber cell, triggering a MUSCLE ACTION POTENTIAL.
As an action potential that was started by motor neuron stimulation travels down the T tubules and sarcolemma of the muscle fiber, ___ ___ (voltage gated) open, causing Ca2+ to be released from the ___ ___
As an action potential that was started by motor neuron stimulation travels down the T tubules and sarcolemma of the muscle fiber, RYANODINE RECEPTORS (voltage gated) open, causing Ca2+ to be released from the SARCOPLASMIC RETICULUM
___ ___ channels physically link T tubules of the sarcolemma to the deeper parts ____ ___, and ensure that action potentials conducted throguh the T tubules causeCa2+ to be released from the sarcoplasmic reticulum into the sarcoplasm.
RYANODINE RECEPTORS channels physically link T tubules of the sarcolemma to the deeper parts SARCOPLASMIC RETICULUM, and ensure that action potentials conducted throguh the T tubules causeCa2+ to be released from the sarcoplasmic reticulum into the sarcoplasm.
What is calcium induced calcium influx?
when ryanodine receptors between the T tubules and sarcoplasmic reticulum open and release Ca2+ into the sarcoplasm, the ELEVATED CA2+ levels OPEN EVEN MORE CA2+ channels in the SR and cause even MORE Ca2+ release.
This huge amount of Ca2+ is sufficient to activate the tropomyosin complex. In conjunction with ATP, the myosin binding sites on the actin filament complex get exposed, facilitating binding and power stroking of the filaments.
before a muscle can relax, the sarcoplasmic Ca2+ must decrease in order for tropomyosin to move back to cover the binding sites on the actin filament. How is this accompolished? (2 ways)
1) protein parvalbumin.
2) Ca2+-ATPAse; uses ATP to pump Ca2+ back into the SR, building back its stores.
When does tetanus occur?
when action potentials recur at intervals that are too fast for Ca2+ to be brought back into the Sr from the sarcoplasm, resulting in sustained contraction because of HIGH FIRING RATES of motor neurons.
What is myasthetnia gravis? How is treated?
autoimmune disesase resulting in serious muscle weakness because the body develops antibodies to its own acetylcholine receptors
Treatment: drugs that inhibit acetylcholinesterase, to PREVENT Ach breakdown. Allows Ach to stay in the cleft longer and raise the probability to interact with whatever receptors the pt has remaining.
A nicotinic receptor is ionotropic or mechanotropic? Where is it located?
IONOTROPIC. Stimulated by nicotine, blocked by curare. Receptor between pregang and post gang neuron
a muscarinic receptor is a ionotropic or mechanotropic receptor?
MECHANOTROPIC. Stimulatedd by muscarine and blocked by atroping. PNS Ach receptor. Located between Post gang neuron and EFFECTOR organ.
drug that can block acetylocholinesterase
neostigmine
Fast, fatiguable motor units (Type IIx fibers fast glycolytic) produce very ___ contractions
STRONG contractions, but they are extremely fatiguable. Not sustainable
small motor units tend to elicit ___ contractions, and large motor units elicit ___ contractions. Why?
small motor units tend to elicit WEAK contractions, and large motor units elicit STRONG contractions.
Because larger motor units innervate MORE muscle fibers (regardless of typep). When the motor neuron is stimulated, more fibers contract and can pull more forcefully.
T/F: all the muscle fibers innervated by a single motor neuron tend to be of the same time
true.
3 types of “motor units”/muscle fibers
Type Ia: slow oxidative. fatigue resistant
Type IIa: fast, fatigue resistant
Type IIx: fast glycolytic. Fatigues quickly but produces a lot of force at tetanic levels.
As muscle cotnractions get stronger, ____ and ____ motor units are recruited.
LARGER and MORE
skeletal muscle fibers are aka ____ fibers
extrafusal
extrafusal fibers are innervated and encapsulated by ___ ___
connective tissue
inside a muscle spindle, in addition to extrafusal fibers, there are ____ fibers that are thinner and shorter. What are the purpose of these fibers?
INTRAFUSAL FIBERS. They contain less myofibrils than extrafusal fibers and thus contract much more weakly but they contain MECHANOSENSITIVE ION CHANNELS and are SENSITIVE TO FIBER STRETCH.
intrafusal muscle fibers are innervated by ___ motor neurons, and extrafusal muscle fibers are innervated by ____ motor neurons
intrafusal muscle fibers are innervated by GAMMA motor neurons, and extrafusal muscle fibers are innervated by ALPHA motor neurons
cell bodies of gamma neurons that innervate the intrafusal muscle fibers are located ____
in the ventral horn of the spinal cord
T/F: the later a motor unit is recruited during contraction, the earlier it drops out.
TRUE. The motor units were recruited successively (with unit #1 becoming active first) and fell silent in the opposite order.
The later recruited units fired at lower maximum rates.
T/F: Larger motor neurons elicit stronger, faster contractions
TRUE. A motor neuron’s surface area (based on mean cell body and primary dendrite diameters) is positively correlated with axonal conduction velocity and with the contractile force elicited by activating the neuron.
___ sensory and gamma motor neurons innervate the intrafusal fibers in muscle spindles.
SPIRALING
Afferent Peresis
failure of sensory competance (cannot detect stretching and movement) because of deterioration of afferent neurons.
stimulation of gamma motor axons convey ____movement.
positional
most flower spray or spiral endings are ___polar, and their cell bodies can be found in the ___ ___ ganglion.
most flower spray or spiral endings are UNIpolar, and their cell bodies can be found in the DORSAL ROOT ganglion.
Purpose of alpha gamma coactivation.
