Chapter 12 - Muscles (Mechanisms of Control and Neural Control)

Question 1

Extensor =

Answer 1

increases the angle at a joint

Question 2

Flexor =

Answer 2

Decreases the angle at a joint

Question 3

Abductor =

Answer 3

Moves limb away form the midline of the body

Question 4

Adductor =

Answer 4

Moves limb toward the midline of the body

Question 5

Levator =

Answer 5

Moves insertion upward

Question 6

Depressor =

Answer 6

Moves insertion downward

Question 7

Rotator =

Answer 7

Rotates a bone along its axis

Question 8

Sphincter =

Answer 8

Constricts an opening

Question 9

Agonist Muscle =

Answer 9

prime mover of any skeletal movement

Question 10

Antagonistic Muscles =

Answer 10

Flexors and extensors that act on the same joint to produce opposite actions

Question 11

Episium =

Answer 11

Epi = Above / My = muscle, Fibrous connective tissue proteins within the tendorns extend around the muscle in an irregular arrangement, forming a sheeth.

Question 12

Fascicles =

Answer 12

Connective Tissue from the episium extends into the body of the muscles, subdiving it in to cloumes. “Strings of Meat”

Question 13

Perimysium =

Answer 13

Peri = round, Fascicles is surrounded by its own connective tissues sheath.

Question 14

Sarcolemma =

Answer 14

Plasma membrane of muscles

Question 15

A Bands =

Answer 15

Anistropic dark bands. Contains thick filaments (myosin)

Question 16

I Bands =

Answer 16

Instoropic light bands. Contains thin filaments (actin)

Question 17

M Lines =

Answer 17

produced by protein filaments located at the center of the thick filaments/A Band in the sarcomere. These serve to anchor the thick filaments, helping them stay together during contraction.

Question 18

H Bands =

Answer 18

Central lighter regions of A Bands “H for Helle a German word meaing Bright”.

Question 19

What is a “Motor Unit”? Fig. 12.4

Answer 19

A Motor Unit are each Somatic motor neuron, together with all of the muscle fibers that innervate.
A Motor unit consissts of somatic motor neuron and the muscle fibers it innervates.

Question 20

Study figure 12.3, know all of the anatomical parts.

Answer 20

Look up.

Question 21

What are fibers? What are myofibrils, myofilaments (filaments), sarcomeres?

Answer 21

Muscles are really just tubes within tubes: Filaments, Myofibrils, Muscle Fibers, Fasciculus, Skeletal Muscles

Question 22

Myofibrils =

Answer 22

bundles in muscle fiber make up of filaments.

Question 23

Myofilaments (filaments) =

Answer 23

Makes up the smaller structures of myofibril

Question 24

Sarcomers =

Answer 24

Each subunit from Z to Z

Question 25

Titin =

Answer 25

type of elastic protein that runs through the thick filaments from M Lines to Z Disces. This is believed to contribute to the elastic recoil of muscles that helps them return to their resting length during muscle relaxation.

Question 26

Tropomysin =

Answer 26

A filamentous protein that attaches to actin in the thin filaments. Together with another protein called troponin, it acts to inhibit and regulate the attachment of myosin cross bridges to actin.

Question 27

Troponin =

Answer 27

a protein found in the thin filaments of the sarcomeres of skeletal muscle. A subuint of tropopin binds….PG 749

Question 28

Myosin =

Answer 28

Thick mucsle fibers

Question 29

Actin =

Answer 29

Thin muscle fibers.

1. Individual balls on actin is call G-Actin
2. Tropomyosin are between G-Actin
3. Actin is really 3 proteins: G-Actin, Tropomyosin, and Troponin.

Question 30

Be able to draw the structure of a sarcomere much as I did on the board. Use figures 12.6,12.7,12.8 as guides.

Answer 30

REVIEW

Question 31

What is the “Sliding Filament” theory?

Answer 31

The Theory that the thick (myosin) and thin (actin) filaments of a myofibril slide past each other during muscles contraction, decreasing the lenght of the sarcomers but maintaining their own initial length.

Question 32

What are “Cross Bridges”? What are the 2 binding sites on the myosin head?

Answer 32

Extends out from the myosin to the actin. Shaft of myosin head that sticks out. Part of the myosin proteins that extend from the axis of the thick filaments to form an “arm” that terminate in globular heads. Myosin proteins have two globular heads that serves as cross bridges by attaching actin to each side of the sarcomere. They can pull the actin form each side toward the center.
Cross bridges are trying to attach to actins but tropomyosin is blocking the active site.

Question 33

What is the actual structure of a thin filament? (See fig. 12.10)

Answer 33

Thin filament is composed of:

1. Troponin
2. (G)-Actin
3. Tropomyosin

Question 34

What is a “Power Stroke”?

