Lecture 8: Skeletal Muscle Structure

Question 1

What are the three types of muscle?

Answer 1

Smooth, Cardiac and Skeletal.

Question 2

What is epimysium

Answer 2

Epimysium is comprised of fibrous tissue. This layer of connective tissue surrounds skeletal muscle and acts a barrier. This barrier reduces friction between other muscle tissue and/or bone.

Question 3

What is perimysium

Answer 3

Endomysium is a term which literally means “within the muscle”. Endomysium ensheaths muscle cells. Even though endomysium is the smallest piece of connective tissue of muscle, it serves a very important function. This is where a large amount of the chemical processes of muscular connective tissue occurs and is regulated.

Question 4

What is endomysium

Answer 4

Perimysium is connective tissue that forms surrounds muscle fibers into groups or bundles. These groups are called fascicles. This is where movements, more specifically contractile movements, occur.

Question 5

Explain whole muscle structure

Answer 5

Muscle fibres are gathered into bundles called fascicles. Fascicles are then bundled into muscles. All of these are ensheathed in connective tissue. Connective tissue investments are gathered together to form tendons.

Question 6

Explain muscle fiber structure

Answer 6

Myofibres (muscle fibres), are each a bundle of myofibrils. Myofibrils are made of bundles of contractile proteins running the length of muscle called myofilaments. Myofilaments are made of thin and thick filaments. Actin is the thin filament and the thick filament is myosin.

Question 7

Explain muscle cell structure

Answer 7

Myoblasts fuse together to form large multinucleated cells enclosed by a single common membrane (sarcolemma).

Question 8

Draw and label the parts of a muscle getting smaller

Answer 8

-

Question 9

Describe the structure of myosin and actin.

Answer 9

Each myosin fiber is surrounded in a hexagonal array of 6 actin fibers. They are also arranged in a regular repeating unit called a sarcomere.

Question 10

Name the components of the muscle in order of decreasing size.

Answer 10

Muscle > Fascicles > Muscle Fiber > Myofiber > Myofibril > Myofilament

Question 11

What is the membrane of the myofiber called?

Answer 11

Sarcolemma

Question 12

What is a sarcomere?

Answer 12

Actin - Myosin repeating unit is called a sarcomere. The sarcomere goes from one z - line to the next. Thus. muscle contraction can be thought of us pulling the z-lines of the sarcomere closer together. The I-band is where you only have actin filaments and the A-band is where you only have myosin filaments.

Question 13

What are the transverse tubules?

Answer 13

Invaginations on the surface membrane which run from the surface deep into the fiber in a regular array. There function is to conduct electrical signal deep into the structure of the fiber.

Question 14

What is the sarcoplasmic reticulum?

Answer 14

The sarcoplasmic reticulum is a specialised type of endoplasmic reticulum which stores calcium ions important for muscle contraction.

Question 15

What is a ‘triad.’

Answer 15

A transverse tubule which has the terminal cisternae - terminal ends of sarcoplasmic reticulum - on each side.

Question 16

Explain the neuromuscular junction.

Answer 16

The myelinated end of a motor axon terminates at the single end of a muscle fiber. Here due to an action potential a neurotransmitter called Acetyl Cholide is released.