Chapter 10 Study Prompts

Can you list the three types of muscle tissue in the body?

Skeletal, cardiac, and smooth

Do you know which type of muscle cells are referred to as muscle “fibers”?

Long muscle cells of skeletal and smooth muscle tissue are referred to as “fibers”

What characteristic about the cells gives them this name?

These are very long cells compared to other cells in the body, so they are referred to as “fibers”

Do you know what the two types of myofilaments are?

Actin (thin filament) and myosin (thick filament).

Can you define "sarcolemma" and "sarcoplasm"?

1. Sarcolemma- plasma membrane of a muscle cell. Forms the motor-end-plate across from the nerve endings and the t-tubules of the cell.

2. Sarcoplasm- cytoplasm of a muscle cell- contains myoglobin for increased oxygen storing and glycosomes for glycogen storage.

Do you know what prefixes always refer to "muscle" in anatomy?

myo- and mys (and sarco- is used as well, but not exclusively for muscle)

Skeletal Muscle (List the characteristics, functions, and locations)

skeletal

• multinucleated, striated, long, cylindrical cells that are voluntarily controlled and found only in skeletal muscle.

• Their force production is adaptable and they contract rapidly.

• they are formed from the fusion of cells that work together for a common function, so they act as a syncitium.

• Movement of the body or things in the environment.

Smooth Muscle (List the characteristics, functions, and locations)

Smooth

• no striation, one central nucleus and involuntarily controlled.

• Found in the walls of hollow organs for movement of substances.

• Contract slowly.

Cardiac Muscle (List the characteristics, functions, and locations)

Cardiac

• striated, single nucleus, short, fat and branched cells with lots of mitochondria.

• Involuntarily controlled and found in the walls of the heart.

• Moves blood.

Can you list and describe the functional characteristics of muscle tissue in general?

1. Can receive and respond to stimuli. Stimulus is the neurotransmitter from neurons and the response is the contraction and generation of force.

2. Contractility- ability to shorten forcibly

3. Extensibility- ability to be stretched beyond resting length

4. Elasticity- ability to return to resting length after being stretched.

Can you list and describe the functions of muscle tissue in general?

1. Movement- locomotion, manipulation of the environment for skeletal. Movement of a substance through a hollow organ for smooth and movement of blood for cardiac.

2. Posture

3. Stabilizing joints

4. generating heat

Can you list the different types of tissues found in skeletal muscles?

Skeletal muscle tissue, CT sheaths, nervous tissue and blood (another CT)

Can you list and describe the three muscle connective tissue sheaths?

1. Endomysium: surrounds each muscle fiber

2. Perimysium: surrounds groupings of muscles called fascicles

3. Epimysium: out covering of the entire muscle and is continuous with the tendon of the muscle

Can you describe the nervous and blood supply to skeletal muscles

There is one nerve that brings electrical signal to each muscle, one artery bringing blood (oxygen and nutrients) to each muscle and there may be more than one vein taking blood (carbon dioxide and wastes) away from each muscle.

Can you define the "origin" and "insertion" of skeletal muscles? Do you understand these definitions?

1. Origin: end of the muscle that is on the bone that will move least in the action.

2. Insertion: end of the muscle on the bone that will move most in the action. Hint: the insertion will always move toward the origin in the action.

Can you describe the general microscopic anatomy of a muscle fiber?

Multinucleated cell with a specialized plasma membrane called a sarcolemma and cytoplasm called sarcoplasm (contains glycosomes and myoglobin). They are also very long (several centimeters) and not very wide (several micrometers).

Why is a muscle fiber considered a "syncytium"?

Cells fuse together during fetal development to form muscle fibers so they "work together" = syncitium.

What is the cytoplasm of a muscle cell called?

Sacroplasm

Can you define a "myofibril"?

A cylindrical unit packed with myofilaments (actin and myosin) and fill the muscle fibers

What is considered the smallest contractile unit of a muscle?

sacromere

Can you describe the general structure of a sarcomere?

defined from z-disc to z-disc and contains overlapping actin and myosin proteins for contraction.

Z-discs (Can you draw and label the following in a sarcomere, define the terms)

Z disc: sheets of protein that span the myofibril and form the boundaries of the sarcomeres.

A band (Can you draw and label the following in a sarcomere, define the terms)

"Dark" bands. Contains myosin with overlapping actin.

I band (Can you draw and label the following in a sarcomere, define the terms)

"Light" bands. Contain actin only.