During movement(alpha motor neuron activity), the gamma neuron is also activated to provide continuous info about position while the body is moveing. Allows muscle spindles to remain senstive to unexpected changes in muscle length even as the animal moves.
gamma/flowerspray/spiral endings are encapsulated and involved in reflex arcs, which are ____
monosynaptic. Sensory neuron synapses directly to motor neuron in dorsal horn/spinal cord
a contraction that results in a change in force, but not length
isometric
a contraction that results in change in muscle length, but not force
isotonic. Changes joint angle.
when your own mobement triggers the stretch reflex and vestibular system to compensate for balance
postural adjustment.
Explain the reflex of postural adjustment.
as the muscle lengthens/changes position, the muscle spindle fires, and relays the signal directly to the alpha motor neuron in the spinal cord. the alpha motor neuron leaves through the ventral horn of the spinal cord and innervates the extrafusal muscle fibers, initiating a contraction.
What is a jackknife reflex and what is it caused by
A reflex that occurs when force is applied to flex or extend the limb of an animal showing decerebrate rigidity; resistance is replaced by sudden relaxation. This is due to muscle inhibition from golgi tendon organs that inhibits muscle contraction
T/F Golgi tendon organ (tension receptors in the tendon) has an interneuron between it and the motor neuron
TRUE. Muscle spindles in intrafusal muscle has a monosynaptic connection, but golgi tendon organs have an interneuron between the sensory neuron and the motor neuron.
a golgi tendon organ sensor synapses on an ____ interneuron in the spinal cord, which ____ activity of motor unit
a golgi tendon organ sensor synapses on an INHIBITORY interneuron in the spinal cord, which INHIBITS activity of motor unit.
when muscle is stretch to a point, GT activates and muscle tension collapses (prevents breaking and stretch).
the jackknife reflex involves which type of sensor?
golgi tendon organs.
Skeletal muscle contains numerous ____ ____, which consist of multiple ____, each of which contains a series of _____. Individual ____ contain interleaved actin and myosin ______.
Skeletal muscle contains numerous muscle fibers, which consist of multiple myofibrils, each of which contains a series of sarcomeres. Individual sarcomeres contain interleaved actin and myosin filaments.
Motor neurons release _____ at neuromuscular junctions. ___ depolarizes the ____, triggering an action potential that spreads through the _____ system into the muscle fiber’s interior where it triggers ____ release from the sarcoplasmic reticulum.
Motor neurons release acetylcholine at neuromuscular junctions. Acetylcholine depolarizes the sarcolemma, triggering an action potential that spreads through the T-tubule system into the muscle fiber’s interior where it triggers calcium release from the sarcoplasmic reticulum.
muscles are lengthened by ____ ____
antagonistic muscles.
Explain the antagonistic mechanism in pupil contraction.
The smooth pupillary dilator and constrictor muscles (B) also operate as an antagonistic pair: when the dilators contract, the constrictors are stretched; conversely, contraction of the pupillary constrictors lengthens the pupillary dilators.
Contraction of one muscle ____ the antagonistic pair
relaxes
give an example of non antagonistic muscle
myoepithelial smooth muscle cells of the mammary gland.
When these cells contract, the cavity constricts and milk/lipids are pushed out, but there is no muscle to expand the cells again.
Instead, they must rely on additional secretions to push against the cavity walls.
Agonists and antagonist muscles are arranged in ___ ___
opposite pairs.
How can insects beat their wings faster than their wing motor neurons can fire?
What protein is involved that facilitates flight efficiency?
Because the wing muscles are arranged antagonistically and contract automatically when they are stretched. Wing muscles exhibit STRETCH ACTIVATED CO ACTIVATION. When a muscle is stretched by contracting its antagonist, that same muscle is triggered to contract, even if its motor neuron did not fire an action potential–> the motor neuron needs to be activated enough just to maintain elevated CALCIUM LEVELS.
Accumulations of the elastic protein RESILIN at the hinge points store and release potential energy, thereby increasing flight efficiency.
In the heart, Ach ____ ___ HR, while Ne _____ it up.
In the heart, Ach SLOWS DOWN HR, while Ne SPEEDS it up.
the ____ ___ is the heart’s natural pacemaker
sinoatrial node
Which type of ach receptors are found on the heart?
MUSCARINIC receptors. recall: nicotinic receptors are found on the post ganglionic neuron, but muscarinic receptors are found on the effector tissues
T?F: smooth muscle fibers contain sarcomeres
false. they are not as organized.
difference between smooth muscle contraction and skeletal muscle contraction
smooth muscle doesn’t use troponin-tropomyosin complex.
Ca2+ from SR instead binds with calmodulin to create a complex that activates myosin light chain kinase, which will phosphorylate myosin to facilitate attachment to actin and power stroke activity.
Troponin is attached to the protein____ and lies within the groove between actin filaments in muscle tissue. In a relaxed muscle, tropomyosin ____ ____ ___ for the myosin crossbridge, thus preventing contraction.
Troponin is attached to the protein tropomyosin and lies within the groove between actin filaments in muscle tissue. In a relaxed muscle, tropomyosin blocks the attachment site for the myosin crossbridge, thus preventing contraction.
Where does calcium bind on the thin microfilament?
on troponin. Ca2+ binds onto its binding site on troponin, which, in the presence of ATP, moves tropomyosin out of the way and allows for myosin to bind to the myosin binding sites on actin.
nerve endings on skeletal muscle=
nerve endings on smooth and cardiac muscle =
nerve endings on skeletal muscle= MOTOR END PLATE
nerve endings on smooth and cardiac muscle = VARICOSITIES
cardiac muscle fibers are electrically couple via __ ___
gap junctions
