Chapter 8: Using Muscles and Glands

Question 1

many individual muscle fibers are bundled into ____

Answer 1

fasicles

Question 2

why are adult muscle cells multinucleated?

Answer 2

because they develop from the fusing of myoblasts in embryo

Question 3

membrane surrounding each muscle fiber

Answer 3

sarcolemma

Question 4

muscle fiber’s endoplasmic reticulum

Answer 4

sarcoplasmic reticulum

Question 5

why does a skeletal muscle look striped?

Answer 5

because of the parallel myofibrils that are aligned in such a way to give a striped appearance.

Question 6

myofibrils contain arrangements of ___ and ___ that repeat by regular units called ____

Answer 6

myofibrils contain arrangements of ACTIN and MYOSIN that repeat by regular units called SARCOMERES

Question 7

each muscle fiber contains numerous ___

Answer 7

myofibrils.

Question 8

each myofibril contains numerous ____

Answer 8

myofilaments (actin and myosin), arranged in sarcomere units.

Question 9

each sarcomere is separated by a ____

Answer 9

Z line.

Question 10

in the sliding filament model, the myosin-free bands ___ and the myosin-containing bands stay ____

Answer 10

in the sliding filament model, the myosin-free bands SHORTEN and the myosin-containing bands stay CONSTANT IN WIDTH.

Question 11

In order for the myosin head to DETACH from actin, what must be present? what happens if it is not present/

Answer 11

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.

Question 12

2 things needed for cross bridge cycling to occur

Answer 12

Ca2+ and ATp

Question 13

if the end of the muscles are fixed, then further actin-myosin interactions result in an ___ ___ , which is:

Answer 13

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).

Question 14

Briefly explain the need for a neuromuscular junction

Answer 14

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.

Question 15

___ twitch fibers predominate in small muscles that require intricate but weak movements

Answer 15

FAST twitch. ex/ iris or vocal cords.

Question 16

___ twitch fibers predominate in large muscles that tend to stay contracted for long periods of time

Answer 16

SLOW twitch.

Question 17

Describe how myoglobin content affects muscle contraction ability

Answer 17

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.

Question 18

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 ___

Answer 18

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)

Question 19

the synapse between a motor axon and skeletal muscle fiber is called a

Answer 19

neuromuscular junction

Question 20

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

Answer 20

motor unit

Question 21

T Tubules extend from small openings in the ____ deep into the muscle fiber so they can adequately contact the ___ ___

Answer 21

T Tubules extend from small openings in the SARCOLEMMA deep into the muscle fiber so they can adequately contact the SARCOPLASMIC RETICULUM

Question 22

acetylcholine is released from the ___ ___, floats through the neuromuscular junction and diffuses to the post synaptic side of the synapse called the ___ ___ ___

Answer 22

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

Question 23

When acetylcholine binds to cholinergic receptors on the muscle fiber, it allows an influx of ____, depolarizing the ____, triggering an ___ ___ ___.

Answer 23

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.

Question 24

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 ___ ___

Answer 24

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

Question 25

___ ___ 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.

Answer 25

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.

Question 26

What is calcium induced calcium influx?

Answer 26

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.

Question 27

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)

Answer 27

1) protein parvalbumin. | 2) Ca2+-ATPAse; uses ATP to pump Ca2+ back into the SR, building back its stores.

Question 28

When does tetanus occur?

Answer 28

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.

Question 29

What is myasthetnia gravis? How is treated?

Answer 29

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.

Question 30

A nicotinic receptor is ionotropic or mechanotropic? Where is it located?

Answer 30

IONOTROPIC. Stimulated by nicotine, blocked by curare. Receptor between pregang and post gang neuron

Question 31

a muscarinic receptor is a ionotropic or mechanotropic receptor?

Answer 31

MECHANOTROPIC. Stimulatedd by muscarine and blocked by atroping. PNS Ach receptor. Located between Post gang neuron and EFFECTOR organ.

Question 32

drug that can block acetylocholinesterase

Answer 32

neostigmine

Question 33

Fast, fatiguable motor units (Type IIx fibers fast glycolytic) produce very ___ contractions

Answer 33

STRONG contractions, but they are extremely fatiguable. Not sustainable

Question 34

small motor units tend to elicit ___ contractions, and large motor units elicit ___ contractions. Why?

Answer 34

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.

Question 35

T/F: all the muscle fibers innervated by a single motor neuron tend to be of the same time

Answer 35

true.

Question 36

3 types of "motor units"/muscle fibers

Answer 36

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.

Question 37

As muscle cotnractions get stronger, ____ and ____ motor units are recruited.

