Muscle Tissue

Question 1

Properties of muscle tissue

Answer 1

1. Excitability
   – Receive and respond to stimuli
2. Conductivity
   – Conduct electricity along membrane
3. Contractility
   – Shorten forcibly when stimulated
4. Extensibility
   – Ability to be stretched
5. Elasticity
   – Ability to recoil to resting length

Question 2

Functions of muscle tissue

Answer 2

1. Body movement
2. Maintain posture & stabilize joints
3. Protect & support
4. Open & close body passageways
5. Generate heat

Question 3

When a group of muscle fibers is “bundled” as a unit within the whole muscle it is called a

Answer 3

fascicle

Question 4

1) Muscle
2) Fascicle
3) Muscle cell/muscle fiber
4) Myofibril
5) Sarcomere
6) Filaments- actin and myosin

Answer 4

1) Multiple bundles housing many muscle fibers

2) A bundle of muscle fibers

3) Elongated, multinucleated, cylindrical cell

4) Long, cylindrical contractile element within muscle cell

5) A sarcomere is the basic contractile unit of muscle fiber

6) Short contractile proteins of two types: thick and thin

Question 5

Endomysium

Perimysium

Epimysium

Fascia

Endomysium, perimysium, and
epimysium merge to form a tendon

Answer 5

Endomysium
– Areolar connective
– Around each muscle fiber

• Perimysium
  – Sheath around fascicle
• Fascicle = bundle of muscle fibers

Epimysium
– Sheath around group of fascicles

• Fascia
  – Covering outside epimysium
  – Hypodermis
• Endomysium, perimysium, and
  epimysium merge to form a tendon

Question 6

Skeletal Muscle: Attachments

Answer 6

Direct—epimysium fused to:
* Periosteum of bone
* Perichondrium of cartilage

– Indirect—connective tissue wrappings extend beyond muscle
* Rope-like tendon
* Sheet-like aponeurosis

Question 7

Origin vs insertion

Answer 7

• Insertion – movable bone
• Origin – immovable (less movable) bone

Question 8

Axial vs Appendicular

Answer 8

Attach in at least two places

– Axial
* Superior attachment
* Inferior attachment

– Appendicular
* Proximal attachment
* Distal attachment

Question 9

Microscopic Anatomy of a Skeletal Muscle Fiber

Answer 9

• Long, cylindrical cell (up to 20 cm)
• Multiple peripheral nuclei from fusion of myoblasts during development
• Satellite cells (stem cells) can form myoblasts after damage

Sarcolemma = plasma membrane

• Sarcoplasm = cytoplasm

Myofibrils= Densely packed, rodlike elements. About 80% of cell volume.

Contain sarcomeres - contractile units. Region between two successive Z discs. M line runs down the middle. A band (Dark) – where there is myosin. I band (White)– the area around the Z disc where there is no myosin. H zone – the area around the M line where there is no actin.

Sarcomeres contain myofilaments. -

-Actin myofilaments = thin filaments, anchored to Z discs. Myosin myofilaments = thick filaments. Connected at M line.

Question 10

Neuromuscular junction

Answer 10

– Neuron–muscle connection

– Synaptic knob (axon terminal) of
neuron contacts sarcolemma of
muscle cell

– Also called a motor end plate

Question 11

Muscle contraction

Answer 11

/

Question 12

Muscle structure

Answer 12

/

Question 13

Physiology of muscle contraction

Answer 13

Action potential arrives at axon terminal at neuromuscular junction

Action potential in sarcolemma

Neurotransmitter (Ach) is released

Local depolarization

Ion channels on sarcolemma open

AP travels across the entire sarcolemma

AP travels down T tubules

SR releases Ca2+;

Myosin heads bind to actin

Contraction begins

Question 14

A motor unit consists of

Answer 14

1 neuron + all of the muscle fibers it contacts

Question 15

1) Isometric contractions

2) Isotonic contractions

Answer 15

1) Load greater than tension
muscle can develop. Tension increases to muscle’s capacity, but
muscle neither shortens nor
lengthens. Cross bridges generate force but do not move actin
filaments.

2) Muscle changes in
length and moves load– Thin filaments slide.

A) Concentric contractions – muscle shortens and does work

B) Eccentric contractions – muscle generates force as it lengthens

Question 16

The cytoplasm of a skeletal muscle cell is referred to as ______.

Answer 16

sarcoplasm

Question 17

As a result of muscle fiber contraction, the H zone ______.

Answer 17

disappears

Question 18

A contracting skeletal muscle fiber typically shortens as all of its ______ shorten in length.

Answer 18

sarcomeres

Question 19

As a result of muscle fiber contraction the ______ lines or discs in one sarcomere move closer together.

Answer 19

Z

Question 20

A circular muscle is also called a _________ because contraction of the muscle closes off the opening.

Answer 20

sphincter

An example of a circular muscle is the orbicularis oris muscle that encircles the opening of the mouth.

Question 22

In skeletal muscles, fast oxidative (intermediate) fibers are characterized as type ______, and they typically produce ATP through ______ cellular respiration.

Answer 22

IIa, aerobic

Question 23

True or False: The fascicles in a parallel muscle run parallel to its long axis.

Answer 23

True

Question 23

When a muscle fiber contracts, the I bands ______ in length.

Answer 23

shorten

Question 24

A pennate muscle is a type of muscle that resembles the shape

Answer 24

feather

Question 25

Convergent muscle fibers are often ___________ in shape, resembling a broad fan with a tendon at the tip.

Answer 25

triangular

Question 26

Contraction of a pennate muscle generates ________ tension than would contraction of a parallel muscle of the same size because a pennate muscle contains more muscle fibers, and thus more myofibrils and sarcomeres, than does a parallel muscle of the same size.

Answer 26

more

Question 27

An increase in muscle fiber size is called

Answer 27

hypertrophy

Question 28

A muscle that contracts to produce a particular movement is referred to as a(n) ______.

Answer 28

agonist

Question 29

Cardiac muscle cells form a unique Y-shaped structure with branches that join adjacent muscle cells at a specialized type of cell junction known as

Answer 29

intercalated discs

Question 30

What are the three kinds of somites?

Answer 30

These cells differentiate into the following 3 regions: (1) myotome, which forms some of the skeletal muscle; (2) dermatome, which forms the connective tissues, including the dermis; and (3) sclerotome, which gives rise to the vertebrae.