H zone (Can you draw and label the following in a sarcomere, define the terms)

myosin only

M line (Can you draw and label the following in a sarcomere, define the terms)

Formed by myomesin up the center of the sarcomere

Do you know what attaches actin and myosin to the z discs?

a. Actin attached by nebulin

b. Myosin attached by titin

Do you know what actin and myosin are also referred to as?

thin filament and thick filament, respectively

Do you know what the sarcoplasmic reticulum of a muscle cell is? What is its special function in muscle fibers?

it is a modified smooth endoplasmic reticulum. It specifically stores and releases calcium into the sarcoplasm for muscle contraction

Do you know what terminal cisternae are?

• the ends of the sarcoplasmic reticulum (SR) that are coupled to the t-tubule to form triads.

• The calcium is released from this part, which is triggered by electricity coming down the t-tubule.

Can you describe a "T-tubule" and its function in a muscle cell?

Indentations of the sarcolemma. It carries the electric signal deep into the muscle fiber and triggers the SR to release its calcium for muscle contraction.

Can you describe a triad?

two terminal cisternae and one t-tubule between them at the A-I junctions of the myofibrils.

How do the components of the triad work together in muscle contraction?

the t-tubule carries the electric signal to the terminal cisternae, which then are triggered to release calcium into the sarcoplasm for muscle contraction.

Can you describe the "sliding filament model of contraction"?

during muscle contraction, actin is pulled by myosin towards the center of the sarcomere, so actin "slides" past myosin.

Do you know how the actin and myosin interact in the sliding filament model?

the myosin heads "grab" actin to form a crossbridge. Then the myosin heads change shape in a way that pulls actin towards the center of the sarcomere. This action is called a power stroke.

Do you know what type of neurons stimulate skeletal muscle?

motor

Can you describe the structure of a neuromuscular junction?

• the motor neuron ending contains vesicles filled with the neurotransmitter acetylcholine.

• The portion of the muscle sarcolemma across from the motor neuron ending is called the motor end plate and contains receptors for acetylcholine.

• The space between the motor end plate and the motor neuron is called the synaptic cleft.

Do you know what a synaptic vesicle is? Do you know what neurotransmitter will always stimulate skeletal muscle?

a lipid "bubble" formed by a phospholipid bilayer. Acetylcholine

Do you know what the space between the axonal endings and the motor end plate of the muscle cell is called?

cleft

What process releases the neurotransmitter from the axonal terminal?

exocytosis

Do you know how the neurotransmitter is destroyed? Do you understand why it needs to be destroyed?

• an enzyme called acetylcholinesterase.

• As long as it is in the cleft it can bind to the receptors and cause muscle contraction.

• To be able to relax the muscle the neurotransmitter must be removed.

Can you define a motor unit?

a motor neuron and all of the muscle fibers that it innervates.

Can you describe the general structure, location, arrangement and characteristics of a smooth muscle fiber?

spindle shaped cells with only one nucleus. Not striated even though it still has actin and myosin. The actin and myosin are arranged in a cris-cross pattern. There is only a little bit of endomysium.

Can you compare and contrast the structure and function of a smooth muscle cell and a skeletal muscle cell?

• skeletal muscle cells are cylindrical and centimeters long whereas smooth muscle cells are spindle and a couple of hundred micrometers long.

• Skeletal muscle cells contract to move the body and things in the environment whereas smooth muscle cells contract to move substances through hollow organs

Can you define "peristalsis"?

wave-like contractions of smooth muscle in the walls of hollow organs to move substances through them

Can you describe how smooth muscle receives neurotransmitter since they lack a neuromuscular junction?

bulbous swellings called varicosities release neurotransmitter over many smooth muscle cells at once.

How are the actin and myosin arranged in a smooth muscle cell?

in a cris-cross pattern through the cell. This pattern allows the cell to twist and shorten during contraction

Do you know what the intermediate filaments and dense bodies are in a smooth muscle cell?

intermediate filaments are actin and myosin (see definitions under cytoskeleton components in chapter 3) and dense bodies hold them together when they cross in the cell

Can you list and describe the unique characteristics of smooth muscle?

• SR is less developed.

• Indentations called calveoli hold calcium from extracellular fluid for contraction.

• There are no Z-disks or sarcomeres.

• Smooth muscle responds to stretch by relaxing, thus allowing a hollow organ to fill with a substance, such as in the stomach, urinary bladder or uterus.