Lecture 12

Question 1

Which muscle type is striated and voluntary?

Answer 1

Skeletal mm

Question 2

Skeletal mm fibers develop enbryologically from what?

Answer 2

myoblasts: mononucleated cells that fuse into long fibers which become peripheral and multinucleated.

Question 3

Which muscle type is visceral or involuntary?

Answer 3

Smooth mm.

Question 4

Which muscle type is smooth and not striated?

Answer 4

smooth mm… duh!

Question 5

What muscle types are multinucleated ?

Answer 5

smooth mm.

Question 6

What muscle types are mononucleated AND striated?

Answer 6

cardiac mm.

Question 7

Branchiomeric mm is associated with ….

Answer 7

pharyngeal arches

Question 8

describe branchiomeric mm

Answer 8

associated with pharyngeal arches
somewhat of a transition between smooth and striated
innervated by cranial nerves

Question 9

what innervates the branchiomeric muscles?

Answer 9

cranial nerves

Question 10

Voluntary muscle:

Answer 10

• muscle whose action is normally controlled by an individual’s will;
• mainly skeletal muscle, composed of parallel bundles of striated, multinucleate fibers.

Question 11

Involunary muscle:

Answer 11

• a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)

Question 12

Origin (proximal attachment:)

Answer 12

usually proximal, may be fixed with regard to movement

Question 13

Insertion (distal attachment)

Answer 13

usually distal, Usually more moveable

Question 14

Tendons:

Answer 14

attachments between muscle fibers and bone

Question 15

what are tendons made from?

Answer 15

dense collagenous connective tissue

Question 16

Tendons are surrounded by…

Answer 16

peritendineum

Question 17

Tendons are poorly/richly vascularized.

Answer 17

POORLY! Think about how long it takes to heal a sprained ankle!

Question 18

Aponeuroses:

Answer 18

flat, fan shaped tendons, typically giving rise to other tendons

Question 19

5. Describe the gross hierarchical organization of a skeletal muscle, including the connective tissue partitions that subdivide the muscle.

Answer 19

Myofilament, myofibril, myofiber, Fascicle, Muscle

Question 20

What are the two types of myofilament:

Answer 20

myosin and actin

Question 21

which are the thick filaments

Answer 21

myosin

Question 22

which are the thin filaments:

Answer 22

actin

Question 23

Myofilaments are organized into

Answer 23

sarcomeres

Question 24

What is a myofibril?

Answer 24

chain of sarcomeres

Question 25

What is a myofiber?

Answer 25

bundle of myofibrils
Referred to as a muscle cell
Each fiber formed from may fused myoblasts

Question 26

Endomysium

Answer 26

surrounds each muscle fiber

Lies outside the sarcolemma (cell membrane)

Question 27

Perimysium

Answer 27

surrounds each fascicle

Question 28

Epimysium

Answer 28

surrounds each muscle, becomes continuous with tendons, attached to periosteum

Question 29

6. Describe the microscopic organization of the sarcomere and changes that occur when the sarcomere shortens during contraction.

Answer 29

Sarcomere Arrangement
o Myosin and actin filaments are organized into cylindrical units that are aligned end-to-end to form the myofibrils.
o Each cylindrical unit is called a sarcomere.
o A myofibril is, therefore, a chain of sarcomeres.
Sarcomere structure:
•Z-lines:
• Separate adjacent sarcomeres in a fibril
• Composed of Z-actin
• Anchor actin filaments
• Located at each end of a sarcomere
•I-bands:
• Located on either side of Z-line and A-band
• Make up ends of sarcomere
• Composed entirely of actin
• Width changes during contraction
•A-bands:
• Located between two I bands in middle of sarcomere
• Composed of both actin and myosin
• Represents length of myosin chains
• Does not change width during contraction
•H-band:
• In middle of each A-band
• Composed entirely of myosin
• Band width changes during contraction

Question 30

Dark, slow fibers

Answer 30

fatigue resistent, contract slowly, oxidative phosphorylation, large # mito, high myoglobin, low ATPase concentration

Question 31

Light, Fast fibers

Answer 31

white, fatigue easy contract rapidly (fast twitch), rely on glycolysis, small number of mitochondria, low concentration of myoglobin, high concentration of ATPase.

Question 32

Where are phasic fibers found?

Answer 32

all vertebrate groups

Question 33

Do phasic fibers propagate an action potential?

Answer 33

no

Question 34

Which types of fibers are not multiply innervated?

Answer 34

phasic

Question 35

where would we find tonic fibers?

Answer 35

non-mammalian vertebrates

Question 36

Describe where tonic fibers are used:

Answer 36

slow, sustained postural activities. Single nerve cell innervates many fibers (motor unit) but each fiber is innervated by more than one nerve cell.
Contract slowly
DO NOT PROPAGATE AN AP

Question 37

Describe an isometric contraction

Answer 37

length does not change

Question 38

describe an isotonic contraction

Answer 38

length of mm does change

Question 39

Concentric

Answer 39

shorter

Question 40

eccentric

Answer 40

longer

Question 41

Describe a motor unit and its relation to “all or none”

Answer 41

• A single nerve cell (neuron) may innervate from a few to several hundred myofibers.
• A neuron and the myofibers it innervates constitute a motor unit.
• When a neuron fires, all the myofibers in the motor unit contract.
• All-or-none really refers to a motor unit.