Chapter 10 Vocab

Front 1

A band

Back 1

Where the thick filaments are located at the center of a sacromere; The dark bands; The length of the A band is equal to the typical length of a thick filament; includes 3 subdivisions: M line, H band, Zone of overlap; triad found on the edge of the A band in the zone of overlap

Front 2

M line

Back 2

Dark-staining proteins that help stabilize the position of the thick filaments in the A band; connects central portion of each thick filament to its neighbors

Front 3

H band

Back 3

Lighter region on either side of the M line when the sarcomere is at rest; contains thick filaments and no thin filaments.

Front 4

Zone of overlap

Back 4

region in which each thin filament is surrounded by 3 thick filaments, and each thick filament is surrounded by six thin filaments; triad found at the edge of zone of overlap and releases calcium ions into the zone of overlap to begin muscle contraction

Front 5

Sarcomere

Back 5

functional units of myofilaments; approx. 10,000 in a myofibril from end to end; smallest functional unit of the muscle fiber; interactions between thick and thin filaments are responsible for muscle contraction; has dark bands (A band) and light bands (I band)

Front 6

I band

Back 6

contains thin flaments, is made of actin, is the light colored band in the sarcomere; extends from A band of 1 sarcomere to A band of another; Z line is located in the middle of the I band

Front 7

Z line

Back 7

is the boundary between sarcomeres; made of proteins called actinins which interconnect the thin filaments of adjacent sarcomeres; from z lines thin filaments extend toward M lline into zone of overlap; strands of titin extend from the tips of thick filaments and attach to the Z line; intermediate filaments surround the Z line and connnect adjacent myofibrils to each other and to the sarcolemma membrane; this is what gives the skeletal muscle fiber a banded, striated look

Front 8

Titin

Back 8

extend from the tips of thick filaments and attach to the Z line; helps keep thick and thin filament in proper alignment and aid in restoring resting sarcomere length; also helps muscle fiber resist extreme stretching

Front 9

Sarcoplasmic reticulum (SR)

Back 9

related to the smooth endoplasmic reticulum of other cells; forms a tubular network around each myofibril, fitting over like a lacey shirtsleeve; thickens and enlarges on each side of a T tubule (called terminal cisternae); called a triad in conjunction with the T tubule

Front 10

Triad

Back 10

2 terminal cisternae surrounding a T tubule; membranes bound tightly, but fluids totally seperate and different; found on the edge of the A band at the zone of overlap; calcium released from cisternae enter the zone of overlap to begin muscle contraction

Front 11

Terminal cisternae

Back 11

thicker, bounded SR found on each side of a T tubule; Calcium ions are actively transported into the terminal cisternae from the sarcoplasm; 1000 times as many free calcium ions in TC; TC also contain calsequestrin, which binds calcium ions; total free and bound calcium in SR is 40,000 times that of sarcolasm surrounding; this is where a muscle contraction begins

Front 12

Sarcolemma

Back 12

plasma membrane of a muscle fiber; has transmembrane potential due to unequal distribution of positive and negative charges across the membrane; sudden change in this potential is the beginning of muscle contraction

Front 13

Sarcoplasm

Back 13

cytoplasm of muscle fiber; generally low concentration of calcium ions

Front 14

T tubules

Back 14

narrow tubes that are a continuation of the sarcolemma that extend into the cell at right angles to the cell surface; have same general properties of sarcolemma and contain extracellular fluid; action potentials travel across the sarcolemma and down the T tubules to trigger muscle fiber contractions simultaneously throught the fiber; encircle myofibrils

Front 15

Myofibril

Back 15

cyclindrical structures about 1-2 micrometers in diameter that stretch the length of a muscle fiber; hundreds found in one skeletal muscle fiber; made of myofilaments

Front 16

Myofilaments

Back 16

bundles of protein filaments that make up myofibrils; 2 types: thin filaments (made mostlly of actin and thick filaments made of myosin; also contain titn

Front 17

Major Functions of skeletal muscles

Back 17

1. Produce skeletal movement
2. Maintain posture and body position
3. Support soft tissues\
4. Guard entrances and exits
5. Maintain Body Temperature
6. Store nutrient reserves

Front 18

Example of skeletal muscle producing skelatal movement

Back 18

breathing, swimming, moving arm

Front 19

Example of skeletal muscle maintaining posture and body position

Back 19

holding head still; balancing body over feet during walking

Front 20

Example of skeletal muscle supporting soft tissues

Back 20

abdominal wall and floor of pelvic cavity consists of layers of skeletal muscle and supports the weight of internal organs and shield them from injury

