A&p Test 4 - Muscles

Front 1

skeletal muscle

Back 1

striated, voluntary – boundaries of cells are not well defined, multinucleated
• Span joints, attach to bone in two places (origin and insertion)
• Responsible for all locomotion

Front 2

cardiac muscle

Back 2

striated, involuntary – boundaries of cells are well defined, single nucleus
• Muscle of the heart

Front 3

smooth muscle

Back 3

no striations, involuntary
• Found only in the walls of visceral organs (ie: airways of lungs, blood vessels, digestive, urinary, reproductive tracts)

Front 4

sarco

Back 4

"flesh"

Front 5

my

Back 5

"muscle"

Front 6

sarcolemma

Back 6

muscle plasma membrane

Front 7

sarcoplasm

Back 7

cytoplasm of a muscle fiber cell

Front 8

myocyte

Back 8

muscle fiber

Front 9

Epimysium

Back 9

sheath of connective tissue that surrounds skeletal muscle,
fused to the periosteum (exists on the outer surface of the muscle)
-extend past the muscle to form tendons

Front 10

origin

Back 10

sight of attachment to immovable bone of joint

Front 11

insertion

Back 11

sight of attachment to movable portion of joint

Front 12

the three connective tissue sheaths that surround a skeletal muscle and hold it together

Back 12

Epimysium
Perimysium
Endomysium

Front 13

Perimysium

Back 13

organizes muscle fibers into fascicles – interior portion of muscle - surrounds a group of muscle fibers

Front 14

Endomysium

Back 14

wraps around individual muscle fibers – exists inside muscles

Front 15

3 different types of skeletal muscle fibers

Back 15

slow oxidative
fast oxidative
fast glycolytic

Front 16

slow oxidative

Back 16

one of the types of skeletal muscle fibers
-have slow twitch (use ATP slowly)
- fatigue resistant
– used to maintain posture

Front 17

fast oxidative

Back 17

one of the types of skeletal muscle fibers
-have fast twitch (use ATP quickly)
–moderate resistance to fatigue
– used for non-exertive movement

Front 18

fast glycolytic

Back 18

one of the types of skeletal muscle fibers
-have fast twitch (use ATP quickly)
– easily fatigued
– used for more powerful movement

Front 19

transverse tubules

Back 19

portion of sarcolemma that fold inward toward center of fiber

Front 20

how does the sarcolemma generate action potentials?

Back 20

contains both Na+ and K+ voltage-gated channels

Front 21

Sarcoplasmic Reticulum

Back 21

-found in skeletal muscle fibers
-physically associated with transvers tubules
-storage site for intracellular calcium
-responds to an action potential in t-tubules by releasing Ca into sarcoplasm to increase level of calcium
-triggers contraction of muscle fiber

Front 22

what is the Nerve-Muscle Functional Unit?

Back 22

motor neurons from the CNS attach to muscle fibers, can generate action potentials to trigger contraction

Front 23

Motor Unit

Back 23

the anatomical relationship between a motor neuron and all skeletal fibers that it causes to contract

Front 24

Motor Neuron

Back 24

part of the nerve-muscle functional unit
-can branch many times to form many axon termini
-one motor neuron can stimulate many skeletal muscle fibers to contract

Front 25

Neuromuscular Junction

Back 25

a synapse which is the site at which exocytosis of neurotransmitters from a motor neuron cause the generation of an action potential

Front 26

Small Motor Unit

Back 26

small number of muscle fibers in that unit
-control fine movements (ie: fingers, eyes)

Front 27

Large Motor Unit

Back 27

several hundred muscle fibers in one unit
-control the movements of large, weight-bearing muscles (ie: back)
-controls gross movements (ie: arms and legs)

Front 28

Acetylcholine (ACh)

Back 28

a neurotransmitter contained in the synaptic vesicles of the axon termini

Front 29

Motor End Plate

Back 29

a portion of the sarcolemma where the ACh receptors are located

Front 30

Twitch

Back 30

contraction & relaxation of a muscle fiber to a single brief threshold stimulus by a motor neuron

Front 31

3 phases of a muscle twitch

Back 31

Latent Period
Contractile Period
Relaxation Period

Front 32

Latent Period

Back 32

"lag" period of a muscle twitch
-time between the stimulation by a motor neuron and the beginning of contraction (only a few milliseconds)

Front 33

Contractile Period

Back 33

2nd period of a muscle twitch
-when contractile proteins in the fiber hydrolyze ATP causing the fiber to shorten (contract)
-results in an increase in tension (force)

Front 34

Relaxation Period

Back 34

3rd period of a muscle twitch
-when the fiber lengthens
-results in a decrease in tension

Front 35

2 types of skeletal muscle contractions

Back 35

Isometic Contraction
Isotonic Contraction

Front 36

Isometric Contraction

Back 36

"same length"
-muscle contracts and produces tension but does NOT shorten, load is NOT moved
-occurs if the load is GREATER than the tension the muscle can develop

Front 37

Isotonic Contraction

Back 37

"same tension"
-muscle contracts and produces tension
-muscle shortens and MOVES the load

Front 38

How are skeletal muscle contraction varied?

