Lecture 4: Muscle Tissue and Muscles

Question 1

What are the four types of muscle tissues?

Answer 1

skeletal, smooth, cardiac, branchiomeric

Question 2

What are the characteristics of skeletal muscles?

Answer 2

Also called striated or voluntary
Muscle fibers have striated or banded appearance
Under voluntary control
Typically attached directly or indirectly to skeletal system

Question 3

What are the characteristics of smooth muscle?

Answer 3

Not striated
Generally involuntary
Spindle shaped mononucleated cells with centrally located nuclei
commonly associated with viscera

Question 4

What are the characteristics of cardiac muscle?

Answer 4

Only found in heart
Striated
Involuntary
Consists of chains of individual cells that are mononuclear and striated
Have specialized intercellular junctions called intercalated discs

Question 5

What are the characteristics of branchiomeric muscle?

Answer 5

Associated with pharyngeal arches
Transition between smooth and striated muscle tissue
Innervated by cranial nerves

Question 6

In what ways can muscles be named based on characteristics?

Answer 6

Shape
origin-insertion
function
relative size
fiber arrangement
location

Question 7

What is an agonist?

Answer 7

muscle doing the desired action, is a mover when its contraction contributes to the desired movement of a joint, classified as prime mover or assistant mover

Question 8

What is a prime mover?

Answer 8

muscle whose primary function is to cause the particular movement, makes strong contribution

Question 9

What is an assistant mover?

Answer 9

ability to assist in the movement but is only of secondary importance to the movement

Question 10

What is an antagonist?

Answer 10

Muscle that opposes the agonist

Question 11

What is a synergist?

Answer 11

nullify one or more actions of another muscle
Will cause the opposite motion of the prime mover without assisting in the movement
Example: tricep to the biceps elbow flexion, so that biceps can person supination of the forearm

Question 12

What is a fixator?

Answer 12

stabilize the segment (bone) on which another segment (bone) moves

Question 13

What is muscle contraction?

Answer 13

a response to a stimulus

Question 14

What are the types of muscle contraction?

Answer 14

isometric, isotonic, concentric, eccentric

Question 15

Isometric vs isotonic contraction

Answer 15

isometric: length of muscle does not change
isotonic: length of muscle does change

Question 16

Concentric vs eccentric contraction

Answer 16

concentric: muscle gets shorter
eccentric: muscle gets longer

Question 17

What are flexor muscles?

Answer 17

muscles that pass anterior to the axis, can shorter about one half of total length

Question 18

What extensor muscles?

Answer 18

muscles that pass posterior to the axis

Question 19

What are abductors?

Answer 19

muscles that pass lateral to a joint

Question 20

What is an origin?

Answer 20

usually proximal, may be fixed with regard to movement

Question 21

What is an insertion?

Answer 21

Usually distal, may be fixed with regard to movement

Question 22

What are the characteristics of tendons?

Answer 22

Attachment between muscle fibers and bone
Dense collagenous connective tissue
Surrounded by peritendineum
Bundles of collagen fibers
Poorly vascularized

Question 23

What is an aponeuroses?

Answer 23

flat, fan shaped tendons typically given rise to other tendons

Question 24

What is the hierarchical structure of skeletal muscles (smallest to larger)?

Answer 24

myofilament-myofibril-myofiber-fascicle-muscle

Question 25

What are the two types of myofilaments?

Answer 25

actin and myosin

Question 26

What are myofilaments organized into?

Answer 26

sacromeres

Question 27

What is a myofibril?

Answer 27

Chain of sarcomeres

Question 28

What is a myofiber?

Answer 28

bundle of myofibril, referred to muscle cell, each fiber formed from many fused myoblasts

Question 29

what is a fascicle?

Answer 29

under of myofibers

Question 30

What is a muscle

Answer 30

composed of varying numbers of fascicles

Question 31

What is the endomysium?

Answer 31

Surrounds each muscle fiber | Lies outside sarcolemma (cell membrane)

Question 32

What is the perimysium?

Answer 32

Surrounds each fascicle

Question 33

What is the epimysium?

Answer 33

Surrounds each muscle Becomes continuous with tendons Attached to periosteum

Question 34

What is actin?

Answer 34

Thin filamentous protein polymer Each filament is made up of two helical wound polymers of g actin Associated molecules: tropomyosin and troponin

Question 35

What is myosin?

Answer 35

Bundles of long molecules: tail + ATPase head, head attached to tail via swivel mechanism Heads attach to binding sites on actin filaments Attach-swivel-release cycles allow myosin and actin to slide along one another in opposite directions, products contraction

Question 36

What is the z line?

Answer 36

separate adjacent sarcomeres in a fibril, composed of Z- actin

Question 37

What is the I band?

Answer 37

located on either side of Z-line, make up ends of each sarcomere, composed entirely of actin

Question 38

What is the A band?

Answer 38

located in middle of sarcomere, composed of both actin and myosin

Question 39

What is the H band?

Answer 39

in middle of each A band made of myosin, changes width during contraction

Question 40

What is a motor unit?

Answer 40

a motor neuron and all the myofibers it innervates

Question 41

What is the mechanism for muscle contraction?

Answer 41

Action potential arrives at sarcolemma from a motor neuron Synaptic plate is the intervention point between the axon and the sarcolemma Action potential is conducted from sarcolemma into the interior of the myofiber via T- tubules Action potential carried by t-tubules causes the release of calcium ions from the sarcoplasmic reticulum cisternae Calcium ions initiate mechanism by which actin and myson filaments slide over one another resulting in a contraction

Question 42

What are the characteristics of fast twitch muscles?

Answer 42

``` light, white Fatigue easily Contract rapidly rely on glycolysis Have a small number of mitochondria Have a low concentration of myoglobin Have a high concentration of ATPase ```

Question 43

What are the characteristics of slow twitch fibers?

Answer 43

``` dark, red Fatigue resistant Contract slowly Rely on oxidative phosphorylation Large number of mitochondria High concentration of myoglobin Low concentration of ATPase ```