Front 21

Example of skeletal muscle guarding entrances and exits

Back 21

skeletal muscles encircle digestive and urinary tracts and provides voluntary control over swallowing, defecation, and urination

Front 22

Example of skeletal muscle maintaining body temperature

Back 22

muscle contraction requires energy, some of which is converted to heat which keeps body temp in normal range; running heats us up

Front 23

Example of skeletal muscle storing nutrient reseves

Back 23

when body contains inadequate proteins or calories, contractile proteins in SM can be broken down into AAs and used to make glucose or broken down to provide energy

Front 24

Skeletal Muscles

Back 24

organs composed primarily of skeletal muscle tissue but also contain connective tissues, nerves, and blood vessels

Front 25

CT found in a skeletal muscle

Back 25

1. epimysium
2. perimysium
3. endomysium

Front 26

Epimysium

Back 26

dense irregular layer of collagen fibers that surround a skeletal muscle; seperates muscle from surrounding tissues and organs and is connected to the deep fascia

Front 27

Perimysium

Back 27

dense irregular CT; divide skeletal muscle into a series of compartments containing a bundle of fibers called fasciles; possess collagen and elastic fibers, as well as blood vessels and nerves

Front 28

Endomysium

Back 28

surrounds individual skeletal muscle cells (fibers) and loosely interconnects adjacent muscle fibers; elastic CT and areolar CT; contains capillary networks, myosatellite cells, and nerve fibers that control the muscle

Front 29

Myosatellite cells

Back 29

embryonic stem cells found in the endomysium that function in the repair of damaged muscle cells

Front 30

Tendon or Aponeurosis

Back 30

a bundle or broad sheet of the collagen fibers from epimysium, perimysium, and endomysium found at the ends of a muscle; usually attach muscles to bone, extending into the matrix of the bone

Front 31

4 proteins found in thin filaments

Back 31

F-actin, nebulin, tropomyosin, and troponin

Front 32

F-actin

Back 32

1 of 4 proteins found in SM thin filaments; "Filamentous actin"; a twisted strand of 2 rows of 300-400 G-actin (globular molecules); G-actin molecules have active sites where myosin bind

Front 33

Nebulin

Back 33

long strand that extends along F-actin in cleft between rows of G-actin; holds F-actin strands together

Front 34

Tropomyosin

Back 34

cover active sites on G-actin, preventing actin, myosin interaction; a molecule is double stranded that covers 7 active sites and binds to 1 molecule of troponin midway

Front 35

Troponin

Back 35

made of 3 globular subunits -
1. binds to tropomyosin
2. binds to 1 unit G-actin to hold position
3. has receptor that binds 2 calcium ions (starting point of muscle contraction)

Front 36

Thick filament structure

Back 36

300 myosin molecules made of paired myosin subunits twisted; titin core
1. tail: bound to other myosin molecules
2. head: projects toward thin filament and is known as cross bridge when interactin gwith thin filament

Front 37

F-actin

Back 37

1 of 4 proteins found in SM thin filaments; "Filamentous actin"; a twisted strand of 2 rows of 300-400 G-actin (globular molecules); G-actin molecules have active sites where myosin bind

Front 38

Nebulin

Back 38

long strand that extends along F-actin in cleft between rows of G-actin; holds F-actin strands together

Front 39

Tropomyosin

Back 39

cover active sites on G-actin, preventing actin, myosin interaction; a molecule is double stranded that covers 7 active sites and binds to 1 molecule of troponin midway

Front 40

Troponin

Back 40

made of 3 globular subunits -
1. binds to tropomyosin
2. binds to 1 unit G-actin to hold position
3. has receptor that binds 2 calcium ions (starting point of muscle contraction)

Front 41

Thick filament structure

Back 41

300 myosin molecules made of paired myosin subunits twisted
1. tail: bound to other myosin molecules
2. head: projects toward thin filament and is known as cross bridge when interactin gwith thin filament

Front 42

Sliding Filament Theory

Back 42

Explanation for muscle contraction that states thin filaments are sliding toward the center of each sarcomere and because myofibrils are attached to sarcolemma, muscle contracts

Front 43

During skeletal muscle contraction

Back 43

1.H bands and I bands shrink
2.zones of overlap enlarge
3.Z lines move closer together
4.width of A band remains constant

Front 44

Muscle cell tension

Back 44

Muscle cells can only pull an object, never push (no compression)

Front 45

Muscle contraction detail

Back 45

1.skeletal muscles are under control of neural cells; a neuron activates a muscle fiber through stimulation of its sarcolemma (called excitation-contraction coupling)
2.calcium is released from the terminal cisternae of the SR
3.calcium ions trigger interactions between thick and thin filaments, resulting in contraction and use of ATP
4.filament interaction produces active tension