Answer 34

A. Power Stroke is the force that pulls the thin filaments toward the center of the A Band.
B. Once the myosin head binds to actin, forming a cross bridge, the bound Phopspate is released. This results in a conformational change in the myosin cause the cross bridges to produce this.
C. The splitting of ATP is required before a cross bridge can attach to actin and undergo a power stroke, and that the attachment of a new ATP is needed for the cross bridge to release from actin at the end of a power stroke

Question 35

What does the term “Rigor Mortis” mean?

Answer 35

A. Rigor Mortis occurs due to lack of ATP when the muscles dies. Without ATP the ADP remans bound to the cross bridges, and the cross bridges remain tightly bound to actin. The myosin and actin cannot detach.

Question 36

What is the role of Ca++ in contraction?

Answer 36

The role of Ca++ in contraction is the attachment of Ca to troponin causes movement of the troopnin-tropomosin complex, which exposes binding sites on the actin. The myosin cross bridges can then attach to the actin and undergo a power stroke.

Question 37

What is the mechanism that brings Ca ++ back into the sarcoplasmic reticulum?

Answer 37

Ca ++ -ATPase pumps, move Ca ++ from the sarcoplasm into the the sarcoplasmic reticulm. This causes the Ca ++ channels to close and action to stop. These pumps are powered by Hydrolysis of ATP, ATP is also needed for muscle relaxation as well as muscle contraction

Question 38

Twitch:

Answer 38

When a muscle is stimulated with a single electric shock, it quickly contracts and relaxes.

Question 39

Summation:

Answer 39

If a second electrical shock is delivered immediately after the first, it will produce a second twitch that may partially “ride piggyback” on the first.

Question 40

Tetanus (Incomplete):

Answer 40

if the stimulator is set to deliver an increasing frequency of electrical shocks automatically, the relatxion time between successive twitches will get shorter and shorter as the strtength of the contractions increases in amplitude.

Question 41

Tetanus (Complete):

Answer 41

a smooth sustained contraction, during normal muscle contraction in vivo

Question 42

Isotonic:

Answer 42

same force

Question 43

Isometric:

Answer 43

same length

Question 44

What is the “Series Elastic Component”? What is its significance?

Answer 44

Provided by Tendons because they are somewhat elastic and in line with the force of the muscle contractions.
SEC absorbs some of the tension as a muscle contracts and it must be pulled right before the muscle contracts and must be pulled tight before the muscle contraction can result in muscle shortening.

Question 45

Understand the “Length-Tension” relationship for skeletal muscle. Fig. 12.21 (Fig.12.20)

Answer 45

Maximum relative tension dj achieved when the muscle is 100% to 120% of its resting length. Increases or decreases in muscle (and sarcomere) lengths results in rapid decrease of tension.

Question 46

Tension

Answer 46

The force that the muscle generates when it contracts is usually the same force required to prevent it from shortening.

Question 47

Oxygen Debt

Answer 47

the extra oxygen used to get the levels back to the pre existing levels prior to exercise.

Question 48

Slow-Twitch (type 1 fibers)

Answer 48

Also called red fibers (due the presence of myoglobin) these are often referred to as slow oxidative fibers. These fibers are rich in capillary supply, number mitochondria and aerobic respiration enzymes and myoglobin (which help to improve delivery of oxygen

Question 49

Fast-Twitch (type 2 fibers)

Answer 49

White fibers, adapted to respire anaerobically by a large store of glycogen and high concentration of glycolytic enzyme.

Question 50

Intermediate Fibers (Fast twitch fibers)

Answer 50

High-Oxidative, resistant to fatigue.

1. IIA Fibers - fast oxidative fibers - high aerobic ability.
2. Fast Glycolytic Fiber - hight rate of glycolysis (Type IIX Fibers in humans and Type IIB fingers in animals)

Question 51

Muscle Fatigue

Answer 51

Appears to be due to the accumulation of extracellular K, which reduces the membrane potential of muscid fibers and interfere with their ability to produce action potentials.

Question 52

Lower motor neurons

Answer 52

Neurons whose axons innervate skeletal muscles, also called the final common pathway in the control of the skeletal muscles

Question 53

Upper motor neurons

Answer 53

Neurons of the brain that are involved in the control of skeletal movements an that act by facilitating or inhibiting the activing of the lower motor neurons.

Question 54

Extrapyarmidal tracts

Answer 54

neurons in other areas of the brain produce these, the major on is the reticulospinal tract, believed to produce the inhibition of lower motor neurons.

Question 55

Pyramidal Tracts

Answer 55

Neurons in the pre central gyrus of the cerebral cores contribute axons that cross to the contralateral sides in the pyramids of the medulla oblongata.