Muscle Tissues

Question 1

What are muscle tissues?

Answer 1

Tissues that are specialized to actively shorten
- contraction provides means of mobility

Question 2

What are the three types of muscle?

Answer 2

1. Skeletal Muscle: moves and positions the body
2. Smooth Muscle: pushes fluids and solids along digestive tract; and regulates artery diameters
3. Cardiac Muscle: pushes blood through circulatory system

Question 3

How can you distinguish each type of muscle?

Answer 3

1. Skeletal Muscle:
   - striated, multinucleated
2. Smooth Muscle:
   - non-striated, mononucleated
3. Cardiac Muscle:
   - striated, mononucleated, branching fibres

Question 4

What are the functions of skeletal muscle? (6)

Answer 4

1. Skeletal Movement: pulls tendons to move bones
2. Maintains posture and body positions
3. Supports soft tissues: e.g. muscles of the abdominal wall and pelvic cavity
4. Guard entrances and exits: e.g. openings of the digestive and urinary tracts (sphincters)
5. Maintain body temperature
6. Store nutrients: glucose, lipids, and even muscle proteins used during fasting

Question 5

What is the meaning of the word roots myo, mys?

Answer 5

Muscle

Question 6

What is sarco?

Answer 6

Flesh (Gk)

Question 7

What is the sarcolemma?

Answer 7

Cell membrane of a muscle cell

Question 8

What is the sarcoplasm?

Answer 8

Cytoplasm of a muscle cell

Question 9

What is the sarcoplasmic reticulum?

Answer 9

Modified endoplasmic reticulum of a muscle cell (smooth, no ribosomes, stores Ca++)

Question 10

What does myofibre/fibre refer to?

Answer 10

A singular skeletal muscle cell

Question 11

How are skeletal muscles organized? (3; general)

Answer 11

3 layers of connective tissue

1. Muscle fibre (cell surrounded by endomysium)
2. Muscle fascicle (bundle of cells surrounded by perimysium)
3. Skeletal muscle (organ that is surrounded by epimysium)

Question 12

Explain the organization of a skeletal muscle?

Answer 12

A muscle consists of muscle fibres (myofibres) wrapped in a connective tissue called the endomysium. A number of fibres are wrapped together in perimysium to form a fascicle, while fascicles are bundled together to form a muscle, which is wrapped in epimysium or fascia. The three CT layers come togehter to form a tendon. Individual fibres are literally full of contractile organelles called myofibrils, which fill the cell and displace the nuclei to one side

Question 13

What are myofibrils?

Answer 13

Bundle of myofilaments; a systematic arrangement of proteins which form the contractile unit of the muscle called a sarcomere, which gives muscle its striated appearance

Question 14

What creates striations in a muscle?

Answer 14

Sarcomeres

Question 15

What is the connective tissue around cells (myofibres)?

Answer 15

Endomysium

Question 16

What is the connective tissue around fascicles?

Answer 16

Perimysium

Question 17

What is the connective tissue around whole muscle?

Answer 17

Epimysium

Question 18

What are the attachments of skeletal muscles?

Answer 18

Collagen fibers of the 3 different connective tissue layers come together at the ends of the muscle to form tendons (bundles) or aponeuroses (sheets)

structure: tendons in turn are continuous with matrix of the bone that they are attached to

Aponeuroses: layers of flat broad tendons with fewer vessels and nerves
structure: typically both tendons and aponeuroses attach muscle to bone

Question 19

Nerve and blood supply of skeletal muscles?

Answer 19

Nerves and blood vessels penetrate epimysium together and branch through perimysium and endomysium

each cell is:
- adjacent to capillaries
- innervated by nerve fibre axons

Question 20

What are characteristics of skeletal muscle cells?

Answer 20

Striated, lots of mitochondria, lots of capillaries, multi-nucleated

long and thin

Question 21

What are myofibrils?

Answer 21

Rod like structures that come in bundles to form skeletal muscle cells; made up of even smaller structures/proteins called microfilaments

Question 22

What does the sarcoplasmic reticulum contain an abundance of?

Answer 22

Ca++ store; 10000x more than outside the cell

Question 23

Explain the development of a skeletal muscle fibre from myoblast to maturity

Answer 23

Myoblasts: immature muscle fibers
- muscle fibers develop through the fusion of embryonic mesodermal cells called myoblasts

Overtime, most of the myoblasts fuse together to form larger multinucleated cells. However, a few myoblasts remain within the tissue as myosatellite cells, even in adults

The multinucleate cells begin differentiating into skeletal muscle fibers as they enlarge and begin producing the proteins involved in muscle contraction

Question 24

What are T-tubules (Transverse Tubules)?

Answer 24

Tiny tubules that penetrate the sarcolemma and travel deep into the cell surrounding the myofibrils

The T-tubule can conduct waves of electrical activity from the sarcolemma deep into the cell, providing the signal for the cell to contract

Question 25

What is the structure of myofibrils?

Answer 25

Bundles of thick and thin filaments (protein strands)

Question 26

Where is the Z-line?

Answer 26

Line in the middle of thin filaments

Question 27

Where is the M-line?

Answer 27

Line in the middle of thick filaments

Question 28

What is the sarcomere?

Answer 28

From 1 Z-line to the next Z-line

Question 29

pg 24.