Front 46

Neuromuscular junction/Myoneural junction

Back 46

Connection between the nervous system and skeletal muscle fiber

Front 47

Synaptic terminal

Back 47

End of a fine branch of an axon which has branched in the perimysium and stops about half way down the length of a fiber; cytoplasm of synapse terminal contains mitochondria and vesicles filled with molecules of ACh

Front 48

Acetylcholine (ACh)

Back 48

A neurotransmitter that alters the permeability of the sarcolemma and trigger the contraction of muscle fibers

Front 49

Neurotransmitter

Back 49

A chemical released by a neuron to change the permeability or other properties of another plasma membrane

Front 50

Synaptic Cleft

Back 50

Narrow space that seperates the synaptic terminal from the sarcolemma motor end plate; contains acetylcholinesterase (AChE)

Front 51

Motor end plate

Back 51

Part of sarcolemma that contains the Ach receptors; contains lots of folds to increase surface area and # of receptors; contains acetylcholinesterase (AChE)

Front 52

Acetylcholinesterase (AChE)

Back 52

Enzyme that breaks down ACh

Front 53

Steps of neural stimulation

Back 53

1.arrival of action potential
2.release of ACh
3.ACh binding at motor end plate
4.appearance of action potential in sarcolemma
5.return to initial state

Front 54

Action Potential

Back 54

Electrical impulse from a sudden change in the transmembrane potential that travels along the length of an axon

Front 55

Step 1 of neural stimulus of muscle fiber

Back 55

Arrival of action potential at the synaptic terminal

Front 56

Step 2 of neural stimulus of muscle fiber

Back 56

Action potential changes membrane permeability of synaptic terminal and ACh is exported via exocytosis into the synaptic cleft

Front 57

Step 3 of neural stimulus of muscle fiber

Back 57

ACh diffuse across synaptic cleft and bind to receptors on the motor end plate (sarcolemma); this changes the permeability of the membrane to sodium ions, which rush into the sarcoplasm; process continues until AChE binds to ACh in synaptic cleft and ACh unbinds from the receptors at the motor end plate, returning the membrane permeability to normal

Front 58

Step 4 of neural stimulus of muscle fiber

Back 58

Action potential is created in the sarcolemma by the inrush of sodium

Front 59

Step 5 of neural stimulus of muscle fiber

Back 59

ACh has been broken down by AChE and some products will be used by neuron to make more ACh

Front 60

Excitation-contraction coupling

Back 60

Link between action potential in sarcolemma and start of muscle contraction; action potential triggers triads to release stored calcium ions from SR to sarcomere surroundings; calcium binds with troponin, weakening the bond with actin and turning the strand to remove tropomyosin from covering the active sites on actin

Front 61

SM Contraction Cycle

Back 61

1. Exposure of active sites
2. Formation of cross-bridges
3. Pivoting of myosin heads
4. Detachment of cross-bridges
5. Reactivation of myosin

Front 62

Step 1 of SM contraction cycle

Back 62

calcium binds with troponin, weakening the bond with actin and turning the strand to remove tropomyosin from covering the active sites on actin and allowing interaction with myosin heads

Front 63

Step 2 of SM contraction cycle

Back 63

Myosin heads bind to active sites on actin, forming cross-bridges

Front 64

Step 3 of SM contraction cycle

Back 64

The cocked myosin head releases ADP & P as it pivots toward the M line (usually facing away); called the power stroke.

Front 65

Step 4 of SM contraction cycle

Back 65

ATP binds to myosin head and cross-bridge between myosin and actin is broken

Front 66

Step 5 of SM contraction cycle

Back 66

ATP in the myosin head is broken into ADP + P and that energy used to recock the myosin head

Front 67

Myosatellite Cells

Back 67

Stem cells that function in endomysium as part of muscle development and repair; proliferate, differentiate, and fuse into multinucleate muscle cells

Front 68

Isotropic

Back 68

Light in color; I band

Front 69

Dystrophin

Back 69

A thin filament; links actin to sarcolemma and transmit force to sarcolemma and ultimately to the tendons

Front 70

Characteristics of a resting SM fiber

Back 70

1. [Ca2+] in cytoplasm is relatively low vs. SR
2. [Ca2+] in sarcoplasmic reticulum (SR) is relatively high (40,000X higher than cytoplasm)
a. Ca2+ is continually pumped into SR
b. Calsequestrin binds Ca2+ within SR
3. Myosin heads are already “cocked” with ATP
4. Myosin-binding sites on actin are blocked by troponin-tropomyosin complex