Back 38

1. by altering the frequency of muscle stimulation (lower frequency of action potentials tells muscle not to work as hard)

2. by altering the number of muscle fibers that will contract (determined by the number of motor units generating action potentials to the muscle)

Front 39

Incomplete Tetanus

Back 39

occurs with rapidly delivered stimuli, multiple muscle twitches, tension does not return to baseline

Front 40

Complete Tetanus

Back 40

occurs when stimuli are given quickly enough that individual twitches blend together and maximum contractile force is reached

Front 41

Recruitment

Back 41

when more motor units are activated as a result of an increase in stimulus strength

Front 42

Maximum Force

Back 42

is reached when all motor units are activated. it is the most force a muscle is capable of generating, even if stimulus continues to increase

Front 43

Oxidative v. Glycolytic Fibers

Back 43

-oxidative fibers contain greater amounts of mitochondria
-oxidative fibers contain myoglobin

Front 44

Myoglobin

Back 44

found in oxidative skeletal muscle fibers
-maintains a high concentration of oxygen within a fiber for aerobic resp.
-similar in struction to hemoglobin
-provides red color to oxidative fibers
-absence of myoglobin in glycolytic fibers results in white color

Front 45

Myofilaments

Back 45

contractile proteins found in skeletal muscle fibers

Front 46

Myofibrils

Back 46

long bundles of Myofilaments arranged within the sarcoplasm
-composed of 2 myofilaments that overlap: THIN and THICK

Front 47

Sarcomeres

Back 47

the arrangement of myofilaments within myofibrils that creates the look of STRIATIONS
-thousands of sarcomeres per myofibril

Front 48

Banding patterns of myofilaments

Back 48

caused by the arrangement of thin and thick filaments within a sarcomere
-Z disc
-A band
-I band
-H (bare) zone

Front 49

Z disc

Back 49

banding pattern of a sarcomere
- constitutes one end of a sarcomere
- anchors the thin filaments

Front 50

A band

Back 50

banding pattern of a sarcomere
- the length of the thick filaments (both overlapping and not overlapping with thin)

Front 51

I band

Back 51

banding pattern of a sarcomere
- the length of the thin filaments that is NOT overlapping with the thick filaments

Front 52

H (bare) zone

Back 52

banding pattern of a sarcomere
-the length of thick filaments that is NOT overlapping with the thin filaments

Front 53

What happens to the filaments of a sarcomere during contraction and relaxation?

Back 53

-in a relaxed state, thin and thick filaments overlap only slightly
-upon stimulation, thick filaments pull thin filaments toward center of sarcomere, filaments overlap greatly, sarcomere shortens

**as all of the sarcomeres in a muscle shorten, the entire muscle shortens

Front 54

What is the structure of thin filaments?

Back 54

composed of 3 proteins:

-Actin

-Tropomyosin

-Troponin C

Front 55

What is the structure of thick filaments?

Back 55

-composed of many molecules of the protein MYOSIN
-each myosin has a tail and two heads

Front 56

Myosin heads

Back 56

-portion of the protein myosin, exists in thick filaments
-hydrolyzes a molecule of ATP to get energy to contract
-temporarily binds to actin (of thin filament) pulls on actin to shorten sarcomere

Front 57

Actin

Back 57

one of the 3 proteins found in thin filametns
-- helical, binding site for myosin head of thick filaments

Front 58

Tropomyosin

Back 58

one of the 3 proteins found in thin filametns
**blocks interaction between actin (of thin filaments) and myosin (of thick filaments)

-prevents an unstimulated muscle from contracting

Front 59

Troponin C

Back 59

one of the 3 proteins found in thin filametns
- attached to tropomyosin
-binds to Ca in sarcoplasm during contraction

Front 60

Excitation-Contraction Coupling

Back 60

-binding of ACh opens Na+ and K+ channels
-results in depolarization
-opens volatge-gated Na+ and K+ channels to generate action potential
-action potentials move along sarcolemma into t-tubules
-action potentials in t-tubules cause release of Ca from sarcoplasmic reticulum into sarcoplasm which causes a contraction

Front 61

At the myofilament level, what causes muscle fiber shortening?

Back 61

Myosin (of thick filaments) pulls on Actin (of thin filaments) in a repetitive ratching fashion

Front 62

Cross Bridge Cycling

Back 62

-events of Contraction

Front 63

What occurs during activation of the Myosin head, and when does this happen?

Back 63

-a molecule of ATP is hydrolyzed, energy is then used to change shape of myosin into the high energy state

-this occurs during muscle fiber shortening when thin filaments are pulled towards the center of the sarcomere

Front 64

What is Cross Bridge Formation?

Back 64

-myosin cross bridge attaches to Actin

-occurs after activation of myosin head

Front 65

What is Power Stroke?

Back 65

-Myosin head pivots and pulls thin filament over thick filament

-occurs after cross bridge formation

Front 66

What is Cross Bridge Detachment?

Back 66

-binding of a molecule of ATP to the myosin head, detaches from Actin

-occurs after power stroke

Front 67

What occurs during muscle fiber relaxation?

Back 67

-motor neuron stops the exocytosis of ACh
-remaining ACh is hydolyzed into acetate and choline
-ACh receptors close
-membrane potential returns to resting
-Ca is pumped back into SR = decrease in Ca in sarcoplasm