Answer 37

LARGER and MORE

Question 38

skeletal muscle fibers are aka ____ fibers

Answer 38

extrafusal

Question 39

extrafusal fibers are innervated and encapsulated by ___ ___

Answer 39

connective tissue

Question 40

inside a muscle spindle, in addition to extrafusal fibers, there are ____ fibers that are thinner and shorter. What are the purpose of these fibers?

Answer 40

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.

Question 41

intrafusal muscle fibers are innervated by ___ motor neurons, and extrafusal muscle fibers are innervated by ____ motor neurons

Answer 41

intrafusal muscle fibers are innervated by GAMMA motor neurons, and extrafusal muscle fibers are innervated by ALPHA motor neurons

Question 42

cell bodies of gamma neurons that innervate the intrafusal muscle fibers are located ____

Answer 42

in the ventral horn of the spinal cord

Question 43

T/F: the later a motor unit is recruited during contraction, the earlier it drops out.

Answer 43

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.

Question 44

T/F: Larger motor neurons elicit stronger, faster contractions

Answer 44

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.

Question 45

___ sensory and gamma motor neurons innervate the intrafusal fibers in muscle spindles.

Answer 45

SPIRALING

Question 46

Afferent Peresis

Answer 46

failure of sensory competance (cannot detect stretching and movement) because of deterioration of afferent neurons.

Question 47

stimulation of gamma motor axons convey ____movement.

Answer 47

positional

Question 48

most flower spray or spiral endings are ___polar, and their cell bodies can be found in the ___ ___ ganglion.

Answer 48

most flower spray or spiral endings are UNIpolar, and their cell bodies can be found in the DORSAL ROOT ganglion.

Question 49

Purpose of alpha gamma coactivation.

Answer 49

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.

Question 50

gamma/flowerspray/spiral endings are encapsulated and involved in reflex arcs, which are ____

Answer 50

monosynaptic. Sensory neuron synapses directly to motor neuron in dorsal horn/spinal cord

Question 51

a contraction that results in a change in force, but not length

Answer 51

isometric

Question 52

a contraction that results in change in muscle length, but not force

Answer 52

isotonic. Changes joint angle.

Question 53

when your own mobement triggers the stretch reflex and vestibular system to compensate for balance

Answer 53

postural adjustment.

Question 54

Explain the reflex of postural adjustment.

Answer 54

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.

Question 55

What is a jackknife reflex and what is it caused by

Answer 55

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

Question 56

T/F Golgi tendon organ (tension receptors in the tendon) has an interneuron between it and the motor neuron

Answer 56

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.

Question 57

a golgi tendon organ sensor synapses on an ____ interneuron in the spinal cord, which ____ activity of motor unit

Answer 57

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).

Question 58

the jackknife reflex involves which type of sensor?

Answer 58

golgi tendon organs.

Question 59

Skeletal muscle contains numerous ____ ____, which consist of multiple ____, each of which contains a series of _____. Individual ____ contain interleaved actin and myosin ______.

Answer 59

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.

Question 60

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.

Answer 60

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.

Question 61

muscles are lengthened by ____ ____

Answer 61

antagonistic muscles.

Question 62

Explain the antagonistic mechanism in pupil contraction.

Answer 62

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.

Question 63

Contraction of one muscle ____ the antagonistic pair

Answer 63

relaxes

Question 64

give an example of non antagonistic muscle

Answer 64

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.

Question 65

Agonists and antagonist muscles are arranged in ___ ___

Answer 65

opposite pairs.

Question 66

How can insects beat their wings faster than their wing motor neurons can fire? What protein is involved that facilitates flight efficiency?

Answer 66

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.

Question 67

In the heart, Ach ____ ___ HR, while Ne _____ it up.

Answer 67

In the heart, Ach SLOWS DOWN HR, while Ne SPEEDS it up.

Question 68

the ____ ___ is the heart's natural pacemaker

Answer 68

sinoatrial node

Question 69

Which type of ach receptors are found on the heart?

Answer 69

MUSCARINIC receptors. recall: nicotinic receptors are found on the post ganglionic neuron, but muscarinic receptors are found on the effector tissues

Question 70

T?F: smooth muscle fibers contain sarcomeres

Answer 70

false. they are not as organized.

Question 71

difference between smooth muscle contraction and skeletal muscle contraction

Answer 71

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.

Question 72

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.

Answer 72

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.

Question 73

Where does calcium bind on the thin microfilament?

Answer 73

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.

Question 74

nerve endings on skeletal muscle= nerve endings on smooth and cardiac muscle =

Answer 74

nerve endings on skeletal muscle= MOTOR END PLATE nerve endings on smooth and cardiac muscle = VARICOSITIES

Question 75

cardiac muscle fibers are electrically couple via __ ___

Answer 75

gap junctions