Front 71

Muscle relaxation

Back 71

Motor neuron quits firing Æ no new ACh release
• Acetylcholinesterase (AChE) in synapse is
continually breaking down ACh
Result:
• No new action potential on muscle cell
¸No new Ca2+ release from SR
¸Ca2+ continuously pumped into SR
¸[Ca2+] in cytoplasm drops
• T-T complex covers up myosin-binding sites
¸No interaction between actin and myosin
¸Muscle relaxes passively

Front 72

Rigor Mortis = Stiffness of Death

Back 72

• Myosin heads already “cocked” with ATP
• Ca2+ leaks out of SR (ATP required to pump it back in)
• Intracellular [Ca2+] rises
• T-T complex binds Ca2+ and uncovers myosinbinding
sites
• Contraction occurs
• ATP stores depleted over time
• No ATP available to release myosin from actin
and recock heads
• Rigor mortis

Front 73

Inhibitory effects of drugs/toxins on contraction

Back 73

• Block ACh release - Botulinus toxin
• Block binding of ACh to receptor - Atropine
(belladonna), curare

Front 74

Exhibitory effects of drugs/toxins on contraction

Back 74

• Block acetylcholinesterase - Neostigmine,
DFP (nerve gas)
• Increase ACh release - some spider venoms
• Mimic ACh - Nicotine

Front 75

SM fiber tension all-or-none principle

Back 75

All sarcomeres in a SM fiber contract together in response to a given dose of calcium ions

Front 76

Facors in SM fiber tnesion production

Back 76

1. fiber length at time of stimulation, which affects overlap of actin and myosin
2. frequency of stimulation, which affects duration of calcium ion concentration
3. fiber diameter, which affects the amount of actin and myosin available

Front 77

Ideal range of sarcomere length

Back 77

75 - 130% of optimal length

Front 78

Twitch

Back 78

a single stimulus-contraction-relaxation sequence in a muscle fiber; 3 phases: latent period, contraction phase, relaxation phase

Front 79

Latent period of a twitch

Back 79

stimulation, action potential sweep, release of Ca ions from SR; no tension

Front 80

Contraction period of a twitch

Back 80

tension rises as myosin and actin interact

Front 81

Relaxation period of a twitch

Back 81

calcium ion concentration decreases, active sites being covered, cross bridges declining, and tension returns to normal

Front 82

Treppe

Back 82

"warm up effect"; gradual increase in strength of contraction with same stimulus over time; due to increased calcium available and warmed up fiber (enzymes more efficient at higher temperatures); not common

Front 83

Wave summation

Back 83

when a stimulus to the SM fiber occurs before the relaxation phase ends; can reach 4 times that of treppe

Front 84

Incomplete tetanus

Back 84

muscle never completely relaxing, happens during summation

Front 85

Complete tentanus

Back 85

the relaxation phase in muscle contraction disappears completely; continuous contraction

Front 86

Motor unit

Back 86

all the muscle fibers controlled by a single motor neuron; smaller size = finer control of movement

Front 87

Recruitment

Back 87

the smooth and steady increase of muscular tension by increasing the number of active motor units

Front 88

Factors affecting tension production in a whole muscle

Back 88

1. internal and external tension
2. recruitment
3. muscle size (# of muscle fibers

Front 89

Internal tension

Back 89

tension generated inside a contracting muscle (myosin pulling on actin)

Front 90

External tension

Back 90

tension generated in extracellular fibers; endo, peri, epimysium form tendons that stretch

Front 91

Series elastic component

Back 91

difference in tension between internal and external from simple twitch

Front 92

Muscle tone

Back 92

some motor units active at any one time, change throughout the day; stabilizes bones and joints, maintains body position/posture, allows more rapid activation of whole muscle, contributes to body heat

Front 93

Isotonic contraction

Back 93

"same tension", muscle shortens; muscle starts shortening at point it reaches amount of tension required to move 2 kg of weight

Front 94

Isometric contraction

Back 94

"same length", muscle never shortens because there is not enough tension to lift the weight

Front 95

Creatine

Back 95

small molecule assembled by muscle cells from AA

Front 96

Creatine phosphate

Back 96

CP; the storage of the phosphate broken off of ATP, used in the recreation of ATP during muscle contraction

Front 97

Energy-production systems in muscle

Back 97

1. phosphogen system (ATP & CP reserves)
2. glycolysis
3. aerobic system

Front 98

Phosphogen system

Back 98

found only in muscle cells; involves creatine phosphate (CP) and ATP; fast, short-term method of ATP generation; involves 1 enzyme (creatine phosphokinase)`